Make D a good grade

Vitamin D can help keep you healthy

Vitamin D aids in calcium absorption (which helps build strong bones) and assists with proper muscle and nerve function. But did you know it also helps the immune system fight off bacteria and viruses? Whether it’s during flu season or a pandemic, it’s more important than ever to ensure you’re getting enough vitamin D.

As both a nutrient and a hormone, vitamin D helps to reduce inflammation as well as control processes such as immune function and cell growth, including antigen-presenting cells and regulatory T cells. Research shows that vitamin D plays a variety of roles in immune system functioning, which may improve the body’s first line of defence against foreign invaders and deter the development of autoimmunity (when the body’s immune system attacks its own healthy cells and tissues).

In fact, researchers have been studying the immunity-building benefits of vitamin D as they relate to respiratory infections. Recent studies (see “COVID-19 and vitamin D”) found that using vitamin D supplements showed promise in both preventing and treating respiratory infections.

How much do you need?

Recommendations for vitamin D intake vary from province to province, and the amount of vitamin D needed daily varies by age. Health Canada recommends that most children and adults (ages 9 to 70 years) need 600 international units (IU), or 15 micrograms (mcg), of vitamin D per day, with the tolerable upper intake level being 4,000 IU (100 mcg).

The best way to know how much vitamin D you need is to consult your doctor, suggests Elaine Zhang, a Vancouver-based registered dietitian. “Your doctor or specialist can order a vitamin D blood test,” she says.

Sources of vitamin D

You can meet your daily vitamin D requirement from three sources: food, the sun and dietary supplements.

“Your best food source of vitamin D is fatty fish like salmon, trout and mackerel,” says Zhang. Not a seafood lover? Consume vitamin D–fortified foods, such as milk, which is typically fortified with 120 IU (3 mcg) per cup. “If you’re vegetarian, soy beverages and almond milk are sometimes fortified, but you need to check the labels,” points out registered dietitian Rana Daoud, general director of DRRD Nutrition in the Ottawa and Outaouais areas. Other sources include soft margarine, beef liver, egg yolks, cheese and mushrooms. Also, manufacturers sometimes add vitamin D to certain commonly consumed foods, including dairy milk, plant-based milk alternatives, and breakfast cereals, orange juice and yogurt (look for items labelled as vitamin D fortified).

If you go outdoors for your vitamin D dose, “you want to be cautious with skin cancer prevention,” says Daoud, who advises going outdoors without sunscreen for about 15 to 20 minutes only a few times a week. Perry Holman, executive director of the Ontario-based Vitamin D Society, suggests taking a vitamin D supplement in winter. Based on a vitamin D blood test, your doctor can tell you if you need to supplement as well as the correct dosage and duration, Daoud explains.

She also suggests asking your doctor if vitamin D will interact with any other medications or supplements you’re taking. And check the label of any vitamin D supplements you’re considering to ensure it contains vitamin D3 instead of vitamin D2, Daoud says, “because vitamin D3 is the active format, and more effective in absorption than D2.”

COVID-19 AND VITAMIN D

Vitamin D shows promise in potentially reducing the risk of contracting COVID and limiting the severity of its symptoms.

According to a March 2021 study in The Journal of Clinical Endocrinology & Metabolism, 82% of COVID patients in one hospital were vitamin D deficient. And an October 2021 study in the Journal of the Academy of Nutrition and Dietetics found higher serum nutrient levels—especially of vitamin D and zinc—were associated with decreased risk of contracting respiratory infections, including COVID-19. Vitamin D and zinc were also associated with less severe respiratory infection symptoms and faster recovery times.—LAB