A young woman sits at her breakfast table holding and looking at a plastic bottle of multivitamin pills. In front of her on the table are a glass of milk, a jar of peanut butter, a bowl of wheat cereal, and a variety of fresh fruits
Many people take a daily multivitamin believing it is helping them stay healthy.
But is it?
Let’s find out.
Quick links
- The vitamins
- What happened to vitamins F to J?
- What do vitamins do?
- Does taking multivitamins keep you healthy?
- But they make me feel better
- Too much of a good thing
- Vitamins from food work better
- When can vitamin supplements help?
- More information
The vitamins
There are 13 essential vitamins your body needs for normal, healthy functioning.
These are nutrients that your body cannot make itself (or cannot make enough of). It must get most of them through diet. Nutrients are substances used by living things to survive and grow.
Vitamins are usually only needed in small amounts. Too much of some can cause symptoms or toxicity. (See Too much of a good thing.)
A healthy diet provides all the nutrients needed including the 13 essential vitamins. When vitamins are missing from the diet, poor health and illness can occur. For example, scurvy is caused by a shortage of vitamin C. And rickets is caused by a long-term shortage of vitamin D.
Vitamins were discovered in the early part of the 20th century. Doctors and scientists realised that a shortage of unknown parts of a diet caused problems and went looking for them.
Once isolated, it wasn’t long before they were manufactured. In the 1930s, B-complex and C were the first vitamins to be sold. Multivitamins emerged in the 1950s.
The 13 vitamins are:
- A
- B1
- B2
- B3
- B5
- B6
- B7
- B9
- B12
- C
- D
- E
- K.
Nine vitamins are classified as water-soluble (the eight B-vitamins and vitamin C).
The remaining four are classified as fat-soluble (vitamins A, D, E, and K).
Water-soluble vitamins dissolve in water and are easily excreted from the body. So, a steady intake—ideally from healthy diet—is important.
Fat-soluble vitamins A and D dissolve in fat. They can be stored in fatty tissues and the liver and accumulate in the body. If levels become too high, they can cause symptoms, and even become toxic. (See Too much of a good thing )
What happened to vitamins F to J?
Some were found to not be vitamins. Others were discovered to be related to vitamin B and were renamed to became part of the B complex of vitamins. (They were still regarded as their own vitamins at the time vitamin K was discovered and named.)
What do vitamins do?
Vitamins play important roles in the many chemical reactions that are taking place in your cells all the time. Most vitamins take part in many different reactions, so one vitamin can have many functions:
- They can act as regulators of cell and tissue growth (vitamin A).
- Some are enzymes—biological catalysts that help certain chemical reactions to happen (B-complex vitamins).
- Some have a hormone-like function (vitamin D).
- Others can function as antioxidants, neutralising harmful free radicals. Examples include vitamins C and E.
(Free radicals are highly reactive atoms that can damage cells and cause disease and aging).
Does taking multivitamins keep you healthy?
If you enjoy a nutritious and varied diet, have no vitamin or mineral deficiencies, and are otherwise healthy and well, you can get all the nutrients you need from food. Then taking multivitamins is not necessary.
Research published in the journal BMJ Open looked at more than 21,000 multivitamin users and non-users in the United States. Thirty per cent of the multivitamin users reported better health than the non-users. But when health was clinically assessed, they scored no higher than non-users.
Johns Hopkin’s researchers reviewed evidence from multiple studies. They concluded that multivitamins don’t reduce the risk for:
- heart disease
- cancer
- cognitive decline
- early death.
But they make me feel better
That could be true. The study published in the BMJ Open suggests many of the perceived health benefits of taking multivitamins may be due to the ‘placebo effect’.
Placebos are a substance or treatment that has no therapeutic (disease-healing) value. Even then people still report improved symptoms. Or they expect better health. All while receiving treatment that has no medical or health effect.
You could possibly feel the same benefits as taking multivitamins by feeling confident that your healthy diet is providing you with good health.
Too much of a good thing
As with prescription medicines, multivitamins, minerals, and other supplements can have adverse effects and cause harms if used incorrectly or if doses are too high. This can occur when someone takes a supplement, not realising they are getting more of a particular vitamin or mineral from another source, such as another supplement or from food.
Vitamins and minerals that can be harmful in excess include:
- A (retinol)
- B3 (niacin/nicotinic acid)
- B6 (pyridoxine)
- C (ascorbic acid)
- D (colecalciferol)
- E (alpha-tocopherol)
- calcium
- magnesium
- zinc
- selenium.
For example, taking too much vitamin A (retinol) can cause nausea, vomiting, dizziness, and blurry vision. This can happen even with a large single dose (over 200,000 mcg).
Taking too much long term (over 10,000 mcg per day) can also have adverse effects or cause harms including:
- bone thinning
- liver damage
- joint and bone pain
- birth defects.
The symptoms may differ, but too much of other vitamins listed above can also have adverse effects or cause harms. If you’re unsure how much is safe, ask your doctor or pharmacist. If you’re pregnant, you should check with your doctor before taking vitamins or supplements.
Vitamins from food work better
Research indicates that most vitamins you get from food are better than those found in vitamin or multivitamin pills. This seems to be the case even when the vitamins in the pills are chemically identical with those found in food. (Folate is the exception—the manufactured form is absorbed by your body better than folate from food).
There are other chemicals in food, such as enzymes, minerals and phytochemicals (plant chemicals) that work together with vitamins in complex ways in the body.
Phytochemicals are an important part of a healthy diet and may reduce some diseases such as cancer and heart disease. Vitamin supplements generally do not provide them.
When can vitamin supplements help?
For some people, supplements can be beneficial.
- Pregnant women, or women planning to conceive. Folic acid supplements can be of benefit. They reduce the risk of a baby developing neural tube defects like spina bifida. They may also benefit from a boost in iodine and iron. Talk to your doctor first.
- Vegetarians and vegans may need vitamin B12 supplements. This vitamin mostly comes from meat, fish, and dairy foods. Iron from plants is less easily absorbed and so you may need to take an iron supplement. Talk to you doctor to have your iron levels checked before starting supplementation.
- Post-menopausal women and older adults may need to take calcium and vitamin D supplements to maintain bone health.
- Children who are fussy eaters. Some medical professionals may recommend dietary supplements for them.
- Certain health conditions restrict the diet. Or they can affect the body’s ability to absorb or use certain vitamins and minerals. In these cases, and under medical guidance, specific supplements are needed. Talk to your doctor.
- Nutrients lacking in everyday diet. Depending on where food is grown, some nutrients may be lacking. For example, some areas have soil that is low in iodine, and other areas may have soil lacking in other nutrients. If you feel unwell, or lacking in energy, even if you think your diet is fine, see your doctor and ask for a blood test before you buy supplements.