I’d wager that the word “cancer” is among the most feared words in the English language, right up there with “shark,” “spider,” and “gluten.”
In all seriousness, most of us do everything in our power to reduce our risk of cancer. Avoid tobacco, be smart about your exposure to sunlight, most of us know the basic steps to take. When it comes to food, however, it’s – as usual – more complicated.
Hundreds of lists exist on the Internet proclaiming which foods prevent or even cure cancer, with an equal number listing supposed cancer-causing foods. If you spend more than a few minutes perusing these lists, you’ll notice there’s a lot of disagreement.
A list of the most controversial foods would include coffee, sugar, red meat, soy, organic foods, and GMO’s. What does the evidence say about these foods?
The first important point is that it’s incredibly difficult to isolate the impact of any one particular food on cancer (or any chronic disease) risk. There are too many variables to consider. A definitive study would need to control for the presence of other carcinogens in the lifestyle (which is a very long list), physical activity level, socioeconomic status, stress levels, and – perhaps most challenging – all the other foods eaten in the diet and the impact they have.
For example, you could analyze two individuals who eat an average of five servings of red meat weekly. Outside of that, however, their diets may be totally different. Fruit and vegetable intake could vary significantly, as could how many cups of coffee they each consume and so on and so forth. Those other variables can easily obscure the impact that red meat can have on cancer risk, making it difficult to measure in research.
Statistical analysis website FiveThirtyEight compiled a list of these types of studies from the American Journal of Clinical Nutrition into a handy graphic, which is shown below:
What do you notice? There are trends here – it’s notable that most of the vegetables and plant-based foods on the list appear to be protective – but the picture is murky. It’s easy to cherry-pick the outliers from the list and write sensational headlines about onions increasing cancer risk or beef lowering cancer risk despite the majority of the evidence being to the contrary. Notice the trend that the majority of these studies actually score closest to “neutral.” This makes sense, given that one single food as a variable generally doesn’t have a great deal of impact.
Another consideration is that obesity is a significant risk factor for many types of cancer. Perhaps one of the reasons the foods at the bottom of this graph appear to be protective against cancer is that they also promote a health body weight? Given their relatively low calorie density (while also being nutrient-rich), that could be a piece of the puzzle.
Soy, which you won’t find on the above chart, is a popular punching bag of many online lists of cancer-causing foods. The reality, however, is that soy appears to be more protective against cancer than not.
Perhaps the lesson that you shouldn’t trust everything you read on the Internet seems obvious. But this is especially true of lists regarding food and cancer. While no one food will cause or cure cancer, here are some tips to remember to limit your risks:
Eat your fruits and vegetables! Aim for three cups daily. Don’t worry as much about whether these foods or organic or non-GMO – these factors aren’t likely to have as much impact as simply getting enough fruits and vegetables, which only 8% of Americans do.
Be aware of food portions. Try not to eat past fullness.
Manage a healthy body weight. This may mean weight loss for some and maintenance for others. Engaging in extreme weight-loss behaviors, however, is counterproductive.
Limit alcohol intake.
Consider the whole picture of your diet rather than focusing on individual foods.
Know that there are many variables outside of nutrition that affect your cancer risk, including genetics, tobacco use, sunlight exposure, and more.