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TreatmentUpdate 162

Volume 19 Issue 4

2007 May/June

I COMPLICATIONS AND SIDE EFFECTS: H. Calcium and vitamin D

At least two nutrients are important for the maintenance of bone health—calcium and vitamin D.

The body needs calcium every day and if its needs are not met then calcium is removed from bones. HIV infection damages the intestine and is associated with wasting, suggesting that not enough nutrients are absorbed. One such nutrient may be calcium. Perhaps it is not surprising that some studies have found that some PHAs can have a greater-than-expected degree of bone loss.

Vitamin D is a nutrient that helps the intestines absorb calcium. Vitamin D may also have other, poorly understood effects on the immune and nervous systems. There are several forms of compounds that are called vitamin D. The two usually used in human nutrition are:

  • vitamin D2–ergocalciferol
  • vitamin D3–cholecalciferol

However, only vitamin D3 is the active form of this nutrient.

Although this vitamin can be made when a person is exposed to sunlight, a number of studies have found that some people living in sunny locations such as the Hawaiian Islands have less-than-optimal levels of this nutrient. Studies from Calgary and Toronto, places that experience shorter periods of sunlight in the winter, suggest that consuming 200 IU/day of vitamin D3 was not able to prevent a deficiency of this vitamin.

A study in New Zealand with three different ethno-racial groups—European, Maori and Asian people—found that the level of vitamin D deficiency increased as skin pigmentation increased.

Food

Vitamin D is found naturally in oily saltwater fish. To determine the amount of this nutrient available, researchers at Boston University analysed the flesh of several fish species. In 100 grams of fish, here’s what they found:

  • wild salmon – about 1,000 IU of vitamin D3
  • farmed salmon – about 240 IU
  • blue fish – 280 IU
  • cod fish – 104 IU
  • grey sole – 56 IU
  • Ahi-tuna – 404 IU
  • farmed trout – 388 IU
  • mackerel – 24 IU

Baking the salmon resulted in no change to the vitamin D content. However, frying the salmon in oil resulted in a loss of 50% of the vitamin D.

Overall, this research suggests that the vitamin D3 content of some foods may not be as great as anticipated.

For more information on nutrition and bone health, check out “Good to the bone” in the Fall/Winter 2001 issue of The Positive Side (www.positiveside.ca).

Research on vitamin D

Scientists who study human nutrition and osteoporosis and who are also experts in the field of vitamin D research recommend that a minimum of 700 to 800 IU of vitamin D3 per day is needed by adults. The goal of this level of supplementation, they suggest, should be to raise levels of vitamin D3 in the blood to at least 75 nmol/l.

The safe upper limit of vitamin D intake is not yet clear and physicians caring for patients with osteoporosis may need to guide their vitamin D3 intake by monitoring blood levels of this nutrient. Concentrations of vitamin D3 ranging between 135 to 163 nmol/l have been found in lifeguards and farmers—people who get a great deal of sun exposure. Signs/symptoms of vitamin D3 toxicity occur when levels of this vitamin exceed 200 nmol/l in the blood.

To give some idea of the range of possible tolerable levels of vitamin D3, researchers have found that White people exposed to sunlight for 15 to 20 minutes produced 10,000 IU of vitamin D3. Greater exposure to sunlight did not result in higher levels of vitamin D3. This suggests the possibility that the body can tolerate somewhat higher levels of vitamin D3 than the 400 IU that is often included in daily multivitamins.

Overall, research on relatively high doses of vitamin D3 and its impact—not just on bones but other parts of the body as well—is just beginning. Decades ago, some nutritionists thought that a daily dose of 400 IU of this nutrient was sufficient. However, the trend in the past decade has been to use higher doses in studies of osteoporosis. As scientists find out more about of vitamin D3, this trend is likely to continue.

REFERENCES:

1. García Aparicio AM, Muñoz Fernández S, Gonzales J, et al. Abnormalities in the bone mineral metabolism in HIV-infected patients. Clinical Rheumatology 2006 Jul;25(4):537-9.

2. Vieth R, Bischoff-Ferrari H, Boucher BJ, et al. The urgent need to recommend an intake of vitamin D that is effective. American Journal of Clinical Nutrition 2007 Mar;85:649-50.

3. Whiting SJ, Green TJ and Calvo MS. Vitamin D intakes in North America and Asia-Pacific countries are not sufficient to prevent vitamin D insufficiency. Steroid Biochemistry and Molecular Biology 2007 Mar;103(3-5):626-30.

4. Vieth R. Vitamin D supplementation, 25-hydroxyvitamin D concentrations, and safety. American Journal of Clinical Nutrition 1999;69(5):842-56.

5. Hathcock JN, Shao A, Vieth R, et al. Risk assessment for vitamin D. American Journal of Clinical Nutrition 2007 Jan;85(1):6-18 .

6. Vieth R and Fraser D. Vitamin D insufficiency: no recommended dietary allowance exists for this nutrient. Canadian Medical Association Journal 2002 Jun 11;166(12):1541-2.

7. Lu Z, Chen TC, Zhang A, et al. An evaluation of the vitamin D3 content in fish: Is the vitamin D content adequate to satisfy the dietary requirement for vitamin D? Steroid Biochemistry and Molecular Biology 2007 Mar;103(3-5):642-4.

8. Houghton LA and Vieth R. The case against ergocalciferol (vitamin D2) as a vitamin supplement. American Journal of Clinical Nutrition 2006 Oct;84(4):694-7.

9. Binkley N, Novotny R, Krueger D, et al. Low vitamin D status despite abundant sun exposure. Journal of Clinical Endocrinology and Metabolism 2007 Jun; 92(6):2130-5.

10. Dawson-Hughes B, Heaney RP, Holick MF, et al. Estimates of optimal vitamin D status. Osteoporosis International 2005 Jul;16(7):713-6.

11. Heaney RP. Determinants of vitamin D status in older men living in a subtropical climate. Osteoporosis International 2007 Jun;18(6):833-4.

12. Lappe JM, Travers-Gustafson D, Davies KM, et al. Vitamin D and calcium supplementation reduces cancer risk: results of a randomized trial. AmericanJournal of Clinical Nutrition 2007 Jun;85(6):1586-91.

13. Heaney RP. The case for improving vitamin D status. Steroid Biochemistry and Molecular Biology 2007 Mar;103(3-5):635-41.


Created on: 2007 August 8

Author: Hosein SR

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