Vitamin A (retinol) and Beta Carotene (which converts to Vitamin A) are fat-soluble vitamins with some notable benefits:
Vision has the most notable requirement of Vitamin A. It helps to maintain healthy cells and helps with changes in light, as well as night vision.
Proper immune function and as an antioxidant.
Reproduction and fertility.
High doses have been good for treatment for skin disorders, such as acne and psoriasis.
Most beta carotene supplements are synthetic, but a natural form is also available. The natural forms of beta carotene are available in an algal source (Dunaliella salina), or from a palm source, and have been found to be more bioavailable compared to the synthetic version. The D. salina carotenoids are also a vegetarian source that has vitamin B12 and some amino acids.
10,000 IU of Vitamin A is generally accepted as a safe dose for both men and women. Higher doses for treatment can be safe, with the help and close monitoring of a physician. For Beta Carotene, a daily dosage of 25,000 IU appears reasonable for general health. Liver, dairy products, and cod liver oil are good sources of vitamin A. Besides an algal source, dark green and orange-yellow vegetables are also a source of natural beta carotene.