Exercising and increasing vitamin A intake through fruits and vegetables may reduce the risk of mortality, according to a study.
Vitamin A is a fat-soluble vitamin that is derived from two sources: preformed retinoids and provitamin carotenoids. Retinoids, such as retinal and retinoic acid, are found in animal sources such as liver, kidney, eggs and dairy produce. Carotenoids, such as beta-carotene (which has the highest vitamin A activity), are found in plants such as dark or yellow vegetables and carrots.
In a new study, researchers recruited 713 women between the ages of 70 and 79 who participated in the Women's Health and Aging Studies. The team measured levels of carotenoids and physical activity at baseline and over a period of five years.
A total of 82 women died over the course of the study. The scientists found that physical activity appeared to improve survival rates, since more active subjects had a lower risk of dying than those who were less active. Women who had the highest carotenoid levels were also more likely to survive.
According to the researchers, a combination of exercise and increased consumption of nutrient-rich fruits and vegetables may reduce mortality in older women. However, more studies are needed to better understand and confirm these findings.
Carotenoids are required for biological processes such as vision and cellular growth. A major biologic function of vitamin A (as the metabolite retinal) is in the visual cycle. Research also suggests that vitamin A may reduce the mortality rate from measles, prevent some types of cancer, aid in growth and development and improve immune function.
Recommended dietary allowance levels for vitamin A oral intake have been established by the U.S. Institute for Medicine of the National Academy of Sciences to prevent deficiencies in vitamin A. At recommended doses, vitamin A is generally considered nontoxic. Excess dosing may lead to acute or chronic toxicity.
Vitamin A deficiency is rare in industrialized nations but remains a concern in developing countries, particularly in areas where malnutrition is common. Prolonged deficiency can lead to xerophthalmia (dry eye) and ultimately to night blindness or total blindness, as well as to skin disorders, infections (such as measles), diarrhea and respiratory disorders.
For more information about vitamin A, please visit Natural Standard's Foods, Herbs & Supplements Database.