Study: Vitamin Supplements Might Do More Harm Than Good

Study: Vitamin Supplements Might Do More Harm Than Good
Image: Getty Images

In Australia’s most recent nutrition survey, 29 per cent of people reported having taken at least one dietary supplement. However, a new review of 180 studies found little or no protective effects from taking dietary supplements, and actually found some harm.

The new study aimed to examine the benefits of vitamin and mineral supplements for prevention of heart disease, stroke and premature death (termed “all-cause mortality”). This found the most commonly studied ones had no effect, while some less common ones did have an effect. The review also found some supplements can be harmful.

What did the study find?

The study was a systematic review, meaning the team of researchers examined all relevant research papers (179 in total) and combined the results. The supplements examined included vitamins A, B1 (thiamin), B2 (riboflavin), B3 (niacin), B6 (pyridoxine), B9 (folic acid), C, D, E, beta-carotene, and the minerals calcium, iron, zinc, magnesium and selenium. Multivitamins were defined as including most of these vitamins and minerals.

In studies testing the four common supplements of multivitamins, vitamin D, calcium and vitamin C, there was no reduction in incidence of heart disease, stroke or premature death. This means there was no benefit from taking them, but also no harm.

They also evaluated less common supplements that did have positive impacts on early death, heart disease and stroke. Here they found folic acid supplements showed a reduction in heart disease and stroke.

It was calculated that in order to prevent one case of heart disease or stroke, 111 people needed to be taking folic acid supplements (this is termed the “numbers needed to treat”). For stroke, 167 people would need to take folic acid to prevent one case, and 250 people would have to take B-complex vitamins (which contain folic acid, which is vitamin B9) to prevent one case.

Folic acid was found to have beneficial effects in China where their food is not already fortified. from

Before you rush out to buy folic acid supplements, there are a few cautions. First, there are some concerns that high levels of folic acid in the blood may increase the risk of prostate cancer, although the results are mixed.

Second, of the studies testing folic acid supplements, stroke was reduced in only two of the seven gold-standard studies (called randomised controlled trials). One of these was a very large study of 20,000 people in China. China does not have a folic acid food fortification program, whereas in Australia and the US, it’s commonly added to breads and breakfast cereals.

While a small benefit for taking folic acid was found, researchers also found some adverse effects from supplementation. Among those taking statin medication to lower blood cholesterol, slow or extended release vitamin B3 (niacin) increased the risk of early death by 10%, with a “number needed to harm” of 200. This means 200 people would have to take statins and niacin before we would see one case of early death.

For studies testing “antioxidant” supplements, there was marginally significant increased risk of early death, with a “number needed to harm” of 250 people.

The most studied supplement was vitamin D. Researchers found no benefits for heart disease or stroke prevention, but also no harm. This was a surprise, given vitamin D is commonly taken for other conditions, such as diabetes. But there was no benefit seen for early death, although the study’s authors acknowledged longer follow-up may be needed.

What does it all mean?

The authors concluded there is low-to-moderate quality evidence for taking folic acid for the prevention of heart disease and stroke, and also for taking B-complex vitamins that include folic acid for stroke.

Most people in Western countries don’t have an optimal diet. This review shows taking supplements as an “insurance policy” against poor dietary habits does not work. If it did, there would have been a reduction in early death.

Taking supplements is very different from eating whole foods. Complications or health problems due to nutrient intakes are virtually always due to taking supplements, not eating foods. When you concentrate on one vitamin, mineral or nutrient in a supplement, you miss out on the other phytonutrients found in plant foods that contribute to overall health.

The increase in early death for taking some categories of supplements should be a wake-up call that stronger regulations are needed around supplements, and people need a lot more support to eat better.

The ConversationThe bottom line is we need to eat more nutrient-rich whole foods, including foods high in folate such as green leafy vegetables, legumes, seeds, poultry, eggs, cereals and citrus fruits. Many breads and breakfast cereals in Australia are fortified with folate. Good food sources of niacin (vitamin B3) are lean meats, milk, eggs, wholegrain breads and cereals, nuts, leafy green vegetables and protein-containing foods.

Clare Collins, Professor in Nutrition and Dietetics, University of Newcastle

This article was originally published on The Conversation. .


  • I take a vitamin D every now and then because during the winter I don’t get out much and I cover pretty well because I have fair skin. I’ve come up short a few times in blood tests of the years so now it’s a “haven’t had one of these in awhile” pill.

  • It’s a seriously flawed study. Most likely deliberately done because these flaws had long been pointed out in prior flawed anti-supplement studies. More obvious reason to think it has been intentionally created as a flawed study (which is easy to do with a meta-analysis as this study is) is that the study authors have big vested interests tied to allopathic corporate medicine, a crooked business cartel that makes primarily big money with disease management, using drugs, etc.

    So…. this is mostly the same old propaganda against supplements (disguised as objective straightforward facts) that has been spread among the unwitting public at regular intervals. Propaganda works best if repeated frequently, it’s a prime feature of the advertising business.

    Many of the erroneous twisted accusations and claims against dietary supplements have been quite thoroughly refuted by the real facts (as a good starting point, read the scholarly article “2 Big Lies: No Vitamin Benefits & Supplements Are Very Dangerous” where you will discover the many criminal tricks and shenanigans of the corrupt medical establishment to discredit the use of dietary supplements.

    Gaining a good understanding of this nonsense and politics behind the continuous anti-supplement “studies” and news is worthwhile as not to become a victim of the propaganda disseminated by the immoral anti-supplement zealots.

Show more comments

Log in to comment on this story!