A study published on Feb. 5 this year was motivated by the fact that sarcopenia, an age-related gradual loss of muscle mass, strength, and mobility in older adults, is closely related to vitamin D deficiency and reduced levels of physical activity. It explored the interactive effect of vitamin D and physical activity on muscle mass and function through animal experiments and population surveys. A portion of the study analyzed male 4-week-old mice were fed various diets. One diet was vitamin D deficient, with increased calcium and phosphorus to prevent the effects of abnormal mineral levels of muscle, or a diety supplemented with high levels of vitamin D3. After 24 weeks, the mice were immobilized, and the level of skeletal muscle atrophy in the mice was determined, as well as the protein expression levels of FOXO3a and the E3 ubiquitin ligases MuRF1 and MAFbx. Vitamin D deficiency, with limited physical activity, accelerated the decrease in muscle weight, muscle fiber CSA, and grip strength, and increased the protein expression of all three protein expressions evaluated. Vitamin D inhibited these effects significantly in physically inactive mice whose diets were supplemented with vitamin D.
Part two of the study analyzed date from 4,139 older adults, as part of a survey in Northeast China. The metrics that were assessed included vitamin D3 serum content, physical activity levels, and a muscular regression analysis that was adjusted for covariates. D3 serum content and physical activity were linearly related to better results in a timed up and go (TUG) test and handgrip strength, but not calf circumference or body muscle mass in older adults.
Researchers concluded that the effect of vitamin D on mucle strength and physical performance depends on physical activity level in the elderly, and recommended that older adults strive to avoid both physical inactivity and vitamin D deficiency to mitigate potential muscle atrophy, and protein ubiquitination.
People who live in higher latitudes are more predisposed to vitamin D deficiency in winter months. It was found in a study of 1,400 people living in high altitude regions in Canada between the ages of 50 and 74 years old that vitamin D supplementation appeared to have a protective effect against high-risk adenomatous polyps (HRAPS) with individuals who took the recommended daily intake of 600IU vitamin D.
The statistical results had an adjusted odds ratio of 0.78, signifying that vitamin D may offer a protective effect against the development of polyps in populations living in high-latitude regions where vitamin D deficiencies are more prevalent.
A review published by the National Institutes of Health calls for greater clinical research into the role that micronutrients have on the immune system, along with the influence of environmental factors such as pollution, stress, and infection, on the interplay between micronutrient intake and immune function.
“Immune support by micronutrients is historically based on vitamin C deficiency and supplementation in scurvy in early times. It has since been established that the complex integrated immune system needs multiple specific micronutrients, including vitamins A, D, C, E, B6, and B12, folate, zinc, iron, copper, and selenium, which play vital, often synergistic roles at every stage of the immune response,” the authors wrote. “Daily micronutrient intakes necessary to support immune function may be higher than current recommended dietary allowances.”
Essentially, the authors believe that contradictory results on micronutrients and immune function call for better human clinical study designs addressing dosage and combinations of micronutrients in different populations. Among the other studies evaluated in the review, five meta-analyses of the most high-quality studies found by the authors demonstrated that a wide-range of doses of vitamin D could reduce the risk of respiratory tract infections in adults and children, and this risk reduction was most prevalent in participants who had low vitamin D status at the beginning of their respective trials. The authors characterized the evidence that vitamin D can improve immune function in the wake of tuberculosis, influenza, and upper respiratory tract infections as low-to-moderate quality, while some of the studies they evaluated found no benefit from vitamin D supplementation in participants with tuberculosis, influenza, pneumonia, or diarrhea.
There is a rationale to bridge a gap between nutritional deficiencies and immune function, and thus, improve resistance to infection, the authors said.
Researchers have determined that the prevalanece of oral squamous cell carcinoma may be associated with vitamin D deficiency, indicating that the micronutrient may have a role in prevention of this form of cancer.
In an analysis of the baseline vitamin D levels, a total of 51 patients with oral squamous cell carcinoma were tested and matched with two cancer-free subjects each, who served as controls, whose serum vitamin D levels were also measured. 75% of the patients who were evaluated were found to have moderate to severe vitamin D deficiencies, whereas only 20% of the control group had deficiencies, none of which were severe. Researchers concluded that vitamin D deficiency, especially in serum levels below 25 ng/ml is associated with a risk of oral squamous cell cancer. Therefore, researchers said, a routine prescription of vitamin D supplements in patients with these deficiencies may be necessary to decrease the chances of OSCC development.