When should you start taking a vitamin D supplement after summer ends? Here’s what a dietitian says

“We need this vitamin because it is necessary for building healthy bones, plays an important role in immune function, reduces inflammation, and promotes proper muscle function and nerve connections,” says Barkoukis.

“If a person doesn’t have enough, they will be at very high risk for bones that are not properly mineralized, putting them at risk for fractures.

“If a person has low levels of vitamin D or a deficiency, then the absorption of calcium is compromised. In this situation, the body will take the calcium it needs for optimal health functioning from the person’s bones. This will weaken the bones and that loss of calcium from bones translates into higher fracture risk.”

Without testing your blood, it is hard to identify a specific vitamin D deficiency. You will usually have symptoms of inadequate calcium intake due to the relationship between the two nutrients.

Barkoukis says that unless you’re told not to take a vitamin D supplement by a health professional, you should be taking one year-round.

“This nutrient is called a risk nutrient, meaning vitamin D is at risk for inadequacy, and a significant percentage of the population consumes inadequate amounts,” she says.

“Sun exposure on the skin is an important source of the vitamin, but most individuals use sunscreen lotions, cover up, or avoid the sun entirely,” says Barkoukis. “Anyone with darker skin has more of a compound called melanin and this reduces how much of the vitamin can be produced from sunlight.”

She also explains that the elderly, children and those with digestive disorders that cause fat malabsorption may be at risk of a deficiency. Vitamin D is a fat-soluble vitamin and you need dietary fat to absorb it properly.

“We can’t assume that because someone lives in a U.S. state with more sunshine days, that they would not be at risk for a deficiency,” says Barkoukis. “A better habit is to take a daily supplement, year-round.”

“These supplements come in two forms: D2, from plant sources called ergocalciferol; and D3, from animal sources called cholecalciferol,” says Barkoukis. “Both forms can be used to meet human requirements, but D3 is generally considered a bit more effective.”

Barkoukis also suggests taking the supplement with a meal containing some fat to help absorption.

“Dietary supplement intake over 4,000 international units is not recommended,” says Barkoukis. She explains that because the vitamin is fat-soluble, it is stored in the fat cells of the body and can build up. This, in turn, impacts the level of calcium in the body, putting you at risk for a painful condition called hypercalcemia. So it’s best to adhere to the NIH dietary guidelines for your dosage.

“One will not overdose on the body’s natural production of the vitamin from the sun’s exposure to your skin,” adds Barkoukis. “As your body achieves the necessary amount of the vitamin, the natural production of the active form of the vitamin will stop. The risk of too much vitamin D comes from dietary supplements, not sun exposure.”