Blog Directory - Blogged foodliterate: Dairy - Do or Don't?

Saturday, October 11, 2008

Dairy - Do or Don't?

Much has been said about consumption of dairy products, especially the fat content of dairy products (saturated & trans-fats) these last couple of years, which has led to much confusion about its place in our diet. Personally, I'm pro-dairy, but no one should make a decision based on my feelings so let me share some information with you.

It is true that milk contains saturated fats, in fact, 62% of the fat in milk is saturated. What isn't as widely known is that the saturated fat in milk is different than other saturated fats. The sat fats in milk have very short chain lengths and they follow a distinctive metabolic pathway (how they are used by the body) that differs from other saturated (or even unsaturated) fats. So while it still shows up in the sat fat line on the nutritional panel, its physiological effect is different.

It is also true that milk contains naturally occurring trans fats. For those who haven't read my post: Oh My Omega, I will quickly review a trans fat. All fats with a C=C bond (mono & poly fats) have a configuration, meaning the hydrogen atoms are either attached to the same side or to opposite sides of the double bond. When the hydrogen atoms are on the same side of the double bond, it is called a cis isomer. When the hydrogen atoms are on the opposite sides of the double bond, it is called a trans isomer. Because the carbons on cis isomers are on the same side their chains usually have a "V" shape, but because the hydrogens are on opposite sides of the trans isomers, their chains are straight like saturated fats. Naturally occurring trans fats are produced by biohydrogenation, of the unsaturated fats consumed by the cow, in the rumen aided by bacterial enzymes. (In English - the bacteria living in the cow's stomach convert the polyunsat fat to trans fat by adding a hydrogen atom to the fatty acid chain)

Now, these trans fats are not like the industrially produced trans fats. Where the trans configuration occurs naturally does not look at all like where the trans configuration happens industrially. Where the double bond exists on the carbon chain matters quite a bit to how we metabolize fats. Naturally occurring trans fats in milk are mostly found on the 11th carbon, while industrially produced trans fats are more evenly distributed across many of the carbon atoms. The most common fatty acid found in milk is conjugated linoleic acid (CLA) and of the CLA content in milk, the most common configuration (90% of total CLA) is the c-9, t-11 (cis isomer at the 9th carbon, trans isomer at the 11th carbon).

CLA is of particular interest because of some recent study results. The National Academy of Science in 1996 stated: "CLA was the only fatty acid shown unequivocally to inhibit carcinogenesis in experimental animals". Now, we aren't lab animals but this is a great finding and it started some clinical trials on humans to see if the connection carries to us. What the scientists do know is that the c-9, t-11 isomer is preferentially taken up and accumulated in mammary tissue. This connection is being studied to see if milkfat plays a role in the prevention of breast cancer. CLA is also being studied in regards to heart health. It appears that 3 grams per day has a favorable effect on blood lipid levels (those would be triglycerides, HDL and LDL cholesterol).

So, now you have some information about dairy, and specifically its fats, to form your own position on this nutrient and its place in your diet. I do hope you found this post moooving (couldn't resist) and that you check back to find out what I write about next!

No comments: