The exact cause is unclear but oxidative stress is believed to play a role. It distorts the sharp, central vision needed to see fine details such as for reading and driving. Another was that lycopene-rich foods often contain other cancer-protective compounds, so it would be difficult to isolate any health benefits to lycopeneĪge-related macular degeneration (AMD) is a common painless eye condition but a leading cause of vision loss among people age 50 and older. However, an FDA review stated that definite conclusions about lycopene could not be made, one reason being that accurate reporting of lycopene intake is difficult due to variations in lycopene content during cooking and storage. A 2015 meta-analysis of 26 studies found that higher lycopene intakes appeared protective from prostate cancer incidence. A Harvard study of more than 51,000 men from the Health Professionals Follow-up Study found a protective effect from advanced stages of prostate cancer in those with higher intakes of tomato sauce. Observational studies and clinical trials have shown either a protective effect of lycopene-rich foods (specifically tomatoes) or supplements, or no effect. Unfortunately, studies have not provided a clear answer specific to lycopene. Observational studies have noted a decreased risk of prostate cancer in men who eat high amounts of fruits and vegetables. There has been interest in lycopene’s effects on cancer due to its antioxidant properties. Prostate Cancer: Lycopene is a carotenoid that gives fruits and vegetables a pink or red hue, as in tomatoes and grapefruit. Preventive Services Task Force advises against the use of beta-carotene supplements for the prevention of any cancer, stating that there is potentially greater harm in using these supplements than any suggested benefit. Additionally, based on current evidence the U.S. Therefore, it is recommended that current or former smokers and workers exposed to asbestos do not use high-dose beta-carotene and retinyl palmitate supplements. In fact, two of those three trials actually found a significant increase in lung cancer risk among study participants taking supplements with beta-carotene or retinyl palmitate (a form of vitamin A). However, three large clinical trials did not find that supplements of beta-carotene and vitamin A helped to prevent or reduce lung cancer risk. Lung Cancer: Observational studies following nonsmokers and current or former smokers have found that higher intakes of carotenoids from fruits and vegetables are associated with a lower risk of lung cancer. The evidence suggests that eating a variety of foods rich in vitamin A, especially fruits and vegetables, is protective from certain diseases, though the health benefit of vitamin A supplements is less clear. The UL for vitamin A from retinol is 3,000 micrograms of preformed vitamin A. UL: The Tolerable Upper Intake Level is the maximum daily intake unlikely to cause harmful effects on health.RDA: The Recommended Dietary Allowance for adults 19 years and older is 900 mcg RAE for men (equivalent to 3,000 IU) and 700 mcg RAE for women (equivalent to 2,333 IU).
Under the Food and Drug Administration’s (FDA) new food and dietary supplement labeling regulations, as of July 2018 large companies will no longer list vitamin A as IU but as “mcg RAE.” However, the Institute of Medicine lists the Recommended Dietary Allowances (RDA) of vitamin A in micrograms (mcg) of retinol activity equivalents (RAE) to account for different absorption rates of preformed vitamin A and provitamin A carotenoids. Vitamin A is currently listed on the Nutrition Facts label measured in international units (IU). There are other types of carotenoids found in food that are not converted to vitamin A but have health-promoting properties these include lycopene, lutein, and zeaxanthin. Carotenoids are found naturally in plant foods. Preformed vitamin A comes from animal products, fortified foods, and vitamin supplements.
The two main forms of vitamin A in the human diet are preformed vitamin A (retinol, retinyl esters), and provitamin A carotenoids such as alpha-carotene and beta-carotene that are converted to retinol. Vitamin A also stimulates the production and activity of white blood cells, takes part in remodeling bone, helps maintain healthy endothelial cells (those lining the body’s interior surfaces), and regulates cell growth and division such as needed for reproduction. Vitamin A can’t give you superpowers of night vision or cure your dependence on contact lenses, but eating an adequate amount will support eye health. A carrot’s main nutrient, beta-carotene (responsible for this root vegetable’s characteristic orange color), is a precursor to vitamin A and helps your eyes to adjust in dim conditions. It’s only a semi-myth that eating carrots will help you see in the dark.
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