Bottles of multivitamins take up entire rows of most pharmacies and supermarkets. Millions of people take them, around 1/3 of people in Western countries, and billions of dollars worth are bought each year.
They are usually combined with dietary minerals and so a more accurate name would be a “multivitamin/mineral supplement” and the USA Food and Drug Board define them as
“a supplement containing three or more vitamins and minerals that does not include herbs, hormones, or drugs, where each vitamin and mineral is included at a dose below the tolerable upper level and does not present a risk of adverse health effects”.
It is hotly debated in medical circles as to whether healthy people should take them. Some health professionals argue that they are a waste of time and money as there is no good evidence that they can help prevent diseases such as cancer or heart disease. Others (myself included) argue that it is very hard to study the effects of taking multivitamin supplements, and that they provide “nutritional insurance” ie. they top up almost anything important that we may be missing in our diet. That is the reason I take one: I try to eat as healthily as possible, but I don’t know if my body is low in one or even several important minerals or vitamins. Despite having a good diet, many New Zealanders are low in a number of important nutrients such as vitamin D, particularly in the winter, and selenium, due to the low levels in our soil and therefore our food.
I could, and some people do, regularly test my blood for all the important minerals and vitamins. But this takes time and costs a lot of money. Taking a good multivitamin is much simpler and if you do not need some or all of the ingredients you will just pee them out. Despite a few scare stories in the media over the last few years, in my view it is perfectly safe to take a multivitamin tablet every day.
There is some interesting new evidence to support my case. The evidence comes from a study which was undertaken in the USA but the results are likely to be very similar here. Researchers found that 24% of adults had one nutrient deficiency, about 6% had two nutrient deficiencies, and another 2% of adults had three or more vitamin/mineral deficiencies. In total, they found that around one in three American adults had at least one vitamin or mineral deficiency.
Then they looked at the effect of taking a “full spectrum multivitamin” which was defined as containing 12+ vitamins and 6-14 minerals, in other words, a good multivitamin tablet or capsule. The results were compelling: while 31% of those who did not take a multivitamin had at least one vitamin or mineral deficiency, only 12% of people who took a multivitamin had one or more nutrient deficiency. In other words, people who do not take a multivitamin are 2.5 times more likely to have a nutrient deficiency compared to those who do.