Many studies have linked certain nutrients, foods and food groups to cancer risk.

Calcium and dairy consumption, for example, has been tied to a lower risk of colorectal cancer while drinking coffee is associated with protection against liver cancer.

Yet, individual foods and nutrients can’t account for the complex interactions between the combination of food components that a person regularly eats.

That’s why studies investigating the effect of diet as a whole – dietary patterns – on cancer risk have become increasingly common over the past 15 years. The results of such studies are also more easily translated into dietary recommendations.

Now, a comprehensive review of existing evidence has concluded that adhering to certain dietary patterns can significantly reduce the risk of several cancers.

Here’s a breakdown of the findings, plus tips to help you adopt a cancer-fighting diet.

The study, published in the February issue of the American Journal of Clinical Nutrition, reviewed 74 meta-analyses of prospective observational studies that evaluated dietary patterns and cancer risk. (A meta-analysis combines the results of many studies to draw conclusions.)

The meta-analyses were published from 2010 to 2023. Among them, 23 different dietary patterns were assessed for their effect on the risk of 16 types of cancer.

Associations of dietary patterns with breast cancer and colorectal cancer accounted for most of the meta-analyses, followed by lung cancer, pancreatic cancer and prostate cancer.

For each of the 74 meta-analyses, the researchers evaluated the credibility of the evidence (e.g., convincing, highly suggestive, suggestive, weak). They also graded the quality of the meta-analyses (e.g., high, moderate, low, very low), which indicates the level of certainty in its results.

There was convincing evidence that higher adherence to the 2007 World Cancer Research Fund/American Institute for Cancer Research (WCRF/AICR) dietary guidelines was tied to a significantly lower risk of overall cancer in adults aged 60 and older.

Evidence that following a “prudent” diet pattern lowered the risk of breast cancer was also convincing. A prudent diet is characterized by a high intake of vegetables, fruit, whole grains, pulses (e.g., kidney beans, chickpeas, lentils), fish and seafood.

High adherence to a diet pattern emphasizing vegetables, fruit and whole soy foods (e.g., soybeans, tofu, tempeh soymilk) was also convincingly found to reduce the risk of breast cancer.

There was highly suggestive evidence that the WCRF/AICR dietary advice, as well as the DASH dietary pattern, lowered the risk of colorectal cancer. DASH stands for Dietary Approaches to Stop Hypertension.

Evidence that diet patterns with high inflammatory scores increased the risk of colorectal cancer was highly suggestive, too. Contributors to higher dietary inflammatory scores include added sugars, refined grains, sugary drinks, fried foods, processed meats and red meat.

The evidence that high adherence to the 2007 WCRF/AICR dietary guidelines reduced the risk of all cancers, breast cancer, colorectal cancer and prostate cancer was graded as “high quality,” indicating a high level of certainty of the findings.

It’s estimated that 40 per cent of cancer cases could be prevented by following healthy lifestyle recommendations.

The WCRF/AICR’s cancer prevention guidelines, updated in 2018, include seven specific diet recommendations.

One is to eat a diet plentiful in whole grains, vegetables, fruit and pulses by including these foods in most meals. Doing so will help you achieve the WCRF/AICR’s recommended fibre target of at least 30 g per day.

Consumption of “fast foods” and other processed foods such as snacks, bakery products, desserts and candy should be limited. These foods tend to be calorie-dense and high in refined starches, fats or added sugars.

Red meat (beef, veal, pork, lamb, goat) should be limited to three servings per week, equivalent to a weekly total of 12 to 18 ounces (cooked weight).

Processed meats such as ham, salami, sausage, hot dogs, jerky and bacon should be eaten sparingly, if at all. Processed meats have been altered by smoking, salting, curing or other processes to improve taste or shelf life.

Beverages of choice include water and other unsweetened drinks. Sugar-sweetened drinks such as pop, iced tea, energy drinks and sports drinks, as well as pure fruit juice, should be limited.

Since consuming alcoholic beverages increases the risk for several cancers, even at low levels of consumption, the WCRF/AICR guidelines state that it is best not to drink alcohol.

The WCRF/AICR also recommends to not take supplements for cancer prevention. For most people, regularly choosing healthy foods and beverages is more likely to guard against cancer than supplements.

Leslie Beck, a Toronto-based private practice dietitian, is director of food and nutrition at Medcan. Follow her on X @LeslieBeckRD