Obesity Linked to Vitamin D (and thus Sunshine) Deficiency
Researchers from Spain’s University of Carlos Malaga have determined in a large scale study that a deficiency of vitamin D leads to an increased risk of obesity.
The researchers followed 1,226 adult human subjects initially, including 988 of those subjects through six years later, and then 961 subjects through another three years later. In total, 961 subjects were followed through the entire eleven years of the study, from 1996 through 2007.
The researchers analyzed each subjects’ body mass index, weight, height, waist and hip measurements, along with fasting blood glucose levels, vitamin D status and other blood analyses. They also conducted oral glucose tests each year on the subjects.
The researchers measured blood levels of 25-hydroxyvitamin D along with intact-parathyroid hormone (iPTH) levels. (Hyperparathyroidism can also produce low levels of vitamin D, so this possibility was screened).
Serum levels of 25-hydroxyvitamin D that were below or equal to 20 nanograms per milliliter (ng/ml) were qualified as being deficient in vitamin D. This is consistent with the Endocrine Society standards.
A direct relationship between existing obesity and vitamin D deficiency was not established in this study. The researchers did find, however, that 39% of obese subjects were deficient in vitamin D at the second testing, compared to 33% deficient among non-obese subjects. This difference was considered not significant enough to make a broad conclusion.
However, when the standard of vitamin D deficiency was reduced to 17 ng/ml from 20 ng/ml, there was a definite and significant relationship between being deficient in vitamin D and becoming obese within the next four years. Those who had less than 17 ng/ml of 25-hydroxyvitamin D in their blood during the testing had more than double (2.35 times) the incidence of becoming obese in the next four years than those who had 17 ng/ml or greater levels of 25-hydroxyvitamin D in the bloodstream.
In their discussion the researchers stated clearly:
“The results of the present study suggest that lower 25-hydroxyvitamin D values in obese subjects may not have been secondary to obesity, but may in fact precede obesity.”
Other studies have also found that obesity is related to low vitamin D levels. A 2010 study from Norway’s University of Tromsø studied 10,229 people and then followed 2,656 people for fourteen years. Their results concluded that increased body mass index was directly associated with lower vitamin D levels.
The Norway researchers also found that:
“The very obese need higher vitamin D doses than lean subjects to achieve the same serum 25(OH)D levels.”
While vitamin D can be supplemented, one of the easiest and cheapest ways to produce high levels of 25-hydroxyvitamin D is by safe sun exposure.
González-Molero I, Rojo-Martínez G, Morcillo S, Gutierrez C, Rubio E, Pérez-Valero V, Esteva I, Ruiz de Adana MS, Almaraz MC, Colomo N, Olveira G, Soriguer F. Hypovitaminosis D and incidence of obesity: a prospective study. Eur J Clin Nutr. 2013 Jun;67(6):680-2.
Jorde R, Sneve M, Emaus N, Figenschau Y, Grimnes G. Cross-sectional and longitudinal relation between serum 25-hydroxyvitamin D and body mass index: the Tromsø study. Eur J Nutr. 2010 Oct;49(7):401-7.