Vitamin D, probiotics and zinc reduce seasonal infection and boost immunity

Kids who took vitamin D warded off flu, adults with higher vitamin D levels avoided respiratory tract infections, and probiotics and zinc increased immune response, several new studies reveal.

In a children’s flu study, researchers said Danish scientists recently discovered that vitamin D triggers immune-system killer T-cells—white blood cells that attack viruses—but remain inactive when vitamin D is low. In this study, 334 kids took 1,200 IU of vitamin D per day or a placebo from December through March.

Over this time, 19 percent in the placebo group got influenza A compared to 11 percent for vitamin D. In those with asthma, 12 in the placebo group had an asthma attack compared to two in the vitamin D group. The researchers believe vitamin D could have been even more effective in preventing flu because it takes about three months to build up a base level in the blood, and the study began after flu season had started.

In a related study, researchers measured vitamin D levels in 195 men and women, aged 20 to 88, during the fall and winter. Over four months, 84 participants got viral infections. In those whose vitamin D levels were lower than 38 nanograms per milliliter of blood, 55 percent had no respiratory tract infection. In those whose vitamin D levels were higher, 83 percent had no infection.

In two lab studies, researchers exposed white-blood killer T-cells to influenza A and other viruses before and after healthy donors had taken the probiotic Bacillus coagulans or 15 mg of zinc per day for the previous month. In both studies, killer T-cell activity significantly increased after taking probiotics or zinc.

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