Milk and Health
Translate from N Engl J Med 2020; 382:644-654
Cow's milk includes a complex combination of macronutrients, micronutrients, and growth- promoting factors that can contribute to human nutrition; however, all these nutrients can be obtained from other sources (as has been the case in many traditional societies with histori- cally low intakes of dairy products). For adults, the overall evidence does not support high dairy consumption for reduction of fractures, which has been a primary justification for current U.S. recommendations. Moreover, total dairy con- sumption has not been clearly related to weight control or to risks of diabetes and cardiovascular disease. High consumption of dairy foods is likely to increase the risks of prostate cancer and possibly endometrial cancer but reduce the risk of colorectal cancer. It is important to note that the reported health effects of dairy foods de-pend strongly on the specific foods or beverages to which they are compared; for many outcomes, dairy foods compare favorably with processed red meat or sugar-sweetened beverages but less favorably with plant-protein sources such as nuts. Furthermore, no clear benefit of consuming reduced-fat dairy over whole dairy products has been established.
The effects on children of consumption of cow's milk are less clear because of children's greater nutritional requirements for growth, and data are more limited. If mother's milk is not available, cow's milk may provide a valuable substitute in early childhood. Milk promotes growth velocity and greater attained height, which confer both risks and benefits. The high nutrient density of milk can be particularly bene-ficial in regions where overall diet quality and energy intake are compromised. However, in populations with generally adequate nutrition, high consumption of milk may increase the risk of fractures later in life, and the association of greater height with the risk of cancer remains a concern.
In our opinion, the current recommendation to greatly increase consumption of dairy foods to 3 or more servings per day does not appear to be justified. The optimal intake of milk for an individual person will depend on overall diet quality. If diet quality is low, especially for chil-dren in low-income environments, dairy foods can improve nutrition, whereas if diet quality is high, increased intake is unlikely to provide sub-stantial benefits, and harms are possible. When consumption of milk is low, the two nutrients of primary concern, calcium and vitamin D (which is of particular concern at higher latitudes),can be obtained from other foods or supplements without the potential negative consequences of dairy foods. For calcium, alternative dietary sources include kale, broccoli, tofu, nuts, beans, and fortified orange juice; for vita-min D, supplements can provide adequate intake at far lower cost than fortified milk. Pending additional research, guidelines for milk and equivalent dairy foods ideally should designate an acceptable intake (such as 0 to 2 servings per day for adults), deemphasize reduced-fat milk as preferable to whole milk, and discourage consumption of sugar-sweetened dairy foods in populations with high rates of overweight and obesity.