Is it Healthy to Eat Meat and Poultry?

Townsend Letter for Doctors and Patients,  Oct, 2001  by Melvyn R. Werbach

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The decision of whether to eat animal meat and poultry is often made on religious or ethical grounds. We will examine the issue on the basis of human health.

Benefits

Animal muscle tissue consists primarily of protein with a varying amount of fat. An adequate protein intake is clearly important to health. Moreover, animal protein is a complete protein source, that is, it contains all the amino acids which are essential for human metabolism.

Meat and poultry are good sources of B vitamins except for folic acid. They are also rich in zinc and, except for veal, in iron. ('Milkfed' veal comes from young calves that are fed nothing but iron-poor milk. This causes anemia and gives the meat a pale color.)

Dangers

Fat and Cholesterol

Meat and poultry contain quite a bit of fat, and about one-third of that fat is saturated. Saturated fatty acid in the diet has been shown to be positively correlated with total blood cholesterol levels, [1] and negatively correlated with (beneficial) HDL cholesterol levels. [2] In fact, plasma cholesterol levels are believed to be more sensitive to saturated fat intake than to dietary cholesterol. [3]

Atherosclerosis is not the only illness that is promoted by a high intake of saturated fat. Saturated fat intake is at least as closely related to arterial and venous thrombosis, and is more closely related to the clotting activity of platelets and their response to thrombin than serum cholesterol. [4] A high intake of animal fat may increase the risk of a number of cancers, including cancer of the colon, breast, prostate and pancreas. [5] Saturated fat intake is also a risk factor for gallstones [6] and dementia. [7]

Meat and poultry are also a source of cholesterol. Using 300 mg of dietary cholesterol as a reasonable daily limit, a small (4-ounce) portion of cooked red meat contains about one-third of that amount -- roughly the same amount as that found in poultry or fish.

Infections

The first case of a cow infected with bovine spongiform encephalopathy ('mad cow disease') was diagnosed in Great Britain in 1986. Since then, variant Creutzfeldt-Jakob disease has been found to be caused by eating infected beef. Widespread safety measures have been taken, yet there is still concern in European countries of contracting this fatal disease. Many other potentially serious infections are possible from eating or handling infected meat or poultry, including infection with salmonella and pathogenic E.coli, yet inspection systems are unable to prevent infected animals from reaching the public. [8]

Drug Exposures

In modem farms, animals are routinely treated with hormones, antibiotics and other drugs [9] Some of these drugs are stored in their bodies, so that consumption of the meat results in human exposure. The consequences may sometimes be unfortunate, such as hormonal effects or the development of antibiotic resistance.

Cooking Hazards

Certain cooking methods add to the health risk. Heterocyclic amines (HCAs) are mutagenic [permanently change gene chemistry] and carcinogenic (cancer-causing) chemicals created when meat, poultry or fish are cooked at high temperatures. Grilling, barbecuing, broiling, and pan-frying are more likely to produce HCAs than baking or roasting because the cooking temperature is higher, while cooking with liquid (boiling, steaming, poaching, stewing, etc.) generates no HCAs. Neither does most microwaving -- although this cooking process affects food composition in a manner that may also be unhealthful. [10,11]

Also worthy of mention are polycyclic aromatic hydrocarbons (PAHs), such as benzo[a]pyrene, since they are also mutagenic and carcinogenic. While our major dietary sources of these substances are usually cereals and vegetables, meat cooked on an open flame produces high levels. [12] This is because, when animal fat drips on aflame, heating element or hot coals, PAHs form which travel in the smoke and land on the food.

Discussion

While beef and poultry are excellent sources of protein, they share a number of potentially adverse health effects. Some of these can be minimized. Beef fat, for example, can be minimized by choosing the leanest cuts of USDA 'select' grade beef, while poultry fat can be minimized by eating white meat (except for wings) and removing the skin. Cooking with liquid can prevent the production of HCAs. Also, the risk of infection can be minimized by washing the hands as well as the countertop after preparing raw meat and poultry, and only eating hamburgers that are thoroughly cooked (i.e. no redness inside). Even so, consumers will have to decide whether their enjoyment of eating these animal foods is worth the dangers.

References

(1.) Caggiula AW, Mustad VA. Effects of dietary fat and fatty acids on coronary artery disease risk and total and lipoprotein concentrations: epidemiologic studies. Am J Clin Nutr 65(suppl):1597S-610S. 1997

(2.) Cobb MM, Teitlebaum H. Determinants of plasma cholesterol responsiveness to diet. Br J Nutr 7l(2):271 82, 1994