Five nutrition myths debunked
Cycling is filled with many wives tales and there’s no shortage of inaccurate nutritional advice that’s been spread over the decades. In this post, dietitian Alan McCubbin debunks some of those myths by looking at the research.
1) If some is good, more must be better
Athletes make this assumption about most nutrients. I’ve seen many a cyclist chug down massive amounts of protein powder after a training session, assuming that two scoops must be better than one.
But research doesn’t support this assumption. When feeding different doses of egg white protein after exercise, researchers found a plateau effect in muscle protein synthesis (ie. building new proteins in the muscle) at doses of around 20-40g of protein. It appears that the extra protein is simply used as an energy source (measured in the study below as Leucine oxidation), with a marked increase in protein burnt as calories between the 20 and 40g doses of protein.
There are plenty of other examples of a plateau effect with nutrition and performance. For example the reported effects of caffeine on cycling performance seems to be the same no matter whether you feed 3mg per kg body weight or three times that dose. And there’s no evidence that large doses of vitamin and mineral supplements improve performance either (unless of course there was a deficiency in the first place). In fact of the twelve published studies of Vitamin C in quantities of 1000mg or more a day, four of them found the megadoses significantly reduced performance, and a further four found either no difference or a slight impairment.
2) Don’t eat carbs at night because they’ll be stored as fat
This one’s a very deeply entrenched myth, across a variety of sports. I’ve had many clients tell me proudly that they don’t eat any starchy foods for dinner, because they “already know that this is a problem for people trying to lose weight”.
To understand this myth, let’s look at some basic biochemistry. When carbohydrate is eaten and digested, it’s broken down into sugar, which is absorbed from the gut into the blood. Once in the blood, the sugar can do one of two things – be used immediately as an energy source or be stored for later use. If you’re out riding and producing some decent watts then the majority will be used as a fuel source at the time. If not then it’ll be stored in your muscles, liver and brain as glycogen. This glycogen storage is exactly what happens when you carbohydrate load, and exactly the point of doing it – storing up as much carbohydrate as possible in the body so it’s there to be used the next day in a race. If this myth were true then it would make no difference if you ate rice or a block of cheese for dinner – they’d supposedly have the same effect.
That’s not to say that carbohydrate can never be converted into fat. If your glycogen stores are completely full and you’re forcing more carbs into the body without using it, then you’ll convert any excess into fat, in a process called de novo lipogenesis. But given how much a cyclist needs to eat to completely maximise their glycogen stores, and how frequently the average cyclist taps into those stores in training and racing, it’s hard to imagine that de novo lipogenesis would be a factor. Not only that, but about 25% of the calories from the carbohydrate is lost just in converting it into fat, so not all of those carbohydrate calories are actually “stored”.
So should you be eating a big bowl of pasta or rice every night for dinner? That really depends on your training schedule (and any underlying medical issues). As a sports dietitian my job is to design eating plans that compliment an athlete’s training schedule, so the choice of whether or not to include plenty of carbs in the evening is based around whether or not I think it’s important for the athlete to start the following morning with plenty of carbohydrate available to them. That can (and usually does) vary from one day to the next.
3) If it’s absorbed faster/increases fat burning/improves the level of (insert nutrient/hormone/blood test result here) then it’ll lead to improved performance
Consider the following statements (made by various sports nutrition product manufacturers):
- “Added support for the nutrient delivery of the glucose polymers, creatine, arginine and amino acids. This may help support an anabolic environment inside the body, and ATP production, which means more energy in the muscle!”
- “… purest protein on the planet, extracted using exclusive cation exchange technology”.
- “By using (name removed so no one gets sued), you can ensure water absorption and retention are superior to water alone”.
And my personal favourite, these selling points I found on the website of one protein product:
- Research proven, pure Whey Peptide Isolate
- 100% Hydrolyzed Whey Fractions, “Bio-Active” Peptide Isolates
- Highest Nitrogen Retention
- Gram for Gram More Protein Than Any Other Protein Made
- Glutamine Enhanced
This is the sort of language that sports food, drink and supplement manufacturers love using to convince you to buy their products. Of course the implication is that these properties translate into improved athletic performance, but do they really? If taking supplement X led to an actual, measurable improvement in performance that was confirmed in scientific research then why wouldn’t they be promoting that fact? After all, as a cyclist you shouldn’t care whether your protein absorbs faster than the other brand, only whether or not it actually improves power output.
And this is where the vast majority of these claims simply don’t stack up. There’s countless examples of supplements that have come on to the market on the back of research that shows they boost the level of something in the blood that sounds impressive. But when it comes to examining their effect on performance that’s meaningful to athletes they frequently fail to deliver. Improved biochemistry or physiology does not always means improved performance.
For a good general overview of what categories of supplements are worth considering (or avoiding), check out the Australian Institute of Sport’s sports supplement page.
4) The more elite I am, the more I need supplements
This is an extremely commonly held view amongst athletes in a variety of sports. The perception is that as you get to the pointy end of your chosen sport, sports supplements will start to become more important to get you over the line.
Interestingly however the research tends to suggest that the biggest benefits from nutritional supplements occur in the least fit individuals, which is often where the initial studies are undertaken. Supplements such as quercetin, nitrates and beta-alanine all seem to have much larger performance effects when studied in relatively inactive subjects compared to high level club or professional athletes. In fact quercetin appears to have no beneficial effect at all in well trained cyclists (it does in mice and unfit people though).
The dose of nitrates in a one-off serve of beetroot juice also looks like being inadequate to make any difference. Consensus is moving towards consuming beetroot juice for around a week leading up to a competition, or taking nitrates in another more concentrated form.
Why is this? The theory that some of my colleagues have thrown around is that many of these supplements enhance systems in the body that are already upregulated as a result of training anyway. So a well-trained cyclist has already come close or achieved a “ceiling” in their potential for adaptations, whereas an unfit person has much greater room for improvement, which can be fast-tracked through some types of supplements. We know that carbohydrate loading and consuming large quantities of carbs in events of 1.5-3 hours is less critical in well trained athletes, because their ability to use fat as a significant energy source over these time periods is sufficient. But for a not-so-fit cyclist who’s competing over those distances there may still be a much greater benefit of aggressive carbohydrate intakes. And over longer distances (think the Melbourne-Warrnambool or endurance mountain biking) aggressive carbohydrate intakes are likely to benefit all levels of riders.
5) Electrolytes in sports foods and drinks improve performance
People make the assumption that because sports drinks, salt sticks and other sports products contain electrolytes (eg. sodium, potassium, magnesium, calcium, etc.) that they must be in there to benefit performance (i.e. increase power output). However the reality is that I’ve not seen a single study that’s shown any of these electrolytes make a measurable difference to sports performance. Yes they may increase the speed of fluid absorption from the gut. They may make the product taste better, or make you want to drink more. They may help increase fluid retention in the blood and prevent the need to pee quite so much during exercise too. But none of these things actually influence the amount of wattage you can put out on a bike.
That’s not to say that nutrition is not important for performance. Carbohydrate in longer events plays a significant role, as can caffeine and drinking adequate fluid (although the debate still rages as to what’s considered “adequate” to optimise performance). Some people would argue that electrolytes can prevent cramping and therefore improve performance that way. The science however suggests that the majority of cramps experienced during exercise are not related to electrolytes at all, although other non-exercise related cramps may well be caused by lack of particular electrolytes (as per a previous post “Nutrition and Muscle Cramps- what does the science say?)