Vitamin A

What is Vitamin A?

Vitamin A is a fat-soluble vitamin that exists in several forms, including retinol, retinoic acid, and retinal.  All-trans retinol is the most active form and is the form that is present in foods.  Carotenoids are precursors to retinol (a provitamin), and approximately 50% of the Vitamin A consumed in America comes from plant carotenoids.1

Why is vitamin A part of my treatment plan?

Your genetic profile indicates a change in the CRABP2 gene, which oversees the transport of vitamin A into the cells.  Higher levels of vitamin A are necessary when this genetic change is present.  Retinol increases collagen production, the hair growth factor IGF.2

Vitamin A is used topically to enhance skin cell health and reduce skin inflammation.3 

Retinol is associated with hair growth and improvement in scalp skin conditions.  It is a crucial vitamin for the growth, maturation, and maintenance of hair follicles.4

What are the food sources of vitamin A?

Eggs, milk, butter, fish, other animal proteins, & liver are sources of all-trans retinoic acid.  Plant sources of carotenoids include kale, spinach, squash, avocado, sweet potatoes, and carrots.

How do deficiencies in vitamin A occur?

Malnutrition, liver disease, malabsorptive diseases, and pancreatic insufficiency are causes of vitamin A deficiency.5

Hodge C, Taylor C. Vitamin A Deficiency. [Updated 2021 Jul 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:

What are the symptoms of vitamin A deficiency?

Symptoms of vitamin A deficiency include vision loss, night blindness, increased infections, impaired immunity, dry skin, acne, and poor wound healing.5

What does vitamin A do in the body?

Vitamin A is an essential vitamin for the regulation of vision, cell growth and differentiation, immune cell function, bone development, skin integrity, cholesterol and steroid metabolism, and signaling between nerves in the brain.6

Does vitamin A have adverse effects?

Vitamin A is well tolerated up to doses of 10,000 IU daily. Amounts above this are associated with hair loss, liver toxicity, coma, and death.  Other adverse effects of high amounts of Vitamin A include skin redness, hyperpigmentation, skin peeling, diarrhea, nausea, and vomiting.7


  1. Hickenbottom SJ, Follett JR, Lin Y, et al. Variability in conversion of beta-carotene to vitamin A in men as measured by using a double-tracer study design. Am J Clin Nutr 2002;75:900-7
  2. Wicke C, Halliday B, Allen D, et al. Effects of Steroids and Retinoids on Wound Healing. Arch Surg. 2000;135(11):1265–1270. doi:10.1001/archsurg.135.11.1265
  3. Zeichner JA. Optimizing topical combination therapy for the treatment of acne vulgaris. J Drugs Dermatol. 2012;11(3):313-317.
  4. Yoo HG, Chang IY, Pyo HK, et al. The additive effects of minoxidil and retinol on human hair growth in vitro. Biol Pharm Bull. 2007;30(1):21-26. doi:10.1248/bpb.30.21
  5. Hodge C, Taylor C. Vitamin A Deficiency. [Updated 2021 Jul 27]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2021 Jan-. Available from:
  6. H. Herschel Conaway, Petra Henning, Ulf H. Lerner, Vitamin A Metabolism, Action, and Role in Skeletal Homeostasis, Endocrine Reviews, Volume 34, Issue 6, 1 December 2013, Pages 766–797,
  7. Vitamin A. Natural medicines - login. (n.d.). Retrieved October 30, 2021, from,-herbs-supplements/professional.aspx?productid=964#adverseEvents.