If you believe the headlines, multivitamins do not protect against heart attack or stroke. The fact that they’re not supposed to seems to have escaped the researchers. But even so, when you look at the actually study – things become a lot less clear than headlines suggest.
Firstly, this is not a new study but a new analysis of 18 carefully selected old studies, some of which were published as long ago as 1970. Oddly, case-control studies were excluded (which would have shown better comparisons between matched people, some of whom took a multivitamin and mineral supplement, and some who did not.) Also, studies targeting people with a specific condition, such as previous myocardial infarction or certain vitamin deficiencies, were also excluded. Yet these were the very studies that could have shown benefit.
Even so, the selected studies did involve over 2 million people, and did look for associations between taking multivitamins and cardiovascular disease outcomes, so what did the data actually show? We can’t really draw any robust conclusions, because only 5 studies specified the dose or type of vitamin and mineral supplement involved – 13 did not!
The heart multivitamins involved
There is no one healthy heart vitamin or mineral, but of the few studies in this analysis that defined what multivitamin they were looking at, these were:
- A combination of 120 mg of ascorbic acid, 30 mg of vitamin E, 6 mg of β carotene, 100 mcg of selenium, and 20 mg of zinc; that is NOT a multivitamin and mineral supplement, it’s an antioxidant supplement.
- A combination of 60 mg vitamin C, 9 mg vitamin E, 1.2 mg thiamine, 1.4 mg riboflavin, 1.8 mg vitamin B6, 3 mg vitamin B12, and 400 mg folic acid; that is not a multivitamin and mineral supplement either, it’s a B group supplement with some additional vitamin C and E.
- One study defined a multivitamin as containing 3 or more vitamins and at least 1 mineral (dose unspecified) which is a pretty shabby definition of a multivitamin and mineral supplement on which to draw such sweeping conclusions.
- One study defined a multivitamin as providing least 10 vitamins and minerals with doses unspecified.
- One study defined a multivitamin as providing 20 to 30 vitamins and minerals and nutrient levels of ≤100% recommended daily amounts (now that’s what I call a good standard for a multivitamin and mineral supplement)
- One study used Centrum Silver, at a dose of 1 tablet daily (a good one).
- One specified doses of ‘generally close to recommended daily amounts’ for vitamins A, C, D, E, B1, B2, B3, B6, B12 and folic acid, and said the minerals usually included are iron, zinc, copper, calcium, magnesium, chromium, selenium and iodine.
So, right away, there is a difficulty in drawing any convincing associations between any particular multivitamin and mineral supplement blend or dose, and risk of developing or dying from cardiovascular disease.
What the healthy heart vitamin study found
After crunching all the data from these carefully selected 18 studies, the study focussed on the fact that the absolute relative risk of dying from cardiovascular disease in those taking a multivitamin supplement was 1.0. No effect was seen either way – no protection against heart disease (which of course a multivitamin is not designed to do) but no harm either.
What the press release failed to highlight was that, in eight cohort studies involving 397,743 people, those who took a multivitamin supplement had a 12% lower risk of developing coronary heart disease compared with those who didn’t take a multivitamin supplement (relative risk 0.88; 95% CI, 0.79–0.97) so a pretty robust finding.
They also found that taking a multivitamin supplement was especially associated with a lower risk of developing coronary heart disease in studies performed outside of the United States by a massive 26% (relative risk 0.74; 95% confidence interval 0.62–0.89 so a really robust finding).
In studies performed outside the United States, taking a multivitmain and mineral supplement lowered the risk of developing coronary heart disease by 9% (relative risk, 0.91; 95% CI, 0.83–1.00, but as the confidence interval reaches 1.0 this could have occurred by chance alone).
Most newspaper reports have missed out these beneficial findings. If you want to see the data yourself, the full paper is available here: Association of Multivitamin and Mineral Supplementation and Risk of Cardiovascular Disease.
A multivitamin and mineral supplement IS a good idea
A multivitamin and mineral supplement is intended to prevent nutritional deficiencies in people who know their diet is not as good as it should be – whether you’re cutting back on food to lose weight, skipping meals, or avoiding certain foods due to intolerances, dislikes or dietary preference.
In the UK, the recent National Diet and Nutrition Survey (NDNS) results show that significant numbers of people (including 17% of all adults) are deficient in vitamin D all year round, for example.
At least one in two women aged 19 to 65 years obtain less than the EU recommended daily intake of vitamin A, Vitamin B1, folic acid, vitamin D, Calcium, iodine, iron, magnesium, selenium and zinc (based on median intakes).
And when you look at the percentage of adults with a vitamin or mineral intake below the lower reference amount (and who are therefore at great risk of nutritional deficiency diseases such as anaemia), the percentages are as follows:
Vitamins & Minerals
% Men below LRNI
% Women below LRNI
|Riboflavin (vitamin B2)||6%||14%|
Unless you know your diet is as good as it can be, you are probably at risk of at least one vitamin or mineral deficiency.
Diet should always come first, but for many people a multivitamin is an important preventive health intervention. I can’t say that taking a multivitamin and mineral supplement will protect against serious diseases, such as coronary heart disease or cancer. What I can say is that it will act as a nutritional safety net and may very well help to protect against iron-deficiency anaemia, folate deficiency, thinning bones (osteoporosis) and the wide range of conditions now known to be associated with a lack of vitamin D.
Image credit: robin_hp/bigstockphoto