News

Women at risk of vitamin A deficiency

November 24, 2009

Almost half of UK women could be suffering from a lack of vitamin A because of a previously undiscovered genetic variation, scientists at Newcastle University have found.

From a volunteer group of 62 women, the researchers found that 29 of them – 47 per cent – carried the genetic variation which prevented them from being able to effectively convert beta-carotene into vitamin A (1). The study also showed that all volunteers consumed only about a third of their recommended intake from “preformed” vitamin A – the form found in dairy products such as eggs and milk – indicating that those volunteers carrying the genetic variation were not eating enough vitamin A-rich foods to reach the optimum level their body required to function.

Worryingly, younger women are at particular risk, the researchers commented. Older generations tend to eat more eggs, milk and liver, which are naturally rich in preformed vitamin A, whereas health-conscious youngsters on low-fat diets are relying heavily on the beta-carotene form of the nutrient. In cases of a poor vitamin A status due to low intake of preformed vitamin A, a daily intake of beta-carotene in the range of 2-4 mg – recommended by European health authorities – might not sufficiently correct the individual vitamin A status. There is much evidence suggesting that a daily intake of approximately 7 mg of beta-carotene is required to reach the vitamin A recommendations if current low intakes of preformed vitamin A do not change. If the gene-related restrictions on the utilization of beta-carotene are taken into account, then the daily recommendation would need to be even higher for those who carry the genetic variation.

Vitamin A – also known as retinol – plays a vital role in strengthening the immune system, protecting against common infections such as flu and winter vomiting. Vitamin A also helps to maintain healthy skin and mucus linings such as inside the nose and the lungs. In some physiological situations, such as pregnancy and lactation, vitamin A has a particularly important role in the healthy development of the child, and an increase in vitamin A (retinol) intake has been recommended. However, consumption of high doses of retinol during pregnancy is known to cause malformations in the newborn. The potential toxicity of high doses of preformed vitamin A during pregnancy does not occur with the intake of high doses of beta-carotene: the conversion of beta-carotene is regulated through feed-back mechanisms. Therefore, only the required amount is metabolized to retinol, making beta-carotene a safe source for vitamin A.

The next step in the study is to assess whether the effect of the genetic variation can also be observed in men and whether body composition influences the ability to absorb and convert beta-carotene into vitamin A.

References

  1. Lietz G. et al. Two common single nucleotide polymorphisms in the gene encoding beta-carotene 15,15’-monoxygenase alter beta-carotene metabolism in female volunteers. The FASEB Journal. 2009; 23:1041–1053.