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Nutrition

Debunking Three Common Nutrition Myths

Lily Bedford consider three nutritional myths and their relevance to keen sportsmen and women.

We are greeted with nutrition messages through a variety of media sources and while some newspapers, magazines and online sources can be counted on to provide evidence-based advice, this is not always the case. As a result there is a lot of dubious advice in relation to what we should be eating in circulation, much of which has become ingrained beliefs. While some of this advice is harmless, following other snippets could potentially be harmful and is not necessarily suitable for athletes.

Taking high dose vitamin C supplements can prevent colds

Athletes who undertake intense training can be more susceptible to infections, which studies suggest is due to a decline in immune function. You will often hear people talk about the importance of drinking orange juice or eating plenty of citrus fruits when you have a cold to aid recovery, which relates to their vitamin C content and some go a step further taking a supplement containing this vitamin to ward off a cold. However, is the link between vitamin C and the prevention or treatment of a cold supported by the results of scientific studies?

A review by Heimer et al. (2009)[1] of all the available research on the subject identified that while a vitamin C supplement could reduce the duration of a cold, it did not reduce the severity of its symptoms or make someone less likely to develop a cold. However, it did highlight that athletes training in sub-arctic conditions could obtain a preventative effect from taking a vitamin C supplement; though a more recent position statement has advised there is insufficient evidence to advocate the use of high dose supplements to promote immune function amongst athletes.

While taking part in regular intense exercise does appear to increase requirements for vitamin C - suggested to relate to that needed for repair and growth of muscle tissue and to aid iron absorption to support their greater number of red blood cells - the amount required daily is estimated to be in the magnitude of 200 milligrams. This is significantly lower than the supplements containing 1000 milligram or more of the vitamin taken by some athletes.

While vitamin C cannot be stored by the body and excess will be excreted via the urine, some evidence indicates that long-term use of high dose supplements may increase the risk of developing cancer. Bearing this in mind and the lack of conclusive evidence for the benefit of vitamin C for athletes, obtaining sufficient from the inclusion of citrus fruits, berries, kiwis, tomatoes, peppers and green vegetables in the diet appears the better option.

We need to include more polyunsaturated fats in our diet

There is evidence to link the intake of saturated fat from animal produce with raised levels of LDL cholesterol, which is associated with an increased risk of heart disease. For decades we have been advised to replace butter with margarine and to cook with vegetable oil instead of lard, as these are lower in saturated fat and contain polyunsaturated fats, which help to lower cholesterol.

However, using more sunflower, soya and corn oil in our diets may bring their own problems. These oils contain fatty acids known as omega-6 polyunsaturates. While these lower LDL cholesterol, they also bring down the protective HDL cholesterol; low levels of this are associated with an increased risk of heart disease. This is not the only issue though, as omega-6 fatty acids are susceptible to oxidation by free radicals, the by-products of metabolism, which damage cells and are associated with a number of chronic diseases; a study by Mata et al. (1997)[2] suggest a higher intake of these fats increases the build up of plaques in the arteries.

As more free radicals are generated during exercise than at rest, athletes' bodies are at greater risk of free radical attack, so they need to be cautious in their intake of omega-6 fatty acids. Additionally, omega-6 polyunsaturates stimulate inflammation, which increases the likelihood of heart disease developing. Including omega-3 fatty acids from oily fish, flaxseed oil and green vegetables is known to reduce the risk of heart disease, but evidence suggests that the largest proportion of fat in our diet should be from monounsaturates present in olive and canola oil, as these are most beneficial for cholesterol levels and heart health.

To counteract the problem of increased free radical production, the inclusion of a range of brightly coloured fruit and vegetables each day will provide a supply of antioxidants, which neutralize their effects.

The amount of protein we eat is the most important factor for building muscle

It is a huge misconception that we need to eat large amounts of protein for muscle growth, but this myth is still doing the rounds and being taken on board by many people. You will not see an increase in muscle mass without taking part in resistance training, but what you eat is also important. While not eating sufficient protein will hinder your efforts to increase lean body mass, there is a limit to how much protein your body can use, which is lower than many people realize.

For this reason the American College of Sports Medicine recommends a protein intake of between 1.2 and 1.7 grams of protein per kilogram of an athlete's body weight. Whether athletes are meat-eaters or vegetarian, it is important to eat a range of protein sources, as these provide a different complement of amino acids and all are necessary for the growth of new tissues.

Strict vegetarians or vegan athletes with a restricted diet who are unable to eat a variety of pulses, nuts, seeds and wholegrains may struggle to obtain an adequate intake of certain amino-acids; supplements such as L-Glutamine powder can be taken by those who are concerned their intake might be lacking. However, even if you have an intake of the right balance of proteins, muscle growth will be impaired without adequate carbohydrates, as these provide the fuel to complete sufficient resistance training and the energy needed for new tissue growth. Therefore do not skimp on your intake of carbs at mealtimes.

Some nutrition fallacies are easy to spot, whereas others have become so well accepted that at times it is difficult to know where you stand with the nutrition information available to you. The key is to use trusted print sources[3], which use scientific studies to back up their advice, as well as the knowledge your coach or sports nutritionist can offer.


References

  1. HEIMER, K.A. et al. (2009) Examining the evidence for the use of vitamin C in the prophylaxis and treatment of the common cold. Journal of the American Academy of Nurse Practitioners, 21 (5), p. 295-300.
  2. MATA, P. et al. (1997) Monounsaturated and polyunsaturated n-6 fatty acid enriched diets modify LDL oxidation and decreases human coronary smooth muscle cell DNA synthesis. Arteriosclerosis, Thrombosis and Vascular Biology, 17 (10), p. 2088-2095.
  3. RODRIGUEZ, N.R. et al. (2009) Position of the American Dietetic Association, Dietitians of Canada and the American College of Sports Medicine: Nutrition and athletic performance. Journal of the American Dietetic Association, 109 (3), p. 509-527.

Page Reference

If you quote information from this page in your work then the reference for this page is:

  • BEDFORD, L. (2013) Debunking Three Common Nutrition Myths [WWW] Available from: https://www.brianmac.co.uk/articles/article123.htm [Accessed

About the Author

Lily Bedford is a freelance writer.

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