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There are many misconceptions about vitamins and the health benefits they offer. Vitamin supplements are commonly misused and taken as a form of medicine to treat ailments such as colds or to counteract lifestyle issues such as stress. Contrary to popular belief, vitamins aren’t drugs or miracle cures. They are organic compounds that participate in various metabolic functions. It is best to get vitamins from eating a healthy, well-balanced diet.
Recommended dietary intakes
Many people mistakenly believe that since small amounts of vitamins are good for you, then large amounts must be better. In the case of vitamins, it is better to follow the rule of ‘less is more’. The vitamins A, D, E and K are fat soluble, which means they can be stored in the body. High doses of these vitamins over a long period of time, especially vitamin A, without an underlying clinical deficiency can result in harmful levels in the body.
Some of the water soluble vitamins can also cause side effects in high doses. For instance, vitamin B6 has been linked with nerve damage when taken in large doses.
For a healthy adult, if supplements are used, they should generally be taken at levels close to the recommended dietary intake (RDI). High-dose supplements should not be taken unless recommended under medical advice.
Deficiencies and illness
The human body is able to store vitamins. The fat soluble vitamins A, D, E and K can be locked away in the liver and body fat and stored for a long time. The water soluble vitamins, including B-complex and vitamin C, are mostly only stored for a shorter period of time.
A vitamin deficiency takes weeks or months before it will affect your health. For instance, it would take months of no vitamin C before you developed scurvy. An occasional lapse in good eating will not harm you if your usual diet consists of a wide variety of fresh foods.
Sometimes supplements are needed
Some groups of people may need to take vitamin supplements at the RDI, for example:
- Vegans, who eat no animal products, may risk B12 deficiency.
- Women of childbearing age may need 400µg of folate per day for a month before conception and for the first three months of pregnancy. Otherwise they risk having a baby with neural tube defects, like spina bifida.
- Smokers use up to twice as much vitamin C for their metabolic processes as non-smokers.
- People on very low fat diets are at risk of fat soluble vitamin deficiencies (vitamins A, D, E and K).
- People on long-term restrictive weight loss diets may need supplements.
- People on restrictive diets due to allergies or food intolerances may lack some nutrients.
- People who drink alcohol above the recommended safe amount (two standard drinks a day for women and four for men) may be deficient in some nutrients.
- People recovering from serious illness or surgery may have inadequate intakes of several vitamins and minerals.
- People with malabsorption problems such as diarrhoea, coeliac disease or pancreatitis are another group who may benefit from supplements.
If you need to take a supplement, it is preferable to take multivitamins at the RDI level, rather than single nutrient supplements or high dose multivitamins.
The common cold and vitamin C
Many people think that vitamin C helps prevent the common cold. Despite exhaustive research across the world, there is still no strong evidence to prove this. Some studies have shown that taking large doses of vitamin C (more than 1000mg per day) continuously or at the start of a cold may ease some of the symptoms and the duration – on average, making it about half a day shorter. It does not prevent you catching a cold.
You also need to consider the health risks associated with taking large doses of vitamin C. Large doses may cause nausea, abdominal cramps, headaches, fatigue, kidney stones and diarrhoea. It may also interfere with the metabolism of other nutrients – for example, it could lead to dangerously raised levels of iron. Excessive amounts of vitamin C in the body can also interfere with medical tests, such as diabetes tests, giving a false result.
Adults need about 45mg of vitamin C per day and any excess amount is excreted.
Stress, depression and anxiety
Some vitamin and omega-3 fatty acid deficiencies can lead to emotional disturbances; however, other causes are much more likely, such as personal problems and unhealthy lifestyle habits. Feeling under pressure doesn’t automatically lead to a vitamin deficiency, so taking a vitamin supplement won’t necessarily make the stressful feelings go away. More serious mental illnesses, such as schizophrenia and bipolar disorder, aren’t caused or prevented by vitamins either.
Vitamin E and heart disease
Vitamin E is widely promoted as a beneficial antioxidant to take to help prevent heart disease. Unfortunately, several large-scale reviews of the evidence for vitamin E supplements in preventing death from heart disease have universally reached the conclusion that they offer no benefit. In fact, there may be greater risk of all-cause death from taking such supplements.
Cancer cures
Vitamin A in large doses does not cure cancer and can be toxic, particularly if taken as pills rather than food. There is some evidence that vitamin E could play a small role in preventing some cancers although, equally, there is evidence that it could hasten the onset of other types of cancer; however, this has not been conclusively proved or disproved.
While it is argued by some that megadoses of antioxidants can help with the effectiveness of conventional cancer treatments such as chemotherapy and radiotherapy, the evidence is far from supportive of this. In fact, it has been shown that megadoses of antioxidants can actually interfere with some medical treatments of cancer by helping to protect the cancer cells that the therapies aim to eradicate.
Research shows that isolating the ‘active ingredient’ is not the answer
When vitamins are taken as high-dose supplements, they are introduced into the body at levels that could never be achieved by eating even the healthiest of diets. They are also sent in ‘alone’. When they occur in food, vitamins have many other companions to help them along the way. For instance, provitamin A (beta-carotene) in food is accompanied by hundreds of its carotenoid relatives.
It is the combination of a whole range of compounds (most of which we probably don’t even know about) in plant foods that gives us the protection. When you artificially remove one of them and provide it completely out of context, it can have negative effects.
Some research findings
The following studies using supplements had some very negative findings:
- A study using beta-carotene (thought to protect against cancers and heart disease) had to be stopped because mortality was higher in the people taking the supplements.
- A study of 22,000 men taking beta-carotene for 12 years found that they were no better off than the men on placebo (dummy tablets).
- A study of 18,000 smokers and former smokers found that those who took beta-carotene supplements had an almost 30 per cent increased chance of developing lung cancer compared to those who took the placebo. They also had a 17 per cent increased chance of dying of any cause and a 46 per cent greater chance of dying from lung cancer compared to the placebo group. The trial was stopped.
- Several long-term studies have shown that prostate, breast and lung cancer risk are not decreased by taking high-dose supplements containing vitamins E or C.
- People taking high-dose vitamin E supplements have been found to have higher rates of mortality (early death).
Anti-ageing vitamins
Vitamin E is often singled out as the potential fountain of youth. However, there is no evidence that taking large doses of any vitamin can either stall or reverse the effects of ageing. Neither can any one vitamin restore a flagging sex drive or cure infertility.
Where to get help
Things to remember
- Vitamins are not drugs or miracle cures.
- Taking large doses of vitamins can be harmful because your body only needs vitamins in very tiny amounts.
- Eating plenty of fruits, vegetables, grains and cereals will give your body most of the vitamins your body needs at the right level and in the right balance.
- Vitamin supplements can’t replace a healthy diet, but a general multivitamin may help if your diet is inadequate.
- Those who may need vitamin supplements include pregnant and breastfeeding women, people who consume alcohol in amounts over the recommended safe level, drug users and the elderly.
You might also be interested in:
Healthy eating tips.
Nutrition - women's extra needs.
Scurvy.
Sporting performance and food.
Vegetarian eating.
Vitamin and mineral supplements.
Vitamin B.
Vitamin D.
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