Nutrient Spotlight: Vitamin A
- Meaghan
- Jun 23, 2023
- 5 min read
Updated: Jun 27, 2023
Everything you need to know about Vitamin A, what it is, why you need it, and how to get more of it.
In this series, we’ll be breaking down the specifics of each vitamin to hopefully make it a little easier to understand why they’re so important and how to be sure we’re getting adequate amounts of them.
Here is everything we'll go over, feel free to skip ahead!
Let's start at the very beginning.. What even is a vitamin?! Vitamins are essential nutrients that help our bodies function each and every day in countless ways. Each vitamin has its own to-do list for where and how it helps the body.
Some vitamins are fat-soluble, and some are water-soluble. This just means that some are absorbed with fats in the diet and are stored in fatty tissues and the liver so that your body can access them as needed. Others dissolve in water and they are easily absorbed so the body doesn’t really need to store any extra (essentially you just pee out what you don’t need).
Vitamins A, D, E, and K are all fat-soluble, so pair foods high in these with some healthy fats in the diet. The B Vitamins (there are a lot, we’ll get to that later…) and Vitamin C are all water soluble.
Vitamin A is actually a group of several different little compounds huddled under an “umbrella” that we call Vitamin A. It is super important for vision, supporting the immune system, and the development of several organs including the heart, lungs, eyes, and kidneys. [1]
Vitamin A in the Diet
When it comes to food sources, there are two main types of Vitamin A. The first kind is called “preformed” Vitamin A (super science names are retinol, retinyl esters). It is found in foods from animal sources such as eggs, dairy, fish, and organ meats like liver. [1-3]
The second kind of Vitamin A, called provitamin A carotenoids, is from plants. These nutrients are considered “precursors” because the body converts these into Vitamin A after they’re ingested. You’ve maybe heard of beta-carotene? This is an example of a provitamin A carotenoid. For food sources, think leafy greens, tomatoes, and yellow and orange vegetables.
There are also some foods that aren’t naturally very high in Vitamin A so they are *fortified* to have higher levels (aka, added in after-the-fact). This includes food like milk, margarine, and some cereals. [1]
Some foods that are naturally high in Vitamin A are:
Organ meats (especially liver)
Salmon, tuna, trout, clams, and oysters
Dairy products including whole milk certain types of cheese
Eggs
Red and orange vegetables (sweet potato, winter squash, carrots, red bell peppers, tomatoes)
Dark leafy greens (kale, collards, chard, spinach, and turnip greens
Yellow and orange fruits like (mango, cantaloupe, papaya, and apricots)
What Does the Research Say?
So far, the majority of research done on Vitamin A has to do with its impact on cancer (specifically lung cancer) and age-related macular degeneration.
Some studies suggest that those who consume a lot of foods containing beta-carotene (remember those plant sourced provitamin A carotenoids?) may have a lower risk of developing certain types of cancer, specifically lung and prostate cancer, because of the antioxidants in these foods. This is only from food sources, though. Studies have not yet linked Vitamin A from supplements to a protective effect from these diseases. Some studies actually suggest that smokers who take Vitamin A supplements may have an increased risk of lung cancer. [3]
As for macular degeneration, supplements containing antioxidants, zinc, and copper (with or without beta-carotene) may help slow the progression of the disease, which is among the most common causes of vision loss in older adults. [1]
Too Much vs Too Little
Vitamin A deficiency is rare in the United States, but the most common symptom of a deficiency is called xerophthalmia, which causes dry eyes and makes it difficult to see in low light. This can lead to night blindness or total blindness in severe cases. Deficiency can also lead to hair loss, hyperkeratosis (thickening of the outer layer of the skin), and poor immune function. [1-3]
With fat soluble vitamins, Vitamin A included, your body uses what it needs and then tucks the rest away in your liver (among other places) to save for later. This means that with high enough intakes of preformed Vitamin A, too much can accumulate and cause side effects like headaches, blurred vision, nausea, dizziness, muscle aches, and coordination problems. [2]
Routine intakes of super high doses can cause dry skin, muscle joint pain, fatigue, depression, and abnormal liver test results. Excess Vitamin A intakes during pregnancy can also lead to birth defects. [1]
Provitamin A carotenoids (like beta-carotene) on the other hand, are not toxic when consumed at high levels since the body only transforms this into Vitamin A when it needs it. Eating a ton of these foods for an extended period of time may cause an oompa-loompa effect and turn you orange for a bit, but this should resolve itself if you just back off of those foods for a bit. For those who have medical conditions that interfere with the body’s ability to convert beta-carotene into Vitamin A, a physician or registered dietitian should be consulted to make sure harmful levels do not accumulate.
For physical signs of a Vitamin A deficiency, look for Bitot’s spots (triangular “foamy” looking spots in the eyes), or bumpy, scaly, dry, or itchy skin. If you are worried you may have a Vitamin A deficiency, talk with your doctor about having micronutrient labs checked.
Do I Need A Supplement?
According to the National Institute of Health, the recommended daily allowance (RDA) for Vitamin A in adults over 19 years of age is 900mcg RAE (retinol activity equivalents) for men and 700mcg RAE for women. [1]
As an example, ½ cup of raw carrots contains 459mcg RAE. That’s over 50% of the RDA for both men and women!
For the general population in the US, enough Vitamin A is consumed through a balanced diet and a supplement is likely not needed. Certain groups, however, may have difficulty absorbing Vitamin A and other fat-soluble vitamins, and a supplement may be needed to help meet the RDA. These include people with cystic fibrosis or gastrointestinal disorders like Crohn’s disease or ulcerative colitis [1]. Premature infants, young children, and pregnant/breastfeeding women in developing countries may also require a supplement.
Supplements can contain various forms of Vitamin A, both preformed and provitamin A, and may contain other vitamins and minerals as well. Many multivitamins include Vitamin A as part of their formula. Because excess intakes of preformed Vitamin A can lead to undesirable side effects, it may be better to choose a supplement that contains a majority of its Vitamin A in the form of beta-carotene.
The Bottom Line
Vitamin A can be consumed as preformed Vitamin A (found in animal sources) or provitamin A (found in plant sources).
Adequate intakes are important for vision, immune support, and reproduction/development.
Vitamin A may help protect against macular degeneration and certain types of cancer
Deficiency is rare in the United States but can lead to symptoms such as dry eye, blindness, hair loss, skin problems, and increased risk for infection.
It is possible to consume too much Vitamin A so if taking a supplement, try and choose one that has provitamin A (beta-carotene) as a main component.
If you think you have a deficiency or are considering taking a supplement, we recommend consulting a doctor or registered dietitian.
Resources
[1] Harvard School of Public Health. (2019, July 2).Vitamin A. The Nutrition Source. Retrieved June 14, 2022, from https://www.hsph.harvard.edu/nutritionsource/vitamin-a/
[2] Kubala, J. (2022, April 6). Vitamin A: Benefits, Deficiency, Toxicity, and More. Healthline. Retrieved June 14, 2022, from https://www.healthline.com/nutrition/vitamin-a
[3] U.S. Department of Health and Human Services. (2022, March 23). Office of dietary supplements - vitamin A and carotenoids. NIH Office of Dietary Supplements. Retrieved June 14, 2022, from https://ods.od.nih.gov/factsheet/VitaminA-HealthProfessional/
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