expert opinion

Conference Report: New Developments in Carotenoids Research

March 11, 2011

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Summary of selected key lectures:

“The clinical importance of vitamin A as an essential nutrient has become increasingly clear. Adequate vitamin A is required for normal organogenesis, immune competence, tissue differentiation and the visual cycle. Deficiency, wide-spread throughout the developing world, is responsible for a million or more instances of unnecessary death and blindness every year. The intake of preformed vitamin A from animal products is not sufficient in major parts of the population all over the world, including Europe, the US and Asia. Beta-carotene is a safe source of vitamin A. Its pro-vitamin A function is a crucial contribution to the required total vitamin A intake in both developed and developing countries. Recent studies suggest that suboptimal levels of vitamin A and beta-carotene, even well above those causing clinical deficiency syndromes, can be a contributing risk factor in chronic diseases.

In 2001 the old ratio of 6:1 beta-carotene to vitamin A equivalence (1 retinol equivalent = 6 micrograms of beta-carotene) was jettisoned in the US for a new ratio of 12:1, based on new and reproducible stable isotope data. However there is great variation of the bioconversion equivalence depending on the food being tested (e.g., for green leafy vegetables > 20:1 and for carrots ~ 15:1). In addition, there is new evidence that foods with a simple, digestible matrix have an equivalence that is much better than 12:1. Moreover, the bioavailability and vitamin A equivalency of beta-carotene can be affected by characteristics of the target population, such as vitamin A status, nutrient deficiencies, gut integrity and genetic polymorphisms associated with beta-carotene metabolism. Thus the variability in estimates of vitamin A equivalency is high across studies and between individuals within studies.

The results of epidemiological and human supplementation studies with beta-carotene in chronic disease prevention indicate that intervening in populations with low beta-carotene status in order to improve it may be a more promising approach than intervening in populations with adequate status in order to raise it to a “supra” adequate status. This more personalized approach to nutrient-based intervention, however, is critically dependent on the availability of biological markers of status, in this case, carotenoid status. Recent advances in the development of promising new methods for rapidly and non-invasively assessing carotenoid status suggest that it is increasingly feasible to identify persons most likely to benefit from carotenoid interventions, allowing for future intervention trials with greater likelihood of demonstrating beneficial effects seen to date.

Study results have shown that beta-carotene and lycopene -rich diet or supplementation provide protection against skin damage from sunlight. Although photoprotection through individual carotenoid intake is considerably lower than that achieved using topical sunscreens, optimal supply of antioxidant micronutrients to the skin increases basal dermal defense against UV irradiation, supports longer-term protection and contributes to maintenance of skin health and appearance.

A high intake of tomatoes and tomato products have been found to reduce the risk of certain chronic diseases in many epidemiological studies, yielding evidence that lycopene (a major carotenoid in tomatoes) is a micronutrient with important health benefits, such as chronic disease prevention (e.g., various types of cancer). Whether the effect of lycopene on various cellular functions and signaling pathways is a result of the direct actions of intact lycopene or its derivatives, remains unknown.

Abundant epidemiological evidence suggests that the macular pigment carotenoids lutein and zeaxanthin play key roles in the prevention and treatment of age-related macular degeneration (AMD), a leading cause of irreversible visual loss in the elderly in the developing world. There is also evidence that lutein and zeaxanthin seem to improve visual performance in healthy subjects. Moreover, epidemiological studies suggest that intake of dietary carotenoids may be of benefit in maintaining cognitive health. Given their role as antioxidants and anti-inflammatory agents, lutein and zeaxanthin may play a role in the prevention or the delay of cognitive decline. Among all of the carotenoids, these two are the only ones that cross the blood- retina barrier to form macular pigment in the eye.”

Boston, March 2011

Selected speakers: Alfred Sommer (Johns Hopkins University, USA), Robert M. Russell (National Institutes of Health, USA), Keith P. West (Johns Hopkins Bloomberg School of Public Health, USA), Marjorie J. Haskell (University of California, USA), Susan T. Mayne (Yale Schools of Public Health and Medicine, USA), Francine Grodstein (Harvard Medical School, USA), Helmut Sies (Heinrich-Heine University, Germany), A. Catharine Ross (Pennsylvania State University, USA), Xiang-Dong Wang (Tufts University, USA), Steven K. Clinton (Ohio State University, USA), Paul S. Bernstein (University of Utah, USA), B. Randy Hammond (University of Georgia, USA), Elizabeth J. Johnson (Tufts University, USA).