If you want healthy skin and eyes and a bolstered immune system, get your daily dose of vitamin A. This vitamin keeps skin membranes and the mucosal cells that act as a first defense against infection healthy. It’s also required for growth, bone formation, wound healing and reproduction. This nutrient is found in foods as preformed vitamin A and provitamin A carotenoids. Your body doesn’t have to work as hard at metabolizing the former, making these foods more efficient at increasing your vitamin A levels.
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You consume vitamin A in one of two forms. Preformed vitamin A, also known as retinoids, is found in animal sources. Provitamin A carotenoids are from plant sources and include beta-carotene, alpha-carotene and beta-cryptoxanthin. Your body doesn’t absorb beta-carotene as efficiently as preformed vitamin A because it must covert the former to retinal or retinol. For example, 12 micrograms of beta-carotene from food is equivalent to 1 microgram of retinol in your body. It takes 24 micrograms of alpha-carotene and beta-cryptoxanthin to produce 1 microgram of retinol.
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The Institute of Medicine recommends adult males consume 900 micrograms of vitamin A daily and adult women consume 700 micrograms daily. This is in the form of retinal activity equivalents to account for the various sources of vitamin A. The best sources of preformed vitamin A are in liver and fish oils. This includes beef, calf, chicken liver and cod liver oil. A 3-ounce serving of beef liver contains 6,582 micrograms of retinal activity equivalents and 1 teaspoon of cod liver oil has 1,350 micrograms. Other quality sources include whole-fat dairy products, such as milk, yogurt, cheese and butter.
Eating beta-carotene will also elevate your vitamin A stores. Beta-carotene is a fat-soluble nutrient that gives fruits and vegetables their color. Deep yellow and orange fruits and vegetables are an excellent source of beta-carotene, including sweet potatoes, carrots, pumpkin, cantaloupe, apricots, peaches and mangoes. Dark green leafy vegetables, such as spinach, broccoli, kale and collards, also provide beta-carotene.
Vitamin A can be toxic and even cause liver failure and death if consumed in excessive amounts. The upper limit for this vitamin is set at 2,800 micrograms for adults. According to the Office of Dietary Supplements, vitamin A toxicity usually occurs via supplements, but it can happen through dietary intake. Symptoms include nausea, dizziness, dry skin and bone and joint pain.