Curbing Cancer: Dietary Patterns Reduce Risk in Older Adults
By KC Wright, MS, RDN
Vol. 24 No. 7 P. 38
The whole diet is more important than individual nutrients.
The risk of developing cancer varies from person to person based on exposure to both unique environmental influences and lifestyle. Although inherited genetic mutations play a role in about 5% to 10% of all cancers, a range of modifiable environmental and lifestyle factors can help reduce cancer risk.1 The World Health Organization has suggested that almost 40% of all cancers can be prevented with attention to lifestyle, smoking avoidance, limiting alcohol, and exercise.2 As cancer continues to burden our society and health care system, it’s critical to practice intervention to reduce its incidence.
Role of Diet in Cancer
Nutrition epidemiology studies often are subject to measurement error as they have relied on a one-time dietary assessment using a self-reported food frequency questionnaire. Dietary patterns appear to identify the synergistic effects of nutrients in foods on health better than determining the effect of isolated foods or nutrients on disease risk. Eating a healthful diet over time has the potential to reduce cancer risk, particularly colorectal cancer, by 10% to 20%.3 Specifically, a regular diet rich in whole grains, vegetables, fruits, and legumes and lentils should be prescribed to lower cancer risk.4 Strong evidence suggests that sugar-sweetened beverages (soft drinks, fruit punch, lemonade, and sports and energy drinks) are a cause of weight gain, overweight, and obesity—all factors that increase cancer risk. If a whole food, plant-based diet is protective against cancer, then it only makes sense that a diet of fast processed foods contributes to cancer risk. Most of the research on fast foods has considered beef burgers, fried foods, and sugar-sweetened beverages or milkshakes made with saturated fats as characteristic of a typical Western diet.
Red and processed meats are associated with an increased risk of cancer.5 The evidence is most compelling for colorectal cancer, where every 50 g per day of processed meat (for example, one hotdog, three strips of bacon, or 2.5 slices of baloney) consumed increases colorectal cancer risk by 16%; while every 100 g of red meat intake daily—about a 3.5-oz deck-of-cards–sized hamburger—increases colorectal cancer risk by 12%. Processed meat has been altered by salting, curing, fermentation, smoking, or other methods to help preserve the meat or enhance its flavor. All types of mammal muscle are considered red meats, eg, beef, lamb, pork, veal, mutton, horse, and goat.
Most processed meats are made from red meats (eg, salami, ham, hot dogs, chorizo) although other meats can be processed, such as chicken sausage, turkey bacon, and deli turkey. Meat is a good source of some essential nutrients, especially protein, iron, vitamin B12, and zinc; thus, it doesn’t have to be fully excluded from the diet. Rather, the recommendation for red meat in the diet, especially when it comes to cancer, is to limit consumption to about three portions per week, totaling no more than 12 to 18 oz cooked weight.6 In practical terms, this would equate to 4 oz of hamburger, 4 to 6 oz of steak, or four to six slices of pork tenderloin. These recommendations were made to balance the advantages of eating red meat as a source of essential macro- and micronutrients with the disadvantages, specifically risk of colorectal cancer and other noncommunicable diseases.
People who choose not to eat meat at all can obtain adequate amounts of its nutrients through other foods in a healthful diet. Poultry and seafood are healthier protein sources and contain essential nutrients. Plant foods also are healthful alternatives to red meat: Legumes are a good source of protein, iron is found in various plant foods (though it’s less bioavailable than in meat), zinc can be obtained from whole grains, and vitamin B12 is found in fortified foods such as breakfast cereal.
The recommendation concerning processed meat is to consume very little, if any. Martin Wiseman, international medical and scientific adviser to the World Cancer Research Fund, stated, “The evidence on processed meat and cancer is clear-cut. The data shows that no level of intake can confidently be associated with a lack of risk.”7
Coffee is one of the most commonly consumed beverages worldwide. Due to its antioxidant and anti-inflammatory properties, coffee has been suggested to protect against illnesses such as cancer that are precipitated by inflammation. A recent meta-analysis found increased coffee consumption to be associated with a decreased risk of developing both liver cancer and basal cell carcinoma. This same study confirmed an inverse relationship between consumption of dairy foods and colorectal cancer risk.8 Due to dairy’s high calcium concentration, calcium forms insoluble soaps in the colonic lumen by binding to tumor-promoting free fatty acids and bile acids.
Adult weight gain may be the most significant risk factor for postmenopausal breast cancer, as it creates more fat cells in the breast, which are the major source of circulating estrogens that can increase cancer risk over time. Adults gain weight progressively through middle age, and although the average annual weight gain is 1.1 to 2.2 lbs, when accumulated for years, it can lead to obesity. Sustained weight loss after menopause appears to reduce the risk of breast cancer.10 Women over 50 who lost and kept off a modest 5 to 10 lbs of weight over 10 years had an 18% lower risk of breast cancer than did weight-stable women. The risk was 32% lower in women who lost and sustained 20 lbs or more.9
Extra fat mass, as noted by a higher BMI, greater waist circumference, and greater waist-to-hip ratio (WHR), significantly increases the risk for several cancers. Each five-point increase in BMI is associated with a 50% higher risk of endometrial cancer, 48% higher risk of esophageal adenocarcinoma, 30% higher risk of kidney cancer, 30% higher risk of liver cancer, 12% higher risk of postmenopausal breast cancer, 10% higher risk of pancreatic cancer, and 5% higher risk of colorectal cancer. For every four-inch increase in waist circumference, risks of cancers increased by 34% for esophageal adenocarcinoma; 11% for pancreatic cancer, kidney cancer, and postmenopausal breast cancer; 5% for endometrial cancer; and 2% for colon cancer. A healthy WHR is 0.9 or less for men and 0.85 or less for women. Every 0.1-unit WHR increase significantly increases the risk of esophageal adenocarcinoma by 38%, kidney cancer by 26%, endometrial cancer by 21%, pancreatic cancer by 19%, postmenopausal breast cancer by 10%, and colorectal cancer by 2%. During adulthood, every 11-lb increase in weight is significantly associated with a 16% higher risk of endometrial cancer and 6% higher risk of postmenopausal breast cancer.11
This association of obesity with cancer risk resembled recent results from researchers at the University of California San Diego School of Medicine, who used a mouse model to determine that mice fed a Western diet rich in calories, fat, and cholesterol, progressively became obese and developed diabetes and nonalcoholic steatohepatitis (NASH), which progressed to hepatocellular carcinoma and chronic kidney and CVD. The study results showed that by simply changing from the Western diet to a normal chow diet—where calories are derived from proteins and carbohydrates rather than fats—and consuming no cholesterol, NASH and liver fibrosis were improved while cancer progression and mortality were prevented.12
Evidence from a meta-analysis of 52 epidemiologic studies demonstrated that the most physically active subjects had 24% less risk of colon cancer than did those who were the least physically active.13 Another meta-analysis of 31 prospective studies showed that the average breast cancer risk reduction associated with physical activity was 12%, with the strongest protective effect in postmenopausal women.14
Other research suggests that postmenopausal women who increase their physical activity to about an hour of brisk walking per day also may have a lower risk of breast cancer than women who walk for less than an hour a week.15 As patients retire from their jobs, they can become more sedentary by spending extended amounts of time sitting, reclining, or lying down, which may increase cancer risk.16 Specifically, research on sedentary behavior that compared the highest with the lowest levels of sedentary time showed increased risks of endometrial, colon, and lung cancers by a statistically significant range of 20% to 35%.17
In an exercise intervention trial, 320 sedentary postmenopausal women were randomly assigned to perform aerobic activity for 3.75 hours per week or to maintain their usual activity level. After one year, estrogen levels were lower in the increased exercise group, although in other trials, the hormones didn’t change significantly.18 Other randomized controlled trials sought to get postmenopausal women with overweight or obesity to lose weight, increase physical activity, or both.19 Women assigned to decrease calories had estrogen levels drop by 21%, while women who decreased calories and increased exercise had a 26% drop in estrogen. On average, the diet group lost 20 lbs while the diet plus exercise group lost 22 lbs. The exercise group demonstrated additional health benefits of lower levels of insulin and C-reactive protein inflammatory marker.18
In 2018, there were more than 2 million new cases of breast cancer, the most common cancer in women and the leading cause of cancer death worldwide.20 A preliminary report of research presented at a recent meeting of the American Society for Nutrition Excellence in Nutrition Research and Practice found that 350,000 women whose diets were high in foods that cause inflammation had a 12% increase in their breast cancer risk compared with women who consumed more anti-inflammatory diets.21 Inflammation is one of the hallmarks of cancer, with chronic inflammation associated with several types.22 In an almost linear progression, risk of breast cancer increased when subjects moved to a more proinflammatory diet of foods such as red and processed meat, butter, margarines, frying fats, and sugars from an anti-inflammatory diet, including fruits, vegetables, legumes, tea, and coffee. Although many breast cancer studies focus on a single nutrient or food, this research examines overall dietary patterns, emphasizing the importance of the whole diet rather than single components, reflecting an interactive, synergistic, and combined effect of dietary components.23 These new results are based on data from the European Investigation into Cancer and Nutrition study, where diet was assessed for a year with food frequency or diet history questionnaires that were used to calculate an inflammatory score for each subject based on their intake of 27 foods.
Lifestyle has been cited as a very powerful predictor of breast cancer, as the incidence increases when populations move to the United States from low-risk countries such as Japan and China.24 Diets high in antioxidant carotenoids, such as carrots, winter squash, and green leafy vegetables, are associated with a lower risk of breast cancer. Higher blood levels of carotenoids are indicative of increased fruit and vegetable consumption; thus, lower cancer risk benefit also might be explained by a high produce intake and/or a healthful lifestyle.25 Dietary supplements likely wouldn’t have the same preventive influence. The carotenoid effect appears to be beneficial even in genetic variants of breast cancer.
In the PREDIMED trial, researchers gave women aged 60 to 80 extra-virgin olive oil (EVOO) for five years, who demonstrated a 70% lower risk of breast cancer compared with those in a control group. However, this was a small cohort with only eight women in the EVOO group and 17 controls who were diagnosed with breast cancer during the study; thus, more data are needed to determine any influence of EVOO.26 A study of almost 80,000 French women tracked over an average of six years found that those who consumed the most added sugars, more than 10 tsp daily, had a 52% higher risk of postmenopausal breast cancer than did those who ate the least, less than 4 tsp daily.27
The effects of soyfoods on breast cancer have been controversial for years. In a 1996 pilot study, women who ate almost a pound of tofu daily for several months had more abnormal cells in their breasts compared with when they were given no soy.28 As many women began to avoid soyfoods, a larger 2013 study found no difference in abnormal cells.29 In Asian studies, where women’s diets are rich in soy, there was no increase in postmenopausal breast cancer.
According to the 2020–2025 Dietary Guidelines for Americans, older adults may need to supplement their food intake with additional vitamin B12 if it’s not absorbed naturally, along with calcium, vitamin D, and/or vitamin B6 if the diet is insufficient in these micronutrients.30 Certainly, dietary supplements have merit if adequate intake of the micronutrient can’t be achieved through diet alone. Of interest, the use of dietary supplements increases with age, highest among women older than 60 at a usage rate of 80.2%. Moreover, about 25% of adults older than 60 take four or more dietary supplements daily.31 Dietary supplements aren’t approved or rejected by the FDA; rather, they’re aggressively marketed to consumers with messages suggesting healthful promises and downplaying risk. Yet randomized controlled trials have demonstrated that high-dose beta-carotene supplements may increase the risk of lung cancer.6 Other than calcium for colorectal cancer, there’s no strong evidence that dietary supplements can reduce cancer risk. For most people, a healthful dietary pattern is more likely to protect against cancer. In fact, the World Cancer Research Fund and the American Institute of Cancer Research don’t recommend high-dose dietary supplements for cancer prevention.
The consumption of alcoholic beverages has been causally linked to cancers of the mouth, esophagus, colon, liver, and breast.32 In fact, a new study led by scientists from the International Agency for Research on Cancer found that alcohol use causes a substantial burden on cancer, estimating that in 2020, 741,000 new cancer cases were associated with alcohol consumption globally.33 These data indicate that heavy drinking patterns (more than two alcoholic drinks daily) represented the largest cancer burden, 86% of all cases, whereas light to moderate drinking (up to one alcoholic drink daily for women, and up to two alcoholic drinks daily for men) represented 1 in 7 alcohol-attributable cancer cases, accounting for more than 100,000 new cases worldwide. Whether the alcohol is from beer, wine, or liquor, these data prevail. Most recently, an umbrella review of the evidence affirmed alcohol consumption as a major risk factor for several cancers.8 After alcohol is metabolized, it degrades into chemicals that can bind to DNA, resulting in mutations that are potentially carcinogenic. Alcohol can also increase levels of hormones linked to certain types of breast cancer.
Although many people feel that their risk of developing cancer is either related to genetics or chance, much of what’s known today about cancer prevention is associated with lifestyle, of which dietary patterns and nutrition play a large part. There’s much evidence to support that healthful dietary patterns, physical activity, and alcohol moderation can influence an older person’s risk of developing cancer.
— KC Wright, MS, RDN, is a research dietitian advocating for sustainable foods and planetary health eating at wildberrycommunications.com.
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30. US Department of Agriculture; US Department of Health and Human Services. 2020–2025 Dietary Guidelines for Americans. https://www.dietaryguidelines.gov/sites/default/files/2020-12/Dietary_Guidelines_for_Americans_2020-2025.pdf. Published December 2020.
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