Biography

Betty J. Burri, Ph.D. is a research chemist who studies phytonutrient functions and metabolism at the USDA-ARS-Western Human Nutrition Research Center. 

Dr. Burri received her Ph.D. in chemistry from the University of California San Diego, and then continued with postdoctoral research at the Scripps Research Institute. 

In 1985, Dr. Burri joined the Western Human Nutrition Research Center, where she began her investigations in vitamin A and carotenoids. 

Dr. Burri is also an Adjunct Professor of Nutrition at the University of California Davis and a member of the UC Davis Graduate Group in Food Science. 

She is a member of the American Society of Nutrition, the American Chemical Society, the International Food Technologists society, the New York Academy of Sciences and the International Carotenoid Society. 

Research Accomplishments

Dr. Burri established that carotenoid depletion decreases antioxidant activity in humans and that low physiological concentrations of beta-carotene normalize this activity.

High pharmacological concentrations of carotenoids did not further improve antioxidant activity, which explains why most epidemiological studies show strong correlations between beta-carotene intakes and reduced mortality, but most clinical trials show little benefit and a potential for harm with high dose supplements.

Measured the metabolism of beta-carotene and its conversion to vitamin A using isotopic techniques and found that absorption is more variable than metabolism or excretion.  

Our laboratory, in collaboration with the University of California Davis, showed that the conversion of beta-carotene to vitamin A is both poorer and more variable than assumed.  Furthermore, it is necessary to measure both retinol and retinyl esters to accurately calculate the conversion of beta-carotene to vitamin A. 

Demonstrated that retinyl esters—the storage form of vitamin A—could be formed by DGAT 1 (diacylglycerol acyltransferase 1).  DGAT 1 was the first enzyme identified as an ARAT (acyl retinol acyltransferase).  ARATs are responsible for one pathway of retinoid metabolism, so identifying the first ARAT means that we can find out why some people absorb and store vitamin A much better than others. 

Current Research Objectives

We have been investigating the possibilities of using food-based interventions, instead of supplements and placebos, in nutrition research.  Recent studies that investigated lycopene absorption and metabolism using Tangerine tomatoes compared to red tomatoes have shown that this approach is difficult but feasible. 

We are currently investigating the absorbance and metabolism of two vitamin A-forming carotenoids:  alpha-carotene and beta-cryptoxanthin.  We are comparing the metabolism of these carotenoids to that of beta-carotene, the best known carotenoid that forms vitamin A.  A current project is to compare the effectiveness of orange fleshed sweet potatoes (an excellent source of beta-carotene) and mandarin oranges (a good source of beta-cryptoxanthin) in improving vitamin A status in lactating women in Bangladesh, who have low vitamin A stores.