Health Hotline Magazine | April 2025

Do you struggle with frequent colds and infections? Low vitamin D may be the culprit. Research shows there’s a link between low vita min D levels and respiratory tract infections like the common cold, bronchitis, pneumonia, RSV, COVID-19, and influenza. Studies also show that improved vitamin D levels translate to a significant decrease in the risk of developing these types of infections. So what is the ideal level of vitamin D to prevent viral respiratory illnesses? One study investigated the relationship between declin ing vitamin D levels seen in the fall and winter and frequency of infections in 198 healthy adults living in New England. Blood levels of vitamin D 38 ng/mL (a common measurement of vitamin D) and higher were associated with a “significant two-fold reduction in the risk of developing acute respiratory tract infections and with a marked reduction in the percentages of days ill.” The researchers also noted that “light skin pigmentation, lean body mass, and sup plementation with vitamin D were found to correlate with higher concentrations [of vitamin D].” Supplementing with vitamin D to achieve this higher level is key. A randomized, double-blind, placebo-controlled trial of school aged children comparing vitamin D supplements with a placebo and the incidence of influenza, revealed that children who took 1,200 IU of vitamin D daily for four months saw a 42 percent reduction in the risk of getting the flu. Another randomized, con trolled trial of vitamin D supplementation in pregnant women and infants determined that when healthy pregnant women supple mented with 2,000 IU of vitamin D daily, and their infants re ceived 800 IU in the months after birth, the child experienced a significant reduction in the number of acute respiratory infections between six and 18 months of age. Long COVID—which can include neurocognitive, cardiorespi ratory, gastrointestinal, musculoskeletal, and taste and smell dis orders—is an emerging syndrome affecting 50 to 70 percent of those who contract COVID. In one recent double-blind, randomized, placebo-controlled trial, patients with post-COVID symptoms saw significant improve ments in fatigue, anxiety, and cognitive symptoms after taking 8,500 IU of vitamin D daily for eight weeks compared to the placebo group. The study concluded, “High-dose vitamin D sup plementation may benefit patients with post-COVID syndrome by reducing fatigue, alleviating anxiety, and improving cognitive symptoms, with minimal side effects.” Vitamin D is also essential for muscle development and repair. It plays a large role in supporting healthy muscle mass and overall muscle function, and low levels of vitamin D are associated with reduced muscle mass and strength. Studies show that supple menting with D improves these parameters. In two randomized, controlled trials of 160 postmenopausal wom en (aged 50–65 years) with insufficient-to-deficient vitamin D levels (mean serum levels less than 20ng/mL), supplementation with 1,000 IU vitamin D daily for nine months resulted in a lower incidence of falls and improvement in postural balance, and was shown to preserve lean muscle mass and improve muscle strength.

Vitamin D is essential for strong bones and healthy teeth. It helps the body absorb and retain calcium and phosphorus, which are required for maintaining strong bones, and is positively associated with bone mineral density (BMD). Vitamin D also reduces the risk of bone fractures. A meta-analysis of 11 randomized, controlled trials involving more than 30,000 adults aged 65 and older, nearly 90 percent of whom had insufficient vitamin D levels, found that vitamin D supplementation (800–2,000 IU daily) reduced the risk of hip fractures by 30 percent and nonvertebral fractures by 14 percent. According to a 2023 study in children ages two to 17, serum vita min D levels below the normal range had twice the risk of experi encing a fracture compared to those with normal vitamin D levels. For each unit increase in serum vitamin D levels, the likelihood of fractures at various locations in the forearm decreased by up to seven percent. Researchers also found that when children with fractures and low vitamin D levels were supplemented with vita min D and calcium at 2,000 IU and 600 mg per day, respectively, healing improved. Vitamin D is also essential for oral health in both children and adults. A 2023 meta-analysis of 16 studies found that individuals with periodontitis (gum disease) have lower serum vitamin D levels compared to healthy individuals without periodontitis.

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