Jan 29, 2015No Skim For The Slim
By James L. Harris III, MS, RD, SCCC
Many have heard the slogan “Milk does the body good.” But does that mean all forms of milk?
In today’s health conscious society skim milk has become very popular because of the absence of fat and presence of valuable nutrients like Calcium and Vitamin D. It has become a staple in the diets of top athletes and body builders around the world and prescribed by doctors, trainers and sports nutritionist for those with bone issues like breaks, and stress fractures. The question that should be asked is why choose skim over other milk sources that contain fat? Does an athlete’s milk choice contribute to their risk of bone issues? Are health professionals ignoring basic nutrition principles when prescribing skim milk?
To answer these questions we must closely examine skim milk and its nutritional composition. Skim milk is made by processing whole milk, which has about 8g of fat. In the old days the milk was allowed to settle and the fat or cream would rise to the top. At this point all of the fat would be “skimmed” off to produce a non fat beverage. Currently whole milk is spun at very high speeds to separate the milk from the fat. According to the label, an 8-ounce glass of skim milk contains about 85 calories, 8g of protein, 12 g of carbohydrate and 0g of fat. The label also boasts that 30 percent of calcium and 25 percent of vitamin D needs can be met based upon a 2000-calorie diet. This translates out to be about 300mg of Calcium and 100 IU of Vitamin D. Compare this to the fat content of other form of milk it is no wonder why athletes and even health professionals choose skim milk.
At first glance most think all athletes should include this nutritional beverage in their training routines as a way to follow a regimen of reduced dietary fat intake. This would be true if we were only looking for a good source of protein and carbohydrate but many look to skim milk to maintain bone health. If bone health is the motivation for incorporating dairy into the diet we must look at Vitamin D. This Vitamin can be produced by the body in the presence of the sun in most instances and is essential in the absorption of Calcium. In fact, it is so essential that it’s fortified in most milk products because natural production can be hampered by climate, exposure to the sun and other factors.
It is well known that Vitamin D enhances the absorption of Calcium but what macronutrient is needed to absorb Vitamin D? The answer is FAT! Vitamin D is a fat soluble vitamin bound to the milk protein and absorbed in the intestine. When the fat is removed from milk this chain of dependence is broken. Some calcium is still absorbed but simple logic can see the importance of dietary fat during this process.
Part of being a lean athlete is incorporating a low fat diet with a challenging exercise routine. This combination produces individuals with low subcutaneous fat. In these athletes we must be careful that their dietary fat intake is not too low as to interfere with Vitamin D absorption and normal hormone production. Regardless of sex this process can lead to the elements of the female athlete triad. Disordered eating can be unintentional as the athletes are simply trying to eat healthy to improve performance. Low dietary fat leads to decreased fat intake, poor hormone production, reduced vitamin D and Calcium absorption and possibly irregular menstrual cycles in females. This leads to poor bone health and ultimately to injuries.
Part of the solution may be found in prescribing 1 percent milk as an alternative to skim milk to athletes who participate in sports that are notorious for stress fractures like track and field and cross country. The switch may also be beneficial in athletes who exhibit very low body fat percentages like those found in the at risk sports. Of course, this hypothesis needs more research but has seen some anecdotal success in practice with college and professional athletes. Milk should also be purchased in cardboard containers as light can damage the structure of Vitamin D. Another interesting suggestion would be to add healthy fats like Fish and olive oils that contain Vitamin D to these athletes’ regimens to aid in healthy hormone production, Vitamin D and Calcium absorption and maybe even bone health.
James L. Harris III, MS, RD, SCCC, is Assistant Athletic Director for Student Athlete Development at the University of Oregon.