The study joins a raft of recent research that suggests carotenoids, used extensively in the food industry as colouring agents, may have a preventative effect on heart disease and certain cancers as well as reduce the risk of degenerative diseases.
Prostate cancer is one of the biggest cancer killers in industrial countries and affects more than 500,000 men worldwide every year. This number is expected to increase with the ageing population.
Akira Asai and colleagues at the National Food Research Institute in Japan investigated the effect of gastric acidity on the rearrangement of spinach neoxanthin in vitro and the anti-cancer effects of the furanoid metabolites of neoxanthin.
"Both neoxanthin and neochrome steroisomers dose-dependently inhibited the proliferation of human prostate cancer cells," they report in the September issue of the Journal of Nutrition (2004, 134: 2237-2243).
The findings are further evidence of the potential value of carotenoids - commonly found in yellow, red and green vegetables - to the food industry, which so far has been slow to push the health benefits of the ingredient. Mostly used as a natural colouring, carotenoids have been 'under-utilised' by Europe's health food industry, according to a recent Frost & Sullivan report on the $348.5 million (€291.4m) market, and consumers are still unaware of their health benefits.
Asai also investigated the gastro-intestinal epoxide-furanoid rearrangement and the absorption of neoxanthin in mice. They report that report that two hours after the oral administration of neoxanthin, unchanged neoxanthin and neochrome stereoisomers were detected in the plasma, liver and small intestinal contents of the mice.