Wednesday, February 27, 2008

Bone Health, Vitamin D, and Obesity - Again!

Vitamin D deficiency is common with obesity. When vitamin D is deficient, calcium tends to be deficient, too. But the body has a way of keeping the calcium level in the blood looking normal. That is, by raising the level of a hormone called "parathyroid hormone" (has nothing whatsoever to do with thyroid hormone), calcium is actually taken away (say, stolen away) from the bones, to keep its level looking normal in the blood. The bones lose calcium, and become weaker, more fragile and more likely to break. We are talking osteopenia and osteoporosis.

A new study from the University of Nebraska Medical Center, Omaha, was published recently in the Journal "Obesity Surgery". The study found out that vitamin D deficiency is common in obese patients at the time of bariatric (weight loss) surgery and is also accompanied by an increased level of parathyroid hormone, approximately half the time. So, vitamin D deficiency after bariatric surgery is not purely a complication of bariatric surgery. It is, at least in part, caused by vitamin D deficiency before the surgery itself. To reach those conclusions, the authors did blood tests to measure the levels of 25-hydroxyvitamin D, iPTH (intact parathyroid hormone), and calcium in 41 patients before undergoing Roux-en-Y gastric bypass. Then, they compared them to healthy non-obese matched controls. About half of the pre-bariatric surgery patients had elevated hyperparathyroid hormone level, compared to only 2% of controls. Levels of vitamin D (25-hydroxyvitamin D) were significantly low in more than half of the obese patients.

This actually reminds us of a previous study that we reported here. In that study, from Maine, before bariatric surgery, 34% of patients had suboptimal levels, and 54% had deficient levels, of 25-hydroxyvitamin D in their blood. By one year after Roux-en-Y gastric bypass surgery, the vitamin D deficiency improved remarkably with the intake of vitamin D supplements. The researchers actually recommended higher-than-average doses of vitamin D supplementation.

Reference Article:

Goldner WS, Stoner JA, Thompson J, Taylor K, Larson L, Erickson J, McBride C. Prevalence of vitamin d insufficiency and deficiency in morbidly obese patients: a comparison with non-obese controls. Obes Surg. 2008 Feb;18(2):145-50. [PMID: 18175194] (Abstract)

More References:

Nelson ML, Bolduc LM, Toder ME, Clough DM, Sullivan SS. Correction of preoperative vitamin D deficiency after Roux-en-Y gastric bypass surgery. Surg Obes Relat Dis. 2007 Jul-Aug;3(4):434-7. [PMID: 17400028] (Abstract)