When it comes to cancer, here’s what you should sweat and here’s what you shouldn’t

We all want to avoid cancer. That’s a given. But when cancer risk seems to lurk everywhere, it’s hard to know what you really need to do to protect yourself.

The stakes are high. As many as 40% of cancer cases, and about half of all cancer deaths, could be prevented with a healthy lifestyle, according to a study by Harvard researchers published in the journal JAMA Oncology.

So what steps really matter, and which don’t measure up? Here’s a look at what you should sweat over — and not — when it comes to preventing cancer.

SWEAT IT

No smoking zone

Lung cancer is the deadliest cancer in the United States by far, and smoking is the single most obvious and avoidable cause. That’s why so many people are giving up the habit, says Dr. Graham Colditz, a cancer prevention expert at Washington University School of Medicine in St. Louis. By latest count, only 15% of Americans smoke, down from a high of 42% in the 1960s. That’s the good news. But it also presents a challenge: “Four out of five people will have to do something else to reduce their risk,” Colditz says.

SWEAT IT

Weight and see

Extra pounds can raise the risk of at least 13 different cancers, including those of the breast, colon and pancreas. Body fat encourages inflammation, promotes oxidation of cells and weakens the immune system — a recipe for cancer, says Cynthia Thomson, a nutritionist and cancer prevention expert at the University of Arizona in Tucson. Fat in the midsection is especially risky, she says. “Even if your weight is normal, you can be at risk for colon cancer if you have a lot of abdominal fat,” she says.

SWEAT IT

The anticancer workout

A regular workout can give you a definite edge against cancer. “You need to exercise to gain lean mass and lose fat mass,” Thomson says. According to the American Cancer Society, staying active can reduce the risk of more than a dozen cancers, especially breast, colon and uterine cancer. The U.S. Department of Health and Human Services recommends two and a half hours of moderate aerobic activity and one hour and 15 minutes of more vigorous activity every week.

SWEAT IT

Protect your skin

While most cancers are becoming less common, cases of skin cancer — including potentially fatal melanomas — are on the upswing, according to the Centers for Disease Control and Prevention. “Indoor tanning is a part of that story for sure,” Colditz says. He recommends avoiding artificial sunlight and lathering up whenever you’re spending time with the real thing. “Sunscreen is an easy remedy,” he says.

SWEAT IT

Go easy with alcohol

Alcohol can help set cancer in motion by damaging cells in the esophagus, digestive tract and liver. It also raises levels of estrogen, which can encourage breast cancer. The more you drink, the greater the risk. According to the American Cancer Society, men should limit themselves to two alcoholic drinks a day and women should have no more than one.

SWEAT IT

Eat your veggies

“Is there a magic food that’s going to cure cancer? Probably not,” Thomson says. You can’t find a silver bullet in the produce aisle, she says, but there’s no doubt that a diet heavy on fruit, vegetables and whole grains can help control your weight while providing the nutrients your body needs to fight all sorts of diseases, cancer included.

DON’T SWEAT IT

Cellphones

After many years of studies, there’s still no clear evidence that the radiation from cellphones can raise the risk of cancer even slightly, Colditz says. Just as important, nobody has been able to explain how the type of radiation that emanates from cellphones — which isn’t powerful enough to damage DNA — could set cancer in motion. “The biology doesn’t support the folklore,” he says. The National Cancer Institute notes that the incidence of brain cancer has barely budged in the last decade despite the proliferation of mobile devices. That’s a strong sign that we can all live safely with our phones.

DON’T SWEAT IT

Power lines

As with cellphones, the radiation that surrounds power lines is too weak to damage DNA. And even though lots of people live near power lines, there’s no proof that those people are at a higher risk for any type of cancer, according to the National Cancer Institute.

DON’T SWEAT IT

Organics

When shopping for produce, don’t get too hung up on labels, Thomson says. Food doesn’t have to be organic or pulled fresh from the ground to be healthy. “I had a woman call me in tears because she couldn’t find baby carrots that weren’t in a plastic bag,” she says. “I said, ‘Don’t worry. I just want you to eat fruits and vegetables.’ ”

DON’T SWEAT IT

GMOs

Despite all of the fear and furor surrounding genetically modified organisms, the American Cancer Society says that these foods haven’t been shown to cause cancer or any other health problem. In the U.S., GMOs have to meet the same standards of health and safety as any other food product. A study suggesting that genetically modified corn caused tumors in rats made headlines in 2012, but it was widely debunked and eventually retracted. The World Health Organization notes that “no effects on human health have been shown as a result of consumption of such food.” In other words, don’t sweat it.