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Cooling effect of menthol
Menthol (peppermint) is known for its familiar perceived cooling effect and fresh sensation in the mouth and nose. The feeling of freshness we experience when we use menthol containing products is in part because of the trigeminal nerve in the brain. This nerve is involved in temperature detection and perception and is also the nerve largely responsible for ice-cream headaches or ‘brain freeze’. Digging deeper, menthol stimulates TRPM8 receptors; a relatively recent discovery, TRMP8 receptors are stimulated by cool-cold temperatures and compounds that mimic this temperature range, such as menthol. An action potential is then generated and the ‘cold signal’ is transmitted to the brain for interpretation. So, menthol acts at a cellular level to mimic cold temperatures and thus produces a cooling sensation.
History of menthol
The idea of menthol use in sport and exercise has been borrowed largely from respiratory medicine. Research into the pharmaceutical effects of menthol began in the late 19th century with a handful of researchers espousing its benefits in the treatment of respiratory conditions associated with tuberculosis. Menthol’s ability to stimulate thermoreceptors was identified as early as 1896. This work was built upon throughout the 20th century by using animal models to assess how menthol affected a host of variables from nasal congestion to ventilation, via digestion, taste and temperature detection.
This was built upon in human models to show that not only could menthol induce feelings of cold in the mouth, but it could also desensitise the mouth to warm sensations, such as capsaicin, the active ingredient in chilli. These effects are often accompanied by a pleasant taste and a peppermint smell, hence why menthol is used in many confectionary and medical products, especially those involved with nasal and respiratory conditions.
Menthol in sport
In sport, we have built upon this knowledge by implementing menthol mouth swilling, and other menthol containing strategies, during exercise in hot environments. This has been most successful in a range of endurance sports lasting 20-70 minutes, with no benefit shown in intermittent protocols that represent team sports to date. The timing of menthol throughout an exercise bout is an interesting area for researchers going forwards; most researchers have employed repeated doses but new evidence suggests that menthol mouth swilling may extend time to exhaustion if applied close to the point of fatigue (2). Concentration of menthol also needs to be considered, with ranges of 0.01-0.1% recommended (1) and allowing for personalisation of a menthol swilling strategies.
Conclusions
Physiologically, menthol may relieve discomfort associated with breathlessness or laboured breathing and as such a compensatory increase in ventilation occurs, with no change in the oxygen cost of exercise reported to date. Athletes also commonly report improved feelings of thermal comfort and or decreases in thermal sensation and ratings of perceived exertion following menthol mouth swilling (3). More simply, athletes feel less hot, or can better tolerate the heat and this may be reflected in how hard they feel exercise is. Taken together this can lead to improved performance as the thermal challenge is perceived as less of a threat to maintaining exercise intensity.
It is still early days for menthol and sports science. There are few studies in the area, but with encouraging findings thus far and many future directions still to be explored, menthol may be a hot topic for a while to come.
References
1. Best, R., Spears, I., Hurst, P. and Berger, N. (2018) ‘The Development of a Menthol Solution for Use during Sport and Exercise’, Beverages, 4(2), pp. 44–10. doi: 10.3390/beverages4020044.
2. Jeffries, O., Goldsmith, M. and Waldron, M. (2018) ‘L-Menthol mouth rinse or ice slurry ingestion during the latter stages of exercise in the heat provide a novel stimulus to enhance performance despite elevation in mean body temperature.’ European Journal of Applied Physiology, 118(11), pp. 2435-2442.doi: 10.1007/s00421-018-3970-4
3. Stevens, C. J. and Best, R. (2017) ‘Menthol: a fresh ergogenic aid for athletic performance’, Sports Medicine, 47(6), pp. 1035-1042. doi: 10.1007/s40279-016-0652-4.
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Many agree that the future of nutrition is personalized nutrition. However I also often hear that “we have been doing this for years”. Of course both claims are valid. Some form of personalisation has been the basis of the work of a sports dietitian or sports nutritionist. However, there are different levels of personalized nutrition.
Three tiers
Ronteltap and colleagues identified three different levels of personalized nutrition (1). At the basis we find the most traditional form of personalized sports nutrition: typical tailored advice of a dietitian that is based on an individual’s dietary intake. A dietary assessment is made and, based on the outcome, suggestions for improvement are communicated to the individual that are specific to that individual. The second tier of personalized nutrition is based on an individual’s diet as well as phenotypic markers such as anthropometric measurements or blood biochemical markers. Examples include the measurement of iron status or vitamin D levels. If iron or vitamin levels are low, the diet is modified or supplements are recommended. The third level, the top of the pyramid, builds on the previous two levels but includes genotypical information. A professional service including information about genotype is less readily available (2). Nevertheless, when personalized nutrition is discussed in the mainstream channels, the first two levels are often ignored and the focus is often on DTC (direct to consumer) test kits that provide genotypical information.
There are now several companies that specifically target consumers, suggesting they should test their genotype and adapt their diet accordingly. Although this is an attractive idea, the usefulness of such tests is subject to debate.
Is personalisation based on genotype better?
Although personalization could be achieved by taking into account dietary, phenotypic and genotypic characteristics, the big question is of course whether personalized nutrition will result in better, more sustainable, or more cost effective behaviour changes than conventional dietary advice. Will personalised nutrition result in better health or better performance for our athletes? One could argue that if personalized nutrition means that we can prevent iron deficiency, we can avoid gastro-intestinal problems and we can optimise glycogen resynthesis, this may in many cases result in improved exercise performance. But does personalisation based on genotype add any additional value? In order to answer this question we need to answer a few other questions first:
Is there sufficient evidence to base genotype-based dietary advice on? If athletes receive genotype based advice are they more likely to change their behaviour?If athletes receive genotype based advice will they see greater benefits than other forms of personalized nutrition.
At present we would have to conclude that there is limited evidence connecting genotypical information to nutrition and performance and there is no evidence that receiving genotypical information will induce behaviour changes or greater improvements in performance.
Reliability
The problems can also be illustrated by a simple example. A simple google search will reveal a number of examples of individuals who have sent off their saliva samples, with the same genetic information, to different DTC companies for genotyping. The companies then send a report back with recommendations. If this approach would work, we would expect some consistency in these reports. Unfortunately this is not the case. There is huge inconsistency in the analysis as well as in the reporting. Different companies will provide different advice, based on the same sample. Even when the outcome of the analysis is comparable, there is difference in the interpretation of the results and the recommendations that follow. We clearly need more research to connect certain genes to nutrition and health and a lot more research than we have to date connecting genes, nutrition and performance.
Conclusion
Personalized nutrition is important but at the moment, genotyping has no role to play in nutrition advice. Personalized nutrition based on genotype is not ready for prime time and it will be a long time before it will be ready…
In sport where performance is the main outcome of interest rather than health, we have far less research and therefore this timeline is even longer. For now, personalized sports nutrition is about clearly defining the goals of the athlete, and tailoring the advice to these goals, and the specific training needs of that individual.
References
1. Ronteltap, A., van Trijp, H., Berezowska, A., & Goossens, J. (2013). Nutrigenomics-based personalised nutritional advice: in search of a business model? Genes Nutr, 8(2), 153-163. doi:10.1007/s12263-012-0308-4
2. O'Donovan, C. B., Walsh, M. C., Gibney, M. J., Gibney, E. R., & Brennan, L. (2016). Can metabotyping help deliver the promise of personalised nutrition? Proc Nutr Soc, 75(1), 106-114. doi:10.1017/S0029665115002347
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Pre-workout supplements are popular. What do they consist off? What do they do? Are they useful? What is the evidence? Are they safe to take? What strikes me, is that the most frequently asked question is: which one is the best? and the question not often asked is: do they work? or are they necessary?
The magic blend
Pre-workout supplements often contain a mystery blend of ingredients ranging from caffeine to BCAAs to creatine to some more exotic ingredients. These supplements are claimed to bring your body in a state of “readiness” for the training! Although there are hundreds of these supplements on the market and they are all different, there seem to be a few ingredients that can be found in most of these products. A recent study showed that 44.3% of investigated supplements contained a proprietary blend of ingredients. This means that the exact amounts are not disclosed and thus it is impossible to link the potential effects to any of the ingredients. If we want to evaluate the effects of these pre-workout supplements, we need to look at the evidence behind each of these ingredients. We will start with some of the most common ones, because if they are in all products, they must be the most effective ingredients. In the infographic the most common ingredients are listed according to a recent publication (1).
Beta alanine
Beta alanine ingestion over a period of several weeks can increase the muscle buffering capacity because the concentration of muscle carnosine may increase. One of the side effects of beta-alanine is parasthesia (tingling fingertips and nose). The higher the dose the more severe the side effects. But some people like it because now the supplement you are taking seems to do something... you notice something after taking it... so it must work. The amounts of beta-alanine found in most pre-workout supplements is far too small to have these effects. Besides that, the carnosine concentration needs about 4-6 weeks to increase, thus just taking a small dose just before exercise will have no effect at al.
Caffeine
It is known for a long time that caffeine improves alertness and can improve endurance exercise performance. The evidence that it improves performance during high intensity exercise workouts and resistance training is much less convincing, but it is possible. Caffeine, in whatever form would need to be ingested about 1 hour before the workout. One could also argue that the source of the caffeine does not matter. For example, drinking coffee would have the same effect as the synthetic caffeine in most of these pre-workout products, so we would not necessarily need a pre-workout supplement for this effect.
BCAA
Branched-chain amino acids or BCAAs is a group of three essential amino acids: isoleucine, leucine and valine. BCAAs are building blocks for protein and leucine also has a role in turning on protein synthesis. Studies have shown that BCAA alone are ineffective in raising protein synthesis and they would have to be ingested with protein. One way to do this is a supplement but chicken for example has more essential amino acids and more BCAA than most supplements. So why not eat the protein. Besides that, this is not an acute effect and there is no need to take it before exercise. Studies show that protein post exercise is at least as effective or more effective. So why not just have a meal after exercise? Also other claims of BCAAs do not seem supported with evidence (read more here).
Citrulline Malate
Citrulline malate is another amino acid that is produced in the body through the other amino acids that are consumed. Some studies have used citrulline as a precursor for arginine, with the goal to improve blood flow. The effects have been very small and several studies have not been able to find any effects.
Creatine
Creatine is a popular supplement. It is one of the few that has evidence that it can be beneficial in some situations for some people. If body stores of creatine are suboptimal, creatine supplementation for 5 days (high doses of 20 g per day) have been shown to restore the creatine stores. Studies have shown that higher muscle creatine concentrations are linked to improved repeated high intensity exercise performance. Creatine ingested at 3g/day for 30 days will achieve the same. However, ingesting 1-3 grams of creatine just before a workout will not improve that workout.
Electrolytes
Electrolytes like magnesium, potassium and sodium are buzz words. If we call them ”salt” this is seen as “bad” ingredient and the message is to reduce salt intake. If we call them “electrolytes” they become “good” and we need them before a workout. The reality is: they will not do anything before a workout and you don’t need them. It is marketing fluff.
Protein
Protein delivered to the body through pre-workout drinks and meals will help it to increase protein synthesis by delivering more amino acid building blocks. The result is increased muscle growth. But most sources of protein will do this and there is no need to have protein pre-exercise.
Taurine
An amino acid, taurine is used in energy drinks. It is not exactly clear what it is supposed to do and research does not support a role in exercise performance.
Vitamin B12
Vitamin B12 plays an important role in metabolism and erythropoiesis. However, there are no studies that show that vitamin B12 affects exercise in any way, especially if there is no deficiency.
You will get the picture by now. We discussed a list of ingredients that are popular in pre-workout supplements and we must conclude that caffeine is the one ingredient that may affect subsequent performance. The rest of the products are mostly fillers and marketing gimps. Some products may contain illegal ingredients with unknown health effects or with known negative effects. The one that has received most attention is probably DMAA.
DMAA
DMAA is sometimes added to pre-workout supplements. DMAA (1,3-dimethylamylamine) is an amphetamine derivative that has been marketed in sports performance and weight loss products, many of which are sold as dietary supplements. DMAA is linked with brain haemorrhage and several deaths have been linked to its use as a dietary supplement. DMAA is a drug and not a dietary ingredient, and DMAA-containing products marketed as dietary supplements are illegal and their marketing violates the law in many countries (including USA, Canada, New Zealand, Sweden, Australia, Finland, the UK, and Brazil. Despite multiple warning letters from the FDA as of 2018, the stimulant remains available in sports and weight loss supplements. For a subgroup of consumers the fact that they are banned means that they must be very effective! In fact supplement manufacturers on their web sites proudly display that the supplements are banned. A quick google search took me to a web site that showed all the "banned" products and the mentioned "it is basically legal meth"... There seemed to be some confusion between legal and banned...
DMAA is also included in various products under different names including the following:
1,3-DMAA
1,3-Dimethylamylamine
1,3-Dimethylpentylamine
2-Amino-4-methylhexane
2-Hexanamine, 4-methyl- (9CI)
4-Methyl-2-hexanamine
4-Methyl-2-hexylamine
Dimethylamylamine
Geranamine
Methylhexanamine
Methylhexanenamine
DMAA may have received a lot of attention, but there are many other ingredients used in pre-workout supplements with unknown health effects. These ingredients are in some cases not even listed on the label.
Summary
So, in summary, pre-workout supplements are claimed to get you ready for your workout. They contain a mix of ingredients. The consumer is tricked into thinking that the more ingredients something contains, the better, it must work. However, if you have 10 ingredients that don’t work, or 20, it does not make a difference. Having said this, these supplements may work to some degree. They may act as a placebo. They are part of a ritual. The ritual could be a cup of tea, some stretching, some loud shouting, or maybe you could hit yourself in the face a few times… but (with the exception of caffeine), the supplement does not seem to help the workout because of the action of its ingredients.
References
(1) Jagim AR, Harty PS, Camic CL. Common Ingredient Profiles of Multi-Ingredient Pre-Workout Supplements. Nutrients. 2019 Jan 24;11(2). pii: E254. doi: 10.3390/nu11020254.
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The story of the Tower of Babel is well known, famous and often referred to. A tower was being built that would reach into heaven. But this tower could not be completed because God had the workers speak different languages from one moment to another. Imagine a discussion about a topic where you think you are talking about vacation, using words that mean joy and pleasure to you. These same words however mean pain and misery to someone else. It will be very difficult to come to a consensus about vacation. To some degree this is what happens when people talk about low fat diets, high fat diets and their effects.
Source of confusion
The non-uniform use of terms has caused confusion and miscommunication in the popular press but also in the scientific community. The literature is full of terms that are not defined well enough and interpreted in different way by different people. There are many topics this applies to, but in particular to low carbohydrate, high fat diets. Terminology is confused. We talk about high fat diets, low carb diets, keto diets but we may be talking to someone who has different views on what "high fat" means, what "low carb" means and what a "keto diet" consists of. Very often I speak to athletes who are on a low carb diet supplemented with carbohydrate around training? Is this still low carb? In a recent paper we discussed this problem and called for scientists to sit together and come up with commonly accepted definitions that would help the confusion that is currently out there. For a link to the full paper click here.
Percentages versus absolute
Historically, even the scientific literature has provided confusing information. For example, carbohydrate needs were expressed as the ratio of energy contributed by carbohydrate in the athlete’s diet as the single metric of the adequacy of carbohydrate intake. A 50% carbohydrate intake for triathlete may be a whopping 1 kg per day and for a female gymnast as little as 200 grams. In the first case this would be a high carbohydrate intake, in the second one low carbohydrate intake, but they would both be classed as moderate intake. Clearly a percentage of energy intake is not a good way to express carbohydrate requirements. Therefore, carbohydrate requirements are usually expressed as grams per kilogram. In mainstream media we see these percentages still pop up.
Other ways to express carbohydrate needs
There are also many ways to express carbohydrate needs for athletes. For example, the term carbohydrate availability refers to the amount of carbohydrate available to do the work. If glycogen is depleted and no carbohydrate is ingested, carbohydrate availability is low and training in this state is referred to as “train low”. If we haven’t trained too much, we have eaten carbohydrate rich and we consume carbohydrate before and during training we are “training high”. Studies suggest that in order to get the effects of training low (for example changes in fat metabolism), carbohydrate availability needs to be low a certain level. However, in real life this is difficult to measure. So even for scientists it is not easy to define these terms and indicate exactly what is “low” and what is “high”.
Amplifying confusion
The press and social media amplify the confusion by mispresenting/misreporting sports nutrition research or practice and by generally oversimplifying the sophistication of contemporary sports nutrition knowledge.
Here is an example: In July 2016, Tour De France winner Chris Froome uploaded a photo of his breakfast on a rest day during the middle of this grueling stage race. This single picture of eggs, smoked salmon, and avocado caused an avalanche of claims and counterclaims about Froome’s advocacy of the low-carb high-fat diet, despite wider evidence presented by the athlete himself that he follows a plan in which carbohydrate availability is periodized according to his specific goals. Dr James Morton who works with this athlete and has written extensively on the general philosophy of “fueling for the work required”, as well as nutrition support for the Tour de France in particular, has worked with Team Sky for years and is also one of the authors of our recent paper. He believes that there is a role for lower carbohydrate intake on some days but very high intake on other days, especially those days when performance matters.
Team Sky recently released data to illustrate the sophisticated periodization of body mass and energy/carbohydrate intakes according to the demands of each stage in a cycling tour, including estimates of Froome’s intake on the critical 19th day of his 2018 Giro D’Italia title: an astonishing 6,663 kcal (27.98 MJ) and 18.9 g/kg CHO (Check report here).
Keto adaptation
Another example: "keto-adaptation".... This term is used (or should I say abused) a lot! No one has ever defined it. I am not quite sure what it means or how it is measured... and so far no one has been able to explain it to me. Some people are quick to state things like "there wasn't enough time for "keto adaptation".... without knowing exactly what this means and without ways to measure it, it is impossible to make such claims! So, if we want to use such terms, lets define what they actually mean. let's determine how we measure them and then measure it! So that we can test the hypothesis! Without that this topic will remain in the domain of pseudoscience.
Conclusion
There will always be different views on a variety of sports nutrition themes, and some of this is healthy and important to move science forward. However, if these discussions are based on misunderstandings, different definitions or unclear terms, thus discussion is less than helpful and will not move science forward. Therefore, in the paper we ask both research scientists and practitioners to collaborate and share discussions, underpinned by a commonly accepted and consistent terminology. This will help to strengthen hypotheses and experimental/experiential data around various strategies. We also propose that athletes and coaches would be better served by less confusion and misinformation in all levels of literature.
With common definitions, evidence-based thinking, and a constructive attitude we might just have a fighting chance of complete the Tower of Babel one day.
Reference
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The seemingly mythical status of breakfast stems from age-old tales of reduced appetite later in the day and legendary feats such as ‘kick-starting metabolism’ to avoid ‘starvation mode’, all leading to that holy grail of dieting: to lose weight while eating whatever you like (not to mention rumours of improved cognitive and physical performance along the way). Like most mythical tales, however, these accounts are only partly grounded in the truth and there is no such thing as breakfast.
What is a breakfast?
Defining ‘breakfast’ is notoriously difficult and we do not all have a shared understanding of what it actually is (see this paper for a detailed discussion). Opinions are often therefore divided about what constitutes this thing called breakfast, so it is difficult to know whether someone has eaten it. Even just considering morning meals typical to Westernised cultures alone, which many people might agree are ‘breakfast foods’ (e.g. a high-fibre/low-sugar cereal, pancakes with maple syrup or a ‘full-English’); we would not expect similar acute metabolic responses or chronic health outcomes when ingesting such nutritionally diverse foods. These complexities in defining breakfast are relevant because we are repeatedly presented with the overly simplified concepts that breakfasts in general may or may not be important and, moreover, that two physiologically distinct categories of humans exist: breakfast consumers versus breakfast skippers. The concept of chronotype certainly has empirical support (whereby one individual may be more of a morning-type than another), yet the reality is that breakfast habits are neither a binary variable nor a stable trait. A person cannot therefore be reliably classified as a ‘breakfast skipper’ because that would depend entirely on the definition employed and time-scale in question.
Mainstream media confusion
The over-simplification of breakfast in the mainstream media has made it almost impossible to decipher consistent public health messages on this topic. Individuals trying to make an informed decision about whether to consume breakfast might then be forgiven for any confusion when considering the range of headlines in recent years (even the same news outlet can publish two utterly contradictory reports within a matter of weeks - about the same original scientific paper!).
Do we know enough?
Is further research required before any evidence-based conclusions can be drawn? More data would certainly be helpful but current understanding is nonetheless at a stage where several effects of breakfast have now been established. Regarding the question of whether breakfast makes us eat less later in the day, it has in fact been verified using various levels of evidence and across a range of experimental designs that total daily energy intake is more likely to be lower if we skip breakfast. This has been a reasonably consistent finding using cross-sectional diet surveys, laboratory-based meal tests and randomised controlled trials under free-living conditions.
Does eating less mean weight loss?
Some people may then immediately assume that eating less overall is a good thing based on the (false) expectation that weight-loss will necessarily follow, so argue against consuming breakfast. Conversely, others may be puzzled that people who report skipping breakfast tend to eat less overall given that cross-sectional studies clearly show regular morning fasting is actually associated with being moreoverweight. In addition, randomised controlled trials have not revealed any effect on body weight irrespective of whether or not the overnight fast remains unbroken until the afternoon.
Whilst it might at first seem paradoxical that morning fasting can reduce daily energy intake without resulting in weight loss, this merely indicates that compensatory reductions in metabolic requirements must occur to offset any energy deficit. Despite the common belief that this is achieved via a slower baseline level of metabolism day-to-day when not regularly consuming breakfast, the available evidence does not support this view as resting metabolic rate is quite stable in the absence of weight change and so remains predictable based simply on body mass. Instead, a more likely explanation emerging from recent trials is that the compensatory response to prevent weight-loss with fasting is achieved by limiting the energy expended above resting metabolism via lower engagement in spontaneous low-level physical activities (i.e. movement).
Don't forget physical activity
One interpretation of the above pattern of results is that skipping breakfast is ineffective for weight-loss because the attained level of caloric restriction is directly undermined by lower physical activity (especially considering that a sedentary lifestyle is an independent risk factor for chronic disease). However, unlike if the compensatory response to fasting had involved a slower resting metabolic rate (i.e. adaptive thermogenesis), the apparent behavioural response is thankfully under a degree of conscious control. Therefore, although you cannot be certain whether what you eat each morning truly qualifies as breakfast or whether you then fit the nominal category of a habitual consumer, we can recognise our increased natural propensity for sedentary behaviour prior to breaking the overnight fast and so actively seek opportunities for greater engagement in physical activity.
References
Betts JA, Chowdhury EA, Gonzalez JT, Richardson JD, Tsintzas K, Thompson D. Is breakfast the most important meal of the day?Proc Nutr Soc. 2016 Nov;75(4):464-474.
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Is breakfast the most important meal of the day? A recent meta-analysis suggests that this might be one of the myths in nutrition. The article published in the British Medical Journal (BMJ)
argues that the studies used to indicate that breakfast is the most important meal of the day may be biased. The case for breakfast was built on the fact that the idea that spreading out meals throughout the day and eating little and often (grazing rather than gorging) to avoid “stress” on the body from having to digest large meals. Studies also showed that obese and diabetic people skipped meals more often than thin people. From this it was deducted that thus having breakfast was essential for maintaining a healthy body weight.
Context
Before I discuss the study and the evidence, it is important to pause and put the study into context. The study in the BMJ was about breakfast and weight change and/or energy intake; or in other words breakfast and maintaining a healthy weight. There are of course many other reasons why people eat breakfast. Weight loss is not the only reason for having a breakfast in the morning. For example, an athlete might eat breakfast for performance or continued recovery from the training the day before. The article in the BMJ is a summary of studies about preventing weight gain or effects on energy intake later in the day, not about performance, recovery or any other aspect. Without any doubt this context will be forgotten in many views that will be published in the aftermath of this publication in BMJ and will finds its way to the general population through popular magazines, social media and other channels. The message will be “breakfast is not important” or perhaps “it is better to skip breakfast”… My answer to the question to the question “Is breakfast the most important meal of the day?” is still “It depends”. It depends on the goal of the breakfast. For a cyclist, who has an important one-day bike race, breakfast may indeed be the most important meal of the day. It is the only meal where he or she can stock up on carbohydrate and benefit during the race. Starting the race without the breakfast would have consequences for performance. The meals after the race are too late to affect performance even though they are of course important for recovery.
Goal
If the goal is weight loss, the review in BMJ shows that having a breakfast is not essential. It may even be better to have no breakfast. Studies have shown that if breakfast is skipped, this may mean that intake is somewhat compensated later in the day and physical activity may be reduced later in the day but not enough to make up the lower energy intake at breakfast.
The BMJ study
Of 13 included trials, seven examined the effect of eating breakfast on weight change, and 10 examined the effect on energy intake. Meta-analysis of the results found a small difference in weight favouring participants who skipped breakfast (mean difference 0.44 kg, 95% confidence interval 0.07 to 0.82). The authors also note that there is quite a bit of inconsistency across trial results. Participants who had a breakfast had a higher total daily energy intake than those assigned to skip breakfast (mean difference 260 kcal/day). The authors also state that all of the included trials had only short term follow-ups (a few weeks for weight changes and a couple of weeks for energy intake) and that the quality of the included studies was mostly low. The authors thus state that the findings should be interpreted with caution. So the authors are careful kin their conclusions and discuss limitations, but these will not be picked up and discussed by the media outlets that will now report that “breakfast is not important”…
The conclusions
What is a little puzzling to me is the conclusion of the BMJ study: The authors conclude: this study suggests that the addition of breakfast might not be a good strategy for weight loss, regardless of established breakfast habit. This suggests that people are having breakfast with the purpose of losing weight. Personally, I am not aware of anyone who eats breakfast with the goal to lose weight. I know of people who skip breakfast to lose weight… and maybe those people are indeed doing something that might work for them. I am also aware of the advice to not skip breakfast for weight loss. But this is not the same as eating breakfast to lose weight, but maybe these are semantics. My opinion: Whether breakfast is the most important meal of the day depends on the goal. In many cases there is little or no evidence to suggest that there is a problem with skipping breakfast, but especially for athletes and when performance is important, breakfast is a very important meal. On certain days when training low is in the athlete’s training plan, training without a breakfast may be appropriate. It depends.
Reference
BMJ 2019; 364 doi: https://doi.org/10.1136/bmj.l42 (Published 30 January 2019)
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The Medical and Scientific Commission of the International Olympic Committee assembled a panel of experts in at their offices in Lausanne, Switzerland, to discuss the place of dietary supplements in the nutrition strategy of the high-performance athlete (read the consensus paper
). Participants from fields of practice, policy and research were selected because of their experience and expertise in one or more relevant areas, including nutrition, dietetics, physiology, pharmacy, medicine and anti-doping. Detailed discussion papers were prepared in advance of the meeting and were circulated to all participants. The evidence that informed these papers was presented and analysed in depth over the three days of the meeting. The papers are also published in the International Journal of Sports Nutrition and Exercise Metabolism.
Practitioners who work with Olympic and highly competitive athletes know that the pressures of elite sport and the substantial rewards that follow success provide a high level of motivation to adopt any safe and legal strategy that might promise even the smallest performance gain. Dietary supplements operate in this space, whether they promise a large performance boost or just create the fear that an athlete cannot afford to miss out on what their rivals are using. Dietary supplements encompass a wide range of products, including essential nutrients (vitamins, minerals, proteins, amino acids, etc), herbals and botanicals, and specific products with potential for maintenance of health and optimisation of performance. The use of dietary supplements is widespread among elite athletes, as it is in the general population. Users cite many different reasons for consuming dietary supplements, though these reasons are often based on unfounded beliefs rather than on any clear understanding of the issues at stake, and may reflect encouragement from individuals who are influential rather than being experts on this topic.
There is now a widespread acceptance that some supplements can offer benefits to the elite athlete if used appropriately but that some may be harmful to health and/or performance. Benefits from the use of supplements and sports foods may include convenience and provision of a known amount of a key nutrient, as, for example, in the use of protein supplements after training with the aim of promoting training-induced adaptations in muscle and other tissues. Supplements should be used by athletes only when safety is assured - though an absolute guarantee is seldom possible - and a health or performance benefit is likely, but there is limited evidence of efficacy of most supplements. More well-conducted and sports-specific studies research on supplements are needed, as many of the published studies have used inappropriate experimental models and subject populations that are not representative of the elite athlete. Assessment of the evidence requires a consideration of potential limitations to study design, including confounding variables and bias, and of the relevance to real-life practices of elite athletes, as well as the need for verification of the composition of supplements used. Performance changes should be interpreted in light of what is meaningful to the outcome of sporting competition. It must be remembered, though, that absence of evidence of efficacy is not the same as evidence of absence of efficacy.
A comprehensive nutrition assessment is the first step in advising athletes on dietary strategies or medical uses of supplements. Nutrition assessment requires the systematic collection, verification and interpretation of the data needed to identify nutrition-related problems, their causes and their significance. A complete assessment should include dietary evaluation, body composition analysis, biochemical testing, nutrition-focused clinical examination, and patient health and performance history. Assessment should take account of maturation status, sex, ethnicity and culture. The limitations and uncertainties in all of the methods employed must be recognised, though valid and reliable methods are available for some specific nutrients.
A few specific supplements may offer performance benefits to some athletes, but their use requires careful evaluation. Supplements supported by good evidence of efficacy, in at least some exercise models, include carbohydrate, protein, caffeine, creatine, specific buffering agents and nitrate. Because responses seem to vary between individuals and depend on the exercise model used, supplements should be thoroughly trialled in training or simulated competition before implementation into a competition environment. Indeed, it is possible that deleterious responses may outweigh any expected performance-enhancing affect.
Over the past two decades, a new hazard related to supplement use has emerged: inadvertent ingestion of substances that are prohibited under the anti-doping codes that govern elite sport, but are present in some supplement products. In some cases, the level of banned or toxic substances in supplements presents a health hazard for all consumers. In other cases, the content may be too small to cause any health or performance effect but large enough to record an Anti-Doping Rule Violation for athletes who submit to doping tests. These problems may arise from poor quality assurance during production or from deliberate adulteration of otherwise ineffective products.
The lack of evidence to support claims made about a supplement may be ignored by athletes because the stakes are so high: the cost:benefit ratio therefore favours experimentation in the absence of clear proof. The use of dietary supplements should not compensate for poor food choices and an inadequate diet, except as a short-term strategy when nutrient intake is challenged or dietary changes are not possible. Use of products that have been subjected to one of the available quality assurance schemes can help to reduce, but not eliminate, the risk of an inadvertent doping infringement. Vulnerable populations, including especially young athletes, may require particular support in making choices about supplement use. In general, use of supplements by young athletes is discouraged except when full evaluation of nutritional status suggests that it is warranted.
The full text of the review paper can be found at: http://dx.doi.org/10.1136/bjsports-2018-099027
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High protein intakes are considered essential to support the demands of training, and as such, athletes are recommended to consume more protein (between 1.2 and 1.6 g/kg/day, with up to 2.2 g/kg/day considered useful in some situations [1])than the general population (currently 0.8 g/kg/day). At the same time, there is a long held belief that higher protein intakes may actually have a negative influence on bone health. This is based on the “acid-ash hypothesis”, which suggests that animal proteins are acidic, and so can disrupt body pH. A balanced pH is essential for function of all body cells, and so the body will counterbalance an acidic state by increasing the availability of alkaline minerals, so normalising pH. The problem is, that most of the bodies alkaline minerals (e.g.,calcium) are stored within the bone. A chronic need to normalise pH in response to habitually high protein intakes, can, in the long term, result in bone mineral loss and weakening. Supporting this hypothesis is evidence that diets with a high potential renal acid load (PRAL), namely those high in animal proteins, are associated with a greater loss of calcium in the urine. This may be associated with lower bone mineral density, and an increased rate of bone loss [2].
The acid-ash hypothesis does have some possible merit, but it also describes just one of the pathways through which high protein intakes may theoretically influence bone, and is by no means the full story. For a start, the acid-ash hypothesis assumes that the calcium lost in the urine when protein intakes are high, comes from the bone. It seems, however, that higher protein intakes actually increase the amount of calcium that is absorbed from foods [3], and the increased calcium found in the urine when protein intake is high comes from this increase in calcium availability, and not from the bone, as was originally assumed.
Another important point, is that calculations of dietary acid load, are not only influenced by a high intake of acidic foods, but also by a low intake of alkaline foods. Most alkaline foods (e.g.,fruits and vegetables) are also rich in a wide range of micro- and phyto-nutrients that are essential to bone health. It is possible, therefore, that the poorer bone outcomes reported in individuals who consumed an acidic diet [2], were not actually due to high protein, but to a shortage of nutrient rich fruits and vegetables.
More importantly, evidence exists to show that not only is protein not harmful to bone, it can actually be beneficial [4]. Bone tissue is made up of ~50% protein, which makes it essential that athletes consume sufficient protein to support the increased rate of bone turnover caused by athletic training. Additionally, protein ingestion is known to increase the production of a number of hormones and growth factors, such as IGF-1, which are also involved in the formation of bone. Perhaps most importantly, the physical loads caused by exercise training are recognised as the main determinant of bone. Athletes in high-impact sports are frequently reported to have stronger bones that non-athletes. These loads come from a combination of both gravitational and muscular forces. It follows, therefore, that if higher protein intake positively impacts muscle mass function, and the capacity to undertake exercise training, it should also positively influence bone.
Considering all of these factors, it seems paradoxical to believe that higher protein intakes could really harm bone. Ultimately, the only way to determine the net influence of protein intake on bone, is to examine original studies that investigate this. A large number of these types of studies have been conducted, and the results have subsequently been statistically combined in high-quality meta-analyses [5]. Considering all available evidence, the answer is clear: Provided calcium intake is adequate, there is no evidence to indicate a negative influence of protein on bone, and instead a positive, albeit small, effect on bone mineral density and fracture risk has been identified. And so, the consensus is that protein is an essential nutrient, not only for muscle, but also for bone.
References:
1. Morton R, Murphy K, McKellar S, Schoenfeld B, Henselmans M, Helms E, et al. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. Br J Sports Med. 2018;52:376–84.
2. Macdonald HM, New S a, Fraser WD, Campbell MK, Reid DM. Low dietary potassium intakes and high dietary estimates of net endogenous acid production are associated with low bone mineral density in premenopausal women and increased markers of bone resorption in postmenopausal women. Am J Clin Nutr. 2005;81:923–33.
3. Kerstetter J, O’Brien K, Caseria D, Wall D, Insogna K. The impact of dietary protein on calcium absorption and kinetic measures of bone turnover in women. J Clin Endocrinol Metab. 2005;90:26–31.
4. Dolan E, Sale C. Protein and bone health across the lifespan. Proc Nutr Soc. 2018;10.1017/S0029665118001180.
5. Rizzoli R, Biver E, Bonjour J, Coxam V, Goltzman D, Kanis JA, et al. Benefits and safety of dietary protein for bone health — an expert consensus paper endorsed by the European Society for Clinical and Economical Aspects of Osteopororosis , Osteoarthritis , and Musculoskeletal Diseases and by the International Osteoporosis. Osteoporosis International; 2018; 10.1007/s00198-018-4534-5.
6. Papageorgiou M, Dolan E, Elliott KJ, Craig S. Reduced energy availability : implications for bone health in physically active populations. Eur J Nutr. 2017; 57(3): 847-859.
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Coconut water is said to be a “superior form of rehydration”, a “natural sports drink” and a low carbohydrate alternative to juices. It has gained in popularity the last few years and has grown into a multibillion-dollar global industry. This growth is in line with trend that consumers are looking for more pure ‘organic’ products. There is more competition and there are many ways to adulterate the product (adding sugar, adding electrolytes, adding water). This article will address 2 questions:
How “natural” and “pure” is coconut water. A recent study suggests that it may not always be as “natural” as we think. Is coconut water really superior to water as a rehydration beverage?
In a recently published study (1) 30 authentic coconut waters (extracted from coconuts in the lab) were analysed as well as 24 commercial coconut waters (bottled) purchased from grocery stores. The researchers measured the carbon isotope range of pulp, total sugars, sucrose, glucose and fructose. This analysis can reveal if sugars were added to the coconut water. A whopping 38% of the coconut waters tested was adulterated (i.e, sugars were added to the water). This analysis only focussed on sugars, so one wonders what happens with dilution of coconut waters, and the addition of salts.
Then there is the second question: is it really a superior rehydration beverage? The claims are based on the fact that coconut water contains electrolytes and some carbohydrate. Below are estimations of the composition of water, a sports drink and coconut water. Coconut water contains a lot of potassium but this has little role in the rehydration process. Sodium, which is important for absorption of fluid and for fluid retention, is low in coconut water. Carbohydrate content is also low, maybe a little too low for rehydration purposes as studies have shown more rapid restoration of fluid balance with higher concentrations of carbohydrate (2, 3).
It must also be noted that coconut water varies tremendously in the composition depending on many factors including the maturation process 4, so the values below are just rough figures of an average coconut water.
Although the composition varies throughout maturations, at no instance did the coconut water contain sodium and glucose concentrations of potential value as an oral rehydration solution (4).
Studies confirm this and found that the hydrating properties of coconut water are not different from those of water (5). When sodium was added to coconut water the hydrating properties improved and the sodium enriched coconut water resulted in more complete hydration than plain water (6).
Therefore claims that coconut water is a superior source of hydration are unfounded. However, it is a natural way to restore fluid balance and it contains some carbohydrate and electrolytes…. “Natural”, if you can find an unadulterated source of coconut water…
References
1. Psomiadis D, Zisi N, Koger C, et al. Sugar-specific carbon isotope ratio analysis of coconut waters for authentication purposes. J Food Sci Technol 2018; 55(8):2994-3000.
2. Osterberg KL, Pallardy SE, Johnson RJ, et al. Carbohydrate exerts a mild influence on fluid retention following exercise-induced dehydration. J Appl Physiol (1985) 2010;108(2):245-50.
3. Evans GH, Shirreffs SM, Maughan RJ. Postexercise rehydration in man: the effects of osmolality and carbohydrate content of ingested drinks. Nutrition 2009; 25(9):905-13.
4. Fagundes Neto U, Franco L, Tabacow K, et al. Negative findings for use of coconut water as an oral rehydration solution in childhood diarrhea. J Am Coll Nutr 1993;12(2):190-3.
5. Kalman DS, Feldman S, Krieger DR, et al. Comparison of coconut water and a carbohydrate-electrolyte sport drink on measures of hydration and physical performance in exercise-trained men. J Int Soc Sports Nutr 2012; 9(1):1.
6. Ismail I, Singh R, Sirisinghe RG. Rehydration with sodium-enriched coconut water after exercise-induced dehydration. Southeast Asian J Trop Med Public Health 2007; 38(4):769-85.
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Soon the 3rd Edition of the textbook Sport Nutrition by Professor Mike Gleeson and myself will hit the shelves. For the last 18 months we have been working closely with the publishers Human Kinetics to get this more than 600 page- book published. A lot has happened in the world of sports nutrition and the new textbook will reflect this! Here we will briefly discuss what is new in this textbook and why it should be adopted for Sports Nutrition courses around the world.
Mike Gleeson and I believe that in order to understand and apply the principles of sport nutrition, some basic understanding of nutrition is necessary, as is some knowledge of the biochemical and physiological processes that occur in cells and tissues. It is also important to understand the way in which those processes are integrated throughout the body. This book will introduce the reader to the principles that underpin sport nutrition and its relation to sports performance.
One of the reasons why we have so much confusion about nutrition and sports nutrition is that many people who do not possess knowledge of this important background (nutrition, physiology, biochemistry) communicate beliefs without really understanding the background.
A book is needed that provides a scientific underpinning of sport nutrition guidelines and advice: a book that provides a scientific basis for sport nutrition that covers the principles, background, and rationale for current nutrition guidelines for athletes.
Readers of this book do not need a deep understanding of biochemistry, biology, chemistry, or physiology, but they should be familiar with some of the main concepts because the physical, chemical, and biochemical properties of cells and tissues determine the physiological responses to exercise and the effect that nutrition has on these responses.
So what is new in this edition? First, this new edition contains a complete update of the nutrition guidelines, which have changed considerably since the last edition of the book. This includes a new chapter on healthy eating.
Another important new chapter examines adaptations to training and how they can be altered by nutrition. Major advances in this area have occurred, mostly because of developments within molecular biology. To understand the role of nutrition on adaptations to exercise training, it is essential to understand the underlying molecular changes. For example, how is it possible that resistance exercise results in more muscle whereas endurance training does not change muscle mass but may improve the quality of the muscle (e.g., its capacity to oxidize fat)? Molecular processes underlie these distinctly different adaptations to exercise. We have incorporated a bit more basic knowledge of the regulation of protein synthesis and gene expression. A completely new chapter is devoted to personalized nutrition which covers aspects related to nutrigenomics, periodized nutrition, sex differences, nutrition requirements for the young and the older athlete, the nutrition challenges for the diabetic athlete, and nutrition for different sports and situations.
The book is also improved in terms of illustrations.
Here is a link where you can get a preview into the new book: http://bit.ly/jeukendrupandgleeson
In brief, this new edition has been updated in all areas and has been significantly expanded in areas that are most important in sport nutrition. But not only the theory has been updated, expanded and improved, the practical applications gets a lot more attention too.
We think anyone interested in sports nutrition can benefit from this book. It is not a book to read on a beach with a cocktail. Someone on twitter, asked if this would be available as an audiobook because he did not like to read.... well, this book is definitely not for this purpose. This book is for someone who wants to really expand their knowledge of sports nutrition, really get a deeper understanding and is willing to study! The book can of course also be used to look up a particular topic and thus function as a Encyclopedia or Wikipedia of sports nutrition.
The book will be available in October but you can pre-order this book now!

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