Vitamin D Deficiency & Tropical Sprue

Vitamin D, a fat-soluble vitamin, is chiefly absorbed in the gut from food sources such as fish, eggs, cod liver oil and vitamin D-fortified milk; they are rich sources of vitamin D. Your body needs vitamin D to absorb calcium. Vitamin D is initially inactive; it has to be processed by the body to be active. If you have tropical sprue--typified by poor absorption of nutrients, usually affecting individuals living in tropical regions--your body doesn't sufficiently absorb vitamin D, leading to a deficiency of the vitamin in the blood.

Tropical Sprue's Effect on Vitamin D Absorption

In the small intestine, the enterocytes are cells that are involved in absorption. The enterocytes have finger-like projections called villi, increasing the surface area for the absorption of nutrients. In tropical sprue, the layer of enterocytes lining the interior of the small intestine is inflamed or irritated. This irritation results in the destruction and flattening of the villi, thereby reducing the surface area for nutrient absorption. In tropical sprue, the flattening of villi mainly affects the absorption of fats and fat-soluble molecules. Vitamin D is fat-soluble, and therefore its absorption is affected.

Complications

Poor absorption of vitamin D leads to low blood calcium. Low blood calcium is a problem for the heart, which requires adequate calcium to function properly. Low blood calcium causes an irregular pulse. Very low blood calcium is a potential cause of irreversible heart failure.

Typically, the parathyroid gland secretes more parathyroid hormone because of low blood calcium. Excess parathyroid hormone causes excessive bone breakdown and weakening.

Tropical sprue also leads to poor absorption of iron, vitamin B12 and folate; deficiency in any of these nutrients causes anemia.

Observed Symptoms

Shortness of breath while lying down occurs when the heart is weak as a result of very low blood calcium. Leg and abdominal swelling can occur when calcium is very low. Low blood calcium also causes tetany, a condition of uncontrollable muscle contractions and strange sensations over the lips and tongue.

Low blood calcium leads to weakening of the bones because calcium is needed to form strong, healthy bones. Excessive parathyroid hormone released as a consequence of low blood calcium stimulates the breakdown of bone in order to release calcium to the blood. This breakdown of bone results in pain; other symptoms are generalized weakness, abdominal pain, nausea and sometimes depression.

The anemia associated with tropical sprue results in tiredness and weakness.

Evaluations

Evaluation of vitamin D deficiency begins with the sampling of blood from a vein of the arm. The sample of blood is tested for levels of active vitamin D. A normal level of active vitamin D should be above 30 nanograms per milliliter, or ng/mL; if less than 30 ng/mL, then it's abnormal. An active vitamin D level below 20 ng/mL is defined as vitamin D deficiency.

Treatment

People with tropical sprue should get appropriate antibiotics for their disease. Vitamin D should be supplemented as well to prevent loss of bone density. The U.S. Department of Health & Human Services recommends the supplementation of vitamin D at doses of 700 to 800 international units, or IUs, with 500 to 1,200 mg of calcium; this is effective in preventing loss of bone density.

Dietary modifications, including the intake of fish, eggs, vitamin D-fortified milk and cod liver oil, should be considered. Tthese foods are abundant sources of vitamin D.