The Health Benefits of Vitamin A

Vitamin A is a member of the fat-soluble family of vitamins that also includes vitamin D, vitamin E, and vitamin K.

Found in many foods, including carrots, sweet potatoes, and liver , vitamin A is important for normal vision, adequate growth, and cell division and differentiation. It's essential for immune system function and necessary for healthy skin and mucous membranes.

Vitamin A deficiency is rarely seen in developed countries, but when it occurs it can cause vision problems and loss of healthy immune system function.

Vitamin A is found in both plants and animals. Animal sources, such as butter, egg yolks, fish, liver, meats, and whole milk, contain preformed vitamin A, or retinol.

Plant sources of vitamin A are called provitamin A carotenoids and include beta-carotene, alpha-carotene, and beta-cryptoxanthin. Your body takes these precursors and converts them to the form of vitamin A your cells need. Carotenoids are found in dark green, yellow, and orange fruits and vegetables.

Health Benefits

A nutrient that is essential for good health , vitamin A has been shown to be effective for preventing and treating specific conditions. Here's a look at the research:

Age-Related Macular Degeneration

Getting enough vitamin A can helps protect against age-related macular degeneration (AMD). Research published in JAMA Opthalmology shows that higher blood levels of the carotenoids in vitamin A including lutein and zeaxanthin may reduce the risk of AMD by about 40 percent.

According to researchers, carotenoids protect macular tissue by lowering levels of oxidative stress.

Prevent Fractures

A 2017 study reports that higher dietary consumption of vitamin A may help keep bones strong and healthy. The meta-analysis of more than 300,000 adults over the age of 20 found people with lower blood levels of vitamin A are at greater risk of bone fractures.

Possible Side Effects

In normal doses, vitamin A is safe and does not appear to cause any side effects. However, large doses of vitamin A may cause nausea, vomiting, vertigo, and blurry vision. 

In addition, long term supplementation of large doses (10 times the minimum daily requirement) can cause bone thinning, liver damage, headaches, diarrhea, nausea, skin irritation, pain in joints and bones, and birth defects. 

Interactions

If you are taking any of the following medications, do not take vitamin A supplements:

• Anticoagulants: Vitamin A may increase your risk of bleeding
• Hepatotoxic Drugs: Taking vitamin A in conjunction with drugs that cause liver damage may increase the risk of liver disease. 
• Oral Retinoids: Taking both retinoids and vitamin A may result in dangerously high levels of vitamin A in the bloodstream. 
• Targretin (Bexarotene): Taking vitamin A along with this topical cancer drug may increase the drug’s side effects, including itchy and dry skin. 

Dosage and Preparation 

Vitamin A is available in multivitamins and as a stand-alone supplement, often in the form of retinyl acetate, retinyl palmitate, or beta carotene.

The National Academies of Sciences, Engineering, and Medicine has determined dietary reference intakes (DRI) for vitamin A based on age and sex. It represents the daily amount that's needed by the average healthy person. If you have any medical issues, you should speak to your doctor about your vitamin A requirements.

Vitamin A is typically listed on food and supplement labels in international units (IUs), however, the daily recommended allowances are listed in as retinol activity equivalents. This is because the different variants of the vitamin convert into retinol differently.

The recommended daily allowance of vitamin A, depending on age, gender, and type of vitamin A, is the following:

• 1 to 3 years: 300 micrograms of retinol activity equivalents (mcg RAE) per day, which equals 90 IU retinol, 40 IU beta-carotene in dietary supplements, 15 IU beta-carotene from food, or 7.5 IU alpha-carotene or beta-cryptoxanthin.
• 4 to 8 years: 400 mcg RAE per day, which equals 120 IU retinol, 60 IU beta-carotene in dietary supplements, 20 IU beta-carotene from food, or 10 IU alpha-carotene or beta-cryptoxanthin.
• 9 to 13 years: 600 mcg RAE per day, which equals 180 IU retinol, 30 IU beta-carotene in dietary supplements, 30 IU beta-carotene from food, or 15 IU alpha-carotene or beta-cryptoxanthin.
• Females 14 years and older: 700 mcg RAE per day, which equals 210 IU retinol, 105 IU beta-carotene in dietary supplements, 35 IU beta-carotene from food, or 17.5 IU alpha-carotene or beta-cryptoxanthin.
• Males 14 years and older: 900 mcg RAE per day, which equals 270 IU retinol, 135 IU beta-carotene in dietary supplements, 45 IU beta-carotene from food, or 22.5 IU alpha-carotene or beta-cryptoxanthin.

What to Look For 

When selecting a brand of supplements, look for products that have been certified by Consumer Labs, The U.S. Pharmacopeial Convention, or NSF International. 

Other Questions 

Can vitamin A prevent cancer?

Some studies have indicated that people with certain types of cancer have lower levels of vitamin A in the blood. And because vitamin A is involved in cell differentiation, some people have recommended taking vitamin A supplements for treating or preventing cancer, but there's no evidence for this recommendation. In the case of cigarette smokers, taking beta-carotene supplements may actually increase the risk of cancer.

What are good food sources of vitamin A?

Vitamin A is plentiful in many foods including sweet potatoes, liver, spinach, carrots, cantaloupe, red peppers, eggs, and apricot.