This is a condensed version of part of the article describing the American Cancer Society (ACS) Guideline for Diet and Physical Activity for Cancer Prevention. The full article (including references), which is written for health care professionals, is available online in CA: A Cancer Journal for Clinicians at: https://acsjournals.onlinelibrary.wiley.com/doi/full/10.3322/caac.21591
At least 18% of all cancers and about 16% of cancer deaths in the US are related to excess body weight, physical inactivity, alcohol consumption, and/or poor nutrition. Many of these cancers could potentially be prevented by following the ACS recommendations on nutrition and physical activity.
Follow a healthy eating pattern at all ages
A healthy eating pattern includes:
- Foods that are high in nutrients in amounts that help you get to and stay at a healthy body weight
- A variety of vegetables – dark green, red and orange, fiber-rich legumes (beans and peas), and others
- Fruits, especially whole fruits in a variety of colors
- Whole grains
A healthy eating pattern limits or does not include:
- Red and processed meats
- Sugar-sweetened beverages
- Highly processed foods and refined grain products
In recent years, the effects of dietary patterns on the risk of cancer (and other diseases) have taken on more importance, as opposed to the effects of individual nutrients.
In general, the dietary patterns showing the most health benefits are based mainly on plant foods (including non-starchy vegetables, whole fruits, whole grains, legumes, and nuts/seeds), healthy protein sources (higher in legumes and/or fish and/or poultry, and lower in processed meats and red meat), and include unsaturated fats (such as mono- and polyunsaturated fat). These patterns are also lower in added sugar, saturated and/or trans fats, and excess calories.
Studies have provided consistent and compelling evidence that such healthy dietary patterns are linked with a lower risk of cancer, certain other diseases, and dying at a younger age.
Several components of healthy dietary patterns are also independently linked with cancer risk.
Vegetables and fruits
Vegetables (including beans) and fruits are complex foods, containing vitamins, minerals, fiber, and other substances that may help prevent cancer. Research is being done on the potential cancer-preventing properties of certain vegetables and fruits (or groups of these), including dark green and orange vegetables, cruciferous vegetables (such as cabbage, broccoli, cauliflower, and Brussels sprouts), soy products, legumes, allium vegetables (onions and garlic), and tomato products.
Vegetables and fruits may also lower cancer risk by their effects on calorie intake and body weight. Many vegetables and fruits are low in calories and high in fiber, as well as having a high water content. This may help lower overall calorie intake, and thus help with weight loss and keeping unwanted weight off.
Eating plenty of vegetables and fruits has also been linked with a lower risk of other chronic diseases, especially heart disease.
For cancer risk reduction, the ACS advises following the US Dietary Guidelines, which is to consume at least 2½ to 3 cups of vegetables and 1½ to 2 cups of fruit each day, depending on a person’s calorie requirements.
Legumes (including kidney beans, pinto beans, black beans, white beans, garbanzo beans (chickpeas), lima beans, lentils, and soy foods and soybeans) are rich in protein, fiber, iron, zinc, potassium and folate. They have a nutrient profile similar to that of vegetables and other good sources of protein, and are excellent sources of both.
Whole grains include all of the parts of the original kernel, and therefore have more fiber and nutrients than refined (or processed) grains. Research has shown that whole grains probably lower colorectal cancer risk. In addition, whole grains and foods high in dietary fiber seem to be linked with a lower risk of weight gain and being overweight or obese, which can also contribute to cancer risk.
The US Dietary Guidelines recommends getting at least half of your grains as whole grains. The ACS guideline recommendation to choose whole grains is consistent with these guidelines.
Dietary fiber, found in plant foods such as legumes, whole grains, fruits and vegetables, and nuts and seeds, is probably linked with a lower risk of colorectal cancer, as well as a lower risk of weight gain and being overweight or obese. Fiber can also affect bacteria in the gut, which might also play a role in some cancers.
Studies of fiber supplements, including psyllium fiber and wheat bran fiber, have not found that they reduce the risk of polyps in the colon. Thus, the ACS recommendation is to get most of your dietary fiber from whole plant foods, such as vegetables, fruits, whole grains, nuts and seeds.
Red and processed meats
Red meat refers to unprocessed meat from mammals, such as beef, veal, pork, lamb, mutton, horse, or goat meat, as well as minced or frozen meat. Processed meat has been transformed through curing, smoking, salting, fermentation or other processes to improve preservation or enhance ﬂavor. Examples include bacon, sausage, ham, bologna, hot dogs, and deli meats. Most processed meats contain pork or beef, but they may also contain other red meats, poultry, or meat byproducts.
Evidence that red and processed meats increase cancer risk has existed for decades, and many health organizations recommend limiting or avoiding these foods. In 2015, the International Agency for Research on Cancer (IARC) concluded that processed meat is in Group 1 (“carcinogenic [cancer-causing] to humans”) and that red meat is in Group 2A (“probably carcinogenic to humans”), based on evidence for increased risks of colorectal cancer. Recent studies also suggest a possible role of red and/or processed meats in increasing risk of breast cancer and certain forms of prostate cancer, although more research is needed.
It is not known if there is a safe level of consumption for either red or processed meats. In the absence of such knowledge, while recognizing that the amount of increased risk isn’t certain, the ACS recommends choosing protein foods such as fish, poultry, and beans more often than red meat, and for people who eat processed meat products to do so sparingly, if at all.
Added sugars and other high-calorie sweeteners (such as high-fructose corn syrup) are often used in sugar-sweetened beverages and energy-dense foods (for example, traditional “fast food” or heavily processed foods). They are linked with a higher risk of weight gain and being overweight or obese, which increase the risk of many types of cancer.
Energy-dense and highly processed foods are also often higher in refined grains, saturated fat, and sodium.
The US Dietary Guidelines recommend limiting calories from added sugars and saturated fat, and specifically getting less than 10% of your calories a day from added sugars.
The health impact of highly processed foods is an area of increasing public concern. Some types of processing—such as peeling, cutting, and freezing fresh vegetables and fruit for later consumption—have important health benefits that increase the safety, convenience and taste of foods. But there is a spectrum of food processing, from less processed foods such as whole grain flour and pasta, to highly processed foods that include industrially produced grain-based desserts, ready-to-eat or ready-to-heat foods, snack foods, sugar-sweetened beverages, candy, and other foods that often do not resemble their original plant or animal sources.
Highly processed foods tend to be higher in fat, added sugars, refined grains, and/or sodium, and have been linked with unwanted health outcomes, including cancer, in a small number of studies. Still, up to 60% of the calories consumed per day in US households is from highly processed foods and beverages.
Calcium, vitamin D, and dairy products
Some research has linked diets high in calcium and dairy products to a lower risk of colorectal cancer, and possibly breast cancer as well. However, some studies have also suggested that calcium and dairy products might increase prostate cancer risk. Because the intake of dairy foods may lower the risk of some cancers and possibly increase the risk of others, the ACS does not make specific recommendations on dairy food consumption for cancer prevention.
Vitamin D, which is made by the body when the skin is exposed to ultraviolet (UV) rays, is known to help maintain bone health. Dietary sources include a few foods in which it is found naturally (such as fatty fish and some mushrooms), as well as foods fortified with vitamin D (such as milk and some orange juices and cereals) and supplements. Some studies have suggested a potential role of vitamin D in lowering cancer risk, especially colorectal cancer. However, large studies have not found that vitamin D supplements lower the risk of colorectal polyps (pre-cancerous growths) or cancer.
Most Americans do not get enough vitamin D in their diets, and many have low vitamin D levels in their blood. While the role of vitamin D in lowering cancer risk is still an active area of research and debate, avoiding low vitamin D levels is recommended. People at higher risk of having low vitamin D levels include those with darker skin, those living in Northern latitudes, and those who stay indoors and who do not consume sources of vitamin D.
Dietary supplements are a diverse group of products defined under current US laws and regulations as containing vitamins and minerals as well as amino acids, herbs/botanicals, and other kinds of ingredients. Vitamin and/or mineral supplements can have important health benefits for people who don’t get enough of these micronutrients from foods, or for those with malabsorption disorders.
But many other products that are marketed as dietary supplements are not truly “dietary” because they come from sources other than foods and contain substances not found in foods. They are also not “supplemental” because they do not increase intake of micronutrients that have been scientifically shown to be important for human health. Furthermore, current laws and regulations do not guarantee that products sold as dietary supplements actually contain substances in the quantities claimed on their labels, or that they are free from undeclared substances that can be harmful to human health.
Although a diet rich in vegetables, fruits, and other plant-based foods may reduce the risk of cancer, there is limited and inconsistent evidence that dietary supplements can reduce cancer risk. Further, some studies have found that high-dose supplements containing nutrients such as beta-carotene and vitamins A and E can actually increase the risk of some cancers. Nonetheless, more than half of US adults use one or more dietary supplements.
Many different types of compounds are found in vegetables and fruits, and it’s likely that these compounds work together to have healthful effects. There are likely to be important, but as yet unknown, components of whole foods that aren’t included in dietary supplements.
Some supplements are described as containing the nutritional equivalent of vegetables and fruits. However, the small amount of dried powder in such pills often contains only a small fraction of the levels in the whole foods, and there is very little evidence supporting a role of these products in lowering cancer risk. Food is the best source of vitamins, minerals, and other important food components. If a dietary supplement is used for general health purposes, the best choice is a balanced multivitamin/mineral supplement containing no more than 100% of the ‘‘daily value’’ of nutrients.
At this time, the ACS does not recommend the use of dietary supplements for cancer prevention.
It is best not to drink alcohol
- People who do choose to drink alcohol should have no more than 1 drink per day for women or 2 drinks per day for men.
Alcohol use is the third most important preventable risk factor for cancer, after tobacco use and excess body weight. Alcohol use accounts for about 6% of all cancers and 4% of all cancer deaths in the United States. Despite this, public awareness about the cancer-causing effects of alcohol remains low.
A drink of alcohol is defined as 12 ounces of beer, 5 ounces of wine, or 1½ ounces of 80-proof distilled spirits (hard liquor). In terms of cancer risk, it is the amount of alcohol (ethanol) consumed that is important, not the type of alcoholic drink.
These daily limits do not mean you can drink larger amounts on fewer days of the week, since this can lead to health, social, and other problems.
Alcohol is a known cause of cancers of the:
- Throat (pharynx)
- Voice box (larynx)
- Colon and rectum
Alcohol may also increase the risk of cancer of the stomach.
Alcohol also interacts with tobacco use to increase the risk of cancers of the mouth, larynx, and esophagus many times more than the effect of either drinking or smoking alone.
Some research has shown that consuming any amount of alcohol increases risk of some types of cancer, most notably breast cancer.