Vitamin D Deficiency Closely Linked to Obesity

Vitamin D deficiency has been linked to obesity and metabolic syndrome.

Exogenous vitamin D absorption is reduced in obese individuals and endogenous vitamin D production is typically reduced in non-athletic populations implied to be obese. Hence, the relationship between vitamin D and obesity is convoluted.

A recent issue of Inflammation Research included a literature review on the associations among vitamin D levels, obesity, weight loss, and systemic inflammation. Using a wide variety of terms related to this issue, the researchers conducted a comprehensive search.

Serum 25-hydroxy vitamin D levels greater than 30 ng/mL are necessary for healthy bones. Previous studies have suggested that a recommended dietary intake of 15,000 ng of vitamin D in those aged 19 to 69 years old, and 20,000 ng in those aged older than 70 years. Even higher doses are generally deemed necessary to correct vitamin D deficiency.

Maximal oxygen consumption (VO_2max) is inversely associated with vitamin D levels and body mass index. A modest weight loss of 10% of total body weight increases vitamin D bioavailability and VO_2max by 10%, even when vitamin D intake remains consistent.

Vitamin D levels are most closely related to visceral adiposity, which was associated with increased heart disease and inflammation in previous studies.

Vitamin D also acts as a suppressor of inflammatory cytokines, tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6), which are associated with obesity and metabolic imbalances. Vitamin D regulates toll-like receptors on monocytes, macrophages, and adipose cells that affect TNF-α and IL-6.

Some research has suggested that vitamin D supplementation could be helpful for dietary- and exercise-induced weight loss, but more studies are needed. Nevertheless, vitamin D supplementation may reduce TNF-α and IL-6 levels, and also improve cholesterol profiles.

Existing evidence supports the notion that vitamin D, obesity, and inflammatory markers are intimately associated with one another. Shared causative factors include sedentary lifestyle, the inhibitory role of vitamin D on inflammation, and obesity’s reduction in vitamin D bioavailability.