cows milk

• Modern dairying methods are cruel to cows and place too great a burden on the environment. Such matters have nothing to do with whether milk is good for you, and I won't address them here. But you should know that human health is not the central issue for many milk opponents.  
• Many people can't tolerate milk, children are often allergic to it, and in many cultures no one drinks milk once weaned. True, but so what? Though most folks of northern European descent can handle plenty of dairy, an estimated 75 percent of blacks, Latinos, and Native Americans--and 90 percent of Asians--don't produce enough lactase, the enzyme needed to digest milk sugar, or lactose. Maybe 1 to 2 percent of children under two are hypersensitive to cow's milk. The antidairy faction sees this as evidence that cow's milk is an unnatural Anglo vice; dairy fans lament that so much of the world is unable to enjoy milk's benefits. Suffice it to say that milk consumption among northern Europeans has a long history, and their low level of lactose intolerance suggests they've adapted. Since you asked, we drink cow's milk because cows are big enough to produce up to 100 pints per day (try that with a rat). As for cats, who cares what's bad for them?  
• Milk causes heart disease. Sure, if you drink whole milk. It's easy enough to switch to the low-fat variety. But milk opponents say: the skimmed fat just gets recycled into ice cream, cheese, and processed foods. Also true--to keep fat consumption under control, you need to stick to low-fat everything, not just milk. 
• Milk causes cancer, diabetes, osteoporosis, and so on. Here we get into murky territory. Some studies say cow's milk promotes breast cancer; others say it suppresses it. Some studies suggest milk is linked to significantly elevated risk of prostate cancer; other says the risk is insignificant or nonexistent. A purported link between milk and diabetes is likewise controversial. Some investigators have found milk protects against colorectal cancer; others say the opposite. In short, research to date has been all over the place. Don't trust blanket statements about little-known dangers or benefits of milk--for example, PETA's claim that milk causes osteoporosis. (For the record, current evidence suggests that young women who drink milk reduce their risk, but that the protective benefit diminishes as they age.) The use of recombinant bovine growth hormone (rBGH) to increase yields has raised concerns that milk may be contaminated with hormone residue, pus from rBGH-related udder infections, antibiotics used to treat those infections, and dangerously elevated levels of a natural growth factor called IGF-1. At this point no human health risk stemming from rBGH use has been demonstrated, but one never knows. 
• All the nutrients milk provides are available from other sources. True, but the typical American diet doesn't include too many of them. To get calcium without consuming dairy products, for example, you're supposed to eat canned salmon or sardines, legumes, kale, broccoli, and other green vegetables, plus calcium-fortified orange juice or soy milk. A determined adult can get the recommended daily dose (1,000 milligrams) this way, but good luck getting a kid to eat all that.

Don't misunderstand--there's a lot to be said for a nondairy diet (assuming you cut down on other animal products too); adults in other cultures get along without milk, and so can you with a little ingenuity. But I wouldn't try giving up milk purely because of the supposed health benefits--and I definitely wouldn't take it away from the kids, who will surely consume enough beer without being told it's good for the planet.