Vitamin D Deficiency and Bariatric Surgery

Vitamin D is very important since it helps to maintain appropriate calcium levels in the blood and keeps helps to make calcium available to strengthen bones.

The vast majority of bariatric operations including a Roux en-Y Gastric Bypass, Gastric Sleeve or Adjustable Gastric Band have little or no effect on Vitamin D absorption. Only the relatively rare bariatric operations that greatly shorten the last half of the small intestine such as a Duodenal Switch, Biliopancreatic Bypass or a Modified Gastric Bypass that leaves a very short portion of the small intestine to absorb nutrients result in inadequate absorption of vitamin D.

Nevertheless vitamin D deficiency is a frequent problem for all patients of size. Although some of the vitamin D we need in taken in as part of the food we eat, some of the vitamin D is formed by sunlight converting colesterol to vitamin D in our skin. Since I am a bariatric surgeon in Columbus, Ohio, 89% of all of my patients are found to be vitamin D deficient even before surgery!

That is the reason each patient that enters our program is tested to determine their vitamin D level. We routinely start our patients on vitamin D when they begin in our program.

Why do our patients often have low vitamin D levels? It is not because of surgery.

Vitamin D deficiency occurs partially because we live in Ohio instead of Phoenix! Ohio is not known for sunny weather. Also people of size often are not out in the sun very much. In addition there is some evidence that Vitamin D is stored in our fat deposits and it may take higher amounts of vitamin D to saturate all of the storage sites.

Vitamin D is converted to an active form as blood is circualated though our kidneys. A normal Vitamin D level is necessary to absorb calcium from the intestine and preserves calcium from being released in the urine.

After absorption, calcium circulates in the serum and is stored in bone. The balance between the amount of calcium circulating in the blood and stored in bone is controlled by a hormone released by four small quarter inch size glands located just behind the thyroid gland in your neck called the parathyroid glands. It is essential to your nerves, heart and other body tissues to have a normal level of calcium in the blood. Therefore if your calcium starts to decrease the parathyroid glands produce more parathyroid hormone which in turn tells some of the cells in the bone to take calcium out of bone and release the calcium into the circulating blood. If this goes on for a long time you can lose so much bone strength that you put you at risk of causing breaks in the bone called fractures. This circumstance is called osteoporosis because the bones, (osteo-), becomes more porous, (porosis).

Therefore, if your vitamin D level is low you will not absorb enough calcium and your calcium level will be low. This will result in higher levels of parathyroid hormone stimulating the bone cells to mobilize more calcium from the bone and make your bones weaker and more prone to break. The bones at most risk are your hips and the bones of your back.

You should take at least 800 mgs of calcium every day, (as calcium citrate for gastric bypass patients) and make sure your vitamin D level is checked yearly. Take Ergocalciferol 50,000 units each week to treat a low vitamin D level. In addition periodic bone density tests will check how much calcium is stored in your bones reflecting how strong the bones are. If you have a mild decrease in bone density called osteopenia, correcting the vitamin D deficiency and taking more calcium may be enough. However, if your bone density is low enough to be called osteoporosis you should speak with your primary care physician about taking a medicine that will reverse the bone loss such as Boniva or Reclast.

From Stephan R. Myers, MD, FACS, bariatric Surgeon, Columbus, Ohio