“Those that can heal can harm; those that can cure can kill.” Celia Rees
Many people believe that taking supplements represents a magic bullet for disease prevention and a longer, healthier life. It’s been estimated that one in two adults take some forms of supplements, and one in six people on prescription medication take at least one dietary supplement daily.
Our love of supplements began in 1970 when the chemist and two-time Nobel Prize winner, Linus Pauling declared that taking 3,000 mg of vitamin C every day may prevent the common cold. He was a devoted vitamin C evangelist promoting that claim for almost two decades with enough determination to drown out all of the studies disproving it. The vitamin C craze began, and by the 1990s the industry was producing a broad range of supplements with increasingly bold claims.
So, what are these dietary supplements?
Supplements are usually products that contain a so-called "dietary ingredient" intended to supplement the diet. They are therefore considered foods, not medications. Most common supplements are vitamins, minerals, herbal products, amino acids and pretty much anything that can be bottled.
The interesting thing is that since supplements are considered foods, not drugs, they are not regulated the same way as prescription or even over-the-counter medications. When we read about a new drug coming up, we hear more about the side effects than the potential benefits. This is because all drugs require rigorous clinical trials for safety, efficacy (the performance under ideal and controlled circumstances), and a proof of effectiveness in a larger population (the performance in the real world). Any drug must pass through each of the three phases successfully before it is eligible for consideration. In addition, the phase three requirement is for two independent studies.
Curiously, none of this applies to supplements. In other words, they don’t need to be tested the same way as drugs.
According to the Nutrition Business Journal, supplement sales have increased by 81% in the past decade. The reason is easy to understand. Since many observational studies have shown a consistent association between greater fruit and vegetable consumption and lower risk of heart disease, cancer and other chronic illnesses, companies started producing supplements that carry out the promise of an easy fix that is more natural and safe than traditional medications.
Vitamin manufacturers argue that a standard diet doesn’t contain enough vitamins, and the more supplements we take, the better. Most of us assume therefore that taking vitamins can be helpful or at least can’t do any harm. Let's go to the research to find out if these assumptions are valid.
In a Finish randomised controlled clinical trial published in The New England Journal of Medicine researchers were looking at how vitamin E and beta-carotene supplementation may influence the risk of lung cancer and heart disease. Scientists enrolled more than 29,000 men, all smokers, giving them a daily dose of vitamin E, beta carotene, both or a placebo. The study found that men taking beta-carotene for five to eight years were more likely to die from lung cancer or heart disease than those who were taking placebo.
A couple of years later the same journal published another randomised clinical trial on vitamin supplementation. In this study, researchers examined more than 18,000 people at high risk of lung cancer due to smoking or asbestos exposure. All participants received a combination of vitamin A and beta-carotene, or a placebo. The study ended when the researchers noticed that the risk of death from lung cancer in people taking the vitamins was 46% higher than in a placebo group.
A large meta-analysis of 14 randomised clinical trials for the Cochrane Database found that supplementation with vitamins A, C, E, beta-carotene, and selenium, taken for intestinal cancer prevention, actually increased mortality.
These findings were confirmed in another large review published in the Annals of Internal Medicine. Scientists studied 19 clinical trials of nearly 136,000 people and found again that vitamin E supplementation increased mortality. The results raised serious concerns, and a few more studies were designed to examine the link between vitamin E supplementation and chronic diseases. One study on people with cardiovascular disease and diabetes found that vitamin E increased the risk of heart failure. Another study published soon after in the Journal of the American Medical Association linked vitamin E supplementation to a higher risk of prostate cancer. Finally, a Cochrane review stated that “beta-carotene and vitamin E seem to increase mortality, and so may higher doses of vitamin A.”
A couple of years ago researchers enrolled more than 14,600 men age 50 years and older to see whether taking multivitamins may lower the risk of cardiovascular disease and cancer. All men were taking either multivitamins or placebo and were followed on average for more than eleven years. The researchers concluded that for the outcome of cardiovascular events taking multivitamins didn't make any difference. Regarding cancer, however, the results were different. It turned out that men who were taking multivitamins had an 8% reduced risk of all kind of cancer.
Since the results were encouraging, researchers started investigating how taking multivitamins may affect other types of cancer, like breast cancer.
A study published recently with 35,000 women was looking at whether the use of multivitamins may be associated with the risk of breast cancer. The outcomes were once again surprising: “these results suggest that multivitamin use is associated with an increased risk of breast cancer” researchers concluded.
The results were confirmed in another study that was looking at the link between the use of multivitamins and the risk of prostate cancer. Men who used multivitamin had doubled the risk of prostate cancer, probably due to zinc content.
Similar results come from many other observational studies which haven’t clearly demonstrated an association between multivitamin use and a lower risk of either cardiovascular disease or cancer. Some studies suggest benefits; other say that supplements pose a risk or have no effect at all. Large-scale, long-term randomised controlled trials on showing whether multivitamins play any role in the prevention of major chronic illness are rather limited.
A 2013 report from the Government Accountability Office (GAO) found that between 2008-2011 the FDA received more than 6,300 reports of health problems from dietary supplements, including 92 deaths, hundreds of life-threatening conditions, and more than 1,000 serious injuries or illnesses. It's worth mentioning that due to underreporting, the real number of incidents may be far greater.
We need to remember that supplements are highly processed substances with a lot of added colours, fillers and allergens. We know exactly what we get when asking for a prescription medicine, but the quality of supplements is often inconsistent due to the lack of manufacturing standards. Often the form of the nutrient may be cheap or poorly absorbed by the body. Many raw products particularly herbs may not be even tested for toxins like mercury.
It’s also very difficult to assess what the optimal dose is or what product to choose. The current regulations don’t require that the dose on the label needs to match the dose in the pill.
Another problem is that most chronic diseases are inherently multifactorial. In other words, we know that there are many risk factors for cancer or cardiovascular disease, hypertension or diabetes and there is no way that supplements are going to be representing all of those factors. Additionally, when nutrients are isolated from whole foods they don’t always act the same way.
We have evolved over thousands of years to eat real, not encapsulated foods. The US Department of Agriculture states that “an adequate and balanced diet should provide necessary nutrients without the need for dietary supplements.”
The idea of an all-in-one pill quick fix only distracts us from the broader importance of good quality nutrition and wiser, more conscious lifestyle choices. As a result, we may not realise that taking supplements could actually increase the risk of cancer or heart disease and do more harm than good. The less we put into our bodies, the better.