Vitamins - common misconceptions  

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. Most vitamins need to be taken through food.

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 vitamins A and D, 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. The Australian Recommended Dietary Intakes (RDIs) for vitamins should be observed.

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 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 got 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 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.

We need about 40mg 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. Taking vitamin supplements will not cure or prevent stress, depression or anxiety. 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 raised that megadoses of antioxidants may 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.

In another study, subjects taking beta-carotene supplements combined with alcohol developed more bowel polyps.

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.

Food and drink

What you eat and drink can have a big impact on how you feel. It can help to:

• ensure that you eat a balanced diet and have regular meals - even if you don't feel like cooking, for information see Related topics
• cut down gradually on caffeine and alcohol - especially in the evenings
• gradually increase your portion sizes and your overall calorie intake if you are underweight
• control your weight by increasing the amount of exercise you do and eating less if you are overweight

Physical activity

Being unfit makes you susceptible to tiredness. And being tired often means you don't exercise enough. Try to break out of this cycle.

• Introduce physical activity into your routine, gradually increasing the duration and intensity. Aim to do 30 minutes of moderate-intensity physical activity on at least five days a week.
• If you exhaust yourself for some reason, don't give up. Do a small amount of exercise again the next day and gradually increase the amount.
• Exercise at least three hours before bed, as exercise can invigorate you.

For information, see Related topics.

A balanced lifestyle

Think about what you could change to achieve a more balanced, stress-free lifestyle.

• Have realistic expectations about what you can achieve and aim to gradually increase what you can manage over time.
• Learning to relax will help to improve sleep and to relieve stress-related symptoms such as frustration, irritability and tiredness. Your GP surgery or local library may have details of local adult education classes, books, CDs or website that can help.