Vitamin D or “calciferol” is a fat-soluble vitamin that is naturally available in some foods. It is also produced within the body when ultraviolet (UV) rays from sunlight strike the skin and trigger vitamin D synthesis. Supplements of vitamin D are also available.
Difference between Vitamin D3 and Vitamin D2
Vitamin D has two major forms, vitamin D2 (ergocalciferol), and vitamin D3 (cholecalciferol). Vitamin D without a subscript refers to either D2 or D3, or both. Supplements of vitamin D have two different forms: vitamin D2 and vitamin D3. Vitamin D2 is made from plants. Vitamin D3 is naturally produced in the human body and it is found in animal foods. Research has found that D3 supplements raise blood concentrations of the vitamin more and sustained than those of D2.
Daily Intake of Vitamin D
The required amount of vitamin D each day depends on the age. Average daily recommended amounts are listed below in micrograms (mcg) and International Units (IU):
| Life Stage | Recommended Dose |
|---|---|
| Birth to 12 months | 10 mcg (400 IU) |
| Children 1–13 years | 15 mcg (600 IU) |
| Teens 14–18 years | 15 mcg (600 IU) |
| Adults 19–70 years | 15 mcg (600 IU) |
| Adults 71 years and older | 20 mcg (800 IU) |
Food Sources of Vitamin D
Foods that are naturally rich in vitamin D3 are flesh of fatty fish and cod liver oils. Smaller amounts are also found in egg yolks, cheese, and beef liver. Certain mushrooms when exposed to high amounts of ultraviolet light contain some vitamin D2. Foods and supplements fortified with vitamin D like dairy products and cereals are also available in market. Always check labels prior to purchase.
| Food Source | Vitamin D |
|---|---|
| Cod liver oil, 1 tablespoon | 34 mcg (1360 IU) |
| Fish, salmon, chinook, smoked, 100g | 17 mcg (685 IU) |
| Fish, salmon, sockeye, raw, 100g | 14 mcg (563 IU) |
| Mushrooms, white, raw, sliced, exposed to UV light, ½ cup | 9.2 mcg (366 IU) |
| Soy milk, sweetened, plain, refrigerated, 100g | 4.63 mcg (185 IU) |
| Almond milk, unsweetened, plain, refrigerated, 100g | 1.59 mcg (63 IU) |
| Egg, 1 large, scrambled (61g) | 1.1 mcg (44 IU) |
Can We Get Vitamin D from the Sun?
When bare skin is exposed to the sun (UVB light), our body makes vitamin D3 by a chemical reaction occurs in human skin. Most people get at least some vitamin D this way, however, following are conditions that decrease exposure to UVB light and therefore lessen vitamin D absorption:
- Sunscreen can reduce vitamin D absorption by more than 90%.
- Wearing clothes that covers the skin.
- Spending less time outdoors.
- Darker skin tones due to having higher amounts of the pigment melanin, which acts as natural sunscreen.
- Older ages
Effect of Vitamin D on Bone Health
Osteoporosis is the condition in which bones become fragile and break easily. This condition occurs due to long-term shortages of vitamin D and calcium. Shortage of vitamin D may lead to weak and painful muscles. Getting adequate amount of vitamin D and calcium from foods (and supplements) will help maintain healthy bones and prevent osteoporosis.
Inadequacy of Vitamin D
Food, sunshine and dietary supplements are the sources of vitamin D. Inadequacy of it is measured by a blood test. In the blood, a form of vitamin D known as 25-hydroxyvitamin D is measured in either nanomoles per liter (nmol/L) or nanograms per milliliter (ng/mL).
- Levels of 50 nmol/L (20 ng/mL) or above are adequate for most people for bone and overall health.
- Levels below 30 nmol/L (12 ng/mL) are too low and might weaken your bones and affect your health.
- Levels above 125 nmol/L (50 ng/mL) are too high and might cause health problems.
Symptoms of Vitamin D Deficiency
Symptoms of vitamin D deficiency may include:
- Fatigue
- Bone pain or achiness
- Muscle weakness
- Getting sick more easily
See Also: Vitamin C Benefits
Sources
[1] U.S. Department of Agriculture, Agricultural Research Service. FoodData Central, 2019.
[2] Tripkovic L, Lambert H, Hart K, Smith CP, Bucca G, Penson S, Chope G, Hyppönen E, Berry J, Vieth R, Lanham-New S. Comparison of vitamin D2 and vitamin D3 supplementation in raising serum 25-hydroxyvitamin D status: a systematic review and meta-analysis. The American journal of clinical nutrition. 2012 Jun 1;95(6):1357-64.
[3] Thacher TD, Clarke BL. Vitamin D insufficiency. Mayo Clin Proc. 2011 Jan;86(1):50-60. doi: 10.4065/mcp.2010.0567. PMID: 21193656; PMCID: PMC3012634.