Course of quercetin raises metabolism

The flavonoid quercetin [structural formula below] temporarily raises the amount of energy burned by the body. Obesity researchers at the Pennington Biomedical Research Center in the US discovered this in a trial with mice. When fattened mice were given the phyto-supplement it didn’t help them lose weight, but did make them healthier.

Why do we put on weight so quickly? According to one theory it’s because we eat increasing amounts of processed foods that no longer contain the compounds our bodies need to keep our metabolism up to a healthy level.

We no longer drink tea but soft drinks. No more whole grains but processed food bars. No fresh vegetables but deep-frozen pizzas. As a result our intake of flavonoid compounds and other phenols has gone down drastically. In their study the researchers wanted to see whether adding the flavonoid quercetin to the mice’s diet would stop them from getting fat while on a fattening diet. Quercetin is a well-researched flavonoid, and is found in red wine, tea, apples and onions.

The researchers gave their mice a diet in which 45 percent of the energy came from fat [HF]. That’s a diet that’ll make mice grossly fat. A second group also got high-fat food, but with 1.2 percent quercetin added [HF+Q].

When the experiment started the mice in the HF-Q group were slightly lighter and less fat, and remained so throughout the eight weeks of the experiment.




The figure above shows the effect of HF and HF+Q on the mice’s fat percentage. No difference. But the researchers did discover that the quercetin was having an effect when they looked at the mice’s energy burning. In week 3 it was higher in the HF+Q group.



The top figure shows energy expenditure in week 3. The figure below it shows energy expenditure in week 8. The effect has died down, probably because the mice’s metabolism has started to break down the compound more quickly as the experiment got further. Evidence of this is that the researchers found considerably less quercetin in the blood of the mice in week 8 than in week 3.



The quercetin supplement reduced the production of stress proteins like interleukin-1 and -4. The figure below compares the HF and HF+Q group in week 8.



Natural bodybuilders are experimenting with high doses of quercetin, usually taken just before training. They report an increase in energy and in the long term a reduction in fat percentage. This may be due to the mechanism that the Americans have identified. Or it may due to the reduction in cortisol levels that quercetin causes. Whatever the mechanism is that explains how quercetin works, this research seems to indicate that quercetin only works at an optimal level for a few weeks.

Source:
Metabolism. 2008 Jul;57(7 Suppl 1):S39-46.

interesting