by Graham Colditz, MD, DrPH
Article originally appeared in the Washington University – Institute for Public Health Blog
When it comes to cancer, there are few topics as supercharged as diet. A quick search of “diet and cancer” in Google News alone returns over 3 million stories. And yet, however large these numbers are, they don’t fully capture the passion that many people feel about the food/cancer link. There’s something special, elemental even, about making sure the food we eat is as safe and as healthy as possible – for us and for our loved ones.
Yet, however motivated people are to make healthy food choices, there are a lot of mixed signals out there on what to eat to lower cancer risk. Magazines and websites often tout “superfoods” and “cancer-busters” that rarely match up with official eating recommendations, and even these official recommendations seem to change month to month with the release of new – and often seemingly contradictory – study results.
Trying to decide what to eat can be an exercise in frustration, a sentiment captured perfectly in findings from a 2007 paper on public beliefs about cancer prevention. In this national sample survey, over 70 percent of respondents agreed with the statement that “there were so many recommendations about preventing cancer that it’s hard to know which ones to follow” (1).
The reality, though, is that when all the evidence on the links between diet and cancer are looked at together, clear and simple messages rise to the surface. These messages contain no “superfoods” or “cancer-busters” and, so, may not always lead the headlines. But what they may lack in headline-grabbing flash, they more than make up for by being recommendations based in solid science. And that’s really what matters.
Watch the calories
We see them listed everywhere and so have become inured to them in a way, but calories really matter when it comes to cancer risk. In fact, they’re probably the single most important aspect of diet when it comes to preventing cancer. Consistently eating too much can lead to weight problems. And, among other health risks, obesity is an established risk factor for at least eight different cancers and is responsible for 120,000 cases each year in the United States (2,3).
Over two-thirds of the nation is either overweight (BMI 25 – 29.9) or obese (BMI 30 or over), and studies consistently demonstrate that people have difficulty recognizing if they – or their children – are an unhealthy weight. Add to this the increasingly sedentary lifestyles that go along with modern society, and it takes a concerted effort by most people to moderate calories and keep weight in check over the course of their lives (4). These simple tips can help keep calories and weight in control:
- Avoid sugary drinks, like sodas, energy drinks, and sports drinks. Even 100% juice should be kept to small amounts each day.
- Focus on eating mostly plant-based foods, like whole grains, fruits, and vegetables.
- Be a more mindful eater. Start with smaller portions, eat slowly, and try to eat only when truly hungry.
- Fit physical activity into each day. More is almost always better, but any amount is better than none.
- Weigh your self on most days. It’s easy, keeps surprise weight gain at bay, and helps you make diet/activity adjustments in a timely manner.
Limit food from animals
You don’t need to go full vegetarian – unless you want to – but there’s compelling data that eating fewer animal-based foods can lower the risk of colon cancer, prostate cancer, and possibly breast cancer (5-7). Try to eat fewer than three servings of red or processed meat each week, and choose more plant-based sources of protein and fat, like nuts, beans, and vegetables.
Focus on fruits, vegetables, and whole grains
The data linking fruits and vegetables as a whole with lower cancer risk aren’t as strong as you might think, but there are still a lot of compelling reasons to eat more plant-based foods when you look at individual cancers and specific foods (4,8). For example, diets rich in fruits and vegetables have been shown to lower lung cancer risk. Tomatoes and tomato-based foods have been shown to lower the risk of prostate cancer (8). Diets with a low glycemic load – which typically have fewer refined grains and sugars – lower the risk of endometrial cancer (9). And diets high in fiber can lower the risk of colon cancer 5. Growing data also suggest that eating higher amounts of vegetable protein in youth (from sources like soy, nuts, and vegetables) may improve breast health and lower the risk of adult breast cancer (10). Shoot for at least five servings of fruits and vegetables each day, and at least three servings of whole grains. Keep refined grains (like white bread and white rice) to a minimum.
Drink alcohol in moderation, if at all
Often lost in the messages about the heart-health benefits of moderate drinking are its related cancer risks. Moderate alcohol intake has been shown to increase the risk of colon cancer, with just a few drinks a week increasing breast cancer risk 5. Drinking in youth and young adulthood seems particular hazardous for later adult breast cancer risk (figure) (11).
Older adults who likely stand to benefit from the heart-health benefits of moderate drinking (less than one drink a day for women and less than two for men) probably don’t need to stop drinking. Those adults who don’t drink, though, shouldn’t feel the need to start. Without saying, youth should completely avoid alcohol, and college-aged adults should minimize alcohol and avoid binge drinking, which can lead to problem drinking and other risky behaviors.
Consider a daily multivitamin.
Though it remains a topic of debate, a daily multivitamin is a cheap and potentially powerful nutrition insurance policy (4). When added on top of a healthy diet, the vitamins and minerals in a daily multivitamin may provide added protection against a number of chronic diseases, including cancer. Calcium and vitamin D have been found in key studies to lower the risk of colon cancer. Folate may also lower colon cancer risk, as well as lower the excess risk of breast cancer in women who regularly drink alcohol (12,13). Choose a simple 100% Daily Value (DV) multivitamin, and avoid “mega” vitamins.
The Bottom Line
The food we eat can have an important impact on cancer risk. Key goals are to keep calories in check, eat more plant-based foods, limit red and processed meats, and avoid too much alcohol. A daily 100% DV multivitamin can be a good nutrition insurance policy.
1 Niederdeppe, J. & Levy, A. G. Fatalistic beliefs about cancer prevention and three prevention behaviors. Cancer Epidemiol Biomarkers Prev 16, 998-1003, doi:10.1158/1055-9965.EPI-06-0608 (2007).
2 American Institute for Cancer Research. Updated Estimate on Obesity-Related Cancers, <http://www.aicr.org/cancer-research-update/2014/march_19/cru-updated-estimate-on-obesity-related-cancers.html> (2014).
3 Renehan, A. G., Tyson, M., Egger, M., Heller, R. F. & Zwahlen, M. Body-mass index and incidence of cancer: a systematic review and meta-analysis of prospective observational studies. Lancet 371, 569-578, doi:S0140-6736(08)60269-X [pii]10.1016/S0140-6736(08)60269-X (2008).
4 Willett, W. C. & Stampfer, M. J. Current evidence on healthy eating. Annu Rev Public Health 34, 77-95, doi:10.1146/annurev-publhealth-031811-124646 (2013).
5 World Cancer Research Fund / American Institute for Cancer Research. Continuous Update Project Report. Food, Nutrition, Physical Activity, and Cancers or the Colon and Rectum. (2011).
6 Michaud, D. S. et al. A prospective study on intake of animal products and risk of prostate cancer. Cancer Causes Control 12, 557-567 (2001).
7 Colditz, G. A., Bohlke, K. & Berkey, C. S. Breast cancer risk accumulation starts early: prevention must also. Breast Cancer Res Treat 145, 567-579, doi:10.1007/s10549-014-2993-8 (2014).
8 World Cancer Research Fund/American Institute for Cancer Research. (2007).
9 World Cancer Research Fund / American Institute for Cancer Research. Continuous Update Project Report. Food, Nutrition, Physical Activity, and Endometrial Cancer. (2013).
10 Berkey, C. S. et al. Vegetable protein and vegetable fat intakes in pre-adolescent and adolescent girls, and risk for benign breast disease in young women. Breast Cancer Res Treat 141, 299-306, doi:10.1007/s10549-013-2686-8 (2013).
11 Liu, Y. et al. Alcohol intake between menarche and first pregnancy: a prospective study of breast cancer risk. J Natl Cancer Inst 105, 1571-1578, doi:10.1093/jnci/djt213 (2013).
12 Zhang, S. et al. A prospective study of folate intake and the risk of breast cancer. JAMA 281, 1632-1637, doi:joc81167 [pii] (1999).
13 Zhang, S. M. et al. Plasma folate, vitamin B6, vitamin B12, homocysteine, and risk of breast cancer. J Natl Cancer Inst 95, 373-380 (2003).