8 Things You Think Prevent Cancer—but Don’t

Updated: Nov. 19, 2018

You’ll be surprised to find out which common “cancer-fighting” habits aren’t nearly as effective as you think

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Taking vitamin D supplements

Because cancer patients tend to have low levels of vitamin D, researchers have wondered whether getting the “sunshine vitamin” in pill form could protect against cancer. But a study of 2,300 healthy postmenopausal women showed that after four years, those who had supplemented with vitamin D3 and calcium didn’t lower their risk of cancer.

Those results were confirmed in an even larger study in the New England Journal of Medicine a year later. Researchers at Brigham and Women’s Hospital and Harvard followed more than 25,000 healthy adults over about five years and found that vitamin D was no better than a placebo at protecting against cancer or cancer-related deaths. There was some evidence that vitamin D might protect people with a healthy BMI but not overweight people, but that was before the researchers factored in other things like age and sex. Find out 15 things oncologists do to prevent cancer.

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Taking fish-oil supplements

In a partner study to the 25,000-person trial, the Harvard University and Brigham and Women’s Hospital researchers also gauged whether omega-3 fatty acids offered any protection against invasive cancer. After five years, they found no significant differences in cancer rates or cancer deaths between those who took fish oil and those who didn’t.

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Taking vitamin E supplements

Because vitamin E is an antioxidant, researchers have suspected that it might offer protection against cancer. For ten years, 14,600 male doctors took either vitamin E, vitamin C, or a placebo and kept tracking their health status for another four years. Neither vitamin offered evidence of protecting against prostate cancer or any other type of cancer, according to the results. Those findings were repeated in a later trial of more than 35,000 men, which found that vitamin E was no better than a placebo at protecting against tumors. Don’t miss these 30 simple ways to prevent cancer.

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Eating organic food

Clean eaters might have been excited to see headlines about a study that linked organic food to a decrease in cancer rates. About 69,000 French adults reported how often they ate organic food, and researchers tracked how many of the participants got cancer. After seven years of follow-ups, the results showed that the more organic food people ate, the lower their risk of cancer. That sounds promising enough, but the results weren’t applicable to everyone—notably, the cancer risk for organic eaters didn’t change among men, younger adults, or people with overall high-quality diets.

Another, even larger study didn’t find a connection between how often 623,000 British women ate organic foods and their risk of cancer. What’s more, an analysis of more than 6,000 studies found no health risks associated with GMO corn. There’s a good chance that people who choose organic happen to be healthier in other ways that have a bigger impact on their cancer risk. Organic or not, load up on these 30 foods proven to help fight cancer.

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Getting every cancer screening possible

Having your doctor test for certain types of cancer won’t keep the disease from appearing in the first place, of course, but you might wonder, can being screened catch it early and improve your prognosis? Not necessarily. While a handful of cancer screenings—breast cancer in women 50 and older, cervical cancer in women younger than 65, colorectal cancer in adults ages 50 to 75, and lung cancer in smokers between 55 and 80—do help doctors find and treat the disease earlier, the same doesn’t necessarily hold true for other types of cancer. Unless you have risk factors or symptoms, the CDC recommends against screening for ovarian, prostate, thyroid, testicular, or pancreatic cancer because it hasn’t been shown to improve death rates.

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Drinking red wine

The jury is still out on this one, but health experts agree that you shouldn’t pick up a wine habit in the name of health. While resveratrol—an antioxidant found in red wine—has shown some promise in protecting against cancer, experts say that’s not a green light to drink the red beverage. Studies have also shown that wine drinkers aren’t protected against prostate cancer, ovarian cancer, or colorectal cancer. And in general, even light to moderate amounts of alcohol could slightly raise your risk of cancer, according to a BMJ study. America’s official Dietary Guidelines recommend having no more than a drink (for women) or two (for men) per day and discourage people from starting to drink to gain any potential health benefits. Learn the truth about 29 things you think cause cancer—but don’t.

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Giving up coffee

Some coffee addicts may have been nervous in spring 2018 when California considered putting cancer warnings on coffee products. When coffee beans are roasted and brewed, a likely carcinogenic chemical called acrylamide forms. But the FDA argued that a cancer warning would mislead customers because the acrylamide levels were too low to pose any threat. In fact, a 2016 analysis of 31 studies found that the more coffee people drink, the lower their risk of dying from cancer, as long as they don’t smoke. Learn the truth behind these other 50 cancer myths you need to stop believing.

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Eating an alkaline diet

Blood naturally skews on the alkaline side (the opposite of acidic) of the pH scale, and early evidence suggested that cancer cells are found in acidic environments. Those two factors led to claims that eating an “alkaline diet” and avoiding high-acid foods like sugar, dairy, fruits, and wheat could stop tumors in their tracks. But no studies have been able to establish a link between alkaline diets and cancer prevention, and a deeper look at the science could reveal why.

For one thing, cancer cells seem to create an acidic environment rather than vice versa, integrative oncologist Mitchell L. Gaynor, MD, told Cure magazine. But perhaps more telling, what you eat won’t affect your blood’s pH levels, which your body does a good job keeping steady. Instead, a high-alkaline diet would probably change the acidity of your saliva and urine, which are unrelated. Instead, try these 37 science-backed ways to prevent cancer.