Eggs are a highly bioavailable source of lutein, the carotenoid thought to help fight disease and eyesight degeneration, shows a small trial presented in the US this week.
Major dietary sources of lutein include green vegetables such as spinach but Elizabeth Johnson from the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University, reported that eggs, not often considered a source of lutein, may provide more of the nutrient than both spinach and two types of supplements found on the market.
The study, presented on Sunday at the annual American Dietetic Association Conference in San Antonio, also found no difference in bioavailability between natural lutein esters and lutein supplements.
Lutein has been strongly implicated in protection against age-related macular degeneration and cataracts, thought to be due to its antioxidant power. Supplement makers are benefiting from increased consumer awareness of lutein's role in eye health, but there has been some dispute over the bioavailability of the nutrient offered in different products.
Johnson's trial tested serum lutein concentration in 10 healthy men, before and after daily consumption of 6mg lutein obtained from four different sources - eggs from chickens that had been fed marigold petals, which are high in lutein, spinach (one of the most widely known sources of dietary lutein), lutein ester supplements and lutein supplements.
Differences in serum response to the various lutein doses were observed the day after the first dose, reported Johnson. At this stage, the serum lutein response to egg was significantly greater than the supplements but not different to the spinach dose. But after nine days of a daily lutein dose, the serum lutein response was significantly greater in the egg phase than either of the supplements or the spinach.
Cognis, which supplied its Xangold natural lutein esters for the trial, welcomed the results as they showed equal bioavailability between its product and a competing brand of free lutein. The company has been involved in legal arguments in the past with key competitor Kemin, which supplies purified lutein.
"This research provides additional validation and important information our customers and prospects can use when formulating their products," said Carrie Potaczek, Cognis' product manager for the Xangold product. "Now we have clear evidence that the body digests lutein esters, converting them naturally to release free lutein, which is readily absorbed by the body," she added.
"The similar results between free lutein and lutein esters suggest that ester hydrolysis is not a limiting step for the absorption of lutein from lutein diesters. These results are consistent with other studies that have used lutein ester supplements and resulted in substantial increases in free lutein concentrations," confirmed Johnson.
The study, which was supported by the US-based Egg Nutrition Center, does however suggest that lutein-rich foods may be a more effective means of boosting lutein concentration at the eye than supplements.