Milk: Does It Really Benefit Bones?
It’s a fact—humans need calcium and vitamin D to build strong bones. And drinking milk that’s fortified with vitamin D is an easy way to get those nutrients. But does that mean drinking milk will help prevent osteoporosis-related fractures?
If you follow the health news, you may have noticed a report from researchers in Sweden; they reviewed data from more than 100,000 adults and found that drinking three glasses of cow's milk a day did not lower the risk of fracture, and was associated with an increased risk of premature death.
The report follows the publication of a commentary co-authored by Walter Willett, M.D., a well-respected nutrition scientist. In the piece, which was published in 2013 in JAMA Pediatrics, Willett and his coauthor challenge the government’s advice on milk consumption for adults and children. What’s more, some research suggests that consuming a lot of milk and other dairy products may be associated with an increased risk of prostate and ovarian cancers.
If you are at risk for or have osteoporosis, you may be wondering if there’s any good reason to drink milk. Here’s a look at the controversy—and our advice.
A rational recommendation?
The U.S. government, in its Dietary Guidelines for Americans, has long recommended 3 cups (8 ounces) of milk a day for adults. The rationale: Milk provides a wealth of nutrients, including calcium and vitamin D, making it important for bone health. In recent years, the guidelines have recommended fat-free or low-fat milk over whole milk due to concerns about the cardiovascular risks associated with saturated fat.
But Willett and his co-author contend that the recommendation for 3 cups daily—an amount that comes close to supplying the recommended intake of 1,000 to 1,200 mg of calcium a day for adults—is not based on solid scientific evidence. They argue that, in an evolutionary context, animal milk is a fairly new and unnecessary addition to our diet. Indeed many populations throughout the world today consume little or no milk for biological reasons (lactase deficiency), lack of availability, or cultural preferences. And, paradoxically, bone fracture rates tend to be lower in countries that do not consume milk compared with those that do.
Willett is no lightweight. His opinion is informed by his extensive research in this area. For example, he is a co-author of:
• A 2014 study in JAMA Pediatrics that reported that high milk consumption in adolescence, theoretically when the most calcium is needed to promote peak bone mass and prevent fractures later in life, actually raises the risk of hip fracture in men later in life by 9 percent and doesn't reduce the risk in women.
• A 2011 study in the Journal of Bone and Mineral Research that analyzed data from nine studies involving more than 270,000 adults and found that drinking cow’s milk did not appear to protect against fracture in women. There was insufficient data on men to reach a conclusion.
Findings from the Swedish study, which was reported in 2013 in The BMJ, cast further doubt on the role of milk in fracture prevention. The researchers followed 61,433 women, who were age 39 to 74 at the start of the study, on average for 20 years; the 45,339 men in the study were ages 45 to 79 at the start, and they were followed for an average of 11 years. Over the years, the participants completed questionnaires about the foods they consumed, as well as how frequently they consumed them.
The researchers found that consumption of at least three glasses of milk each day (a total of 21 ounces or more) was associated with an increased risk of fracture in women and did not lower fracture rates in men. In addition, women who drank three glasses or more daily had a 93 percent increased risk of dying prematurely compared with women who drank less than one glass per day; men had a slightly increased risk of premature death. The researchers suggested that a compound called galactose found in milk could be to blame: When given to lab animals, galactose promotes premature aging, a shortened life span, and chronic inflammation.
To drink or not to drink?
If fracture prevention is your goal, the evidence suggests that drinking milk is not sufficient. But that doesn’t mean you shouldn’t drink it. Even Willett believes it’s OK to do so; he’s questioning the blanket recommendation for 3 cups per day for most people.
And what about the prostate and ovarian cancer risks associated with milk? While some studies support this, many others have found no increased risk.
Finally, should you be concerned about the increased risk of premature death reported by the Swedish group? The authors themselves advise interpreting their results with caution. That’s because in observational studies such as this one it’s virtually impossible to establish cause and effect. In this case, the findings are based on participants’ reports of their milk intake, which may not be reliable.
If you like milk, pour yourself a glass or two. If you don’t like or can’t tolerate milk, there’s no reason to feel guilty about not drinking it. You can meet your needs by consuming a variety of other foods that are rich in calcium and vitamin D, such as fortified orange juice, sardines, salmon, and soybeans.
Measures you should take to reduce your fracture risk include not smoking, limiting your alcohol intake, and regularly performing resistance exercises to strengthen your bones and balance exercises to lower your likelihood of falling. In addition, if you’re at increased risk for a fracture, talk to your doctor about bone-boosting medications. Unlike milk, some have proved to reduce the risk of various types of fractures.