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07.01.2010

Milk instead of cola raises IGF-1 level

If you're serious about your exercise, you know you perform better if you eliminate soft drinks from your diet and replace them with low fat milk or buttermilk. Nothing new here. But just in case you still need motivating, Danish researchers have discovered that your IGF-1 level rises if you substitute milk for soft drinks.

Soft drinks are basically water with – if we are to believe the alarming animal and test-tube studies - extra fattening sugars, aroma and colourings. But because we are so gullible we believe all those commercials and drink more and more soft drinks. And less and less milk.

So which is more healthy? Milk or soft drinks? To find out, the researchers, working at the University of Copenhagen, got 11 healthy young men aged between 22 and 29 to drink 2.5 litres of coke daily for 10 days. After that the men drank 2.5 litres of milk each day for the same period of time.

Many fattening foods raise insulin levels and insulin resistance. On that front, both milk and coke scored equally well. Or equally badly, depending on how you look at it. The table below shows that both products had similar effects on the subjects' insulin and glucose metabolism.

But it's a different story when it comes to IGF-1, the most anabolic hormone in your body. If you drink coke your IGF-1 level goes down, as the figure below shows.

Not all IGF-1 in the body is active. It's the IGF-1 that's attached to the binding protein IGFBP3 that's most active. And although the effect wasn't statistically significant, drinking milk did increase the production of this binding protein.

The researchers previously published an article on the effects of milk drinking in eight-year-old boys. In this, the Danes discovered that drinking milk resulted in a big increase in both the IGF-1 and insulin levels. It would seem that dairy products have a stronger growth stimulatory effect on children than on young adults, the Danes concluded.

So from this study it looks as though athletes are better off drinking milk than coke. Apart from the proteins that you find in milk and not in coke, athletes' muscles use IGF-1 to grow and recover after training. However, the researchers are not wholeheartedly positive about the effect of milk on the IGF-1 level. It's true they write, "low levels of IGF-I are associated with cardiovascular disease and type 2 diabetes, osteoporosis and cognitive decline". But on the other hand, "high levels of IGF-I are associated more or less with noncommunicable diseases such as various cancer forms". The researchers do wonder whether it is healthy to drink large amounts of milk.

There are indications that people with high muscle mass have less reason to worry about the damaging effects of high IGF-1 levels, but the evidence is not yet convincing. Rather be safe than sorry? Meat and plant sources of protein raise IGF-1 levels less than milk.

Source:
Br J Nutr. 2009 Oct; 102(7):1047-51.