Beta-carotene from food sources is insufficient in substantial part of population

Dec 2 2010

The intake of preformed vitamin A from animal products is not sufficient in parts of the population in the U.S., Europe and Asia. The vitamin A precursor beta-carotene therefore has an important function in providing for an adequate supply of total vitamin A, international carotenoid experts state in a recently published consensus answer. An appropriate intake of beta-carotene from diet, fortified foods and/or dietary supplements could safely compensate for the lack of vitamin A. However, based on recent data from national nutrition surveys, the dietary intake of beta-carotene from food sources is insufficient in a substantial part of the population. Moreover, many people may suffer from a reduced ability to produce sufficient amounts of vitamin A from beta-carotene due to genetic variations. Consequently, experts are calling for guarantees that recommended intakes of beta-carotene are met or, if the current recommended dietary amounts for vitamin A are not met, that beta-carotene intake should be increased. This would ensure that at least 95% of the population consume an adequate amount of total vitamin A.

Leading experts in the fields of medical and nutritional science from the U.S., Europe and Asia met at a Consensus Conference to elucidate the current knowledge with respect to physiological function, supply situation, and intake recommendations of beta-carotene. The experts reached an agreement formulated in a consensus answer published recently in The Journal of Nutrition.

Vitamin A and beta-carotene intake often critically low

Vitamin A is essential for normal growth and development, immune system, vision and other functions in the human body. In situations such as pregnancy and lactation, vitamin A plays a particularly important role in the healthy development of the child, and an increase in vitamin A (retinol) intake has been recommended under these conditions. However, surveys undertaken in several countries suggest that vitamin A intake patterns vary considerably across Europe, the U.S. and Asia. National survey data show that the intake of preformed vitamin A (retinol) - as such only present in animal products (especially liver) - is often critically low and does not meet the recommendations. Groups especially at risk of inadequate vitamin A supply are pregnant and lactating women, newborns, children with frequent infections, young women, the elderly and people who avoid animal-derived foods.

National Consumption Surveys indicate that beta-carotene - as a vitamin A precursor - contributes significantly to balance inadequate vitamin A supply in large parts of the population. However, European, U.S. and Asian studies show that a substantial part of the population does not reach the recommendation for beta-carotene necessary to compensate the low vitamin A intake from sources containing preformed vitamin A in the regular diet.

Recent evidence has shown that suboptimal levels of vitamin A and beta-carotene, even well above those causing clinical deficiency syndromes, can be risk factors for chronic diseases.

Vitamin A deficiency through beta-carotene-dependent gene variants

The bioavailability of beta-carotene is influenced by numerous factors. In addition to food-related factors, such as food matrix, food processing, dosage, fat in the meal, and dietary fibers, the bioavailability of beta-carotene depends on consumer-related factors including vitamin A status, gut integrity and genetic variations.

Recent research on female subjects has shown that almost 50% of the population have a genetic variation which reduces their ability to produce sufficient amounts of vitamin A from beta-carotene. Studies indicate that younger women carrying the genetic variation are at particular risk as they tend to eat not enough vitamin A-rich foods relying heavily on the beta-carotene form of the nutrient.

Experts call for increase of beta-carotene intake recommendations

It is apparent from a variety of studies that beta-carotene is essential in striving for the recommended vitamin A intake. In cases of a poor vitamin A status due to low intake of preformed vitamin A, the current recommendations for beta-carotene in the range of 2-4 mg per day still might not sufficiently correct the individual vitamin A status.

In their consensus answer the experts conclude that ignoring inter-individual differences in the ability to convert beta-carotene to vitamin A and assuming that intakes of preformed retinol do not change, it should be ensured that the current recommended intakes of beta-carotene are attained. At the same time, people with an inadequate intake of preformed vitamin A should increase consumption to 7 mg per day, based on a realistic and now in the scientific community generally accepted conversion efficiency of 1:12 (12 milligrams of beta-carotene are necessary to form one milligram of vitamin A). This should ensure that at least 95% of the population meet the recommended intakes of total vitamin A.

Individuals with reduced conversion efficiencies due to a genetic variability in beta-carotene metabolism might need to increase their daily intakes even further. This is currently being investigated.

No functional difference between natural and synthetic beta-carotene

According to the experts, there is no difference in function between naturally occurring and chemically synthesized beta-carotene, whereas there is a difference in bioavailability from different food sources. In humans, the predominant molecular type is 'all-trans beta-carotene', used for most dietary supplements and fortified foods; it is absorbed preferentially compared to other forms.

As the general population is not obtaining sufficient beta-carotene from fruit and vegetables, foods fortified or colored with beta-carotene and dietary supplements can be important contributors to the daily supply of vitamin A.