If you drink milk to keep your bones strong, there’s good logic in it. Milk and dairy products are concentrated calcium sources, and we know calcium fortifies bones and prevents osteoporosis.
However, a recent study suggests that while some milk may be good, more is not better. In fact, too much milk may be bad for your health.
The study, conducted with over 60,000 women (age 39-74) and 45,000 men (age 45-79) found that too much milk – three or more glasses a day – was not only associated with mortality but also an increased risk of fracture and hip fracture. Researchers found this surprising association after following the men and women in this study for 22 and 13 years respectively. Over this time, study participants completed questionnaires about their milk-drinking habits.
After adjusting for a other variables, they found that women who reported drinking three or more glasses of milk each day nearly doubled their risk of death in relation to women who drank less than one glass each day. Men were not as affected as women, but those who drank three or more glasses of milk each day still showed a significant increase in mortality.
Interpreting the results
Does this mean you shouldn’t drink milk? Don’t go shunning the jug just yet.
There are details to consider in understanding these study results, experts say. While milk and dairy are among the most calcium-rich foods you can eat, there are other substances in milk that may warrant some moderation.
The authors note that D-galactose, found in milk, has been shown to induce oxidative stress damage and chronic inflammation in animals, and such changes have been associated with cardiovascular disease, cancer, bone loss, and muscle loss in humans. They also caution that their findings “merit independent replication before they can be used for dietary recommendations.”
Gail Cresci, PhD, RD, a Cleveland Clinic researcher and dietitian , did not participate in the study but she agrees with the authors’ assessment. She says while the study raises interesting questions, there is not strong enough evidence to warrant a restriction on milk.
The role of vitamin D
She says there are some unanswered questions about the study participants – and whether or not they were lacking in vitamin D.
“Questions about vitamin D stood out to me right away. Calcium is linked with bone health, but vitamin D promotes calcium absorption and maintains adequate blood levels of calcium and phosphate to allow for normal bone mineralization.” Without enough vitamin D bones can become thin and brittle and the formation of strong new bone can be prevented. Vitamin D protects older adults against osteoporosis.
Dr. Cresci says it’s unclear whether or not the milk in the study, conducted in Sweden, was fortified with vitamin D or if a lack of sunlight in that part of the world could have contributed to a vitamin D deficiency.
“Additionally, as the authors point out, they cannot determine if people were taking higher amounts of milk because they were at risk or had osteoporosis and therefore higher risk for fractures anyway,” she says. Her advice? Try to consume 1200 mg of calcium and 600-800 IU of vitamin D daily, especially in winter months.
Dietary sources of calcium
While milk contains 300 mg of calcium/cup, there are many other good dietary sources including cheese, yogurt, greens (collards, kale), soy beans, figs, broccoli, oranges, sardines and salmon (with bones) and many fortified foods.
“If you want to drink milk for strong bones, I recommend no more than one glass a day. Do this in addition to a mixed diet rich in calcium. If you are unable to consume adequate amounts in your diet, consider supplementation, especially in the winter months,” Dr. Cresci says.