Vitamin D

 https://nutritionsource.hsph.harvard.edu/vitamin-d/

🌞 1. Sunlight (Natural Source – Best if available)

UVB exposure to bare skin for 10–30 minutes a few times per week (depends on skin tone, latitude, and time of year).

Best times: midday sun, when UVB is strongest.

> Note: Sunscreen, clothing, windows, and pollution block UVB absorption.

🐟 2. Animal-Based Food Sources (Vitamin D3 - Cholecalciferol)

These are the most bioavailable dietary sources.

Food Approx. Vitamin D per serving

Cod liver oil (1 tsp) 400–1,000 IU

Salmon (wild, cooked) 600–1,000 IU (per 3.5 oz)

Sardines (canned in oil) 270–300 IU (2 sardines)

Mackerel 250–500 IU (per 3.5 oz)

Beef liver 40–50 IU (per 3.5 oz)

Egg yolks 40–50 IU (per yolk, higher in pasture-raised)

Butter (grass-fed) Small amounts

🧀 3. Fortified Foods (Often Vitamin D2, less bioavailable)

Fortified milk (cow, soy, almond, oat)

Fortified cereals

Fortified orange juice

Fortified yogurts

> Check labels. Most offer 100–150 IU per serving.

💊 4. Supplements

Vitamin D3 (Cholecalciferol) is superior to D2 (Ergocalciferol).

Doses: 1,000–5,000 IU daily depending on blood levels and need.

Often combined with Vitamin K2 (MK-7) to direct calcium to bones.

🧬 Bonus: Lifestyle Enhancers

Cholesterol is required to synthesize D from sunlight.

Magnesium is a cofactor to activate vitamin D in the body.

Zinc and boron support vitamin D metabolism.