Milk: Is It Beneficial or Detrimental to the Bones?

Once upon a time (in my youth), milk was considered essential to promoting and maintaining good health, strong bones, and a desirable adult height. Now, despite cries of pain from the dairy industry, some researchers are suggesting that too much milk may actually be harmful to the bones. Should we believe that? In recent years, Americans have been consuming less milk than past generations did. Is that good or bad? Let's find out.

Milk: Defense and Attack

Seems like cow's milk needs some defending these days. Reports everywhere support the fact that milk consumptionin the U.S. is experiencing a significant decline. What are consumers drinking instead?  One popular alternative: almond milk; sales of this product are up 39%.  Other plant-based "milk" products are also popular.

The USDA recommends that adults consume 3 cups of dairy a day. The Academy of Nutrition and Dietetics (which represents nutrition professionals) calls low-fat milk "one of the most nutrient-rich beverages available."  And, in late January, in response to a scientific  study that concluded that more than 1 glass of  milk a day might be harmful to adults, the dairy industry began fighting back with its "Get Real" social media campaign on Facebook and Twitter; it has been reminding consumers of the nutritional benefits of milk. 

What are these nutritional benefits? According to WebMD, "The USDA's recommendations are based on the fact that milk is a prime source for three important nutrients: calcium, potassium, and vitamin D (which is added to fortified milk)." The Tufts University Health & Nutrition Letter points out that one 8 oz. glass of low-fat milk contains 305 milligrams of calcium, 117 IU of vitamin D, and more than 8 grams of protein.

But the same Tufts article discusses studies that found NO association between milk consumption and a lower incidence of hip fractures.  Even more damning is the following data from a Swedish study published in the BMJ (British Medical Journal) in 2014. The Tufts Letter summarizes the main conclusions of the Swedish study: "Women who drank three or more eight-ounce glasses of milk a day were almost twice as likely to die during the follow-up period as those drinking less than one glass a day." They were also more likely to develop fractures, especially hip fractures. "Men who drank three or more glasses a day had a 10% higher mortality risk but no association with excess fracture risk."

The Tufts letter explains that, according to the researchers, the culprit may be a simple sugar found in milk---galactose.  (It has also been linked to premature aging in animals.)  This theory is supported by the finding that fermented dairy products (such as sour cream and yogurt), which have much lower levels of galactose, "were associated with a REDUCED risk of fracture and mortality."

How seriously should we take these conclusions? The authors of the study are not recommending that people change their habits and drink less milk based upon these results.  That would be premature since "the literature on this topic is not consistent." The abstract of the study says, "A cautious interpretation of the results is recommended." 

Bess Dawson-Hughes, MD., director of Tufts' HNRCA Bone Metabolism Lab, says, "I don't see any holes in the paper, but it describes associations only and can't be used to infer causality." She also points out that this widely-discussed study does not negate the importance of meeting the body's calcium needs; doing so with food rather than supplements is better.

We asked food scientist Dr. Karin Allen (a member of the Shelf Life Advice Advisory Board) her reaction to the Swedish study. She describes the results as "very interesting" but offered these words of caution. "The conclusions were based upon self-reporting, not clinical studies.  Subjects participating in studies of this type are likely to over-report behavior they consider healthful and under-report behavior they might be embarrassed about.  Also, the results reported are based upon the conclusions of only one study.  Until further studies confirm these results, people should not make sweeping changes in their diet based upon the conclusions."

In short, don't feel that you must cut down on the quantity of milk you consume but realize that you could consume less milk and still get the recommended 1,000-1,200 milligrams of calcium daily.  (See the following section.)

Ways to Meet Calcium Needs

Some people just don't like milk.  Others--those with celiac disease or a sensitivity to dairy--find that milk (and, in some cases, other dairy products as well) make them sick.  As people age, the body may no longer have the enzyme needed to break down the two parts of the sugar in milk (glucose and galactose), so they may have difficulty digesting milk.  One way to deal with this problem is to take lactase, a pill which contains an enzyme that breaks down the lactose in milk so that it's easier to digest.

Here are some  ways to deal with the problems described above and to satisfy the body's calcium needs, recommended by Consumer Reports on Health (January 2015) and by Dr. Allen.

Lactose-free milk (which costs more than regular milk) may be better tolerated than regular milk, although it contains the same amount of galactose, says Dr. Allen.

Fermented dairy products--such as yogurt, sour cream, and some types of cheese--contain less galactose because the bacteria in them use it up.  These may be better tolerated by sensitive stomachs.

Dark green leafy vegetables are a good source of calcium, but it's quite difficult to satisfy all of the body's calcium needs with these.  To quote Consumer Reports: "To get 1,000 milligrams, you'd have to eat a cup of frozen, cooked spinach (292 milligrams); a cup of frozen cooked collard greens (356 milligrams); 3 ounces of canned salmon with the soft little bones (181 milligrams) and a cup of white beans (192 milligrams) every day."  I think all those veggies in one day would give me a tummy ache!  Low-fat yogurt is a better option.

Calcium supplements are not recommended as the sole source for all an adult's calcium needs, but Consumer Reports says this: "Add up the calcium in your diet, and use supplements only to reach your recommended daily intake.  More calcium isn't better and may raise heart-disease risk without providing extra bone benefits."

For an excellent explanation of why the body needs calcium,  what causes osteoporosis, and other matters related to this topic, check out the Harvard School of Public Health article "Calcium and Milk: What's Best for Your Bones and Health?"

Wondering how much milk (or other dairy products) your child needs?  The Internet has many articles on the topic, but Shelf Life Advice suggests asking your child's pediatrician for his/her advice. 

Sources:

bmj.com (British Medical Journal) "Milk intake and risk of mortality and fractures in women and men: cohort studies"

http://www.bmj.com/content/349/bmj.g6015

Karin E. Allen, Ph.D., Utah State University, Dept. of Nutrition, Dietetics, and Food Sciences

Chicago Tribune, Business section, "Hit with attacks, milk industry lobs back at dairy foes," 

Consumer Reports on Health, "What you must know about milk" and "Do you really need dairy, anyway?"  January 2015.

Tufts University Health & Nutrition Letter, "Possible Downsides of Drinking More Milk," 

hsph.harvard.edu "Calcium and Milk: What's Best for your Bones and Health?"

http://www.hsph.harvard.edu/nutritionsource/calcium-full-story/

WebMD.com "The Pros and Cons of Milk and Dairy"

http://www.webmd.com/diet/dairy-truths