Carotenoids and vitamins are found together in a wide variety of fruits and vegetables, including carrots, sweet potatoes, tomatoes, cantaloupe, watermelon and guava. These compounds have a wide range of activities within the body, some of which are completed separately and others that involve interactions between essential vitamins and specific carotenoids.
Vitamins
Vitamins are organic compounds necessary for life that the body either cannot produce at all or cannot produce in sufficient quantities to maintain health. If the vitamin is not acquired from the diet, symptoms of deficiencies typically develop. Vitamins have letter designations or a combination of letter and number in their name, such as vitamin C, vitamin E and vitamin B12. Some of the B vitamins also have independent names, such as thiamin, niacin and pantothenic acid.
Carotenoids
Carotenoids are a type of phytochemical, plant-derived compounds that benefit human health when eaten. Unlike vitamins, a lack of carotenoids does not lead to deficiency symptoms. Common carotenoids in the American diet include beta-carotene, alpha-carotene, beta-cryptoxanthin, lycopene, zeaxanthin and lutein. In addition to these common carotenoids, there are over 500 other known carotenoids available through foods, and more are likely to be discovered. The complete activity of most carotenoids are not yet known. Carotenoids typically provide red, yellow and orange colors to foods containing them.
Vitamin A
One vitamin particularly associated with carotenoids is vitamin A. Some of the carotenoids serve as precursors to the formation of some forms of vitamin A in the body. A few different related compounds, including retinol, retinoic acid and retinal, make up vitamin A. After being consumed, alpha-carotene, beta-carotene and beta-cryptoxanthin undergo conversion into retinol. The proper development of the retina, and the ability to see at night in particular, rely on retinol. Retinol can also be converted into other forms of vitamin A. Additional functions of the different forms of vitamin A include regulation of the immune system and development of the urinary, intestinal and respiratory tract linings. Consuming either vitamin A or the provitamin A carotenoids can ensure sufficient retinol. However, it takes extremely high amounts of provitamin carotenoids to supply the necessary amount of retinol for eye function. About 12 mcg of retinol provides the equivalent of 1 mcg of preformed vitamin A.
Eye Health and Other Benefits
The provitamin A carotenoids aren't the only carotenoids that affect eye health. Lutein and zeaxanthin operate in the retina and lens of the eye completely independently of vitamin A. The carotenoids, including lutein, zeaxanthin and beta-carotene, may act in conjunction with vitamins E and C to provide protection against the progression of age-related macular degeneration and cataracts. All of the carotenoids also have antioxidant activity, help boost the signalling between cells and may help protect against prostate cancer and cardiovascular disease, according to the Linus Pauling Institute.
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