Vitamin D Knowledge

Vitamin D Knowledge. Graphic © herbshealthhappiness.com. Food images – Wikipedia, lic. under CC (see foot of article for full license info)

Vitamin D is a group of fat-soluble secosteroid hormones and vitamins consisting of cholecalciferol (vitamin D3) and ergocalciferol (vitamin D2). ^[1] Vitamin D can be acquired from sun exposure, food, and supplements. However, it exists in a biologically inert form from these sources, so the body must activate it through two hydroxylation processes before it can be used: first at the liver where vitamin D is converted to 25-hydroxyvitamin D or calcidiol and second in the kidneys where 1,25-dihydroxy vitamin D or calcitriol is formed. ^[2] Vitamin D has long been hailed for its function in bone health – it enables the body to absorb and hence utilize calcium and phosphorus, which are very vital to bone formation and strength. ^[3] Without vitamin D, an intake of these two nutrients becomes pretty useless. Furthermore, vitamin D plays a role in bone growth and bone remodeling by osteoblasts and osteoclasts, ^[2] and bones consequently can turn out to be structurally thin and brittle if there is a lack of vitamin D.

Outside of bone development, vitamin D is very essential too for optimal muscle function, and recent – though controversial – research evidence proposes the potential of vitamin D in preventing type 1 diabetes mellitus, hypertension, and several forms of cancers. ^[4] Vitamin D has an effect on cardiac contractility and myocardial calcium homeostasis and its deficiency has been found to be linked to myocardial dysfunction, death from heart failure, and sudden cardiac death among 3299 Caucasian patients referred to coronary angiography. ^[5] A series of laboratory and animal studies and observational epidemiologic studies implicate high levels of vitamin D in the body with a reduction in cancer risk, particularly colorectal cancer, with vitamin D being involved in preventing the development of cancer. ^[6] According to several cross-sectional studies, a low level of vitamin D is associated with higher systolic blood pressure and a higher incidence of hypertension, though more has to be researched regarding vitamin D being prescribed as a treatment for hypertension in the general population. ^[7]

It is troubling to know that a few otherwise healthy young adults (approximately 36%) and general medicine inpatients (approximately 57%) in the United States and Europe suffer from vitamin D deficiency. Dietary patterns such as low milk consumption, strict vegetarian diet, limited use of dietary supplements, or lack of fish intake have been accounted for the vitamin D insufficiency distinct to some groups. ^[8] An inadequacy of vitamin D results in a wide range of ill effects, from rickets in children from which vitamin D is well known to prevent, to exacerbation of adult osteoporosis, to osteomalacia, to disruption in the attainment of the genetically programmed peak bone mass in children. ^[4] Other than osteoporosis and cancer, low levels of circulating 25-hydroxyvitamin D have also been associated with an increased risk of diabetes and autoimmune disorders. ^[8] It appears that a deficiency in vitamin D upsets insulin synthesis and secretion in humans. ^[9]

Vitamin D holds something unique about it in that the body can produce it endogenously from exposure to sunlight, and our requirements for vitamin D can be satisfied by adequate sun exposure (5-10 min of exposure of the arms and legs or the hands, arms, and face, two or three times per week). ^[10] Although most of our vitamin D needs can be furnished through sunlight exposure, some amounts can be derived from few foods such as fatty fish and fortified dairy products, juices, and cereals. ^[11] Offal and meat, cheese, and egg yolks contain vitamin D too, albeit in small amount. ^[12] Some kinds of mushrooms offer vitamin D2 also. ^[13] Calvo, Whiting, and Barton (2005) had reported that due to the alarming increased risk of melanoma with unprotected ultraviolet (UV) B radiation exposure, a vitamin D supply from dietary sources alone is being suggested. ^[8]

Top 30 Foods Rich in Vitamin D

The USDA National Nutrient Database for Standard Reference, Release 25, lists foods containing vitamin D, providing the nutrient content of foods in micrograms (μg):

1. One-half fillet of sockeye salmon (cooked, dry heat) – 20.3 μg

2. One piece of 106 g swordfish (cooked, dry heat) – 17.6 μg

3. 3 oz of rainbow trout (farmed, cooked, dry heat) – 16.2 μg

4. 3 oz of Chinook salmon – 14.5 μg

5. 3 oz of pink salmon (canned, total can contents) – 11.6 μg

6. One-half fillet of Atlantic and Pacific halibut (cooked, dry heat) – 9.2 μg

7. 1 cup of chocolate malted drink mix (with added nutrients, powder, prepared with whole milk) – 8.2 μg

8. One fillet of Pacific rockfish (mixed species, cooked, dry heat) – 6.9 μg

9. 3 oz of light tuna (canned in oil, drained solids) – 5.7 μg

10. 1 cup of milk (canned, evaporated, nonfat, with added vitamins A and D) – 5.1 μg

11. Four to five heaping teaspoons of natural malted drink mix (with added nutrients, powder) – 4.9 μg

12. One fillet of flatfish, flounder and sole species (cooked, dry heat) – 4.4 μg

13. 3 oz of Atlantic sardine (canned in oil, drained solids with bone) – 4.1 μg

14. 11 fl oz of milkshakes (thick vanilla) – 3.8 μg

15. 1 cup of eggnog – 3.0 μg

16. 1 cup of ready-to-eat cereals, raisin bran – 2.6 μg

17. 1 cup of ready-to-eat cereals, whole grain – 2.5 μg

18. 8 fl oz unsweetened rice drink (with added calcium, vitamins A, and D) – 2.4 μg

19. 3 oz of Atlantic herring (pickled) – 2.4 μg

20. 3 oz of fresh pork (spareribs, separable lean and fat, cooked, braised) – 2.2 μg

21. 1 oz of cheese (pasteurized process, American, fortified with vitamin D) – 2.1 μg

22. 1 cup of cream of mushroom soup (canned, prepared with equal volume low fat (2%) milk) – 1.7 μg

23. 3 oz of white tuna (canned in water, drained solids) – 1.7 μg; 3 oz of fresh yellowfin tuna (fresh, cooked, dry heat) – 1.7 μg

24. 1 cup of New England clam chowder soup (canned, prepared with equal volume low fat (2%) milk) – 1.5 μg

25. One-half cup of chocolate pudding (dry mix, regular, prepared with 2% milk) – 1.4 μg

26. 3 oz of Atlantic ocean perch (cooked, dry heat) – 1.2 μg

27. One extra large egg (whole, raw, fresh) – 1.2 μg

28. 3 oz of Alaska pollock (cooked, dry heat) – 1.1 μg

29. 1 cup of spinach soufflé – 1.1 μg

30. 3 oz of Atlantic cod (canned, solids and liquid) – 1.0 μg ^[14]