If you don't get enough vitamin D in your diet or from sunshine, you might want to consider taking a supplement to help ward off the flu. In addition to helping keep your bones strong and absorbing calcium in your gut, it turns out vitamin D can also boost your immunity.
Brutal stomach flu, known as the norovirus, has closed dozens of schools across the U.S. this year, and while there's no vaccine against that form of the flu, the flu shot protects you against the other strains of the nasty bug. But sometimes the flu shot isn't enough.
Researchers in London pored over 25 studies that included a total of more than 10,000 participants. What they found was that overall, vitamin D supplements seemed to reduce the risk of infection by about 10 percent. People who already had vitamin D deficiencies at the time they enrolled in the study were the ones who saw the most benefit from a supplement, reducing their risk up to about 50 percent.
Recommendation guidelines from the Institute of Medicine say that most adults need around 600 IU (international units) of vitamin D daily. The average multivitamin contains about 400 IU. The Institute of Medicine says adults shouldn't take more than 4,000 IU per day.
A vitamin D deficiency during pregnancy can increase the risk of your baby developing multiple sclerosis, according to Harvard research published in 2016 in the medical journal JAMA Neurology.
However, that doesn't mean you need to get tested routinely, doctors say.
Sunshine provides plenty of vitamin D for most people—except for during the winter months. But your skin has a tougher time producing vitamin D as you age. And if you wear sunscreen, which blocks most of your exposure to UVB rays, your body has a harder time producing vitamin D.
Good sources of vitamin D include fatty fish such as tuna, salmon, mackerel and sardines, cheese and egg yolks. Foods fortified with vitamin D—including some dairy products, orange juice, soy milk, tofu, shiitake mushrooms, almond milk, oatmeal, margarine and cereals—are also a way to get more through your diet.