Like everything in the health and fitness industry there is a lot of noise about vitamin supplementation. Doctors, naturopaths and other health professionals all weigh in on the debate and as a result it can be confusing to know where to look and who has a vested interest, (usually financial), in the information they provide to the public. Rarely is information made available from an independent source, and when it is it is hard to find amongst the swathe of opinions and reading material generally available.
The following list is compiled from independent research and reputable sites. It is a summary of what supplements do and who, if anyone needs them. The source of the research is important – hospitals and independent research organisations such as the Mayo Clinic and Johns Hopkins University have little incentive to provide methodologically unsound research or irrelevant studies that are taken out of context. There is a list of references used in this article at the end for further reading.
There a few things to note. First, the general rule of supplementation is that vitamins and minerals are best ingested as part of a healthy diet. This is partly because the absorption tends to be more efficient. Furthermore, when they are consumed in tablet or capsule form, (or any other non-dietary form), chemicals need to be added to control the release of particular nutrients. Long term, these can be harmful or even toxic as the following discussion will highlight.
This is the most common form of vitamin supplementation. Almost half the adult population in Australia takes some form of multivitamin; however, longitudinal studies have not supported their use. A large study performed in 2013, with a sample size of over 38,000 participants over 25 years found that the overall mortality increased with multivitamin supplementation. There is little evidence that multivitamins boost your immune system, reduce your stress levels or prevent illness. For a more thorough discussion of the individual components of multivitamins, read on. Increasingly, an overriding philosophy of ‘more is better’ is being challenged by a large body of research, which has generally shown that excess amounts of a vitamin is not only unnecessary but can actually be harmful.
Vitamin A/Beta Carotene
Vitamin A is found primarily in plant carotenoids such as Beta Carotene. A general rule of thumb is that Beta Carotene is found in orange vegetables such as carrots, pumpkin and sweet potato, as well as some greens like spinach. Extremely high doses or over-supplementation can lead to higher risk of some cancers, (like lung cancer); though there is some evidence that Vitamin A can be used to combat some types of cancer. Vitamin A is also an anti-oxidant which can reduce the risk of cataracts and improve vision. It also has functions in improving bone metabolism, skin and cellular health, immune function and gene transcription.
Since Vitamin A is fat soluble and accumulates in the human body, chronic supplementation can be toxic. Side effects include nausea, irritability and reduced appetite, as well as spontaneous bone fractures. The most famous case of Vitamin A toxicity is that of Douglas Mawson and his crew of polar explorers, who ate the livers of their sled dogs. Most of Mawson’s companions died and he himself barely survived. There is evidence that Vitamin A poisoning was the culprit. Vitamin A supplementation can also cause birth defects in pregnant women.
The recommended dosage of Vitamin A for male and female adults is 3000mg.This can be found in the daily recommended serves of vegetables. It is not necessary to supplement Vitamin A.
The B vitamins are a group of water soluble vitamins that are important for cell metabolism. There are 8 in total. Most B vitamins are used in the energy cycles to metabolise carbohydrates, (both dietary and those created when fat is metabolised). Folate, (B9), is used in the production of red blood cells and cell division. B Vitamins are found in a variety of dietary sources, from animal fats to leafy green vegetables and grains. The risk of over-supplementation for most B Vitamins is low, however there can be side effects ranging from diarreah to drowsiness and impaired muscle function, to liver damage in more serious cases. In particular, Over-supplementation of Vitamins B6 and B12 can lead to nerve damage. For people who eat a balanced diet it is unnecessary to supplement Vitamin B.
Vitamin C is found abundantly in fruits and vegetables. Its function is in metabolic and enzymatic activity, more specifically in healing wounds and preventing bleeding from capillaries, as well as in reducing oxidative stress. It is generally safe, but supplementation is usually unnecessary. Vitamin C, particularly in supplement form, does not cure or prevent common colds according to an extensive review performed in 2005 which covered 50 years of research. It can, however, increase the chances of kidney stones.
Used in clotting processes and bone density maintenance, vitamin K is found mostly in leafy green vegetables, but also in egg yolks, liver and some cheeses. Average diets are not usually lacking in Vitamin K and therefore deficiency is rare in adults. Allergic reaction is possible, though unlikely, and there is no known toxicity or side effect of high levels of Vitamin K obtained through diet. Synthetic forms of vitamin K have, however, been found to be toxic and can cause anaemia in high doses. For this reason Vitamin K3 is banned from over the counter sale in the US. As Vitamin K is used in clotting processes in the body, newborns are administered small doses of Vitamin K.
Vitamin D can be found in trace amounts in fatty fish such as tuna, mackerel and herring, or in juices and dairy products that are fortified with vitamin D. But about 80%, (or more depending on the individual), of the body’s vitamin D requirements come from exposure to sunlight. Vitamin D is used in bone growth, intestinal absorption, and other metabolic processes. Many individuals need to supplement Vitamin D – for example, patients with bone complaints like osteoporosis, auto-immune diseases, heart complaints, high blood pressure and high cholesterol. The elderly and those with darker skin need more sun exposure to get their vitamin D dosage as they have fewer receptors in their skin to convert sunlight to vitamin D.
It should be noted that some recent studies have shown that Vitamin D on its own does not decrease the incidences of osteoporosis, and furthermore, has no effect on a wide range of diseases and conditions. These studies, published in the Lancet, found that Vitamin D deficiency was actually the result of poor health, rather than the cause of it.
While supplementation is most likely unnecessary for those in good health, there are probably very few side effects. Vitamin D toxicity is uncommon, but can lead to nausea, vomiting, muscle weakness and kidney damage.
One of the more popular anti-oxidant supplements, Vitamin E is actually not recommended for supplementation. The biological function of Vitamin E is neurological function and enzymatic activities. Vitamin E is found in grains such as wheat germ, in sunflower and safflower oils and in some leafy greens.
Evidence from studies compiled by the Mayo Clinic show that the risk of some cancers, (including prostate cancer), are higher in those that supplement Vitamin E. The Cochrane Review in 2012 found that supplementation did not reduce the risk of cataracts. Another clinical study in 2007 found that supplementation did not reduce the risk of heart disease in men. In fact, high dosage supplementation of Vitamin E has been found to increase mortality rates. Lower dosage over-supplementation can lead to Vitamin K deficiencies.
What Should Be Supplemented?
Some women in their child bearing years will need to supplement iron and folic acid, as directed by a doctor. Iron is part of the red blood cell making process and low levels can result in fatigue, nausea and malaise. Folic acid is used in cell division and has been found to reduce the risk of birth defects.
The CSIRO recommends 3 serves of fish per week to ensure the appropriate intake of essential fatty acids such as Omega 3 and 6. These are called essential fatty acids because they cannot be synthesized by the body, but are necessary for the creation of amino acid chains. Fish oil is safe to supplement, and can reduce the risk of cancers and some neurological conditions like Alzheimer’s and Parkinson’s, heart disease and some mental health disorders. It can also reduce inflammation within the body. If seafood does not make up a significant portion of your diet, fish oil may be a safe and effective supplement to consider.
Many adults have low dietary intake of potassium, which is often present in multivitamins. Potassium is vital in the production of energy along with sodium. If sodium is present in high concentrations in a diet, potassium concentrations can often be low. By far the best solution is to increase potassium rich foods like beans, leafy greens, potatoes, apricots, fish and yoghurt, and decrease foods that are high in salt, (sodium chloride), such as processed and take-away foods.
Calcium supplementation is recommended by some doctors for patients at a high risk of osteoporosis. Recent evidence, however, has linked calcium supplementation to an increased risk of cardiovascular disease. Calcium is found in dairy products and in leafy green vegetables. A balanced diet for most individuals is sufficient to ensure good bone health, and a moderate exercise regime is the best way to prevent osteoporosis. For those individuals that need calcium supplementation, a moderate dose of Vitamin D is also suggested.
Who should supplement?
The above discussion details only the dry facts as they pertain to the general population. Of course, there are some people with particular conditions that need to supplement their diet for a variety of reasons. This is usually in direct discussion with a specialist or doctor, for example, pregnant women are often recommended a pregnancy supplement which contains folate and in some cases iron. But for the general public, most diets should be sufficient for adequate vitamin and mineral ingestion, and if they aren’t a smarter strategy would be to change the diet and not add a dietary supplement.