A quick scan of the news often reveals a zillion things we should all allegedly pay attention to if we want to know how to prevent cancer. You can easily find a handful of articles telling you that coffee is part of a fuck-cancer diet or that it’s now being labeled as a carcinogen. Can you trust the sunscreen? Are those chemtrails in the air? There are fish farting in the water supply, is that a carcinogen too?
Take bacon, for example. In 2015 it was causing cancer, or so I read. In a study that scared the crap out of everyone, it was declared that eating certain types of processed meat daily increased your risk of colorectal cancer by 18 percent. But what the media didn’t take into account before going wild with the story was the real world impact of this 18 percent increase. As the American Cancer Society explains it, your average lifetime risk of developing colon cancer is between about four and five percent, so this “increased risk” means a six percent (instead of five percent) lifetime chance of diagnosis (or, 18 percent more than that original five percent risk). Remember, that’s only if you eat the amount of processed meat in the original study every day, which was 50 grams (so, four slices of bacon) every day. If you like bacon, you don’t have to purge your fridge, just practice some moderation.
So yes, the headlines were technically true, but did that make them useful in terms of understanding cancer risk? I’d recommend a chill pill if all of this has you panicking, but who knows, maybe those are linked to cancer, too.
So amid all the scary headlines the media can conjure, what actually causes cancer?
A 2017 study that looked at the risk for 32 different cancer types in 69 countries concluded that about two-thirds of those cancers were due to random gene mutation, meaning there’s not much you can do to prevent them. As an article in Nature covering the study phrased it, “calculations across 32 cancers indicated that about 66 percent of cancer-driving mutations are due to random DNA replication errors, with only 29 percent due to environmental factors and 5 percent to inherited mutations.” The study authors explained that their results are, “consistent with epidemiological estimates of the fraction of cancers that can be prevented by changes in the environment” and that what they found, “emphasizes that not all cancers can be prevented by avoiding environmental risk factors.”
But if a bunch of cancers are all random, what about all those supplements, the antioxidants, the vitamin C, all the green things Gwyneth Paltrow told you to shove where the sun doesn’t shine? It turns out that there is little evidence to support the idea that these supplements do anything to prevent cancer in humans, and worse, some supplements may increase cancer risk in high doses. Remember when we all went out and got as many antioxidants as we could get our hands on? Green tea is still yummy, but the few randomized controlled trials on antioxidants that have been conducted show that they do nada for cancer prevention.
So, are there any evidence-based things you can do to decrease your chances of getting certain cancers? Absolutely.
1. Get the HPV vaccine.
Ali Wong, one of my favorite comedians, pointed out in her Netflix special Baby Cobra, “everybody has HPV, OK? Everybody has it. It’s OK. Come out already. If you don’t have it yet, you go and get it. It’s coming.(…) I have the kind that’s gonna turn into cervical cancer or I have the kind where my body will heal itself. So, basically, either I’m gonna die or you’re in the presence of Wolverine, bitches.”
Wong and I are about the same age, and we grew up in a generation when becoming sexually active meant two things. The first was that you figured out really quickly how to acquire birth control without your parents knowing. The second was that, inevitably, you got HPV. That shit can't be completely protected against—not with condoms, the Hoover Dam, or even vibranium. It really doesn’t matter what you throw at it, you can get one of the hundred or so strains. Most of those strains do nothing, a few cause warts, and some cause cervical cancer. But there’s good news: The HPV vaccine offers protection against the types of HPV that are most likely to cause cervical cancer. In fact, a new Cochrane review that looked at data involving more than 70,000 girls and women found that the HPV vaccine protects against cervical precancer in women who are vaccinated between between the ages of 15 and 26. The vaccine doesn’t protect against all types of HPV and will not prevent all cases of cervical cancer, but skipping this vaccine for that reason alone is like skipping a seatbelt because it won’t prevent all car related injuries. If you’re a person who intends to have sex…ever…and you like not having cancer, you should probably get this vaccine. Because you could be Wolverine, but do you want to take that chance? The CDC recommends HPV vaccinations for women through age 26 and men through age 21. If you're older and still want the vaccine, talk to your doctor about your specific situation.
2. Listen to Baz Luhrmann and slather on the sunscreen.
UV exposure is the leading cause of skin cancer, and it's also largely avoidable. How do you best do that? Cover up and stay out of the sun (and tanning beds). However, since most of us aren’t vampires living in areas of the world confined to total darkness, let’s talk sunscreen. Research has shown that sunscreen can reduce the incidence of skin cancer and protect against melanoma, the deadliest form of skin cancer, according to the Skin Cancer Foundation. There are less reputable corners of the internet that will try to tell you that sunscreen is actually bad for you, even though studies have provided "overwhelming evidence that sunscreens are safe and effective," according to the Melanoma Research Foundation. Even the American Academy of Dermatology agrees that sunscreen is a safe, effective form of protection from the sun. So, in short, I recommend avoiding those parts of the internet whose recommendations go against, well, science.
For full protection, using sunscreen regularly and correctly is part of a strategy that includes covering up and avoiding the sun during the brightest time of day. Your sunscreen should have an SPF of 30 or higher and protect against both UVA and UVB rays (in other words, it should be a broad spectrum sunscreen). No, you should not rely on just the protection in your makeup, or a moisturizer with SPF if you’re going to be out in the bright sun all day. You should apply about an ounce—that’s enough to fill a shot glass (adjusted for your body size)—every two hours. There’s no good medical reason to let yourself be exposed to enough sun to get a sunburn, so keep your skin—and your longterm health—protected.
3. Cigarettes are bad, mmmkay?
I’ve met people who are obsessed with eating organic everything because they’re scared of cancer and, as a kicker, they enjoy organic cigarettes. Newsflash: Organic cigarettes can still give you some goddamn cancer (perhaps it’s organic cancer?). It’s true that not all cases of lung cancer are caused by smoking. However, the evidence is clear that smoking can cause a host of ailments, including lung cancer.
4. Maintain a healthy body weight
One consistent thing we see in headlines is that some sort of food is causing cancer. High-fat foods. Gluten, probably just because it’s so goddamn delicious. And the rumors just won’t die that sugar causes (or “feeds”) cancer. The American Cancer Society doesn’t directly attribute any one food to causing cancer, not even sugar. However, there there does seem to be a link between body weight and cancer risk. This, of course, does not take all factors about weight into account (body composition, family history, activity levels, etc.). And although a direct link between body weight and cancer has not been shown, obesity does seem to be one (among many) factors that can increase cancer risk, possibly because obesity can lead to inflammation in the body, which can lead to other events that could eventually cause cancer. Also, worth noting is that people can and do absolutely get cancer even if they've maintained a healthy body weight (whatever that means) their whole life. Again, this is an observational risk factor, but it comes up often enough that most experts agree it's worth mentioning as a potentially modifiable risk factor. Regularly gaining and losing weight may also increase cancer risk. If you have questions about this and if your weight or other health markers could put you at long term increased risk for cancer, please speak to your doctor.
5. Drink less booze.
I have teamed up with Big Science to kill all your food- and substance-based joy. Don’t worry, you can keep your caffeine. But according to the American Society of Clinical Oncology alcohol is an established risk factor for certain malignancies. It’s also a group one carcinogen according to the International Agency for Research on Cancer (IARC), meaning there is a clear causal relationship between it and cancer. The exact way that alcohol causes cancer has not been determined, but there are known links between it and several cancers, including cancer of the mouth, throat, colon, breast, and, of course, liver. The American Cancer Society recommends limiting daily intake to two drinks for men and one for women.
6. Work smarter, not harder, with the genetics you were handed.
It’s easy to buy into every new health craze you read about online. Acai berries. Antioxidants. Whatever the fuck kale is supposed to do. But as with so many things, a lot of it is left up to the genetic lottery. Does that mean that you should say “fuck it, hand me a cigarette-flavored cocktail, extra asbestos?” No, but it does mean that you should look at your family medical history for some ideas on how to manage your health in the long term. Family history of an aggressive form of colon cancer at a younger age than standard screening? As unpleasant as that particular exam is, request that your doctor start screenings a bit younger than standard. You had one or both parent with a family history of breast cancer? Look into genetic screening for the BRCA1 or BRCA2 mutation that severely increases your risk for breast cancer, and talk to your doctor early about the preventative measures that are right for you. Not that anybody should smoke ever, but if you have a family history of lung cancer (as I do), you should probably ignore advice from people who say “My grandpa smoked a pack a day and lived to be 105.”
Enjoy your green tea because it’s delicious, but not because you think it’ll prevent cancer. Go enjoy the warmth of summer, but wear your sunscreen. And be wary about the next outrageous media headline telling you that something delicious is killing you, because most things in your fridge just need to be taken in moderation.
Yvette d'Entremont holds a B.S. in chemistry, B.A. in theatre, and a master's degree in forensic science with a concentration in biological criminalistics. She worked for eight years as an analytical chemist before her blog focused on debunking bad science, scibabe.com, turned into a full-time job in science communications. Follow her on Twitter and Facebook.