Vitamin A and Beta carotene explained

Eyes, Immune, Vitamins, Nutrition | January 24, 2018 | Author: Naturopath

Immune, Eyes

Vitamin A and Beta carotene explained

Vitamin A is one of the fat-soluble vitamins, along with vitamins D, E, and K. Fat-soluble vitamins are absorbed in the presence of fats in the diet, and can be stored in the body’s fatty tissue.

The different types of vitamin A

There are two main sources of vitamin A, depending on the type of food it comes from:

  • Retinol. A type of vitamin A that is found in animal foods, such as liver, fish oils, dairy products, and eggs.
  • Carotenoids. Plant pigments that are responsible for yellow, orange, and red colours of a variety of fruits and vegetables. The most important one is beta-carotene. In the body, beta-carotene converts into vitamin A (retinol); hence it is considered a precursor (inactive form) to vitamin A. 

The Benefits of Vitamin A

VisionVision. Vitamin A is required for the normal functioning of the retina and also helps lubricating the eyes.

A deficiency can lead to night blindness, and in severe cases deficiency can lead to blindness.

In developing countries, vitamin A deficiency is the leading cause of preventable blindness in children. 

Growth and development. Vitamin A is involved in foetal development of organs, particularly in the development of the spinal cord, limbs, heart, eye ears and lungs.

‚ÄčImmune system. Vitamin A is required for maintaining the integrity of epithelial cells throughout the body. These are the cells that line the internal and external surfaces of the body (such as the airways, digestive tract, and urinary tract) and provide the first line of defense of the immune system Thus, deficiency of vitamin A can impair the barrier against infection, and can increase the risk of respiratory and gastrointestinal infections, especially in children. In addition, vitamin A is involved in the development of T-cells - A type of white blood cell that is part of the immune system and help protect the body from infection and may help fight cancer.

Cancer. Beta-carotene belongs to a group of compounds called phytonutrients. Phytonutrients are components of plants that are powerful antioxidants, and may reduce cancer risk. Women with higher blood concentrations of beta-carotene from food sources are at decreased risk of breast cancer.

Vitamin A and beta-carotene Supplements

Vitamin A and beta-carotene SupplementsVitamin A is available over the counter in multivitamins in varying amounts, and as individual supplements. Some of the supplements have a combination of vitamin A and beta-carotene, and some have one or the other. Vitamin A in supplements often comes in the form of retinol or retinyl palmitate, but other forms can be used. Hence, to know the dose of the supplement, it is important to read the label and determine the actual vitamin A content, expressed in international units (IU).

Vitamin A can also be found in skin ointments.

Who should take vitamin A?

In Australia deficiency of vitamin A is rare as we get enough in our diet. However, your doctor may recommend vitamin A or beta-carotene supplement or cream if you suffer from:

  • Age-related macular degeneration or cataract. Research shows that people who eat more foods with beta-carotene have a lower risk of developing age-related macular degeneration or cataract. You may need to supplement your diet if you are not eating enough of these foods. 
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  • Measles. Vitamin A supplements can reduce the severity and complications of measles in children. However, never give a child vitamin A supplements without a doctor's supervision.
  • Inflammatory bowel disease (IBD). Crohn's disease and ulcerative colitis can interfere with digestion and absorption of nutrients. Your doctor may recommend taking a multivitamin containing vitamin A if you are suffering from nutrient deficiencies.
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  • Acne. A synthetic form of vitamin A called retinoids is used in prescription creams and gels for the treatment of mild to moderate acne, or in Roaccutane capsules for more severe cases of acne.
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  • Other skin conditions. Retinoid ointments are available for skin conditions such as chafed skin, cracked heels, cracked nipples, eczema, and sun-damaged and pigmented skin.

How much vitamin A?

Too much vitamin A can be toxic as it can accumulate in your liver and may result in liver damage.

Recommended daily intakes:

Men – 900 mcg/day (3,000 IU)

Women – 700 mcg/day (2,333IU)

When taken in excess of 3000 mcg (10,000 IU), vitamin A can cause birth defects. If you are pregnant, or considering becoming pregnant, consult your doctor or pharmacist before taking any supplements that contain A.

How much beta-carotene?

Unlike vitamin A, high doses of beta-carotene are not toxic. Too much carotene-rich food in your diet (such as large amounts of carrots) or prolonged and excessive consumption of beta-carotene supplements can turn your skin yellow-orange, a harmless condition that gradually disappears when the amount is reduced or eliminated.

One group that should avoid taking supplements of vitamin A or beta-carotene supplements are people at high risk for lung cancer. A study of 18,314 smokers, former smokers, and workers exposed to asbestos found that taking high doses of these supplements over a long period of time actually increased the incidence of lung cancer.

How can I increase the levels of vitamin A in my body?

Vitamin A from foods is considered safe. As the body makes vitamin A from beta-carotene, you can increase levels of vitamin A in your body, while at the same time enjoy the health benefits of the antioxidants in beta-carotene by:

  • Eating more fruit and vegetables rich in beta-carotene. These include vegetables such as carrot, pumpkin, sweet potato, and fruit, including mango, apricot, papaya, and peach. Leafy greens, such as spinach and kale, also contain beta-carotene, as well as broccoli.
  • Cooking your carrots. Because carrots are high in fibre, the heat from cooking will free the carotenoids from the fibre and make them more available.
  • Drizzling olive oil on your vegetables. As carotenoids are fat-soluble, they are absorbed in the presence of fat.

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References

Bakker, M.F. et al., Plasma carotenoids, vitamin C, tocopherols, and retinol and the risk of breast cancer in the European Prospective Investigation into Cancer and Nutrition cohort 1,2. Am J Clin Nutr. Available at: http://ajcn.nutrition.org/content/early/2016/01/20/ajcn.114.101659.full.pdf

Linus Pauling Institute Oregon State University 2015. Vitamin A |. Available at: http://lpi.oregonstate.edu/mic/vitamins/vitamin-A#introduction

National Cancer Institute. Definition of fat-soluble vitamin - NCI Dictionary of Cancer Terms. Available at: https://www.cancer.gov/publications/dictionaries/cancer-terms?cdrid=560348

National Institutes of Health 2016. Vitamin A — Health Professional Fact Sheet. Available at: https://ods.od.nih.gov/factsheets/VitaminA-HealthProfessional/#h7

Omenn, G.S. et al., 1996. Effects of a Combination of Beta Carotene and Vitamin A on Lung Cancer and Cardiovascular Disease. New England Journal of Medicine, 334(18), pp.1150–1155. Available at: http://www.ncbi.nlm.nih.gov/pubmed/8602180

University of Maryland medical Center 2015. Vitamin A (Retinol). Available at: https://www.umm.edu/health/medical/altmed/supplement/vitamin-a-retinol

Villamor, E. & Fawzi, W.W., 2005. Effects of vitamin a supplementation on immune responses and correlation with clinical outcomes. Clinical microbiology reviews, 18(3), pp.446–64. Available at: http://www.ncbi.nlm.nih.gov/pubmed/16020684

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