Milk is a white liquid produced by the mammary glands of mammals. All mammals, including humans, will normally produce milk to feed their offspring until they are ready for solid food.
It contains valuable nutrients, and it can offer a range of health benefits. Calcium, for example, can prevent osteoporosis.
However, some people are not able to digest lactose, the sugar in milk, after they are weaned, because they do not produce enough of an enzyme known as lactase. Lactase is needed to digest milk properly.
As concerns about lactose intolerance and milk allergies widen, a range of substitute milks, such as almond and soy milk, have become available.
This article, part of a Medical News Today collection of articles on the health benefits of popular foods, will focus mainly on cow’s milk.
Health benefits of milk
Milk has long been seen as a healthy drink, because it is high in a range of nutrients. The U.S. Department of Agriculture (USDA) guidelines for 2015 to 2020 suggest that Americans should consume “Fat-free or low-fat dairy, including milk, yogurt, cheese, and/or fortified soy beverages.”
However, they also recommend consuming fewer than 10 percent of calories each day from saturated fats, citing butter and whole milk as examples of foods high in saturated fat.
Milk and bone health
Milk is good for the bones because it offers a rich source of calcium, a mineral essential for healthy bones and teeth. Cow’s milk is fortified with vitamin D, which also benefits bone health. Calcium and vitamin D help prevent osteoporosis.
Other ways to improve bone health and reduce the risk of osteoporosis include regular physical activity and strength training, avoiding smoking and eating a healthy diet that is low in sodium and high in potassium. Most of the body’s vitamin D is synthesized by the body on exposure to sunlight, so spending time outdoors is also important.
Some studies have concluded that milk consumption does not improve bone integrity in children.
A seven-year study that tracked the diets and physical activity of adolescent girls, indicated that dairy products and calcium did not prevent stress fractures.
In spite of this, milk and milk products are still considered beneficial for bone development in children.
Milk and heart health
Cow’s milk is a source of potassium, which can enhance vasodilation and reduce blood pressure.
Increasing potassium intake and decreasing sodium can reduce the risk of cardiovascular disease, according to a study led by Dr. Mark Houston, director of the Hypertension Institute at St. Thomas Hospital in Tennessee.
The study showed that those who consumed 4069 mg of potassium per day had a 49 percent lower risk of death from ischemic heart disease compared with those who consumed around 1000 mg per day.
According to the National Health and Nutrition Examination Survey, fewer than 2 percent of US adults meet the daily 4700 mg recommendation.
Potassium-rich foods include cow’s milk, oranges, tomatoes, lima beans, spinach, bananas, prunes, and yogurt. A dramatic increase in potassium intake can have risks however, including heart problems, so any changes in diet or use of supplements must be discussed first with a physician.
Cow’s milk also contains a high amount of saturated fat and cholesterol, which have been linked to an increased risk of heart disease.
Milk and cancer
Vitamin D might play a role in cell growth regulation and cancer protection. Research shows that there is a higher risk of dying from colorectal cancer in geographic locations that receive the least amount of sunlight. Milk, too, contains vitamin D that can offer similar protection.
The National Cancer Institute (NCI) states that “Research results overall support a relationship between higher intakes of calcium and reduced risks of colorectal cancer.” They note, however, that the results of studies have not always been consistent.”
The NCI also points to some studies that suggest an increased intake of calcium and lactose from dairy products may help to prevent ovarian cancer.