People have never been more confused over food choices: a growing body of studies add “warning label” to more and more food, making healthy food choices cloudier and consumers warier, not to mention the additional confusion from the food items that used to be wrong but are right now. A study published on March 4 in Cell Metabolism concluded that a high intake of protein from animal sources causes diseases and early deaths. Drawing criticisms already for a wide range of aspects, this study alone may not lead to reduction on protein intake. But if more rounded studies would come out to attack high-protein diet, the pressures on natural resources to supply animal protein can be lessened.
This study, which identified the connection between insulin-like growth factor-1 (IGF-1) and high animal protein intake, was led by Dr. Longo of the University of Southern California over a period of 18 years . The human population in this study are 6,381 U.S. men and women 50-year-old and over using the Third National Health and Nutrition Examination Survey (NHANES III). Mice were also used in the study. Plant-based proteins such as those from nuts and legumes are still good. But animal proteins, including meat, milk and cheese, are found to increase the death risk by 74 percent in people between 50 years old and 65 years old, whose calories consumptions were made up by more than 20 percent of such proteins. An important note is for people over 65 years old the high-protein diet is indispensable for a good health, as researchers think such nutrients help reduce the loss of body weight and muscle mass that occur with aging.
Criticisms for this study are mainly on three fronts. The first is the subjects of the study are all over 50 year old so the conclusion that high-protein diet is bad for middle-aged people only from such narrow age group is inconclusive. The second is the study did not distinguish the sources of red meats when concluding red meats were bad. This distinction is important because Paleo diet avoids factory-farmed, hormone-treated and grain-feed animals, considering them the causes of western-style diet problem. The last is physical activity level was not included as factors impacting health in the study.
Because of these criticism, the recommendation of this study that middle-age people should cut down animal protein intake, particularly red meat consumption, may not lower the demand for meat. But many other studies in recent years did show heavy consumption of read meats is detrimental to health. It is expected more studies would focus on the linkage between high-protein diet and chronic disease not only in U.S. but also in other countries, which grows rich and sees their health care bills soar. The expected attentions and potential attacks on high-protein diet can lead to a reduction on the red meat demand, lessening pressures on natural resources.
The resources needed to produce animal meat are usually way more than people think. The cow in Chick-Fil-A commercials advocating human eat more chicken, is correct on the ground of resource utilization efficiency and greenhouse gas emission. The larger the animal, the less efficient it converts resources into its meat production. To produce one pound of meat, a cow needs eight pounds of feed, while the number for pig and chicken is four and two,respectively. Water is inefficiently used too—producing one pound of grain requires close to 900 gallons of water while one pound of beef needs ten times as much (counting water needed to grow its grain feed). Worldwide, meat provides one third of the protein and accounts for a sixth of the calorific intake, while using approximately a third of crop land, water and grain. Greenhouse gas from animal digestive tracts and land conversions from jungle and forest to pasture land accounts for 8 percent to 18 percent of all greenhouse-gas emissions. And still, the larger the animal, the more greenhouse gas it emits for each pound of protein it produces.
The free-range and grass-fed way to raise animals, as Paleo diet emphasized and as some environmentalists advocated, is not necessarily better than factory-farming in stressing natural resources. Overgrazing has spoiled 20 percent of the pasture worldwide. And factory-farming, when done right, is more efficient and environmental friendlier. A cow in U.S. or Europe, where 70 percent to 98 percent of animal raising are at industrial scale, eats a lot less to produce one pound of protein than a cow in Africa, which has the largest number of traditional animal husbandry. A cow in U.S. or Europe also emits significantly less greenhouse gas comparing to its cousin in Africa. One last improvement is the intensive methods are more effective in turning nutrients in feed into protein production, thus reducing the damaging build-up of nitrogen and phosphorus in soil.
Whether people can agree on high-protein diet is bad for the human health may still be up for debate for now, but there is no disagreement that a reduction on the red meat demand can lessen the pressures on natural resources and is indeed good for the planet. Diseases from domestic animals make more and more headlines and cause increasing concerns. Temporary dips in meat demands happen from outbreak of diseases, but in general it is unlikely the global meat consumption will drop anytime soon, because the rest of the world is catching up with the U.S. in the appetite for meat, which in many countries is a signifier of wealth. The worldwide meat consumption is very likely to double in 2050, even if parts of India remain vegetarian. But the understanding of how resource intensive the meat production is should be beneficial in the discussion of high-protein diet and health, because ultimately the human health is sustained by the health of the natural resources.
Opinion by Tina Zhang