Around half of UK adults currently take a food supplement – but vitamins and minerals are usually only needed in small amounts and too much of a good thing can be bad for you.
Here’s what you need to know about the benefits and risks of some of the most common vitamins and minerals.
Vitamin A
Vitamin A aids the immune system in fighting off infections, helps you see better in the dark and is needed for healthy skin. Most people can get enough vitamin A from eating dairy, oily fish and liver. Yellow and red vegetables such as carrots and peppers, contain beta-carotene, which breaks down into vitamin A in the body. The recommended daily allowance (RDA) is 700 micrograms and 600 micrograms for men and women respectively.
Although your body will store excess vitamin A, some research shows having more than 1.5mg a day over many years may weaken bones. In older people, this can lead to fractures as they are more likely to get osteoporosis. In severe cases, people may experience irreversible liver damage.
If you are pregnant, you should avoid vitamin A supplements completely – excess vitamin A can cause birth defects and miscarriage.
Vitamin B6
Also called pyridoxine, this vitamin is needed to make healthy red blood cells and help the body store energy from food. The RDA is 1.4mg and 1.2mg a day for men and women respectively. This can be obtained by eating, for example, fortified cereal, chicken and soya beans. More than 10mg a day is not recommended as the effects are unclear.
But taking 200mg or more a day has been linked to peripheral neuropathy – when the nerves in the body’s extremities are damaged. This can start with tingling in the arms and legs and lead to loss of feeling. In some patients the effect will stop once the vitamin B6 is stopped. In other patients, nerve damage can be permanent.
Folic acid
Folic acid or folate is needed to make healthy red blood cells. Good sources of folic acid include green leafy vegetables, chickpeas and fortified cereals. The RDA is 200 micrograms daily.
In patients who are pregnant, folic acid is recommended to prevent neural tube defects like spina bifida. Doctors may prescribe higher than recommended doses (5mg) in high risk patients.
Consuming more than 1000 micrograms (1mg) of folic acid can mask symptoms of vitamin B12 deficiency, such as tiredness, tingling hands and feet, sore tongue and muscle weakness. These can indicate a vitamin B12 anaemia. By correcting the anaemia symptoms caused by a B12 deficiency, high folate levels can prevent the detection of an underlying B12 problem, which could lead to brain damage if left untreated.
Vitamin D and calcium
The amount of calcium in the body is controlled by vitamin D. Both nutrients help with healthy bones and teeth. Vitamin D is also needed for the immune system, muscles and nerves. Some foods like fortified cereal contain vitamin D but it is mostly made in the body when the skin is exposed to sunlight. The RDA for vitamin D is 10 micrograms. Those with a vitamin D deficiency may be prescribed higher doses.
People with darker skin or who do not have much exposure to sunlight may benefit from taking a daily supplement. But too much vitamin D over many years can cause kidney failure and irregular heartbeats. It may even be bad for the bones.
A Canadian study found that high doses could be linked to weakened bones. This is because high vitamin D intake causes too much calcium to build up in the body. The body starts to break down bones to lower the calcium.
Iron
Iron is an important nutrient needed to make red blood cells. Sources include red meat and beans. Iron deficiency is the world’s most common cause of anaemia; however, taking too much can be toxic. The RDA for iron varies depending on your sex and age but you shouldn’t take more than 17mg a day. Higher doses can be bought from a pharmacy or prescribed if there is a diagnosed deficiency.
Taking more than 20mg of iron everyday can cause stomach problems such as vomiting, diarrhoea and pain. Prolonged use or higher doses can cause organ damage such as liver failure. This is because it builds up in the organs and interferes with normal cell function.
Fish oil
These supplements contain omega-3 fatty acids. Different fats are needed to support the cells in the body and also to keep the heart, lungs, blood vessels and immune system working properly. Some are essential for brain and eye development in babies. Fish oil has been linked to a lower chance of heart disease. However, studies have mixed results about how effective these really are.
A recent study showed that healthy people taking fish oil supplements may have an increased risk of heart issues like stroke or atrial fibrillation. The benefits are mainly seen in people who already have heart disease. However, there are still benefits from eating food rich in omega-3s such as oily fish.
The British Dietetic Association says it’s better to improve diet before considering supplements. Some groups, like infants, pregnant women and those with a diagnosed deficiency, need supplements. Different supplements have different amounts of vitamins and minerals so always read the label to make sure you’re taking the recommended dose – and avoid taking multiple supplements that could increase your intake of a particular vitamin or mineral beyond safe levels. Ask your doctor, pharmacist or dietitian to check if you need a supplement before taking anything.
Dipa Kamdar does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
This article was originally published on The Conversation. Read the original article.
