You can get too much of a good thing with vitamin D. Here’s how

Vitamin D, the sunshine vitamin, is essential in the gray Northwest. But how much is too much of a good thing?

In 2010 the Institute of Medicine released a report on dietary intake requirements for vitamin D, which absorbs calcium and promotes bone growth. The recommended daily allowance of vitamin D for children one to 18 years and adults through age 70 years is 600 international units (or IUs) daily and 800 IUs daily after 71 years. For pregnant and lactating mothers, it recommends 600 IUs daily. The estimated adequate intake for infants up to 12 months is 400 IUs daily.

Vitamin D toxicity is not a common condition in the gray Northwest, but it can occur, according to Dr. Dawn Hutchinson, a provider at PeaceHealth Medical Group Internal Medicine in Bellingham.

The most common cause of vitamin D toxicity is from unintentional overdosing of supplements or pharmaceutical medications, Hutchinson said.

Vitamin D toxicity has occurred in people taking more than 60,000 IUs daily or when the body makes too much vitamin D in certain health conditions.

Toxicity is medically defined as a 25 hydroxyvitamin D level over 150 ng/ml.

“This is most likely to happen in people who are eating ‘fad’ diets or in patients who take vitamin D supplements for malabsorption, kidney disease, osteoporosis or psoriasis (a skin condition),” Hutchinson said. “It may also occur when patients are inappropriately prescribed high doses of vitamin D or choose to take high amounts of vitamin D supplements for health-enhancing purposes.”

“Prolonged exposure to the sun doesn’t cause toxicity because the unused vitamin D is converted to inactive products.,” Hutchinson said.

Symptoms of vitamin D toxicity occur because of high levels of calcium in the blood. These include confusion, decreased concentration, excessive urination, excessive thirst, lack of appetite, vomiting and muscle weakness. Seizures, coma and death may occur as well. Chronically high levels of calcium may cause kidney disease, kidney stones and bone pain. High calcium levels are generally treated by discontinuing calcium and vitamin D products, IV hydration and medications that help reduce the amount of calcium in the blood.

Vitamin D is a fat-soluble vitamin used to maintain normal calcium levels and bone health in our bodies. There are two sources of vitamin D bodies, the primary one is our skin and the others are a few foods and beverages. There are two forms of Vitamin D that are metabolized by our bodies to exert their effects: Vitamin D2 and D3. Vitamin D3 is made in our skin when exposed to sun. Vitamin D3 and vitamin D2 come from fatty fish, fortified beverages and foods and supplements. Milk, infant formulas and cereals are commonly fortified with vitamin D.

Vitamin D supplementation should be given to infants who are exclusively breastfed because the vitamin D content of human milk is low. Most infant formulas contain 400 IUs of vitamin D per liter, so formula-fed infants should also receive supplementation to meet this goal unless they consume at least 1 liter of formula daily.

The most accurate test to measure vitamin D levels is the 25 hydroxyvitamin D blood test., Hutchinson said.

The blood level at which vitamin D is toxic is not certain, she said. The Institute of Medicine has defined the recommended upper intake of vitamin D for healthy adults and children 9-18 years is 4000 IUs daily. For patients with gut malabsorption issues, higher doses of Vitamin D may be needed.

Correspondent Cindy Uken is an award-winning veteran journalist.