Egg Yolk

Food · Protein · Food, Typed Supps

Almost every nutrient in the egg is here — and so is all the cholesterol.

Stage by stage

Where it all is (The egg): Almost every vitamin and mineral in an egg sits in the yolk, not the white.
Fat-soluble uptake (Small intestine): The lipid matrix makes yolk carotenoids more absorbable than the same amount from vegetables.
Cholesterol (Liver): 1,250 mg per 100 g — and hepatic synthesis downregulates in response for most people.
Vitamin D (Skeleton): 15.51 mcg per 100 g, one of the richest natural sources there is.

Timing

Nothing to time. A single yolk is around 17 g, which is roughly 210 mg of cholesterol.

Time to effect

Per yolk: About 2.6 mcg vitamin D, 22 mcg iodine and 210 mg cholesterol.
Weeks: Serum lipid response, in the minority who respond measurably.

Allergens

Contains: Eggs. Derived from what this food is, not from a product label.

Eating patterns

Fits: Vegetarian, Pescatarian, Halal, Kosher, Keto, Low-FODMAP, Gluten-free.

Satiety

85 on the satiety index, where white bread is 100 — low. Modelled from the Holt et al. (1995) measurements.

Environmental footprint

4.7 kg CO2e and 578 litres of freshwater per kg, matched to "Eggs" in Poore & Nemecek (2018), Science 360.

Cost band

Mid — roughly £4.5 per kg, as a band midpoint rather than a price.

Key nutrients

Vitamin D
Choline
Iodine

Nutrition per 100g

Calories: 347
Protein: 16.1g
Carbohydrate: 0.2g
of which sugars: 0.2g
Fat: 31.7g
of which saturated: 9.6g
Sodium: 47mg

Food vs. supplement

Lutein supplements are sold for eye health, and egg yolk delivers lutein in a lipid matrix that makes it more absorbable than the same dose from leafy greens — one of the few cases where a food beats both the vegetable and the capsule on bioavailability.

Kitchen tip

If you are eating egg whites only, you are keeping the protein and throwing away nearly all of the nutrition.

Common myth

“Throw out the yolk — that’s where the cholesterol is.” In reality: It is also where everything else is. The yolk carries essentially all the vitamin D, iodine, folate, selenium, vitamin A, vitamin E and B12 in an egg; the white is protein and water. Most guidelines dropped the hard cholesterol limit because dietary cholesterol moves blood cholesterol only modestly in most people. A minority are genuine hyper-responders, which is a reason for individual advice rather than for binning the yolk.

In the glossary

Bioavailability