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Why Harvard experts have a beef with the new meat guidelines

The final recommendations do not specify limiting consumption of red and processed meats, which have been linked to cancer risk.

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The report of the Dietary Guidelines Advisory Committee, released in February 2015, suggested that the then-forthcoming update to the Dietary Guidelines for Americans adopt several changes from previous versions. It advised limiting added sugars to 10% of calories; removing the ceiling on dietary fats as long as saturated fat comprises no more than 10% of calories; and limiting consumption of red and processed meat.

When the final guidelines were released by the Department of Health and Human Services (HHS) and the Department of Agriculture (USDA) in January 2016, the caveat on red and processed meat was missing. Through that omission, the guidelines “censored conclusions of the scientific advisory committee,” according to a statement on the website of the Harvard T.H. Chan School of Public Health. Dr. Frank Hu, Harvard professor of nutrition and epidemiology, was a member of the federal Dietary Guidelines Advisory Committee, which spent two years reviewing reams of scientific evidence on diet and health and drafting the guidelines that were submitted to HHS and USDA. “Although there are some areas of improvement in this edition over previous ones, some simple but important recommendations are watered down, especially reducing consumption of red and processed meat,” he says.

Dr. Hu notes that the final guidelines suggest consuming a variety of protein foods, including seafood, lean meats and poultry, eggs, legumes, nuts, seeds, and soy products. In that context, red and processed meats can be interpreted as interchangeable with walnuts or soybeans.

Evidence against red meat

The guidelines fail to acknowledge the conclusions of a 2015 report by the International Agency for Research on Cancer (IARC) of the World Health Organization, which labeled red meat—unprocessed beef, veal, pork, lamb, mutton, horse, or goat—a possible carcinogen.

To reach that conclusion, a panel of 22 experts from 10 countries reviewed 700 observational studies that tracked meat consumption and incidence of cancer. The panel determined that limited evidence indicates that red meat consumption is linked to colorectal cancer. If the association between red meat and colorectal cancer is borne out, your risk of colorectal cancer could increase by 17% for every 100-gram (3.5-ounce) portion of red meat you eat on a daily basis. That may sound alarming, but the chance that the average woman will develop colon cancer over a lifetime is one in 22; a daily serving of red meat could increase it to one in 20.

Although red meat has nutritional value—it is high in protein, minerals, and vitamin B12—we’ve been warned away from it for decades because the juiciest cuts are high in saturated fat. However, recent research has shown that, because of certain compounds it contains, even lean red meat poses health risks. Red meat consumption has also been linked to an increased risk of type 2 diabetes and cardiovascular disease.

Heme iron, which gives meat its color, has been linked to an increased risk of coronary artery disease. Other compounds in red meat are transformed into harmful substances down the line—during processing, cooking, and even digestion. Cooking at high temperatures—grilling, frying, or broiling—can generate polycyclic aromatic hydrocarbons and heterocyclic aromatic amines, which are also suspected carcinogens. Recent research indicates that carnitine, which is abundant in red meat, is converted by gut bacteria into TMAO, a compound linked to atherosclerosis.

Evidence that processed meat is linked to cancer risk

Processed meat—for example, hot dogs, ham, sausages, and corned beef—is meat or meat byproducts that have been smoked, salted, cured, fermented, or canned. The IARC panel found sufficient evidence linking processed meat consumption to colorectal cancer to brand it as a carcinogen. Panelists projected that eating a little less than 2 ounces of processed meat a day (the equivalent of two strips of bacon) raised a person’s colorectal cancer risk by 18%.

What should you do?

It’s a good idea to limit yourself to a small serving of lean red meat—preferably roasted, braised, or stewed—two or three times a week. A weekly serving of bacon or sausage is probably safe. But make that bacon cheeseburger an occasional indulgence.

Posted by: Dr.Health

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