Dietary Sources of Vitamin D
Vitamin D occurs naturally in very few foods, with oily fish and eggs being the primary natural dietary sources, but these alone are insufficient to meet daily requirements, making fortified foods and supplementation essential for most people. 1
Natural Food Sources
Rich Sources (>4 μg/100g)
- Fatty fish (salmon, sardines): 5-25 μg/100g 1, 2
- Fish liver oils: 250 μg/100g 2
- Mushrooms: 21.1-58.7 μg/100g 2
- Reindeer lichen: 87 μg/100g 2
- Dark chocolate: 4 μg/100g 2
Moderate Sources (1-4 μg/100g)
- Eggs (particularly egg yolks): 1.3-2.9 μg/100g 1, 3, 2
- Beef liver: 1.3-2.9 μg/100g 1, 2
- Cheese: 1.3-2.9 μg/100g 2
Important caveat: A cup of milk provides only about 100 IU (2.5 μg) and a serving of salmon contains about 400 IU (10 μg) of vitamin D3, which demonstrates that even "rich" dietary sources provide limited amounts relative to daily needs. 1
Fortified Foods
Fortified foods are critical for achieving adequate vitamin D intake since natural sources are insufficient. 1, 3
Common fortified products include:
- Breakfast cereals (high-fiber varieties) 1, 3, 2
- Milk (low-fat and regular) 1, 3, 2
- Yogurt 2
- Fat spreads/margarines 2
- Orange juice 1, 2
- Plant-based beverages 2
Key limitation: In countries like Ireland where food fortification is voluntary, fortified foods alone cannot provide adequate vitamin D intake, even when consumed regularly. 1
Forms of Vitamin D in Food
- Vitamin D3 (cholecalciferol): Found in animal-derived foods, naturally located in the fatty portion 3, 2
- Vitamin D2 (ergocalciferol): Found in plant sources and some fortified foods 1, 2
- 25-hydroxyvitamin D: Also contributes significantly to dietary vitamin D intake and is found in many animal-derived products 2
Clinical Reality: Diet Alone is Insufficient
Studies consistently show that dietary intake alone cannot meet recommended vitamin D requirements (10-20 μg/day or 400-800 IU/day). 1
Therefore, supplementation is essential:
- Older adults: Daily 15 μg (600 IU) vitamin D supplement year-round 1
- General adults: 600 IU daily for ages 1-70 years, 800 IU for those 71+ years 1
- Safe upper limit: 4000 IU daily 1
High-risk groups for vitamin D insufficiency requiring particular attention to supplementation include: 1
- Individuals with dark skin
- Those living in Northern latitudes
- Those who stay indoors
- Those who do not consume vitamin D sources
Critical point: Since adequate vitamin D intake (15 μg/day) is hard to achieve through diet alone, dietary supplements are usually recommended rather than relying solely on food sources. 2