How much does your diet affect your risk for cancer and what role does it play? For decades researchers have looked for foods that lower your cancer risk or plant-based nutrients that are related to higher or lower risks. While studies in Petri dishes and animals have shown promise, most of that promise disappears once the studies are done in humans.

That’s not to say that food doesn’t play a role in cancer risk. In fact, it plays a substantial role in several ways. Research has shown that dietary choices can raise or lower cancer risk when they are spread out over a lifetime. 

Obesity Increases Cancer Risks

Take body weight, which is heavily influenced by diet. If you’re overweight or obese – nearly 70 percent of Americans fall into one or the other category — then you have an elevated risk for cancer. Excess body weight is thought to be responsible for about 11 percent of cancers in women and 5 percent of cancers in men – and 7 percent of all cancer deaths, according to the American Cancer Society.

Being overweight or obese raises your risk for breast, colon, kidney, liver, ovarian, pancreatic, stomach, thyroid, gallbladder, endometrial and esophageal cancers among others. 

Is a Poor Diet a Contributing Factor?

There is strong evidence to show that a poor diet and lack of exercise (which can lead to obesity) is potentially a contributing factor to increased risks. Beyond weight, diets rich in red and processed meats can raise your risk of colon cancer. A 2019 study found that people who eat red or processed meats four or more times a week had a 20 percent higher risk of colon cancer than those who eat it less than twice a week. 

Alcohol

Alcohol consumption was linked to 740,000 cancer diagnoses worldwide last year alone (particularly esophageal, mouth, colon, rectum, liver and breast cancers), despite studies that suggest red wine may offer a protective effect. Most of these cases were in people characterized as heavy or risky drinkers.

What Kind of Diet Helps Prevent Cancer?

But not all of this is bad news. Diets rich in fruits and vegetables – which can help you maintain or lose weight – have been shown to reduce cancer risk. Multiple studies have linked the Mediterranean diet (which isn’t vegetarian but still heavily tilted towards plants) to lower cancer risk. 

Why? Researchers point to fiber in plants that may reduce the risk of breast and colon cancer. Antioxidant and anti-inflammatory nutrients in plants and fruits may also be protective against the types of cell damage that lead to cancer. Plant-based diets can also help you maintain or lose weight, which may reduce cancer risk. 

Even if you’re not willing to fully adopt a traditional plant-based diet, research suggests that a healthy eating pattern can help you protect yourself from cancer. According to the American Cancer Society, you should eat:

• Foods rich in vitamins, minerals and other nutrients.
• Foods that are low-calorie so you can stay at a healthy body weight.
• Colorful vegetables – dark leafy greens and cruciferous veggies, red peppers and tomatoes and orange foods like pumpkin, carrots and sweet potatoes. 
• Legumes and peas rich in fiber.
• A variety of fruits
• Whole grains and brown rice. 

Meanwhile, avoid or limit foods like red meats (including pork and lamb), processed meats (like bacon and sausage), sugary beverages and highly processed foods. 

Finally, reduce or eliminate alcohol consumption. The more you drink alcohol, the greater your cancer risk.