Vitamin A may be best known as the nutrient in carrots that helps you see in the dark. But it’s not that simple. In fact, the vitamin has various forms and the benefits are much broader than you may realize. It’s also a nutrient that you may not be getting enough of in your diet.
Vitamin A is a fat-soluble vitamin that’s essential for normal vision. It doesn’t quite help you see in the dark, but vitamin A does play a role in helping your eyes adjust in dim lighting. Vitamin A is also important for:
— Immune function
— Growth and development
— Reproduction
— Support of heart, lungs and other organs
There are two types of vitamin A:
— Preformed vitamin A is found in animal-based foods including meat, fish, poultry, dairy products and eggs. This type of vitamin A is in the form of retinol and retinyl esters.
— Provitamin A is found in plant-based foods, primarily deeply hued fruits and vegetables. This type is in the form of carotenoids, primarily beta-carotene, which is converted to vitamin A in the body.
[READ: Vitamins and Minerals: the Essentials for Women.]
How Much Vitamin A Do I Need?
The amount of vitamin A you need depends on your age and gender at birth. The recommended dietary allowance (RDA) for vitamin A is listed as micrograms (mcg) of retinol activity equivalents (RAE), which accounts for the different absorption rates (the proportion of a nutrient that is used by the body) of preformed vitamin A and provitamin A carotenoids.
The RDA is 900 mcg RAE for men 19 years and older, and 700 mcg RAE for women. Because high levels of retinol can be harmful, the daily upper limit is 3,000 micrograms of preformed vitamin A.
[Vitamin Deficiency: Common Symptoms to Watch For]
Foods High in Vitamin A
Vitamin A is found naturally in a variety of foods, while some foods are fortified with vitamin A, including breakfast cereals, juices and dairy products. Here are some of the best sources of vitamin A in animal-based foods and carotenoids in plant-based foods:
— Beef liver and other organ meats
— Some types of fish, such as herring, mackerel and salmon
— Milk, yogurt, cheese and butter
— Eggs
— Orange vegetables such as carrots, sweet potatoes, pumpkin and winter squash
— Broccoli, spinach, kale and other green leafy vegetables
— Red vegetables like tomatoes and red bell peppers
— Orange fruits including cantaloupe, mangos, papaya, apricots and nectarines
— Fortified breakfast cereals and juices
[READ: 17 Best Anti-Inflammatory Foods]
Are You Getting Enough Vitamin A?
True deficiencies of vitamin A in the U.S. are rare, occuring at a rate of less than 1%, the CDC reports. That’s the primary reason why vitamin A is no longer required to appear on nutrition facts labels. In 2016, when the Food and Drug Administration updated nutrition labels, vitamin A and C were replaced by vitamin D and potassium because those nutrients were more likely to be lacking in the American diet.
Yet, it appears that inadequacies of vitamin A, which are not as severe as deficiencies, may still be a problem. Research based on 15 years of national food consumption data found that U.S. adults consistently underconsume vitamin A, with 40% of women and 50% of men not meeting vitamin A recommendations
Certain groups of people are more likely than others to have trouble getting enough vitamin A:
— Infants and young children in developing countries
— Pregnant women in low-income countries
— Premature infants
— People with cystic fibrosis, Crohn’s disease, ulcerative colitis or celiac disease
Health Benefits of Vitamin A
Studies suggest eating a variety of foods rich in vitamin A, especially carotenoids in fruits and vegetables, may be protective against certain diseases. The evidence is focused on:
— Cancer
— Age-related vision diseases
— Cognitive decline
Cancer
Vitamin A or beta-carotene may help lower the risk of certain types of cancer, such as lung cancer, non-Hodgkin lymphoma and pancreatic cancer, studies suggest. However, other observational studies have shown no connection. Some studies have found that in people who smoke cigarettes, or previously smoked, high doses of beta-carotene supplements can increase the risk of lung cancer and death.
Age-related vision diseases
Vitamin A may help reduce the risk of age-related macular degeneration, the most common cause of vision loss in older people. Since beta-carotene supplements may increase the risk of lung cancer, researchers are exploring other options for supplements without beta-carotene.
Newer studies indicate that supplements containing the carotenoids lutein and zeaxanthin instead of beta-carotene reduce the progression of age-related macular degeneration without the increased risk of lung cancer.
Cognitive decline
Eating foods rich in alpha-carotene, a form of vitamin A that includes lutein and zeaxanthin, may help slow cognitive decline, such as maintaining memory and attention, suggests the Mediterranean-DASH Intervention for Neurodegenerative Delay (MIND) trial. In this randomized controlled intervention, higher blood levels of alpha-carotene were associated with higher global cognition scores in a U.S. population at risk for cognitive decline. The higher alpha-carotene levels were due to eating more fruits and vegetables and eating less meat and fried foods.
Health Risks of Too Much Vitamin A
High doses of vitamin A can cause acute vitamin A toxicity, but the dose generally has to be more than 100 times the RDA. This is typically only a risk with the preformed vitamin A or retinol in supplements. However, vitamin A toxicity is more likely to be a problem than a deficiency, says Abby Langer, a registered dietitian and author of “Good Food, Bad Diet.”
Signs of vitamin A toxicity, known as hypervitaminosis A, include the following:
— Severe headaches
— Blurred vision
— Muscle aches and problems with coordination
— Nausea and dizziness
— Coma and death in severe cases
— Birth defects during pregnancy
You don’t need to worry about eating large amounts of provitamin A carotenoids from plant-based foods. Carotenoids will not cause the same problems as high doses of preformed A.
Vitamin A Supplements vs. Foods
Experts recommend food as the preferred source of vitamin A over supplements, especially beta-carotene supplements that may carry risks for some people.
“It’s hard to get toxic levels of vitamin A from foods, unless you are just going to town on liver,” says Taylor Wallace, CEO of Think Healthy Group and editor of the Journal of Dietary Supplements.
People who consume significant amounts of animal-based foods probably have the best likelihood of getting recommended intakes of vitamin A, says Wallace. The majority of vitamin A in the U.S. comes from preformed vitamin A in dairy, eggs and meat, poultry and oily fish.
Unless you’ve been prescribed a stand-alone vitamin A supplement for a medical condition, it’s best to limit extra vitamin A to a multivitamin that typically contains lower levels of vitamin A. Multivitamins alone don’t contribute to toxic levels of vitamin A, says Wallace, but if you are taking several supplements that contain vitamin A, that is where problems can arise. This is one of the reasons to have a registered dietitian nutritionist oversee your supplement regimen.
“You really want to keep supplemental intake of vitamin A below 750 micrograms retinol activity equivalents (RAE) per day (usually labeled as vitamin A acetate or vitamin A palmitate) and no more than an additional 750 micrograms RAE of provitamin A (beta-carotene), Wallace says.
Eating a variety of colorful fruits and vegetables every day will also help you meet vitamin A recommendations.
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Foods High in Vitamin A originally appeared on usnews.com
