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If you have any medical questions or concerns, please talk to your healthcare provider. The articles on Health Guide are underpinned by peer-reviewed research and information drawn from medical societies and governmental agencies. However, they are not a substitute for professional medical advice, diagnosis, or treatment.
In the late 80s, a group of researchers in Finland decided to take on a monumental task. They set out to study the effects of vitamin supplementation on the rate of lung and prostate cancer among smokers.
Coined the Alpha-Tocopherol Beta Carotene (ATBC) trial, 29,133 men between the ages of 50 and 69 were given supplements and followed for about six years. Scientists hoped that giving smokers essential vitamins could lower their risk of certain types of cancer (ATBC, 1994).
To the surprise of those involved in the study, supplementing with ATBC did not lower the risk of lung cancer. In fact, researchers reported a slightly higher rate of lung cancer in the group of patients who took beta carotene compared to those who didn’t (Virtamo, 2003).
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What is beta carotene?
Beta carotene (from the Latin word for carrot) is a pigment found in many fruits and vegetables. It is known as a provitamin A carotenoid. A provitamin is a substance that is converted into a vitamin after you eat it.
So when you eat something that contains beta carotene, it gets converted in your body to the essential vitamin A. Also known as retinol, vitamin A is commonly mentioned for its importance in vision and plays a role in healthy skin and your immune system.
Beta carotene also acts as an antioxidant against free radicals. Think of free radicals as the vandals of the body. They take parts of other molecules, sometimes causing damage to cells in the process and contributing to diseases (Chea, 2020).
Most of your body’s vitamin A storage is in your liver, where it’s stored in a fat-soluble form (as retinyl palmitate). Retinyl palmitate is pre-formed vitamin A. It’s found in dairy and animal products (mostly in the liver, where animals store vitamin A too). Your body converts beta carotene and retinyl palmitate to the active form of vitamin A to keep your levels in balance.
The benefit of having dietary beta carotene is that your body only converts as much as you need. That’s important because high levels of supplemental vitamin A can also result in toxicity, which we’ll discuss in a moment.
What foods are high in beta carotene?
Many foods contain dietary provitamin A or beta carotene. Some of these foods include:
- Green, leafy vegetables (spinach, broccoli)
- Orange/red fruits and vegetables (carrots, sweet potatoes, cantaloupe, mangos, apricots)
- Tomatoes and peppers
The top food sources for pre-formed vitamin A are animal products like beef liver and eggs.
The Institute of Medicine has developed a reference that estimates the amount of dietary vitamin A appropriate for healthy people. They provide the recommendations in a unit called RAEs (which stands for retinol activity equivalents).
For men over the age of 18, the recommended dietary allowance is 900 mcg RAE. This allowance can easily be met by eating one baked sweet potato, which provides 1403 mcg RAE (NIH, 2020).
Vitamin A is also contained in several multivitamins and as a standalone supplement. Some come in the form of beta carotene and others come as retinyl palmitate.
Check the back of the label for information on what form of vitamin A the product contains. Talk to your healthcare provider before taking a vitamin A-containing supplement as the FDA does not evaluate these products.
Benefits of taking vitamin A
Vitamin A deficiency is very rare in the United States because most people get enough in their diet. It is a little more common in developing countries where populations have limited access to various fruits and vegetables.
In these developing countries, it has been reported that up to 300 million children develop vitamin A deficiency each year. If the deficiency is chronic, it can lead to a potentially harmful condition that causes blindness––xerophthalmia (Chea, 2020).
Vitamin A is an essential part of your immune system and is critical to your vision. It even plays a role in the way some of your cells communicate. It also plays a role in the way your cells grow and how they differentiate.
Differentiation is how your cells develop and change into mature cells with unique functions. Because of all these complex roles vitamin A plays in your body, scientists speculate that it could have an impact in preventing or treating certain diseases.
Age-related macular degeneration
Age-related macular degeneration is a condition of the eye that can cause blurry vision and lead to vision loss.
In a trial called the AREDS study, researchers reported that patients who took a combination of vitamins that included beta carotene (in addition to vitamin E, vitamin C, zinc, and copper) had a lower risk of developing advanced age-related macular degeneration by roughly 25% (AREDS, 2001).
Although this trial showed significant results, follow-up studies found that it was unclear if beta carotene specifically was responsible for the positive effect. Larger scale clinical trials are needed to evaluate the benefits and risks of supplementing with beta carotene.
Cancer and cardiovascular disease
In 2014 the United States Preventive Services Task Force put out a recommendation after careful review of available data on using vitamin supplementation to prevent cancer and cardiovascular disease.
The USPSTF recommended against taking beta carotene and vitamin E supplements to prevent heart disease and cancer and cites that the documented potential for harm outweighs the benefits (Moyer, 2014).
What are the risks of taking too much vitamin A?
There are possible health risks from taking too much vitamin A. Because it is a fat-soluble vitamin, all the excess vitamin A is stored in your liver and can accumulate to toxic levels.
While rare, taking too much vitamin A consistently can lead to bodily pain, dizziness, headaches, and nausea. People living with kidney or liver disease should take caution before starting a beta carotene supplement. Vitamin A supplements are also to be avoided by women who are pregnant or breastfeeding.
It is also possible that vitamin A supplements can interact with other medications that you take. A drug interaction can cause side effects or interfere with the vitamin A levels that you have. People who take isotretinoin (brand name Accutane), for example, have a higher risk of side effects if they take vitamin A supplements.
Talk to your healthcare provider before starting any multivitamin or supplement, as they might not be necessary if you have a healthy diet.
- Age-Related Eye Disease Study Research Group (2001). A randomized, placebo-controlled, clinical trial of high-dose supplementation with vitamins C and E, beta carotene, and zinc for age-related macular degeneration and vision loss: AREDS report no. 8. Archives of ophthalmology (Chicago, Ill. : 1960), 119(10), 1417–1436. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1462955/
- Chea, E. P., Lopez, M. J., & Milstein, H. (2020). Vitamin A. In StatPearls. StatPearls Publishing. https://pubmed.ncbi.nlm.nih.gov/29493984/
- Moyer, V. A., & U.S. Preventive Services Task Force (2014). Vitamin, mineral, and multivitamin supplements for the primary prevention of cardiovascular disease and cancer: U.S. Preventive Services Task Force recommendation statement. Annals of internal medicine, 160(8), 558–564. http://www.ncbi.nlm.nih.gov/pubmed/24566474
- NIH Office of Dietary Supplements (2020). Vitamin A. https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/
- The ATBC Cancer Prevention Study Group. (1994). The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. New England Journal of Medicine, 330(15):1029-35. https://pubmed.ncbi.nlm.nih.gov/8127329/
- Virtamo, J., Pietinen, P., Huttunen, J. K., Korhonen, P., Malila, N., Virtanen, M. J., Albanes, D., Taylor, P. R., Albert, P., & ATBC Study Group (2003). Incidence of cancer and mortality following alpha-tocopherol and beta-carotene supplementation: a post-intervention follow-up. JAMA, 290(4), 476–485. https://pubmed.ncbi.nlm.nih.gov/12876090/
Dr. Steve Silvestro is a board-certified pediatrician and Manager, Medical Content & Education at Ro.