Cancer is a group of complex diseases that can have many causes, from genetics to exposure to toxins. A person's diet may also play a role in whether they develop certain types of cancer.
In this article, learn about the links between diet and cancer, as well as what to eat for cancer prevention and recovery.
Studies have not proven that there is a solid link between a specific diet and whether it may increase or decrease a person's chance of getting cancer.
It can be challenging to find direct links between cancer risk and certain foods because people eat a wide range of foods and cook and prepare them in a variety of ways.
Some research, however, suggests that eating certain foods could change a person's cancer risk. These foods include:
A 2018 study of more than 100,000 people concluded that there was a link between consuming ultra-processed foods and a significant increase — more than 10% — of developing some types of cancer.
The authors looked at the consumption of highly processed foods, including:
- packaged breads and buns
- packaged sweet or salty snacks
- sugary drinks
- processed meat products, such as packaged meatballs or hot dogs
- instant soups
- ready meals
- food products made mostly from sugar, oils, and fats
- food products with hydrogenated oils, modified starches, and protein isolates
Red meat and processed meat
Some meats may increase a person's risk of getting cancer.
The authors of a meta-analysis of several studies suggested that regular consumption of processed meat could cause a higher risk of bladder cancer. The authors did not find a link between nonprocessed red meat consumption and bladder cancer.
Processed meats include:
- sliced turkey
- hot dogs
- other deli meats
Other research has found that consuming more than 18 ounces, or three portions, of red meat per week, increases a person's risk of developing colorectal cancer, or cancer that affects the colon or rectum.
There is strong evidence that drinking alcohol can increase a person's risk of cancer in certain areas of the body, including:
- pharynx (throat)
- larynx (voice box)
Although experts do not know precisely why alcohol increases the risk of cancer, it could be due to chemicals in alcohol that damage DNA or weaken the body's ability to process and absorb nutrients.
The American Institute for Cancer Research (AICR) state that alcohol consumption may be even more harmful if a person also smokes cigarettes. They recommend not drinking at all or having no more than two drinks per day for men and one drink per day for women.
More than two-thirds of adults in the U.S. are overweight or obese, according to the National Institute of Diabetes and Digestive and Kidney Diseases.
Experts believe excess weight may cause certain cancers for the following reasons:
- Being overweight can raise insulin levels and insulin growth factor-1 (IGF-1).
- Obesity can lead to chronic inflammation in the body.
- Higher amounts of body fat increase estrogen levels in cells.
- Fat cells may change body processes that have links to cancer growth.
People who are overweight or have obesity may have a higher risk of these types of cancer:
A doctor can help a person determine a healthy weight for them and how to lose weight if necessary. An assessment may start with a body mass index (BMI) calculation and waist measurements.
The strongest evidence for cancer prevention is in a diet rich in fruits and vegetables. Though experts do not know the exact reasons for this effect, they speculate that the phytonutrients that are in these plant foods may help with the following:
- regulating hormones, such as estrogen, which can lead to certain cancers
- slowing cancer cell growth
- preventing inflammation, which can lead to cancer and other diseases
- avoiding damage from oxidants, which alter the body's DNA
Dietary changes cannot prevent all cancers, but eating plenty of nutrient rich fruits and vegetables could help prevent certain types of cancer.
The AICR recommend:
- acai berries
- beans and peas
- chili peppers
- dark green leafy vegetables, such as spinach, kale, and swiss chard
- flaxseeds, ground rather than whole seeds for better absorption
- whole grains, such as brown rice, oatmeal, barley, millet, and in breads
- winter squash
Studies have not found that taking vitamins and other supplements helps reduce the risk of cancer. In fact, some studies showed an adverse effect when people took certain supplements.
The World Cancer Research Fund state that high dose beta carotene supplements may increase the risk of lung cancer. Other research suggests that high doses of vitamin E may increase the risk of prostate cancer.
There is no specific diet for people who have cancer. Each person is different, and their type of cancer and treatment plan is unique.
Some people lose weight during cancer treatment and need extra calories. Other people may wish to try to lose weight to achieve better health during treatment.
Some cancer treatments can make people nauseous or experience other side effects, so they may need to adjust their diet to find which foods do not upset their stomach.
Nonetheless, the American Cancer Society recommend these guidelines for people who are undergoing cancer treatment:
- Try plant based foods in place of meat a few times a week.
- Aim to eat 2½ cups of colorful fruits and vegetables every day.
- Cut back on high fat animal foods, such as processed and red meats.
- Limit smoked, salt cured, or pickled foods.
- Try to eat plenty of nutritious, high protein snacks, including cheese, yogurt, nuts, whole grain cereal, beans, and soup.
- If the person needs extra calories, consider meal replacement shakes and supplements.
A doctor may recommend specific dietary changes to help with symptoms of cancer or the side effects of its treatments.
For instance, some people may need to switch to low fiber foods if they have diarrhea, stomach cramps, or trouble with digestion.
People who have a sore throat may wish to eat foods that are soft and easy to swallow, such as cooked fruits and vegetables.
Eating a healthful diet is not a guarantee that a person will not develop cancer. However, it is a useful way to reduce the risk of many types of cancer and prevent other illnesses, such as heart disease and type 2 diabetes.
With more evidence emerging about the cancer fighting ability of many fruits and vegetables, increasing a person's intake of these foods is a nutritious and safe way to reduce cancer risk.