Vitamin D is a fat soluble vitamin that is available in few foods, it is available as a supplement and it is available in many foods that have been fortified. Since vitamin D is fat soluble it requires some fat in the gut for absorption. Vitamin D is also synthesized from the sun when it hits the skin. All forms of Vitamin D are biologically inert and must undergo two different processes within the body to become active. One process occurs in the liver (25-hydroxyvitamin D) and the last process occurs in the kidney, which produces the active form (1,25dihydroxyvitamin D).
Vitamin D is also needed to promote bone growth and remodeling, without vitamin D bones can become thin, brittle, and misshapen. Many of the benefits of bone health is due to vitamin D’s ability to promote calcium absorption in the gut and maintain adequate serum calcium and phosphate concentrations. Due to these processes vitamin D helps protect against osteoporosis in older adults.
The best indicators of vitamin D status are serum concentrations of 25-hydroxyvitamin D, it reflects the levels obtained from food and supplementation. Its half life is 15 days, which makes it the better choice vs. 1,25dihydroxyvitmain D as it s half life is 15 hours.
These levels can be tested by your doctor with a blood test for serum vitamin d levels. Typically levels higher than 50nmol/L are sufficient, but many naturopathic doctors like to see levels higher than 80nmol/L. Less than 80nmol/L will require supplementation to rise levels to optimal serum levels, which will promote strength, power development, bone health, and inflammation.
The best dietary sources of vitamin D are fatty fish.
Cod liver oil 3 oz – 1360iu
Swordfish 3 oz – 566iu
Salmon 3 oz – 447iu
Tuna 3 oz – 154iu
Sardines (1 can)- 46iu
Beef Liver 3oz – 42
1 egg – 41
Many other foods that are fortified with vitamin D (mostly diary products) with levels of 40-100iu/serving.
The big take away points;
1. Have your levels tested by a doctor
2. Eat more fatty fish (sardines, salmon, mackerel, etc), but avoid excessive tuna and swordfish as they are typically high in toxic load.
3. Vitamin D is important for bone health, strength, power development, etc.
4. Supplement with the vitamin D if levels are low – D3 Excellence from Poliquin Performance
