Definition: "An ergogenic aid is any substance or phenomenon that enhances performance "

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Put on weight easily? Casein may be better than whey

If you eat whey regularly, your insulin level rises. If you eat casein, it doesn't. But eating casein does cause your IGF-1 level to rise, write nutritionists at the University of Copenhagen in Denmark in the European Journal of Clinical Nutrition.

The Danes did a trial with about sixty boys aged eight. In an earlier study they discovered that the boys' insulin level and IGF-1 level rose if they drank milk. In the new study they wanted to determine which component of the milk is responsible for this. Milk contains two kinds of proteins: the small whey proteins and the large casein proteins. Cheese and quark (quark is also cheese) contain casein.

The researchers got their test subjects to drink a shake every day for a week that contained as much whey or casein as one and a half litres of milk. One group of boys drank a shake containing 11 g of whey protein, the other group drank a shake containing 42 g of casein. The researchers analyzed the boys' blood before and after the trial. The results are shown below.

Put on weight easily? Casein may be better than whey

When the researchers used statistics to filter out the significant effects from the analyses, they noticed that consuming whey proteins on an empty stomach drove up insulin levels by 21 percent. Casein had no significant effect on the insulin level.

But casein did lead to a rise in the IGF-1 level; a rise of fifteen percent to be exact. Whey consumption had no effect on the IGF-1.

Put on weight easily? Casein may be better than whey
The researchers used both mineral-enriched and low-mineral types of whey and casein for their trial. That's how they learned that minerals had no effect.

Now, these researchers aren't sports scientists. They are looking for nutritional factors that determine body height. They think that animal proteins, and especially the proteins found in milk, make children grow taller. But the Danish findings are interesting for athletes as well. No, the 11 g of whey that doesn't lead to a rise in IGF-1 levels and the 42 g of casein that does do this are of no interest to athletes. Probably 42 g of whey is just as effective as 42 g of casein when it comes to IGF-1. What is interesting, though, is that casein doesn't cause such a big rise in the insulin level.

If you want to lose weight, or have a tendency to put on weight, a high insulin level first thing in the morning is not a good thing. It makes you feel hungry and encourages the growth of fat rolls. If that's the case, you may do better to avoid whey as a source of protein.

Eur J Clin Nutr. 2007 May 27. [Epub ahead of print].