Vitamin A (Retinol)

Retinol is preformed vitamin A, the version found in animal foods and the version the body can use directly. It is required for the light-detecting pigment in the retina, for the maintenance of epithelial tissue including skin and gut lining, for immune cell function and for cellular differentiation.

Beta-carotene from plants is a precursor rather than an equivalent. Conversion happens in the gut wall, and the efficiency varies widely between people because of common genetic differences in the enzyme that does it. Someone who converts poorly can eat a great deal of carotene and still run low on retinol.

The liver stores vitamin A, so serum retinol is defended and stays fairly flat until stores are meaningfully depleted. That makes a genuinely low result significant.

Below 2 umol/L indicates depleted vitamin A. The earliest recognised effect is reduced night vision, since the retinal pigment is the first thing to suffer when supply falls.

Skin and mucous membranes are next, because epithelial tissue turns over quickly and depends on vitamin A for normal differentiation. Immune function is affected for the same reason.

Fat malabsorption is a frequent cause, since vitamin A is fat soluble. Zinc status also matters, because retinol binding protein depends on zinc, so low zinc can produce a low retinol result even when liver stores are adequate.

Between 2 and 10 umol/L your serum retinol sits inside the reference range for this panel.

Because the liver defends this number, a result in range does not by itself confirm generous stores. It confirms that stores have not yet been depleted far enough to move serum.

Above 10 umol/L is worth attention. Vitamin A is fat soluble and accumulates in the liver, so unlike water-soluble vitamins the excess does not simply leave.

The usual source is supplementation, often cod liver oil taken for its omega-3 or vitamin D content without counting the vitamin A that comes with it. Retinyl palmitate in multivitamins adds to the total.

Preformed vitamin A carries specific risk in pregnancy, so anyone pregnant or planning pregnancy should review a high result and their total intake with their practitioner. Beta-carotene does not carry the same concern, because conversion is regulated.

Organ meats have largely disappeared from Western diets, and they were the main source of preformed retinol. What replaced them was plant carotene, which depends on a conversion step that a substantial fraction of people perform inefficiently.

Low-fat eating patterns compound it, since absorption of both retinol and carotene requires dietary fat in the same meal.

Grass-fed liver, beef or chicken, once or twice weekly is the richest natural source of retinol.

Butter from grass-fed cows, pastured egg yolks and full-fat dairy supply smaller amounts in usable form.

Sweet potatoes, carrots and dark leafy greens provide beta-carotene as a secondary route. Eat them with fat in the same meal, since absorption without it is poor.

Cod liver oil at about a teaspoon daily supplies preformed retinol alongside vitamin D and omega-3. Count it toward your total vitamin A rather than treating it as an omega-3 product only.

Desiccated liver capsules are an alternative where liver itself is not tolerated.

Retinyl palmitate as a standalone supplement only where dietary sources are genuinely insufficient, and with attention to the ceiling. If fat absorption is the limiting factor, addressing that does more than raising the dose.