Vitamin A

Vitamin A
Vitamin name	Retinol
Chemical formula	C₂₀H₃₀O
Solubility	Fat-soluble, stored in liver; requires dietary fat for absorption. Retinyl palmitate is the primary storage form in mammals.
Discovery year	1913 (identified as a fat-soluble growth factor; isolated/named later in 1930s)
Daily requirement (RDA)	700–900 mcg RAE (2,300–3,000 IU) for adults.
Upper limit
Rich food sources	Liver (100g ≈ 30,000 IU), halibut liver oil, egg yolks, cream, butter, cheese, milk. Peat recommends halibut liver oil or retinyl palmitate over carotene sources.

Introduction

Vitamin A occupies a central position in bioenergetic health, it is a fundamental regulator of steroid hormone synthesis, cellular differentiation, and the body's response to stress. Ray Peat's personal investigation into vitamin A began with his own acne and dandruff problems, which led him into studying the steroids and thyroid system.

Structure/Chemical properties

Vitamin A (C₂₀H₃₀O) is fat-soluble and highly unsaturated. This unsaturated nature is critical to understanding both its functions and its potential for harm.

"Since vitamin A is highly unsaturated, in excess it suppresses the thyroid, so it has to be balanced with the thyroid." - Ray Peat, Email Wiki (Blake Scholar thesis) "Vitamin A oxidizes easily and an excess can create symptoms of a deficiency, so vitamin E is the most important thing for correcting it; excess vitamin A, like PUFA, interferes with thyroid hormone transport." - Ray Peat

One blood protein carries both vitamin A and thyroid hormone together, illustrating their biological interdependence.

Function/Mechanism of Action

1. Steroid Hormone Synthesis

This is vitamin A's largest use-the production of pregnenolone, progesterone, and other youth-associated steroids.

"In animals, cholesterol is the basic sterol molecule, which is massively converted into other substances, including the steroid hormones. Thyroid hormone and vitamin A are required for this conversion. The first step occurs in the energy-producing mitochondrion, where cholesterol loses its side-chain and is slightly oxidized, producing pregnenolone."- Ray Peat

"To produce pregnenolone, thyroid, vitamin A, and cholesterol have to be delivered to the mitochondria in the right proportion and sufficient quantity."- Ray Peat,

2. Anti-Estrogen Function

"Vitamin A and estrogen are antagonistic, and while estrogen promotes keratinization (shedding of skin cells), vitamin A opposes it... the combination is effective for increasing progesterone and decreasing estrogen, slowing the turnover of skin cells, and making the skin cells function longer before flaking off."- Ray Peat

3. Skin and Mucous Membrane Differentiation

"One function of vitamin A is to increase progesterone in the skin, and it has to be in balance with thyroid to do that. Another function is to differentiate the skin cells, reducing keratin plugging of the glands." - Ray Peat

Medical uses/Effects

Primary indicators of deficiency:

• Acne
• Dandruff
• Fatigue, poor memory, poor libido
• Vision problems
• Skin issues
• Inadequate sleep
• Anxiety (since it's needed to make pregnenolone and progesterone)

"Acne and dandruff might be two of the biggest indicators for vitamin A status... If I'm vitamin A deficient enough to get dandruff and acne, could that cause anxiety too? 'Since it's needed to make pregnenolone and progesterone, I think it could.'" - Ray Peat

Emanuel Cheraskin's research:

"The nutrition researcher, dentist, Emanuel Cheraskin, did surveys where he found that health complaints and symptoms decreased in a nice linear relation to increasing vitamin A all the way up to 100,000 units a day."- Ray Peat,

Side/Adverse effects

Thyroid suppression is the primary concern with excess:

"The basic toxic effect of giant doses of vitamin A, like several hundred thousand units a day, those invariably will reach a point where they suppress your thyroid." - Ray Peat

Vitamin E prevents oxidative toxicity:

"The toxic effects of extremely big doses, such as 500,000 to a million i.u., seem to be from either oxidative processes (rancidity) that are prevented by adequate vitamin E, or by antithyroid effects." - Ray Peat "About 100 i.u. of vitamin E would help to keep the vitamin A from being wasted by oxidation, and possibly could reduce your requirement for it."- Ray Peat

Self-monitoring indicator:

"I found that when my need for vitamin A began to decrease I tended to accumulate carotene in my calluses; that happens when the thyroid function is lower, reducing the need for vitamin A. Since you are eating foods with carotene, the calluses on your palms or soles should serve as an indicator of when your tissues are saturated with vitamin A." - Ray Peat

Dosing

Baseline for hypothyroid individuals:

"The average person is likely to be hypothyroid, and to need only 5,000 units per day." - Ray Peat

High metabolic rate/sun exposure:

"For several years, when I had an extremely high metabolic rate, I needed 100,000 units per day during sunny weather to prevent acne and ingrown whiskers, but when I moved to a cloudy climate, suddenly that much was too much, and suppressed my thyroid." - Ray Peat

Practical range:

"Very often people have to get up to 20,000 or 30,000 units a day before their acne improves."- Ray Peat

Food-based approach:

"One serving of liver a week and an egg or two every day and milk, for most people that's plenty of vitamin A."- Ray Peat

Topical application:

"I use the vitamin A only on my skin, because I get intense symptoms from even a small amount orally... Vitamin A is light sensitive, so I've used it only on my feet, where sunlight wouldn't reach it under my shoes." - Ray Peat

Pregnenolone substitution:

"When you were taking large amounts of pregnenolone daily, did your need for vitamin A decrease? 'Yes, I stopped taking vitamin A then.'" - Ray Peat, High metabolic rate/bright light exposure dramatically increases requirement,.