Vitamins are essential for good health. This much we can agree on, but then things quickly become murky.
There is so much information, contradictory research and advertising out there about the vitamin needs of endurance athletes, and how they can best be satisfied, that it's hard to know what's what.
While most nutritionists agree that a balanced diet should provide your vitamin requirements, about one third of people in the UK choose to take supplements. The UK market is worth over £300m, so it's no wonder we're bombarded with information. It's safe to say that some people who take supplements have an inadequate diet, so they may be doing themselves some good. But for triathletes the situation is less clear. Endurance athletes place more demands on their body than most of the population, but they tend to compensate by eating more, and generally eating well.
This debate is further complicated by a powerful worldwide vitamin-supplement industry that spends enormous amounts of money each year trying to convince you that you need to supplement your diet to improve performance and stay healthy.
The science part
There are 13 main types of vitamins, most of which we obtain from our diet. Most of our vitamin D, however, is produced from exposure to the sun. The water-soluble vitamins (the B vitamins and vitamin C) are not stored in the body and should be replaced regularly, but we can hang on to fat-soluble vitamins (A, D, E and K). They are stored in the liver and fatty tissues and can reach toxic levels if taken in high doses. It would be extremely difficult to reach such dangerous levels with diet alone. On the other end of the scale, it would take weeks or months before a vitamin deficiency affected your health. The body needs vitamins in tiny amounts but it needs them regularly. Vitamins do not have any calories, and therefore provide no energy. However, they are vital to the energy-producing process, and a deficiency in vitamins in this chain will result in reduced energy and performance levels. A severely reduced intake of B vitamins and vitamin C, for example, can lead to a lowered V02 max and a lower anaerobic threshold.
Some vitamins also have antioxidant properties that may help the triathlete's body cope with the stress and damage caused by long, intense training sessions. For example, some studies indicate that vitamin C and E may have a role in reducing damage to muscle tissue. It has also been suggested that vitamins may help bolster immune systems.
There are many arguments put forward for taking vitamin supplements. If, for example, a triathlete is vegetarian, or omits certain foods from his or her diet, a supplement may make up the missing nutrient. Older triathletes may benefit from taking a supplement, because as it ages the body becomes less efficient at absorbing nutrients from food. People with malabsorption conditions, such as the intestinal condition coeliac disease, may also benefit from supplements. However, you should consult your doctor before making any decisions about supplements.
In Sports Nutrition for Endurance Athletes, nutritionist Monique Ryan notes that, "For endurance athletes they [supplements] are crucially important. Because of your training and the stress it imposes on your body, you may need higher amounts of vitamins and minerals than sedentary people."
The UK-based Health Supplement Information Service makes a similar point: "Vigorous training increases production of free radicals in the body so, when participating in an exercise regime, it may be necessary to increase the intake of antioxidants (beta-carotene, bioflavonoids, vitamin C and vitamin E) as well as ensuring adequate amounts of minerals required to maintain strong, bones and joints (calcium and iron for example)."
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