Astaxanthin eyed as weight loss ingredient

Writing in the journal Bioscience, Biotechnology, and Biochemistry researchers from Tokyo University of Marine Science and Technology report that female mice fed a high-fat diet supplemented with astaxanthin (AstaReal 50F, BioReal) reduced body weight gain, the build-up of fatty tissue, and improved blood fatty acid levels.

"We found that astaxanthin inhibits the elevations in body weight and adipose tissue weight caused by a high-fat diet," wrote lead author Mayuni Ikeuchi.

"These results indicate that astaxanthin might be of value in preventing obesity and the metabolic syndrome in affluent societies."

Astaxanthin, the nutrient that gives salmon its pink colour, has been found to be a potent antioxidant, with tests suggesting that it may have a free radical fighting capacity worth 500 times that of vitamin E. The carotenoid is produced by the Haematacoccus pluvialis algae when water supplies in its habitat dry up to protect itself against the effects of UV radiation.

Research has shown it to have a similar structure to lutein and zeaxanthin, but there are indications that it has an even stronger antioxidant activity.

Research on animals and some human clinical trials have suggested that the carotenoid may help protect against cataracts and UVA damage to the skin, as well as a number of other serious conditions such as stroke.

Annual growth of the global market for astaxanthin for human use is thought to be at least 15 per cent, with current estimates valuing the market at $15-20m (€12.4-16.6m) per year.

The researchers assigned four-week old female ddY mice to one of five groups: one group ate a normal diet (control group) while the other four groups were assigned to a high-fat diet and supplemented with olive oil (placebo), or astaxanthin at concentrations of 1.2, 6, or 30 mg per kg of body weight for 60 days.

The group fed the high-fat diet supplemented with olive oil resulted in a significant increase in body weight, compared to the control group.

"However, feeding a high-fat diet plus astaxanthin at levels of 6 mg/kg or 30 mg/kg significantly reduced the body weight gain induced by the high-fat diet," said the researchers.

The high-dose astaxanthin group also had lower adipose tissue weight, while the lower dose astaxanthin groups did not have significantly lower adipose tissue weight than the olive oil group.

Triglyceride levels were higher in the high-fat diet supplemented with olive oil group than for the control group, but supplementation with astaxanthin at levels of 6 and 30 mg/kg resulted in triglyceride levels about 50 per cent lower than the high-fat diet supplemented with olive oil group.

"In the present study increases in the body weight and weight of adipose tissue were prevented in mice fed a high-fat diet plus astaxanthin without changing the energy intake, except in the normal diet group," wrote the researchers.

The mechanism behind such effects was related to a stimulation of fatty acid utilisation, suggested the researchers, meaning that glucose use decreases and fatty acids are metabolised preferentially as the energy source.

"Further studies are necessary to elucidate the mechanisms," they said.

With 50 per cent of Europeans and 62 per cent of Americans classed as overweight, the food industry is waking up to the potential of products for weight loss and management.

The category estimated to already be worth $7bn (€5.1bn).

Source: Bioscience, Biotechnology, and Biochemistry Volume 71, Pages 60521-1 to 60521-7, doi:10.1271/bbb.60521 "Effects of astaxanthin in obese mice fed a high-fat diet" Authors: M. Ikeuchi, T. Koyama, J. Takahashi, K. Yazawa