Epidemiological data shows that an inverse association between dairy consumption and body weight exists. In addition, both animals studies and human clinical trials show that dairy foods have particular weight loss effects in animals and humans, respectively. The exact reason for the weight loss effects of dairy foods are not fully understood. Some evidence suggests that calcium might be partly responsible for these effects as calcium has been shown to possess anti-obesity effects in humans and animals. However, other factors in dairy foods may explain some or all of the weight loss effect. In particular, milk contains a group of fatty acids collectively named conjugated linoleic acid (CLA) which are structural isomers of the essential fatty acid linoleic acid. Evidence suggests that CLA has anti-obesity effects and supplementation with CLA has shown positive weight loss effects in overweight humans. The CLA content of milk may therefore be an important factor in the body weight of humans who drink milk.
The content of mammalian milk differs based on the diet that the female drinks. Cows are no different in this regard and the food fed to cows significantly affects the content of the milk they produce. Studies have investigated the CLA content of milk and shown that it varies based on the diets of the cows. For example cows fed high oil corn or corn silage produced milk with a CLA content of 3.8 and 3.9 mg/g of total fatty acids1. The CLA content of the milk of the cows was almost doubled from 5.3 mg/g to 8.9 mg/g total fatty acids when a diet of 55 % alfalfa and 45 % grain was supplemented with monensin (an antibiotic for animal feed) and fish meal. Cows fed one third, two thirds or their entire diet from a permanent pasture produced CLA content to their milk of 8.9, 14.3 and 22.1 mg/g total fatty acids. The researchers reported that cows feeding in pasture and receiving no supplemental dietary intake produced 500 % more CLA in their milk compared to typical dairy diets which include both pasture and supplemental feed.
These results suggest that the CLA content of cow’s milk is increased through the use of pasture feeding. Fresh grass therefore appears to be the best food for dairy cows, if the CLA content of the milk is the primary measure of quality. This is not surprising as cows are designed to eat grass, and techniques to increase milk yields have been shown to achieve their goals but often at detrimental cost to the health of the cows and the quality of the milk. As with most farming techniques, the natural way, using humane treatment and traditional farming practices produces the best quality products for human consumption. While organic, pasture fed cows may produce more expensive milk, the extra cost may be justified based on the higher quality of the milk. Of course the CLA content of the diet can be increased through use of dietary supplements, and this has been shown to be an effective way to cause weight loss in overweight humans. Either way happy animals tend to be healthy animals, and these produce significantly higher quality foods.
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