Health Tips

The global dietary supplements market is a lucrative one–it was estimated to be valued at USD$123.28 billion in 2019 and is projected to expand for the years to come. This booming industry has certainly attracted many sellers and entrepreneurs– both scrupulous and unscrupulous– to sell their dietary products to the mass public. 

Among the many dietary supplements products in the market, vitamins supplements have always been the most familiar one. Especially with the occurrence of a global pandemic, the benefits of vitamin supplements in treating Covid-19 have been discussed by many. You may have heard that taking vitamin C, vitamin D or zinc supplements can help to improve Covid-19 symptoms. FYI, the scientific evidence on this is still mixed and confusing. But no harm taking them under the advice of a healthcare professional, though it should not replace the importance of hand washing, social distancing and wearing a mask.

But today, we are going to talk about another vitamin, i.e. vitamin A dietary supplement.

Vitamin A: the virtues

Vitamin A is a fat-soluble vitamin that is naturally present in many foods. Among the scientists, vitamin A is called retinoids– it is a group of compounds consisting of retinol, retinal, and retinyl esters. (1) Vitamin A is important for normal vision, the immune system, and reproduction. Vitamin A also helps the heart, lungs, kidneys, and other organs work properly.  Vitamin A is also a group of antioxidants that may prevent or delay some types of cell damage. They are the compounds that give you loads of benefits– from a healthy, youthful skin to prevention of cancers.

There are two different types of vitamin A. The first type, preformed vitamin A (retinol and its esterified form, retinyl ester), is found in meat, poultry, fish, and dairy products. The second type, provitamin A, is found in fruits, vegetables, and other plant-based products. Both preformed vitamin A and provitamin A are not exactly the active vitamin A itself (they’re the precursor). They must be metabolized by our body cells into retinal and retinoic acid, which are the active vitamin A that our body can use. (2) 

The most common type of provitamin A in foods and dietary supplements is beta-carotene. Beta-carotene presents in many plants such as carrot, the food that is most commonly associated with its richness in vitamin A. It is also what gives this root vegetable’s characteristics orange colour. But it’s only a semi-myth that eating carrots will help you see in the dark. Beta-carotene is a precursor to vitamin A and helps your eyes to adjust in dim conditions. Vitamin A can’t give you superpowers of night vision or cure your dependence on contact lenses, but eating an adequate amount will support eye health. There are other types of carotenoids found in food that are not converted to vitamin A but have health-promoting properties; these include lycopene, lutein, and zeaxanthin.

Vitamin A deficiency?

As vitamin A is found naturally in many foods and is added to some foods, such as milk and cereal, you can easily achieve the recommended amounts of vitamin A by eating a variety of foods. 

Vitamin A deficiency is actually rare in today’s age. Only a certain groups of people are more likely than others to have trouble getting enough vitamin A:

• Premature infants, who often have low levels of vitamin A in their first year.

• Infants, young children, pregnant women, and breastfeeding women in developing countries.

• People with cystic fibrosis. Cystic fibrosis is a progressive, genetic disease that causes persistent lung infections and limits the ability to breathe over time. People with cystic fibrosis have trouble absorbing fats, which means they have trouble absorbing vitamins that need fat to be absorbed, such as vitamin A.

Vitamin A deficiency can lead to an eye condition called xerophthalmia, which is the inability to see in low light, and it can lead to blindness if it isn’t treated.

These groups of people can obtain vitamin A from multivitamin or stand-alone supplement, often in the form of retinyl acetate or retinyl palmitate. (2) A portion of the vitamin A in some supplements is in the form of beta-carotene and the remainder is preformed vitamin A; others contain only preformed vitamin A or only beta-carotene. Check the supplement labels for the percentage of each form of the vitamin and their respective amounts, as they can vary quite widely from products to products.

Excess vitamin A: the vices

We all need vitamin A for a healthy body, period. However, since our daily diet is already loaded with vitamin A, and most of us do not have medical conditions that warrant vitamin A supplement, do you really need to take vitamin A dietary supplement?

In fact, taking too much vitamin A supplement can actually lead to toxicity, known as hypervitaminosis A. This is because vitamin A is fat-soluble, so when it is in excess, our body stores them primarily in our liver, and these levels can accumulate.

Too much vitamin A can be harmful. Even a single large dose — over 200,000 mcg — can cause:

• Nausea

• Vomiting

• Vertigo

• Blurry vision

Taking more than 10,000 mcg a day of oral vitamin A supplements long term can cause:

• Bone thinning

• Liver damage. The damage to the liver can be permanent even after vitamin A supplementation stopped.

• Headache

• Diarrhea

• Nausea

• Skin irritation

• Pain in the joints and bone

• Birth defects

Hypervitaminosis A rarely occurs with eating too much vitamin A-rich foods–the condition is usually a result of consuming too much preformed vitamin A from supplements or medicinal retinoids such as isotretinoin. 

Excess vitamin A is linked to birth defects

Excess use of vitamin A during pregnancy has been linked to birth defects. (2) These birth defects can include malformations of the eye, skull, lungs, and heart. Women who might be pregnant should not take high doses of vitamin A supplements or isotretinoin, a medication used in treating severe acne. If you are or might become pregnant, talk to your doctor before taking them.

Go for beta-carotenes

Interestingly, although excess preformed vitamin A can have significant toxicity, large amounts of beta-carotene and other provitamin A carotenoids are not associated with major side effects. They are also not known to cause birth defects. Weird, huh? (That is why even if you have to take vitamin A supplements, it is important to learn the types of vitamin A the product offers.)

It turns out that this is because carotenoids are converted to vitamin A very slowly. Usually, no symptoms occur. However, when very large amounts of carotenoids are consumed, the skin may turn a deep yellow (called carotenosis), especially on the palms and soles. 

Although beta-carotene doesn’t sound so bad compared with its preformed vitamin A counterparts, studies did uncover some of its negative health effects too. In a study called the ATBC study concluded that beta-carotene supplements (20 mg daily) were also associated with higher chances of dying, mainly due to lung cancer and ischemic heart disease. In another study called CARET study, which ended early, after the investigators found that daily beta-carotene (30 mg) and retinyl palmitate (7,500 mcg RAE [25,000 IU]) supplements increased the risk of lung cancer and risk of dying from cardiovascular disease. Yikes. But carotenoids consumed in fruits and vegetables do not seem to increase this risk. 

So the bottom line is: It is perfectly safe (and even encouraged) to get your vitamin A from fruits and vegetables! But dietary supplements? Uhm, not so much.

Talk to your healthcare provider if you are keen to start taking a vitamin A supplement.

Vitamin A is also in your...face creams?

There have been claims that vitamin A (in the form of retinol or retinyl palmitate) added to some sunscreens, moisturizers, and lip balms can cause vitamin A toxicity or cancer if used excessively. However, there has not been evidence to date to support this. Vitamin A in topical creams is not absorbed into the bloodstream and therefore would not contribute to toxic levels.

Nonetheless, vitamin A derivatives such as retinoids in face creams can cause skin to become highly sensitive to bright light, so it is advised to apply vitamin A creams at night and to avoid strong sun after their use. 

A word from Doc2Us

If you have any questions related to vitamin A supplementation, you can consult our professional doctors and healthcare professionals on Doc2Us. Doc2Us is a mobile application that allows you to talk to a doctor or any healthcare professionals via text chat at any time and from anywhere. For better communication, you can even send our online doctor images or voice messages related to your medical inquiry.

Download Doc2Us app on Apple App Store, Google Play Store and Huawei App Gallery; or use our web chat at https://web.doc2us.com/

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Disclaimer: As a service to our users and general public, Doc2Us provides health education contents. Please note the date of last review or update on all articles. No content on this site, regardless of date, should ever be used as a substitute for direct medical advice from your doctor or other qualified clinician.

References

1. Johnson EJ, Russell RM. Beta-Carotene. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:115-20.

2. Ross CA. Vitamin A. In: Coates PM, Betz JM, Blackman MR, et al., eds. Encyclopedia of Dietary Supplements. 2nd ed. London and New York: Informa Healthcare; 2010:778-91.

3. MSD Manual - Vitamin A Excess

4. Harvard School of Public Health - Vitamin A

5. NIH - Vitamin A (Consumer)

6. NIH - Vitamin A (Healthcare Professional)

Cover image credit: Photo by Pietro Jeng from Pexels

Written by

Ms Joyce Toh