Many women may need increased beta-carotene intake for a sufficient vitamin A supply

Big parts of the female population may have limited abilities to absorb beta-carotene and convert it into vitamin A due to genetic variations, a new UK study suggests.

The study investigated the effects of four common genetic variations (single nucleotide polymorphisms, SNPs) of the enzyme converting beta-carotene to vitamin A (retinal) in 28 female participants with a mean age of 20 years (1). The study results showed that three of the four SNPs significantly reduced the beta-carotene conversion by up to 59%. Furthermore, large variations in frequency of the SNPs were detected among 11 different ethnic groups, with frequencies varying from 43 to 100%.

The researchers concluded that a range of SNPs can reduce the effectiveness of using plant-based provitamin A carotenoids, such as beta-carotene, to increase vitamin A status among at-risk population groups. This effect may vary depending on ethnic origin. Thus, people with reduced ability to convert provitamin A sources into active vitamin A could be susceptible to wide-ranging health risks. They considered this to be especially important since recent research indicates that approximately 45% of all Europeans possess a gene variant that restricts the amount of beta-carotene their bodies can utilize and convert into vitamin A. If the gene-related restrictions on the utilization of beta-carotene would be taken into account, then the daily recommendation might need to be significantly higher, or alternatively, these individuals might have to increase their preformed vitamin A intake from animal sources or supplements.

Recently, international carotenoid experts have stated in a consensus answer that beta-carotene is indispensable as a safe source of vitamin A (2). As the intake of preformed vitamin A from animal products is not sufficient in parts of the population in Europe, the United States, and Asia, beta-carotene is considered to have an important function in providing an adequate supply of total vitamin A.

Vitamin A is essential for normal growth and development, immune system, vision, and other functions in the human body. Because humans are unable to synthesize vitamin A they must consume diets with preformed vitamin A or provitamin A carotenoids. Upon absorption, provitamin A carotenoids are readily converted to vitamin A by the enzyme beta-carotene 15,15’-monoxygenase (BCMO1). Recent research showed that two common SNPs within the BCMO1 coding gene region cause reduced catalytic activity of the enzyme, confirming that genetic variations contribute to low beta-carotene utilizations.

Vitamin A deficiency is a serious public health problem that mostly affects pregnant and lactating women and preschool children, with an estimated 250 million at risk of developing vitamin A deficiency disorders (3). A majority of the vitamin A requirements for the population in the United Kingdom, for example, are not met by dietary intake of preformed retinol, and 15% of young individuals aged 19–24 years have a total vitamin A intake below the lower recommended nutrient intake level (4).

1. Lietz G. et al. Single Nucleotide Polymorphisms Upstream from the ?-Carotene 15,15’-Monoxygenase Gene Influence Provitamin A Conversion Efficiency in Female Volunteers. J. Nutr. Published online November 2011.
   
   
2. Grune T. et al. Beta-Carotene is an important vitamin A source for humans. Hohenheim Consensus Conference. The Journal of Nutrition. 2010; 140(12):2268–2285.
   
   
3. Underwood B. A. Vitamin A deficiency disorders: international efforts to control a preventable "pox". J Nutr. 2004; 134:231–236.
   
   
4. Swan G. Findings from the latest National Diet and Nutrition Survey. Proc Nutr Soc. 2004; 63:505–512.