Highlights from the 2011 Sports Dietitians Australia Conference
Last Saturday Sports Dietitians Australia hosted their first ever stand-alone sports nutrition conference. Normally SDA combines with our sports science or sports medicine colleagues, but with no other conferences scheduled this year it was decided to go it alone. And what a great decision - the conference was one of the best I'd been to in a long time and over 150 delegates came to Melbourne for a day dedicated to sports nutrition research and practice. No international speakers this time, but a bunch of new and interesting topics from our home-grown talent.
For those interested in the latest and greatest in sports nutrition research and practice, I've put together a quick summary of some of the sessions:
The future of sports nutrition
There was a public lecture on Friday night with a Q & A session at the end. I was privileged to be asked to be on the expert panel alongside four of the founding members of SDA - Dr Helen O'Connor (University of Sydney), Prof. Louise Burke (head of AIS sports nutrition) and Glenn Cardwell (author of the phenomenally successful text book Gold Medal Nutrition). The question was raised as to what we thought the future held for sports nutrition. Three themes emerged from the panel:
· As we're starting to be able to measure which genes are being expressed due to exercise and diet, we're able to start to pinpoint much more the beneficial effects of nutrition in optimising training adaptations and recovery. So it's likely that this will help us fine tune some of the broader nutrition messages to athletes and be very specific in our recommendations.
· Research into potentially beneficial nutritional supplements continues at a relentless pace and will continue to do so in the future. In particular focus has turned to some of the non-vitamin, non-mineral components of food, which can be given in much larger quantities in supplement form. So far quercetin and nitrates have started to be researched, but there's bound to be a heap more similar food components identified in the years to come.
· Our understanding of the way the body regulates performance and fatigue has come ahead in leaps and bounds in the last ten years, with a recognition of the enormous role the brain plays in this process. Sports scientists are now starting to investigate not only time trial performance in the lab, but starting to introduce real (or virtual) competitors to examine what effect competition has. Nutritional strategies will have to be re-examined against these ever-sophisticated models of fatigue and pacing, and new studies will look at how nutrition may be able to have an effect not only on working muscles, but on the brain itself.
Sports nutrition supplements
Prof. Louise Burke and Prof. David Pyne (AIS) presented an update on the AIS sports supplement program. This website has recently been revised (including the free, downloadable fact sheets on various supplements) following the institute's annual review of research evidence for each supplement type. They also discussed that they now have a "secret site" for AIS and state institute of sport staff only, to protect a few trade secrets ahead of the London Olympics next year. Expect a few research publications and extra info coming out after the games in 2012.
On the topic of supplements, last week ASADA's annual report was released, highlighting a significant increase in the number of Australian athletes testing positive to banned substances. The main reason for this increase seems to be due to contamination of nutritional supplements (mainly manufactured overseas) with the banned substance methylhexanamine. We always need to remind athletes of the risks in taking nutritional supplements, especially when the quality can be called into question. The AIS manage this by partnering with supplement manufacturers that they feel confident pose minimal risk of contamination.
Nitrate (beetroot juice) supplementation
Matthew Hoon is a PhD student at the University of Sydney, conducting research in conjunction with the AIS into nitrate supplementation. Beetroot juice is the most commonly used form on nitrate supplement - 500mL of beetroot juice or 70mL of a specially concentrated formula provides the required amount.
Nitrate research is still very much in its infancy. We still don't know exactly how or why it benefits performance, but three potential mechanisms have been proposed:
· It may work in the muscle fibre by requiring less energy to produce muscle contractions, essentially making the body more "fuel efficient"
· The conversion of nitrates to nitrite, then to nitric oxide, may increase blood flow, and therefore allow greater delivery of nutrients and oxygen to working muscles
· It may improve the efficiency of the way mitochondria work. Mitochondria take fuel and oxygen and convert it to energy
You can't simply supplement with nitrite, because direct supplementation is toxic, having a similar effect to cyanide! Instead nitrates in beetroot juice are converted to a small amount of nitrite by bacteria in your mouth. The nitrites are then carried through your gut and into the blood via saliva. If you spit out your saliva during exercise, or use mouth wash or chewing gum just before exercise (which kills the bacteria) you'll actually lose the effect of the supplement.
There's still minimal research on the effects of nitrates on sports performance. One study of 4km and 16km time trial cycling found a benefit, but an AIS study where cyclists rode for 4 minutes, followed by 75 minutes rest and another 4 minutes of riding, found no difference in the distance covered in each 4 minute block.
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 but unsubstantiated approach in this industry), and as a result Gary gained significant muscle and reduced body fat compared to his previous diet. This left Gary somewhat perplexed, and as a result we may see some interesting studies emerging in the area to look at if the body building approach does indeed work in most people, and if so why it contradicts virtually all of the scientific research in the area.
Probiotics and immune health in athletes
Prof. David Pyne (Physiologist, AIS) presented on some work looking at the effects of probiotics (live bacteria found in some yoghurts or probiotic capsules) on illness in athletes. Probiotics research is very specific because there are hundreds of different types of bacteria living in our gastrointesintal tract, and the effects of supplementation are specific to an individual strain. One particular strain (Bifidobacterium lactis BI-04) has been shown to reduce the incidence of week-long common colds in athletes, and there's a growing body of research to show that our gut bacteria have effects on our immune system all throughout the body, not just on bowel health.
Endurance Sports Nutrition
In the afternoon it was my turn to present, as the invited speaker on nutrition for endurance sports. Here's a summary of my main points:
· Endurance sports vary enormously, so nutrition strategies should not be a one-size-fits-all approach
· Carbohydrate loading improves performance by about 3-4% in sports of around 2 hours duration, compared to a moderate carbohydrate diet. One study has shown complete carb loading achieved in a single day, but it remains unknown if this result applies to all types of athletes (males Vs females, elite Vs recreational, etc.)
· The more carbohydrate you consume during races of 2 hours or longer, the faster you'll go. The limit to how much you can eat and drink is most likely to be practical (ie. what you can realistically carry and consume) and what you're gut will tolerate. Sports drink manufacturers preach that drinks should not be more than 8% carbohydrate because it reduces stomach emptying, but in reality most athletes consume solid foods as well as sports drinks, and this results in a mixture in the stomach that's much greater than 8%. Most athletes seem to cope just fine.
· Protein during endurance exercise only seems to help if you're not getting enough carbs in. If you're getting more than 60 grams an hour of carbs then there's no advantage of adding protein.
· There's plenty of research showing that 20-25g of whey protein post-weight training benefits recovery and muscle adaptation, however there's very little looking at the benefits of protein post-endurance training. Current results that measure subsequent performance are conflicting, but from a practical perspective there's no disadvantage to taking protein post-training. So my suggestion would be to do it anyway, and it's likely that the science will catch up in the next few years.
· There's been very little hydration research in the last few years, mainly because everyone accepted that dehydration (loss of body weight of over 2%) reduced performance. But going back and examining the fine print of these studies shows that most were poorly designed, and the very limited number of better quality studies show no difference, provided athletes are given enough fluid to drink as they please. My conclusion is that we need to go back to the drawing board and do a lot more (better designed) research in this area, to get some answers one way or the other.
· Caffeine supplementation definitely improves endurance performance when taken in doses of 3-6mg/kg body weight. Quercetin probably only benefits very unfit people, not athletes. Beta-alanine is normally associated with short duration sports like track cycling, rowing and swimming, but may be of benefit to sprint finishes or high intensity hill climbing in cycling and mountain biking. There needs to be a lot more research in this area before we can draw conclusions though. Nitrates are the new kid on the block, and there's no research on endurance performance yet.
· Gastrointestinal problems during endurance exercise are fairly common, particularly in runners and during very long distance events. Several potential reasons have been identified but the exact cause may vary from person to person, and research has failed to link the exact mechanism to the problem as yet.
· Dental erosion and tooth decay may be a particular problem for endurance athletes, because of their frequent consumption of acidic, high carbohydrate foods and drinks (such as sports drinks, gels, lollies, juice, soft drink, cordial, and even some cereal bars and fruit yoghurts). Saliva does help to protect teeth against acidic foods, but during exercise there's often less saliva due to dehydration and/or heavy breathing. These foods and drinks are hard to avoid during competition and heavy training sessions, but can be minimised at other times. One company in Melbourne has produced a less acidic sports drink, but there are no studies yet to show if it (and other dietary changes to reduce acidic foods during exercise) will prevent tooth decay when used over several months.
· Low bone density is well studied in endurance athletes, but coaches and athletes themselves don't seem to talk about it much. It seems to be worst in road cyclists (male and female) who don't combine their cycling with other forms of load-bearing or impact exercise (like weights or running), but it can occur in some runners and triathletes too. In fact cyclists tend to have worse bone density than people who do not exercise at all. And calcium and vitamin D supplements (or a high calcium diet) doesn't help.
There's three potential theories to explain this phenomenon. It may be due to a combination of:
o Lack of weight bearing/impact forces that stimulate bone formation - may be resolved by weight training, running or vibration training
o Dietary restriction to achieve a very lean physique and maximise performance, which can disrupt normal hormonal function and increase bone loss - resolved by eating more calories and gaining some body fat
o Sweat calcium losses during endurance exercise may lower blood calcium levels, resulting in hormonal changes that increase bone loss - potentially resolved by adding calcium to sports drinks/gels (this has never been tested)
The next sports nutrition related conference in Australia will be next year's Exercise and Sports Science Australia (ESSA) conference, in April on the Gold Coast. I'm already looking forward to it. Congratulations to the Sports Dietitians Australia team for putting on a fantastic conference, the venue was buzzing and everyone I've spoken to had nothing but great things to say about the program and the day.