11 Sports Nutrition highlights in 2011

As 2011 comes to a close it’s time to look back on the year that was. 2011 was another busy year in sports nutrition research and practice, and here’s a selection of my top 11 findings, insights and resources from the sports nutrition world.




Number 11 – What’s the best way to bicarb load?


Sodium bicarbonate has been used as a sports supplement for several years now in sports requiring short, high intensity efforts (40 seconds up to 5 minutes). It can be given in several forms including capsules (such as Sodibic), as simple bicarb soda powder or in a flavoured powder together with sodium citrate (sold as Ural). But the side effects from loading up on sodium bicarbonate can be severe. Last year I was lecturing on nutrition for the Cycling Australia coaches’ course, and I asked one of the participants, a former Olympic track cycling medallist, about his bicarb experience. His response – “I’d be sitting on the start line not knowing if I was going to have a great race or s#!t my pants!”


Since that time sports scientists and dietitians have realised that giving bicarb along with plenty of water tends to help lessen the side effects on the gut. And this year the Australian Institute of Sport went one better, publishing a new study that compared eight different methods of bicarb loading.


The findings were that sodium bicarb capsules and gold ol’ baking soda were equally effective, but Ural less so. They also found the most effective dose of water to take with the bicarb was 7mL per kilogram of body weight (490mL for a 70kg athlete). Finally, taking a high carbohydrate snack at the same time also helped minimise side effects with no reduction in effectiveness.

For more information on this study (including the amount of bicarb to take and when to take it) click here to read a previous blog post I wrote on the topic.


Source: Int J Sport Nutr Exerc Metab. 2011 Jun;21(3):189-94.



Number 10 – Study finds an association between percentage weight loss (ie. sweat loss) and marathon finish times


This study first appeared online in December 2010, but was officially published in the British Journal of Sports Medicine in July this year. It investigated the rate of sweat loss in 643 runners during the 2009 Mont Saint-Michel Marathon in France. The runners had an average age of 42, average weight of 72kg before the race, average marathon PB in the previous 12 months of 3.7 hours, and consisted of 560 males and 86 females. The race day was a cool one – just 9oC at the start and 16oC at the finish.



Researchers weighed the athletes before and after the race, and compared the change in weight to race finishing time. As you might expect the researchers found an association between race time and percentage weight loss, but not what you might expect. It was found that the athletes that lost the most weight (which implies greatest amount of dehydration throughout the race) actually finished the fastest!






Degree of body weight change plotted against the race

finishing time (minutes) for the entire group of 643 marathon finishers

(p<0.0000001; r=0.217). Source: Zouhal H et al. Br J Sports Med. 2011 Nov;45(14):1101-5.



So does drinking less actually make you faster? Not at all – the graph simply shows an association, but doesn’t tell you whether one factor caused the other, or if they’re both influenced by a third factor. Recent research in the lab suggests however that it may not be necessary to plan your hydration to prevent a particular weight loss during endurance exercise – for a more detailed explanation and a look at this research check out my blog post on the subject.



Source: Zouhal H et al. Br J Sports Med. 2011 Nov;45(14):1101-5.




Number 9 – Imaging the brain during exercise


For about over a decade sports scientists have been investigating the role of the brain in regulating exercise performance, in particular its role in how we experience and respond to fatigue. But whilst they can create experiments that demonstrate the brain in action, researchers have never been able to actually see what’s going on in there during exercise.


Now for the first time researchers at the University of Capetown in South Arica have come up with an ingenious way of combining an exercise bike with an MRI machine, to be able to take images of athletes’ brains whilst they are exercising. This has intriguing implications for investigating the role of nutrition and fatigue, with everything from carbohydrate and hydration strategies to supplements such as caffeine, beta-alanine and bicarbonate able to be studied in relation to its effect on the brain.


There’s a great video clip on YouTube of this setup – click here to have a look.


Number 8 – Summary of research on nutrition and the immune system published


In the middle of 2011 a two part review paper on exercise and immune health was published. One of these papers summarised the evidence of various nutrition strategies for optimising immune health. Here’s the table from this paper that summarises the evidence for various nutrition strategies:


Summary of rationale and findings for selected immunonutritional supplements. Source: Walsh NP et al. Exerc Immunol Rev. 2011;17:64-103.



Immunonutrition

Supplement

Proposed Rationale

Recommendation Based On

Current Evidence

Vitamin E

Quenches exercise-induced reactive oxygen

species (ROS) and augments immunity

Not recommended; may be prooxidative with heavy exertion

Vitamin C

Quenches ROS and augments immunity

Not recommended; not consistently

different from placebo

Multiple vitamins and

minerals

Work together to quench ROS and reduce inflammation

Not recommended; not different from placebo; balanced diet is sufficient

Glutamine

Important immune cell energy substrate that is

lowered with prolonged exercise

Not recommended; body stores

exceed exercise-lowering effects

Branched chain amino

acids (BCAAs)

BCAAs (valine, isoleucine, and leucine) are

the major nitrogen source for glutamine

synthesis in muscle

Not recommended; data inconclusive, and rationale based on glutamine is faulty

Carbohydrate

Maintains blood glucose during exercise,

lowers stress hormones, and thus counters

immune dysfunction

Recommended; up to 60 g per hour of heavy exertion helps dampen immune inflammatory responses, but not immune dysfunction

Bovine colostrums

Mix of immune, growth, and hormonal factors

improve immune function and the

neuroendocrine system, and lower illness risk

Jury still out, with mixed results



Probiotics

Improve intestinal microbial flora, and thereby

enhance gut and systemic immune function



Jury still out, with mixed results

N-3 PUFAs (fish oil)

Exerts anti-inflammatory effects post-exercise

Not recommended; no different from placebo

B-glucan

Receptors found on immune cells, and animal

data show supplementation improves innate

immunity and reduces infection rates

Not recommended; human study with athletes showed no benefits



Herbal supplements (e.g.,

Ginseng, Echinacea)

Contain bioactive molecules that augment

immunity and counter infection

Not recommended; humans studies do not show consistent support within an athletic context

Quercetin



In vitro studies show strong antiinflammatory,

anti-oxidative, and antipathogenic effects. Animal data indicate increase in mitochondrial biogenesis and endurance performance, reduction in illness.

Recommended, especially when mixed with other flavonoids and nutrients; human studies show

strong reduction in illness rates during heavy training and mild stimulation of mitochondrial biogenesis and endurance performance in untrained subjects; anti-inflammatory and anti-oxidative effects when mixed with green tea

extract and fish oil





Source: Walsh NP et al. Exerc Immunol Rev. 2011;17:64-103.




Number 7 – Beefing up – Who’s right, the scientists or the body builders?


Current research evidence suggests that to gain muscle athletes don't need more than about 1.8 grams of protein for every kg of their body weight. It also suggests that carbohydrate will help to fuel weight training, allowing more weight to be lifted and therefore greater muscle gains over time.

Dr Gary Slater (University of Sunshine Coast) subscribes to this approach as well. However as an experiment he recently visited a body building coach, asking for nutrition advice and presenting him with his current (and theoretically ideal) diet. The body building coach changed his diet to dramatically increase protein and reduce carbs, a typical approach in this industry.

The result – Gary gained significant muscle and reduced body fat compared to his previous diet! This left Gary somewhat surprised, and he presented his experience at the inaugural Sports Dietitians Australia Conference in October.

So perhaps we’ll see some interesting studies emerging in the area to look at if the body building approach does indeed work better in most people, and if so why it contradicts virtually all of the scientific research in the area.



Number 6 – Does taking protein after endurance exercise improve recovery?


This has long been an unanswered question, with protein and training studies restricted to weight training and the effects of protein on size and strength gains. But in 2011 two studies were published which looked at the effect of feeding protein on recovery after endurance exercise. Both studies were published by a team led by David Rowlands from New Zealand.


The two studies followed similar but slightly different methodologies: in the first study 10 competitive cyclists were fed protein or a placebo after 2-2.5 hour intense interval training sessions every day over 3 days. 39 hours after the last session the cyclists were brought back and power output over 10 sprints on the bike was measured. They found the group that took protein after the 3 days of training produced 2.5% more power during the sprint tests compared to the placebo group.


The second study (by the same research team) involved 12 cyclists taking protein supplementation or placebo after sprint interval training sessions over 6 days. After Day 4 and Day 6 a performance test of sprint power output was performed. In this case there was no difference in performance between those who took protein after training and those who received a placebo.


So why the difference in findings? It’s not entirely clear, however the only major difference between the two studies was that in the first study the participants were in negative nitrogen balance, whereas they were in positive nitrogen balance in the second study. This suggests that protein supplementation may be more beneficial for endurance athletes on a restricted diet (for weight loss) or when protein intake is sub-optimal (due to dietary restrictions).


So what’s the practical message? I would suggest that most endurance athletes should be encouraged to consume at least 20 grams of high quality (dairy or other animal based) protein within the first hour after long or particularly intense training sessions and competition. Hopefully more research will follow in the near future to refine this message.


Source:


Nelson A et al. Med Sci Sports Exerc. 2011 Jun 16. [Epub ahead of print]

Thompson J et al. Appl Physiol Nutr Metab. 2011 Apr;36(2):242-53.




Number 5 – Beetroot Juice – Promising theory translates to improved performance


In 2010 and early 2011 there was a lot of media hype around the apparent benefits of beetroot juice, followed by a range of beetroot juice drinks that appeared on the market. Endurance athletes were the early targets of this hype. But whilst initial studies were important in investigating the physiology, it wasn’t until 2011 that a study answered the one question that athletes actually care about - does beetroot juice (and the nitrates contained in it) actually translate in to improvements in performance?


The paper in question was published in the journal Medicine and Science in Sports and Exercise mid-year. The study from the University of Exeter in the UK involved competitive cyclists consuming either nitrate containing beetroot juice or a nitrate-free beetroot juice (placebo). They then completed both a 4km and a 16km time trial in the lab. For both distances the nitrate containing beetroot juice improved time trial performance, by 2.8% and 2.7% for 4 and 16km respectively.

We still don’t know if the effect of nitrates will translate to longer distances encountered in typical endurance sports, but no doubt we’ll see studies that answer this question in the near future.


Source: Med. Sci. Sports Exerc. 2011; 43(6):1125–1131.




Number 4 – Updated AIS sports supplement program and fact sheets 


In August 2011 the Australian Institute of Sport began updating their free sports supplement pages on their website. If you’ve never visited the page I highly recommend it – each year the AIS nutrition department revise their classification of supplements. There are four categories of supplements – a) supplements proven to be effective when used correctly, b) some evidence to support the supplement but not yet conclusive, c) insufficient evidence to suggest a benefit or evidence of no benefit and d) WADA banned substances.


In addition the AIS team have begun updating the supplement fact sheets that describe how the supplements work, the effective dose and how to take them. This website now includes free fact sheets on creatine, beta-alanine, nitrates/beetroot juice and bicarbonate amongst others.


AIS Sports Nutrition Website: www.ais.org.au/nutrition




Number 3 – A meta-analysis of hydration and endurance exercise performance


For those of you who don’t come from a scientific background a meta-analysis is a statistical review of all the research on a topic, where all results are pooled together to give an overall statistical result – in essence a “study of the studies”. Meta-analyses are very rare in sports nutrition research, but this year Eric Goulet from the University of Sherbrooke in Canada published one on the “Effect of exercise- induced dehydration on time- trial exercise performance” in the British Journal of Sports Medicine in April.



Goulet comprehensively trawled through the academic literature up to July 2010, identifying 20 potential papers that were relevant. However of these papers only 5 met the criteria for inclusion, being:
  • Lab controlled studies
  • Dehydration was induced during, not before, exercise
  • Fluid replacement was given by drinking, not by intravenous infusion of fluid
  • All the necessary data to calculate the percentage changes in power output, percentage body weight losses  and complete the statistical analyses was available
  • Body weight (implied to be sweat) loss level in the more-dehydrated group was ≥1% and at least ≥0.45% more than the control group
  • If sports drinks were used as a means to hydrate subjects, subjects in all groups had to receive the same amount of carbohydrate
  • Exercise performance was assessed in an environment allowing effective thermoregulation
  • Only time trial type exercise protocols where the subject knew the end point could be used to test exercise performance




Forest plot of the percentage changes in power output with exercise-induced dehydration observed in each study along with the qualitative interpretation of the importance of the overall effect on time-trial performance. An open lozenge (◊) represents the mean weighted effect estimate. The black line represents the minimal decline in power output required to affect long-distance cycling performance negatively in a practical and meaningful way. A random-effect model was used. Results are means±95% CIs. Source: Goulet E. Br J Sports Med. 2011 Nov;45(14):1149-56.



The graph above shows that whilst a few studies suggested a potential benefit from being well hydrated, none achieved an improvement that could only be due to real differences in hydration. And the combined analysis of the studies showed absolutely no difference between whether people were well hydrated or poorly hydrated.



An interesting sub-plot to this analysis was the further analysis of two particular studies, which compared so called “ad libitum” fluid consumption (described as “drinking according to thirst”) with drinking less or more than thirst. The finding was that ad libitum fluid intake resulted in power outputs 5.4% greater than drinking below ad libitum levels, but there was no further improvement by drinking above the ad libitum levels.



What does all this mean? Well it suggests that drinking according to thirst is certainly beneficial to performance compared to drinking nothing at all, but that deliberately drinking to prevent a certain level of sweat (or body weight loss) may not be as important as we’re often led to believe. For more information about the research on hydration and an analysis of the mixed messages coming from the experts, here’s a blog article I wrote on the topic earlier this year.



Source: Goulet E. Br J Sports Med. 2011 Nov;45(14):1149-56.





Number 2 – More carbs make you faster during Ironman triathlon – a study of real-world eating and competition performance


In November 2010 I sat in a lecture theatre at the Australian Institute of Sport in Canberra, as leading endurance sports scientist Asker Jeukendrup presented on his research looking at combining glucose and fructose during ultra-endurance exercise. I was already very familiar with Asker’s work and had been implementing it with clients for a couple of years, but one new graph really grabbed my attention. On the screen he showed observations from 53 triathletes competing at the 2009 Ironman World Championships in Hawaii. On the horizontal axis was the finish times of the athletes, and on the vertical axis appeared the carbohydrate intake during the race (in grams per hour). What it showed was a correlation, where the athletes consuming the greatest amount of carbohydrate finished the race faster. In fact 30% of the variation in finish times could be explained by carbohydrate intake alone.



Correlation btw. CHO intake & finish time at 2009 Ironman World Championship, Kona Hawaii. R = 0.55, p<0.001. R2 = 0.30. Source: Pfeiffer B et al. Med Sci Sports Exerc. 2011 Jul 19. [Epub ahead of print]



Of course a correlation does not necessarily mean that one factor causes the other, but other lab based studies over the last few years would suggest that is the case, and this is simply some real world data to back that up.


But this paper didn’t just look at carbs and finish times in Hawaii, it also looked at fluid intakes and gastrointestinal problems – not just in triathletes but in marathon runners and professional and amateur road cyclists too. The result is one of the most comprehensive summaries of what endurance athletes are doing in the real world. Below is a table from the study which summarises the nutrient consumption of athletes in all three sports during competition.


 Nutrient intakes during endurance events (mean ± SD). Source: Pfeiffer B et al. Med Sci Sports Exerc. 2011 Jul 19. [Epub ahead of print]



Event

Fluid (mL/h)

kcal/h

CHO (g/h)

Protein (g/h)

Fat (g/h)

Fiber (g/h)

Sodium (mg/h)

Caffeine (mg/h)



2009 IM World Champs - Hawaii



794±309

(146-1617)

258±96

(117-472)

62±26

(22-124)

2±2

(0-6)



1±1

(0-7)



1±1

(0-3)



422±213

(127-1116)

26±22

(0-78)



2009 IM European Champs - Germany

703±238

(352-1656)

292±104

(114-564)



71±25

(33-126)



2±2

(0-10)



1±1

(0-4)



1±1

(0-2)



444±216

(69-975)



33±29

(0-100)

2009 IM Germany 70.3

700±254

(318-1385)

265±105

(96-494)



65±25

(31-122)



3±3

(0-12)

1±1

(0-5)

1±1

(0-4)



403±193

(91-936)

28±24

(0-107)

2009 Munich Marathon

354±187

(81-918)

146±102

(18-527)

35±26

(6-136)



3±5

(0-16)



1±1

(0-13)



2±3

(0-12)



118±87

(9-321)

23±32

(0-125)

Vattenfall Cyclassics amateur cycling race (100 & 150km courses)

643±599

(69-1012)

233±103

(53-557)

53±22

(13-114)

3±3

(0-13)

1±1

(0-5)

1±1

(0-4)

208±183

(15-857)

21±29

(0-108)

Pro cyclists during 2009 Dauphine Liberé & Vuelta a España

711±270

(333-1268)

284±76

(167-431)

64±20

(29-107)

4±2

(0-8)



2±2

(0-6)



1±1

(0-2)



311±156

(164-768)



12±14

(0-45)





Source: Pfeiffer B et al. Med Sci Sports Exerc. 2011 Jul 19. [Epub ahead of print]





Number 1 - The Inaugural Sports Dietitians Australia Conference


 And finally I’m going to be a little bit biased as the Vice President of Sports Dietitians Australia, but my highlight for the year was undoubtedly the very first SDA conference, held in Melbourne in October.

The whole weekend was an amazing one, beginning with the public lecture and SDA’s 15th anniversary cocktail party on the Friday night. It continued on the Saturday with the conference featuring an all Aussie line up (plus one Kiwi) of both researchers and practitioners. Traditionally sports nutrition is an add-on to sports science or sports medicine conferences in Australia, so it was great to have a day dedicated just to us. The programme was probably the strongest I’ve ever seen, and included:

  • An overview on the evolution of the AIS sports supplement program from Louise Burke
  • A comprehensive overview of nutrition and the immune system from David Pyne (also AIS, and one of the authors of the immune review papers described above)
  • Nutrition for injury recovery, including a case study of a rugby player who broke his jaw, twice! (Kirsty Fairbairn, University of Otago)
  • The psychology of athletes in weight restricted sports (Fiona Sutherland, a very experienced dietitian in both sports nutrition and eating disorders)
  • Working with lightweight rowers (Liz Broad, AIS) and jockeys (Helen O’Connor, Sydney University)
  • The interaction of nutrition and gene expression (Mark Hargreaves, University of Melbourne)
  • Nutrition for team sports (Michelle Cort, Geelong AFL team & Cricket Australia)
  • Nutrition for strength & power sports (Gary Slater, University of Sunshine Coast & Australian Rugby Union)
  • Nutrition for endurance sports (yours truly!)

But the highlight of the weekend for me was the number of sports dietitians from all over Australia that attended, networked and shared ideas. I always enjoy catching up with other sports dietitians from interstate, which only happens once or twice a year. It provides a great chance to share ideas and tips with others that work in similar areas – for me that’s Greg Cox who looks after Triathlon Australia on behalf of AIS, Simone Allen from Perth who’s not only worked with many an Ironman but also planned the nutrition for Tom Smitheringale’s attempt to trek solo to the north pole, and Steph Gaskell from Adelaide, an expert in gastrointestinal nutrition and a talented ultra runner in her own right.


So that’s my top 11 of 2011 in the world of sports nutrition. 2012 promises to be another great year – several intriguing PhD students in Australia will present their work on topics such as optimal protein feeding after weight training, measuring body composition of athletes and more performance studies using nitrate supplementation (beetroot juice). But for now I hope you all have a wonderful and relaxing holiday season and new year, and look forward to an action packed summer of sport in January.

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