Possible link between red meat consumption and cancer

Unfortunately for those of us who appreciate a good steak, there is mounting evidence that red meat consumption may contribute to heart disease and cancer. The American Institute for Cancer Research, in cooperation with the World Cancer Research Fund, of which it is a part, recently released a report, five years in the making, entitled Food, Nutrition, Physical Activity, and the Prevention of Cancer: a Global Perspective.

The WCRF/AICR report cites evidence that body fat is directly linked to six cancers, including colorectal and post-menopausal breast cancer. Its first three recommendations advise people to stay lean and then suggest the means for stopping weight gain—primarily diet and exercise. The AICR has published a brochure entitled Guidelines for Cancer Prevention, which the reader can download or order from its web site. The brochure condenses the ten recommendations made by the study to a set of guidelines that advocate attention to diet, maintaining a healthy weight, and obtaining sufficient exercise (at least 30 minutes a day).

The most controversial aspect of the study, however, is that it takes a stand against red meat. The fifth of the study’s ten primary recommendations is, Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats.

Cattlemen choose to differ

In a prepared statement, the National Cattlemen’s Beef Association’s Vice President for Nutrition, Mary K. Young, M.S., R.D., responded, “The WCRF/AICR recommendations about red meat and cancer are unsubstantiated and offer bad advice for consumers. There are volumes of research about the benefits of red meat in a healthy diet that far outweigh anything we’ve seen today.”

Young then went on to cite sources she said had found the opposite of the AICR’s report.

“There is no evidence red meat causes cancer, according to a recent ‘Assessment of Red Meat and Cancer’ by independent scientists,” Young added. “The comprehensive review evaluated every available epidemiological study on red meat and six types of cancer and concluded there was no causal link. How the WCRF review could come to a different conclusion is perplexing,” she said.

However, other studies have reached conclusions similar to the WCRF/AICR report. For example, recent research published in the August 15 issue of the Journal of the American Medical Association found that a Western-style diet rich in red and processed meat, refined carbohydrates and high fat content increased the likelihood of colorectal cancer more than threefold compared to a diet in which little or none of these foods were present. Of course, that study did not single out red meat, but named it as one of a complex of factors.

Research sometimes contradictory

Unfortunately, a lack of specificity in the research goals renders much of the research concerning specific foods, such as red meat, inconclusive. Furthermore, the complexity of the underlying issues seems reflected in the fact that factors seemingly unrelated, such as red meat and diabetes, show a similar correlation with colorectal cancer, according to at least one study.

When multiple unrelated factors correlate positively with various types of cancer, it seems possible that the increase in cancer susceptability shown may be directly related to a hidden or underlying cause that manifests through these same multiple unrelated factors. In other words, diabetes and some forms of cancer may share a common underlying cause in the diet, habits, or environment of the study targets.

Then too, various foods may interact to increase or lessen the likelihood of cancerous outcomes. Specifically, an article published in the November, 2004 issue of Carcinogenesis by researchers at Wageningen University in the Netherlands showed that chlorophyll may prevent the production of carcinogens in the gut that is believed to result from digesting the heme in red meat. Heme is an iron-containing pigment that forms a part of hemoglobin and other iron-containing biological molecules. So, faithfully eating an organic spinach salad with your steak may greatly alter the outcome of your future colonoscopy.

Breast cancer and red meat

A study published in the November 2006 issue of the Archives of Internal Medicine examined the connection between breast cancer and red meat, following more than 90,000 pre-menopausal women over twelve years. (Incidentally, the senior investigator on this study was Dr. Walter Willett, also a co-author of the AICR report.) The results showed that women eating more than three to five servings of red meat weekly have a 14% higher risk of a hormone-receptor breast cancer, while those eating more than five servings a week have a 42% increased risk compared with those who eat three or fewer servings per week. This study was performed on a group of women ranging in age from 26 to 46.

Other studies have shown that as red meat is cooked longer, the likelihood of getting cancer increases, with well-done proving significantly more hazardous than rare.

Clearly, there are studies out there that support both sides of the alleged red meat/cancer link. This is an old dispute, and the combatants leave the average consumer stuck in the middle. It’s possible, too, that both sides are partially right.

hormone-receptor cancers

The correlation between breast cancer and red meat consumption only holds for hormone-receptor cancers, meaning breast cancers whose tumors bind estrogens. What’s more, this is the type of cancer that has been increasing in frequency, as opposed to non-hormone-related cancers. This link causes some observers to suspect that there may be more to the issue than has yet been uncovered.

Specifically, the missing link may be the growth hormones that are fed to cattle to cause them to gain weight more rapidly. Some observers believe organic or naturally-raised beef may be safer, while at the same time, grass-fed—as opposed to grain-fed—beef contains up to five times the beneficial omega-3 fats, which some animal studies have shown to retard growth of cancer cells.

Unfortunately, studies such as those performed by the WCRF/AICR do not distinguish between red meat that is raised organically and red meat from industrial sources. The bulk of commercially raised livestock are fed hormones and antibiotics, not to mention an unnatural grain diet that includes a high percentage of genetically modifiied corn and soy. Assuming meat from such livestock pose an increased cancer risk, this risk will wrongly appear to apply equally to organic and non-organic livestock sources, until such distinctions are incorporated into research studies.

Vegetarianism may not protect against cancer

Then too, the Beef Association is not the only group to take issue with negative findings about red meat. The website for the Weston A. Price Foundation, for example, states that “Vegetarianism does not protect against cancer. In fact, vegetarians are particularly prone to cancers of the nervous system and reproductive organs.”

What’s more, the site proclaims, “Traditional diets, containing animal and plant foods farmed by nontoxic methods, are rich in factors that protect against cancer. Many of these protective factors are in the animal fats.” The Weston A. Price Foundation promotes a diet rich in traditional organic foods, including raw milk and meat from grass-fed livestock.

That site then details a number of cancer-preventing nutrients, many of which are only readily available or are most easily absorbed from animal foods: vitamins A, D, B6 and B12, for example, as well as saturated fats. (The carotenes, precursors to vitamin A readily available in fruits and vegetables, require conversion in the body to become full-fledged vitamin A. Individuals with diabetes, thyroid disease or various other conditions, as well as babies and young children may not be able to promote that conversion. The complete vitamin A is therefore more readily absorbed from animal sources such as cod liver oil.)

Level of acceptance questionable

So the anti-red meat stance of the American Institute for Cancer Research may not receive wide acceptance. Indeed, given the controversies surrounding the claimed link between red meat and cancer, it seems probable that few people will alter their views—much less their practices—regarding red meat as a result of this study. Still, anything that causes consumers to educate themselves on the issues stirred up by the controversy holds hope for future health improvements.

The more mainstream ideas in the report are likely to be well received and are far less controversial. They advocate maintaining a healthy weight and getting adequate exercise, all the while touting the notion that cancer arises as a result of “accumulated life experience.”

One of the study authors, Walter C. Willett, MD, DrPH of the Harvard School of Public Health in Boston, Mass., said, “Whether or not we get cancer has to do with our genes, and with the choices we make everyday. But… our cancer risk is also influenced by our whole accumulated life experience, from conception onwards.” In its second chapter, the study discusses the expression of the genotype (genetic information encoded in the genes) through the phenotype (the individual’s physical body) and elaborates on this concept of accumulated life experience:

Any exposure during the life course that affects the genotype or its expression may also have an effect on the phenotype. At any point in time, the phenotype is related not only to the genotype but also to a host of environmental factors, including nutritional exposures. This accumulated metabolic experience may begin during… [gestation] and proceed throughout a person’s lifetime.

Chapter two of the study further states that “about 5–10 per cent of cancers result directly from inheriting genes associated with cancer, but the majority involve alterations or damage accumulated over time to the genetic material within cells. ”

The study’s final recommendations were, in order:

  1. Be as lean as possible without becoming underweight.
  2. Be physically active for at least 30 minutes every day.
  3. Avoid sugary drinks. Limit consumption of energy-dense foods (particularly processed foods high in added sugar, or low in fiber, or high in fat).
  4. Eat more of a variety of vegetables, fruits, whole grains and legumes such as beans.
  5. Limit consumption of red meats (such as beef, pork and lamb) and avoid processed meats.
  6. If consumed at all, limit alcoholic drinks to 2 for men and 1 for women a day.
  7. Limit consumption of salty foods and foods processed with salt (sodium).
  8. Don’t use supplements to protect against cancer.
  9. It is best for mothers to breastfeed exclusively for up to 6 months and then add other liquids and foods.
  10. After treatment, cancer survivors should follow the recommendations for cancer prevention.

The primary exception to the study’s recommendation to avoid supplements was vitamin D, which the authors acknowledged may need to be supplemented in many individuals.