Vitamins, minerals and exercise
Published by Bupa's health information team, healthinfo@bupa.com, April 2008
This article is for people who exercise and want to know about vitamins and minerals. It discusses whether athletes have different needs, and whether vitamins and minerals can improve your sporting performance.
What are vitamins?
Vitamins are nutrients that everyone needs in small amounts for the body to work properly. Different vitamins have different functions. For example, some enzymes need particular vitamins to work, and other vitamins stop oxygen from damaging your cells. Your body can't make most vitamins (apart from vitamin D), so you have to get them from the food you eat.
There are two types of vitamin:
- water-soluble vitamins cannot be stored in the body and need to be replaced regularly in your diet
- fat-soluble vitamins (including vitamins A, D, E and K) are stored in the body, but should still be part of a healthy diet
What are minerals and trace elements?
Minerals are inorganic elements that are needed in small amounts for your body to function. Trace elements are inorganic elements that are needed in even smaller amounts. Different elements have different functions. For example, you need:
- calcium to make strong bones
- sodium for fluid balance and nerve function
- iron for oxygen transport in the blood and energy metabolism
- iodine for thyroid hormone function
Minerals are as essential as vitamins. Like most vitamins, your body can't make them so you have to get them from your diet.
How much do I need?
Nutritional needs vary from person to person, depending on gender, age and activity levels.
The Department of Health gives guidance on the correct levels of nutrients in the diet, although these are not exact recommendations. You will often see food and supplement packets listing the RDA (recommended daily allowance). This tells you how much of certain nutrients you need in your diet. In the UK, this term has now been replaced by a different way of naming nutritional needs, using dietary reference values (DRVs). DVRs show the amount of energy or an individual nutrient that you need. But the term RDA is still in common use.
Why are vitamins important if I exercise?
Exercise may increase the need for vitamins and minerals because metabolism is higher so there is a faster turnover, and because you need more muscle repair.
Calcium and vitamin D
This is important for building and repairing bone. You're at risk of weak bones and stress fractures if you don't get enough in your diet, and your risk is even higher if you're a woman. Good sources of calcium include dairy products, bony fish and dark green leafy vegetables.
You also need vitamin D for calcium to be absorbed. Your body makes most of the vitamin D you need when you expose your skin to the sun. But sports nutrition experts suggest taking a 5ug daily vitamin D supplement if you train indoors (eg ice skating) and don't see much sunshine.
Iron
Iron is a vital part of the blood, allowing it to carry oxygen around your body. It's common for iron to be low in people who exercise intensively, especially women and distance runners. A shortage in iron leads to anaemia, which can impair performance and affect your health. Good sources include red meat, dried fruit and dark green leafy vegetables.
Zinc
Zinc plays an important role in growth, building and repair of muscle tissue, and energy production. Good sources include meat, shellfish and wheatgerm.
B vitamins
B vitamins may be particularly relevant for athletes because they are important for energy production during exercise, the production of red cells, protein synthesis, and in tissue repair and maintenance. You may need up to twice the recommended amounts of these: thiamine riboflavin, niacin, pantothenic acid, folic acid, B-6 and B-12. Different B vitamins are found in a wide variety of foods, including meat, cereals, milk and eggs.
Antioxidant vitamins
The antioxidant vitamins A, C, E, selenium and beta-carotene are important for protecting your cells from damage by oxygen. In theory, intensive exercise could cause more cell damage. However, your body may adapt to this. Sports nutrition experts are not sure whether you need to take in more of these vitamins if you exercise a lot, but you may need to if you restrict your calorie intake or follow a low fat diet.
Vitamin C is found in fruit and vegetables, such as peppers, oranges and kiwi fruit; vitamin A is found in eggs, cheese and milk; and vitamin E is found in olive and soya oil.
How can I get enough vitamins and minerals?
Like everyone else, you should get all the vitamins and minerals you need from your diet even if you do a lot of exercise. Very active people usually eat more than inactive people because they need more energy. As long as your diet is balanced, any increased need for vitamins or minerals should be met by your increased food intake.
If you're an athlete though, you may want to gain or lose weight to improve performance in your sport. You can gain weight healthily by increasing your calorie intake and increasing strength training to build muscle. But weight loss can sometimes cause problems because restricting calories can leave you short of nutrients, including vitamins and minerals.
You may need to take vitamin supplements if you are following any kind of restricted diet to try to improve your performance eg low-calorie or high-carbohydrate. But you should only follow a special diet with the advice of a registered dietician who has training in sports nutrition. He or she can advise you on the right foods and quantities to eat to make sure you get all the nutrients you need.
Generally, you shouldn't take vitamin supplements unless your doctor or dietician has told you to for medical reasons. For example, you may need an iron supplement if you have anaemia. And if you're pregnant, you should take a daily 400ug folic acid supplement for the first 12 weeks of pregnancy to reduce the risk of birth defects in the baby.
Some vitamins, particularly fat-soluble vitamins, can be harmful in excessive quantities because they tend to build up in the body. For example, too much vitamin D has been linked with weaker bones.
Research published in the Cochrane Database of Systematic Reviews found that vitamins A, E and beta carotene increase your risk of dying early. You shouldn't take these vitamin supplements either alone or as part of a multivitamin supplement, unless advised to by your doctor.
Amounts of water-soluble vitamins that exceed our requirements are simply lost from the body in urine and provide no additional benefit.
Will vitamin and mineral supplements improve athletic performance?
Evidence suggests that unless you are deficient in a nutrient, taking a supplement of that nutrient won't improve your performance in sport. Vitamin supplements will not make you feel less tired when you exercise: if there is a nutrition-related cause of fatigue, it's usually lack of calories or carbohydrates.
Key points
- Most vitamins and all minerals cannot be made by the body, so need to come from your diet.
- A balanced diet should provide all the vitamins and minerals you need.
- If you are well nourished, supplements will not improve your physical performance.
- You shouldn't take vitamin supplements that contain vitamins A, E and beta carotene, unless advised to by your doctor.
- Consult a registered dietician for advice if you plan to try any kind of special diet to improve sporting performance.
Further information
- Food Standards Agency
wwww.eatwell.gov.uk - British Nutrition Foundation
020 7404 6504
www.nutrition.org.uk
Related information
- Carbohydrates and exercise
- Energy, exercise and weight control
- Healthy weight and exercise
- Vitamins and minerals
