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)."
Meet your needs
Many studies suggest that, from a performance and recovery point of view, supplements are unnecessary for athletes eating a well-balanced diet. But there is fresh research almost weekly. Heather Nakamura, a registered dietician with a Masters degrees in Exercise Physiology and Nutrition, says, "It depends on the adequacy of the diet, the calorie intake, individual nutritional needs etc. Many endurance athletes consume a large amount of calories to meet their metabolic and training needs. A higher calorie intake will often provide more nutrients."
However, she points out that some athletes don't maintain a nutritionally balanced diet, even with a high calorie intake. "Others may restrict their calorie intake in an effort to lose weight, limiting not only their calories but their intake of nutrients as well," she says.
And there are other issues to consider that may effect your vitamin intake. While you may be diligent in choosing a healthy diet from the supermarket, you may be the world's most inept person in a kitchen. The nutrients in food may be destroyed by poor storage, preparation and cooking, so you have to know what you're doing once you've bought the lentils.
The vitamin content of food can also be reduced by processing techniques and even fresh fruit can lose vitamins just sitting around in a bowl.
Moderation in all things
If you know your diet is lacking, a multivitamin will do you no harm, but you should bear in mind that vitamins and minerals work best when they are taken as part of a nutritionally balanced diet; a complicated chemical process takes place when you eat that cannot be replicated by popping a pill.
Good nutrition is a tool for the triathlete but how you take in the micronutrients you need to keep you in shape and race ready is up to you.
Vital vitamin statistics
What they're for and where you can get them
Function: Good eyesight, healthy skin, strengthens the immune system Sources: Fish oils, liver, dark-green leafy vegetables
Vitamin B1 (thiamine)
Function: Energy metabolism, maintaining muscle tissue, nervous system Sources: Bread, wholemeal foods, fortified breakfast cereals
Vitamin B2 (riboflavin)
Function: Tissue building, energy metabolism. Helps the body absorb folic acid Sources: Milk, meat (especially liver), green leafy vegetables, eggs
Vitamin B3 (niacin)
Function: Energy metabolism, digestive system Sources: Dairy products, meat, eggs, fortified breakfast cereals
Vitamin B5 (pantothenic acid)
Function: Energy metabolism, producing neurotransmitters Sources: Meat, cereals and grains, potatoes
Function: Protein metabolism Sources: Fish, chicken, brown rice, eggs
Vitamin B7 (biotin)
Function: Cell growth, energy metabolism Sources: Liver, egg yolks
Function: Making red blood cells, maintaining nervous system Sources: Fish, meat, eggs, cheese
Function: Supports the immune system, helps maintain cells and tissues Sources: Citrus fruits, green vegetables
Function: Strong, bones and teeth, helps calcium absorption Sources: Sunlight, oily fish, milk
Function: Powerful antioxidant Sources: Nuts, vegetable oils, green vegetables
Function: Blood clotting, building strong bones Sources: Dark-green leafy vegetables, wholegrain cereals
Function: Works closely with B12, promotes healthy red blood cells Sources: Fortified breakfast cereals, liver, chickpeas