Health benefits of carotenoids questionable to birds, study finds
An international study led by a Monash biologist has challenged the long-held view that carotenoids are beneficial to health.
Carotenoid pigments are widely distributed in nature, where they are reported to play an important role in protecting cells and organisms against the harmful effects of radiation and toxins, as well as serving as colourants.
Dr Rebecca Adrian, a postdoctoral research fellow in the Dowling Lab at Monash University’s School of Biological Sciences, tested whether carotenoid pigments are beneficial to immune or antioxidant defences by comparing two types of domestic canaries with and without internal carotenoids.
The results, published in Nature Communications, show that carotenoids alone provide no detectable benefit to birds.
“While this result must be further tested in mammals, like humans, it questions whether there is any benefit to taking supplements rich in carotenoids (particularly carotenoids that are not precursors to Vitamin A),” Dr Adrian said.
“Our research provides important information about how carotenoids interact with the animal body,” she said.
The research team performed a wide range of basic physiological tests on the canaries, such as measuring antibody levels after vaccination, to examine whether carotenoid-rich birds had any advantages over carotenoid-deficient birds.
Carotenoid pigments, like beta-carotene, are abundant in plant-based food items, and many birds use them to colour their feathers yellow, orange, or red.
Beyond coloration, carotenoid pigments are thought to benefit the animal body by boosting immune defences and preventing cellular damage as antioxidants.
Researchers tested this hypothesis in two strains of domestic canaries: the normal yellow canary, and a special white canary that has lost the ability to acquire carotenoid pigments from its diet.
“We found that carotenoid-rich yellow canaries and carotenoid-deficient white canaries performed identically on a range of physiological tests, including tests of immune and antioxidant defences,” Dr Adrian said.
“These results indicate that carotenoids themselves have no meaningful function within the songbird body, besides colouring feathers.”
According to Dr Adrian, a clear implication of the study is that many of the reported benefits of dietary carotenoid consumption may be due to the fact that many carotenoids are Vitamin A precursors.
This means that some carotenoids, like beta-carotene, are often converted straight into Vitamin A when they enter the body.
“Vitamin A does have known health benefits; in fact, the white canaries I studied had to receive Vitamin A supplements to survive, since they could not generate the vitamin from carotenoids,” Dr Adrian said.
“While supplementation is clearly a complex topic and the results of providing any supplement will vary on a case-by-case basis, it is interesting to consider that Vitamin A may be responsible for many of the reported health benefits of carotenoids—not the carotenoids themselves.”
Silvia Dropulich Marketing, Media and Communications Manager, Science