Sunday, February 13, 2011

Grass-Fed Beef: Does CLA make the difference? Probably Not.

You certainly have heard of the benefits of the meat of grass-fed, i.e. naturally nourished, cows. Well, although I do not want to question its general superiority to corn-fed high omega-6 meat, it probably is not the CLA content which distinguishes good from not so good meat sources.

A recent study, which was conducted by scientists from the Iowa State University (Brown. 2011), scientists investigated the effect of a "balanced nutritionally complete diet" (31% energy from lipid, 13% from protein, and 54% from carbohydrate) with either high (1.17 g/d) or low (0.35 g/d) CLA content on various health parameters of 18 healthy women aged between 20 to 39 years over a 8 weeks period. These are the results:
The CLA diet did not result in any differences in insulin sensitivity, body composition, circulating blood lipids, or other measured disease risk factors as compared with the control diet.
Accordingly, the scientists concluded "that a diet naturally enriched with over a 3-fold increase in CLA from pasture-fed cattle "did not provide a health benefit when compared to "a similar diet composed of foods from grain-fed cattle."

While these results stand in line with the generally equivocal findings on possible health benefits from CLA supplementation in human beings, it remains questionable whether with a "nutritionally less complete [from a government standpoint]" diet, i.e. a diet with less carbohydrate content and a consequently higher meat consumption, the results would not have been totally different.
Figure 1: Fatty acid composition of grass-fed vs. conventional meats.
All that aside, a study by Irish scientists (McAfee. 2011) showed that the CLA content of grass-fed vs. conventional meat is not all that different, anyway. According to McAfee et al. it is rather the n-3 PUFA content of grass fed meat which "can significantly increase consumer plasma and platelet LC n-3 PUFA status" and may thus have a positive influence on metabolic risk factors in general and n-6 to n-3 PUFA ratio in particular.