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Do supplements prevent cancer or heart disease? No evidence

One of the undying beliefs of some people is that a handful of expensive supplements prevent cancer and heart disease. Outside of a few cases where there is a diagnosed medical need for supplements, the only result of taking them is very expensive urine.

I’ve written a lot about various supplements and their potential to treat or prevent cancer and heart disease, and the evidence is sorely lacking. There are good ways to prevent cancer, like not smoking and getting the HPV vaccine, but not a single one of them includes swallowing a bunch of vitamins.

Recently, the US Preventive Services Task Force (USPSTF) issued draft recommendations on supplements – they were unable to give a single recommendation to any of the supplements that they examined. And as we do here, let’s take a look at what they wrote.

Photo by Anshu A on Unsplash

What is the USPSTF?

To be fair, I had never heard of them until I read their draft recommendations about whether supplements prevent or treat cancer or heart disease. The USPSTF is is “an independent panel of experts in primary care and prevention that systematically reviews the evidence of effectiveness and develops recommendations for clinical preventive services.” 

The task force is a volunteer panel of primary care physicians (internal medicine, pediatrics, family medicine, obstetrics and gynecology, nursing, and psychiatry) with expertise in epidemiology, biostatistics, health economics, and other fields. It is funded, staffed, and appointed by the US Department of Health and Human Services’ Agency for Healthcare Research and Quality.

Among its responsibilities is to review whether preventive medications, such as supplements, work for adults and children who have no symptoms. The task force does not consider costs in its evaluation, and it does not perform cost-effectiveness analyses. In the USA, health insurance companies are required to cover, at no charge to the patient, any service that the USPSTF recommends, regardless of how much it costs or how small the benefit is.

Thus, the USPSTF recommendations carry significant weight in health care treatment options in this country.

The USPSTF grades preventative medications in the following manner.

ARecommendedThere is high certainty that the net benefit is substantial
BRecommendedThere is high certainty that the net benefit is moderate or there is moderate certainty that the net benefit is moderate to substantial
CNo recommendationClinicians may provide the supplement to selected patients depending on individual circumstances
DRecommended againstThe Task Force recommends against this. There is moderate or high certainty that the supplement has no net benefit or that the harms outweigh the benefits
IInsufficient evidenceThe current evidence is insufficient to assess the balance of benefits and harms.

The Task Force bases its evaluations on published clinical studies giving more weight to meta-analyses and systematic reviews, which sit at the top of the hierarchy of biomedical research.

Photo by Candace Mathers on Unsplash

USPTF – supplements to prevent cancer and heart disease

The USPTF issued a draft statement on whether supplements can prevent cancer and/or heart disease. Here’s what they said:

  • They gave D’s (not recommended) to vitamin E and beta-carotene. The USPSTF found that there was adequate evidence that beta-carotene and vitamin E do not reduce the risk of cancer or CVD in healthy populations without known nutritional deficiencies, and that beta-carotene increases the risk of lung cancer and persons at increased risk for this condition. 
  • They gave I’s (insufficient evidence) to vitamin A, multivitamins, vitamin C, folic acid, vitamin B3, calcium and selenium.
  • Vitamin D was a special case because two very small studies showed a reduction in cancer mortality. However, the strength of the study was insufficient to make a recommendation.

Of course, there may be cases where some of these supplements have a purpose that has no impact on prevention of cancer or cardiovascular disease. For example, folic acid supplementation is recommended during pregnancy to reduce the risk of neural tube defects. However, folic acid seems to increase the risk of some cancers.

Vitamin D, which seems to be the supplement of choice these days, maybe useful in those with diagnosed low levels of it. However, the Task Force has previously reviewed screening of vitamin D deficiency in asymptomatic adults and concluded that “insufficient evidence to recommend for or against screening for vitamin D deficiency in asymptomatic adults (I statement).”

Better than supplements. Photo by Sam Abtahi on Unsplash.


So, here we go again. Thorough reviews by real scientists, not grifters like Joe Mercola who are trying to market their useless supplements for profit, have shown that supplements just don’t do much for people without specific conditions that require specific supplements.

The vitamin D data is still too sketchy for the USPTF to make a recommendation, even though there are two studies that may reduce the risk of some cancers. Even if this data is eventually repeated in more robust scientific studies, that doesn’t mean taking huge doses is going to eliminate your risk of cancer. It’s going to be a small reduction, if at all.

Once again, if you want some very expensive urine, go ahead waste your money on these supplements. But if you’re healthy and eat an adequate diet, don’t bother. Take that money and have a nice dinner somewhere.

Michael Simpson

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