A multi-center, randomized, prospective study involving 60 patients with chronic gastric ulcers evaluated the effects of vitamin A supplementation on ulcer healing (Patty et al. 1983). Patients were divided into three groups and treated for four weeks with antacids only, antacids plus vitamin A (50,000 IU po tid), or antacids, vitamin A, and cyproheptadine (4 mg po tid). Endoscopic analysis revealed that gastric ulcers were completely healed in 15 out of 40 patients who received vitamin A. The reduction in ulcer size was greater in the group receiving vitamin A plus antacids after both two and four weeks of use. This study suggests that the combination of vitamin A and antacids may be more effective than antacids alone to heal ulcers.

HMG-CoA reductase inhibitors may increase blood vitamin A levels (Muggeo et al. 1995).

In one study involving 17 patients with severe cystic acne, subjects received isotretinoin (0.5mg/kg/day) for 3 months; eight patients continued to receive isotretinoin (0.75 mg/kg/day) for another 3 months (Rollman and Vahlquist 1986). After 3 months of therapy, epidermal retinol content increased by 53%, while dehydroretinol decreased by 79%. These findings were corroborated in another study with 22 subjects (Vahlquist et al. 1990). Administration of isotretinoin (1 mg/kg/day) for four months led to a marked increase in retinol and a decrease in dehydroretinol content in the skin. Individuals should avoid consuming high doses of vitamin A while taking tretinoin unless prescribed by a physician.

In a double-blind study in five healthy males, study participants consumed a standard meal containing vitamin A (300,000 IU) followed by either neomycin sulfate (2 g) or placebo (Barrowman et al. 1972). The rise in plasma vitamin A levels was significantly less after neomycin treatment in all study subjects. Neomycin interferes with the absorption of vitamin A when delivered in a very large bolus dose. The significance of this interaction on daily supplementation of vitamin A is unknown.

Omeprazole significantly suppressed the blood response to beta-carotene (120 mg po) in healthy subjects (Tang et al. 1996). Serum beta-carotene levels were significantly greater during the low gastric pH phase of the study compared to the high gastric pH phase. It is not known if omeprazole or lansoprazole adversely affect carotenoid absorption from foods.

Oral contraceptives increase the levels of vitamin A in women (Tyrer 1984).

Barrowman J, Broomhall J, Cannon A, et al. Impairment of vitamin A absorption by neomycin. Clin Sci. 1972;42:17P.

Muggeo M, Zenti MG, Travia D, et al. 1995. Serum retinol levels throughout 2 years of cholesterol-lowering therapy. Metab. 1995;44(3):398-403.

Patty I, Benedek S, Deak G, et al. Cytoprotective effect of vitamin A and its clinical importance in the treatment of patients with chronic gastric ulcer. Int J Tissue React. 1983;5:301-307.

Rollman O, Vahlquist A. Oral isotretinoin (13-cis-retinoic acid) therapy in severe acne: drug and vitamin A concentrations in serum and skin. J Invest Dermatol. 1986;86(4):384-389.

Tang G, Serfaty-Lacrosniere C, Camilo ME, Russell RM. Gastric acidity influences the blood response to a beta-carotene dose in humans. Am J Clin Nutr. 1996;64(4):622-626.

Tyrer LB. Nutrition and the pill. J Reprod Med. 1984;29(7 Suppl):547-550.

Vahlquist A, Rollmann O, Hollan D, Cunliffe, W. Isotretinoin treatment of severe acne affects the endogenous concentration of vitamin A in sebaceous glands. J Invest Dermatol. 1990;94:496-498.