In short, eating animal-derived foods is not a health risk. Only overconsumption is.
At the public health level, the intensive overproduction practices of industrial-scale livestock and poultry operations pose a unique and novel threat. Recent research conducted by the Johns Hopkins Bloomberg School of Public Health on behalf of the Pew Commission on Industrial Farm Animal Production shows that crowded confinement operations have "amplified opportunities for zoonotic pathogen transmission to humans" and "increased opportunities for the generation of novel viruses." Smaller grass-based animal farms, the Pew Commission concluded, don't pose such risks.
Environmental impacts, too, differ dramatically depending on how and where animals are raised. When farm animals are dispersed rather than concentrated and confined, allowed to graze rather than fed only soy and corn, and integrated into farming operations rather than segregated, they remain healthy and can provide environmental benefits. Under careful stewardship, farm animals can be efficient converters of resources and valuable members of ecological communities.
Moreover, animals, which create high-value foods, often render ecologically sensitive farms more economically viable. Without animals, the movement toward sustainability in U.S. food production would be less likely to flourish.
In considering ethics, it is important to recognize that animals live and die in all kinds of conditions. Whether raised for eggs, milk, or meat, birds and mammals can be treated horribly or humanely. And whether on a ranch, at a slaughterhouse, or in the woods, they can be killed callously, with no concern for their suffering, or killed swiftly and carefully.
As any attentive observer of nature knows, life feeds on life. Every living thing, from mammals, birds, and fish to plants, fungi, and bacteria, eats other living things. Humans are part of the food web; but for the artifices of cremation and tightly sealed caskets, all of us would eventually be recycled into other life forms. It is natural for people, like other omnivores, to participate in this web by eating animals. And it is ethically defensible -- provided we refrain from causing gratuitous suffering.
There is also a practical dimension to consider. Americans are far more likely to stick to a regimen that includes meat, dairy, and eggs, all of them staples of our national diet. Most people have no interest in giving up these foods. Over the past two centuries, various groups -- including religious sects, social reformers, naturopathic physicians, environmentalists, and animal rights advocates -- have promoted vegetarianism in the United States. Yet the diet has never really taken hold. Today, only about three percent of Americans are vegetarian and 0.5 percent are vegan. And surveys consistently show that the vast majority of Americans who do try vegetarianism or veganism -- about three-quarters of them -- return to eating meat. Rather than urging people to consume only plants, doesn't it make more sense to encourage them to eat an omnivorous diet that is healthy, ethical, and ecologically sound?