Vitamin A: An Essential Nutrient for Development, Immunity and Eye Health
Vitamin A comprises a group of fat-soluble compounds crucial to human health, playing a vital role in cellular development, visual function, bone health and immune response. This article explores the various facets of vitamin A, including its sources, benefits, risks associated with supplementation, and dosage recommendations, based on current data and statistics.
Sources and Forms of Vitamin A
There are two main categories of vitamin A: preformed vitamin A (retinoids), found in animal foods such as fish, eggs, dairy products and liver, and provitamins A (carotenoids), found in plant foods such as sweet potatoes, carrots and leafy greens. Some countries fortify foods such as milk and cereals with vitamin A to prevent deficiencies.
Proven Benefits
- Eye Health: Vitamin A is essential for maintaining vision, especially in low light conditions. Vitamin A deficiency can lead to serious visual disturbances such as xerophthalmia.
- Cellular Development: Crucial for the development and maintenance of epithelial tissues.
- Immune Function: Plays a significant role in regulating the immune system, reducing susceptibility to infections.
- Skin Health: Forms of vitamin A, such as tretinoin and isotretinoin, are widely used to treat skin conditions such as severe acne.
Risks and Precautions
Although vitamin A is essential, excessive intake can lead to toxicity, manifesting itself through symptoms such as headache, blurred vision, nausea and dizziness. High doses of preformed vitamin A are also associated with increased risks of bone problems, certain types of cancer and, during pregnancy, birth defects.
Dosage Recommendations
The recommended daily allowance (RDA) of vitamin A varies depending on age, sex and physiological condition. For adults, the RDA is 900 mcg for men and 700 mcg for women. During pregnancy and lactation, requirements increase to 770 mcg and 1300 mcg, respectively. However, due to the potential for toxicity, there is an upper limit of safe intake set at 3000 mcg for adults.
Global Statistics on Vitamin A Deficiency
Vitamin A deficiency is a significant public health concern in many parts of the world, especially in developing countries, primarily affecting children and pregnant women. An estimated 127 million preschool children and 7.2 million pregnant women globally are vitamin A deficient. Supplementation in high-risk populations has been shown to reduce infant mortality by up to 24%.
Conclusion
Vitamin A is an essential nutrient that supports several critical functions in the human body. Adequate intake through a balanced diet is crucial to ensure health benefits, while dosage monitoring is essential to avoid toxicity. Health professionals should guide supplementation, especially in vulnerable groups and during pregnancy, to maximize benefits while minimizing risks.
References
- Clare, CE, Brassington, AH, Kwong, WY, & Sinclair, KD (2019). One-Carbon Metabolism: Linking Nutritional Biochemistry to Epigenetic Programming of Long-Term Development. Annual Review of Animal Biosciences, 7 , 263–287. https://doi.org/10.1146/annurev-animal-020518-115240
- O'Leary, F., & Samman, S. (2010). Vitamin B12 in health and disease. Nutrients, 2 (3), 299–316. https://doi.org/10.3390/nu2030299
- van Campen, CLM, Riepma, K., & Visser, F. C. (2019). Open Trial of Vitamin B12 Nasal Drops in Adults With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome: Comparison of Responders and Non-Responders. Frontiers in Pharmacology, 10 , 1102. https://doi.org/10.3389/fphar.2019.01102
- Markun, S., Gravestock, I., Jäger, L., Rosemann, T., Pichierri, G., & Burgstaller, J.M. (2021). Effects of Vitamin B12 Supplementation on Cognitive Function, Depressive Symptoms, and Fatigue: A Systematic Review, Meta-Analysis, and Meta-Regression. Nutrients, 13 (4), 1222. https://doi.org/10.3390/nu13041222
- Wang, JY, Wu, YH, Liu, SJ, Lin, YS, Lu, PH, & Lu, CW (2018). Vitamin B12 for herpetic neuralgia: A meta-analysis of randomized controlled trials. Complementary Therapies in Medicine, 41 , 277–282. https://doi.org/10.1016/j.ctim.2018.09.016
- Didangelos, T., Karlafti, E., Kotzakioulafi, E., Margariti, E., Giannoulaki, P., Batanis, G., Tesfaye, S., & Kantartzis, K. (2021). Vitamin B12 Supplementation in Diabetic Neuropathy: A 1-Year Randomized Double-Blind Placebo-Controlled Trial. Nutrients, 13 (2), 395. https://doi.org/10.3390/nu13020395
- Pflipsen, M. C., Oh, R. C., Saguil, A., Seehusen, D. A., Seaquist, D., & Topolski, R. (2009). The prevalence of vitamin B(12) deficiency in patients with type 2 diabetes: a cross-sectional study. Journal of the American Board of Family Medicine: JABFM, 22 (5), 528–534. https://doi.org/10.3122/jabfm.2009.05.090048