Vitamin A (retinol)

Vitamin A, also known as retinol, is a fat-soluble vitamin essential for various bodily functions, including vision, immune function, and reproduction. It is available in two forms: preformed vitamin A, which includes retinyl acetate and retinyl palmitate, and provitamin A, which includes beta-carotene 1.

Preformed vitamin A is the preferred form for storing vitamin A in mammals, with retinyl palmitate being the most common form found in animal products such as liver 6. However, retinyl acetate is considered more effective in cancer prevention and treatment studies, and it is the preferred form used by Georgi Dinkov in his supplement, Retinil 2.

Vitamin A has a unique ability to inhibit serotonin synthesis through the inhibition of tryptophan hydroxylase (TPH), which may be beneficial in treating conditions such as autism 1. It also has anti-cortisol effects, which can lead to feelings of tiredness if thyroid function is low 4.

Georgi Dinkov notes that vitamin A accumulates in the liver, even with lower topical absorption, and that an oral dose of 100,000 IU may be equivalent to 40,000 IU topically 7. However, he also cautions that the absorption of vitamin A dissolved in water/ethanol may be lower than that of retinyl palmitate.

Ray Peat recommends a high dose of vitamin A for individuals with high metabolic rates, as it is necessary for producing pregnenolone and progesterone 5. However, Georgi Dinkov notes that Peat's recommendation may be for topical use, not oral supplementation 8.

Overall, vitamin A is a complex vitamin with various forms and effects, and its optimal dosage and method of administration may depend on individual circumstances.