Lactose intolerance and acne vs. calcium and protein—here's the scoop on whether dairy is actually good for you.

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When's the last time you sat down with a glass of cow's milk? Dairy-though long held as an essential part of a healthy diet-is hitting a downslide. New nondairy milk options are intriguing and numerous: Research from Mintel found that nondairy milk sales have grown 61 percent since 2012. You can now buy almond milk, coconut milk, peanut milk, and even pea milk, just to name a few. Meanwhile, traditional milk sales are dropping.

People are asking, now, more than ever: Is dairy actually healthy?

On the one hand, you hear that milk and dairy are good sources of calcium, so you should consume them. On the other, you're told that drinking milk is unnatural and that humans are the only mammals to drink milk from other mammals, plus it has hormones. To the unnatural point, we are also the only species to build and drive cars, so the line of thinking that compares our behavior to that of other mammals isn't that compelling. As for hormones, there isn't adequate, credible research to support that hormones in milk are causing problems for people.

But there's a lot more to consider. Is dairy actually healthy, or is the plant-based movement worth the hype? Here, the facts.

The Pros of Dairy

High in calcium and vitamin D: Milk is a convenient and concentrated source of both these nutrients, which are essential dietary components for bone health. The recommended daily amount of calcium for an adult under 50 years old is 1000 mg, according to the National Institutes of Health, and an 8-oz cup of milk provides about 300 mg of calcium. Vitamin D helps your body absorb calcium and is a pretty common vitamin to be deficient in. While you can get these nutrients in plenty of nondairy foods (calcium is in seeds, beans, and leafy greens; vitamin D is in salmon, portobello mushrooms, and eggs), research shows that following a dairy-free diet may increase your risk of osteoporosis.

Whey and casein: These are the two proteins found in dairy products. Whey is by far the most popular protein used in protein powders, and casein (a slow-digesting protein) has been gaining popularity over the years as well. Both offer unique benefits regarding amino acid profiles and digestion rates. Whey contains an abundance of branched-chain amino acids, which are key for supporting muscle growth while also helping fight soreness from your workouts. (Research confirms that whey is a powerhouse protein for building muscle.) Between whey and casein, one 8-oz glass of milk packs about 8 grams of protein.

Convenience: Whether you choose sliced cheese, cottage cheese, or Greek yogurt, dairy is an easy way to get in a high-protein snack during the day when you're on the go-something many people struggle with. Plus, restrictive dieting (of any kind) can trigger overeating, unnecessary guilt, or nutrient deficiencies.

The Cons of Dairy

Lactose: This dairy sugar is actually two sugars bonded together. Lactase, an enzyme in your body, breaks that bond so the individual sugars can be digested. But for the 65 percent of the world's population that has a reduced ability to digest lactose (aka lactose intolerance), consuming dairy can disrupt the GI tract and provide fuel for bacteria in the gut, leading to bloating and gas. While the worldwide prevalence of lactose intolerance is pretty high, it's actually significantly lower in the U.S., affecting about 10 to 15 percent of adults (an estimated 30 to 50 million people), according to the FDA. If you notice gas, stomach cramps, bloating, nausea, or diarrhea about 30 minutes to two hours after consuming food with lactose, you may be lactose intolerant. (Related: Can Lactose Intolerance Be Cured?)

Lactose intolerance is tricky, as it's on a sliding scale. Because of varying levels of lactase production by different people, some can't go near milk but can enjoy cheese or yogurt (which have less lactose). Your personal lactose tolerance is very individualized and should be something that you determine by removing dairy and then adding back different types to your diet to see how your body reacts. (And, when in doubt, see a doctor or dietitian for help.) You may discover you have no issue at all with lactose, or you may find that you can't handle the lactose in a glass of milk.

Whey and casein: Yes, whey and casein are both pros and cons for eating dairy. The downside of these proteins is that they're the most common food allergens in infants and young children. The consensus is that you outgrow these allergies, but naturopathic doctor Brooke Kalanick, coauthor of Ultimate You, disagrees. (Related: 10 New Smoothies You'll Love)

"I'm not sure anyone's ever explained the 'outgrowing' aspect to me in terms of good science; it seems like one of those things that just gets passed down and taken as fact. In my practice, I see adults that have low-grade digestive issues such as bloating or irregular bowel movements, but congestion is also very common. Most people don't even complain about it or they don't connect it to the food. Then they come off of dairy and are amazed." It's important to note that a milk allergy is different from intolerance. An allergy involves your immune system, according to the Mayo Clinic.

Acne: "Acne is another huge issue for adults with dairy issues," says Kalanick. Indeed, a growing body of research links dairy with acne, though researchers aren't entirely sure why; some possibilities include the use of growth hormones and steroids in cows used for milk production.

Calories: Milk is often touted in dietary recommendations as somewhat of an elixir of life and something you should have at all your meals. The nutrients in milk are great, but it still contains calories-about 120 in one cup of 2 percent milk. If you drink this three times a day (with breakfast, lunch, and dinner) that's an extra 360 calories, which could be 20 percent of your caloric intake for the day. This is a fair amount of calories to be drinking, and that's assuming you only pour 8 ounces. Perhaps this is why the Harvard School of Public Health's "Healthy Plate" (their alternative to MyPlate) emphasizes drinking water, tea, or coffee (with little or no sweetener) and limiting milk to one or two glasses per day. (Related: The Worst Drinks for Your Body)

The Bottom Line: Is Dairy Healthy for You?

Drinking dairy is an individual choice. Some people experience amazing health benefits from giving up dairy-while others swear by the legit health benefits of milk as enough to keep dairy in their routine.

As Kalanick points out, you may be experiencing some low-grade symptoms of a dairy allergy or intolerance that you don't notice or connect with food. But you won't make the connection until you are symptom-free-so try cutting out dairy for two to three weeks and see how it impacts your body. (Related: What Happened When I Gave Up Dairy for a Year) However, if dairy isn't doing you wrong, there's no need to demonize it.