Any dietary or drug treatment with high doses of micronutrients may override the body's own control mechanisms. Therefore, micronutrient therapies may be associated with potential side effects and toxicities. High-dose micronutrients should not be used without medical supervision.
Retinitis pigmentosa, the progressive loss of photoreceptor cells in the eye's retina (20), results in a loss of peripheral and central vision over time.
The results of a randomized controlled trial in more than 600 patients with common forms of retinitis pigmentosa indicated that supplementation with 4.5 mg (15,000 IU)/day preformed vitamin A (retinol) significantly slowed the loss of retinal function over a period of 4–6 years (21).
High-dose vitamin A supplementation to slow the course of retinitis pigmentosa requires medical supervision and must be discontinued if there is a possibility of pregnancy (see Safety).
Because of the role of vitamin A in regulating gene expression, cellular differentiation, and immune function, it has been suggested that retinoids might be beneficial in the treatment of some autoimmune skin disorders.
Both natural and synthetic retinoids, especially 13-cis-retinoic acid, have been used successfully as pharmacologic agents to reduce symptoms of skin disorders such as psoriasis and acne. Retinoids most likely affect the gene expression of skin growth factors and their receptors (1).
The use of pharmacological doses of retinoids by pregnant women causes birth defects (see Safety).
Authored by Dr Peter Engel in 2010, reviewed by Dr. Adrian Wyss on 31.08.2017