An increased proportion of body fat as well as obesity are reported to lower bioavailability of cholecalciferol (vitamin D) due to its preference to accumulate in adipose tissue. This can cause further issues in medical conditions already complicated by obesity.
A randomised, double-blind, placebo-controlled trial observed the effects of calcium and vitamin D co-supplementation on glucose metabolism and lipid concentrations in 104 overweight and obese women with polycystic ovarian syndrome (PCOS).
They were randomly assigned to four groups: 1000mg/day calcium + vitamin D placebo; 50,000 IU/week vitamin D + calcium placebo; 1000mg calcium/day + 50,000 IU/week vitamin D; and calcium placebo + vitamin D placebo. Blood samples were measured at the beginning and after eight weeks supplementation.
Calcium and vitamin D co-supplementation resulted in increased levels of serum calcium and vitamin D compared to the other groups. The co-supplementation group also recorded decreased serum insulin levels, homeostasis model of assessment – insulin resistance score and significant increase in insulin sensitivity check index.
In addition, a significant decrease in serum triglyceride’s and VLDL cholesterol was also measured in this group post treatment. The authors concluded that calcium and vitamin D supplementation was beneficial for vitamin D deficient women with PCOS.
A Swedish study compared vitamin D status and intake between obese and normal-weight women during pregnancy. A blood sample as well as information on diet and sun exposure was collated during each trimester from over 100 women of mixed weights.
Half the obese women tested had substandard levels of vitamin D in the first trimester. Obese women also had lower vitamin D status than normal-weight women even though they reported a higher dietary intake.
The majority of all the women tested did not reach the appropriate intake of vitamin D as recommended in dietary guidelines during pregnancy. The most valuable determinants of vitamin D status were supplement use, body fat mass, season of blood testing and travel to southern latitudes.
- Bellan M, Guzzaloni G, Rinaldi M, et al. Altered glucose metabolism rather than naïve type 2 diabetes mellitus (T2DM) is related to vitamin D status in severe obesity. Cardiovasc Diabetol 2014;13:57. [Full Text]
- Asemi Z, Foroozanfard F, Hashemi T, et al. Calcium plus vitamin D supplementation affects glucose metabolism and lipid concentrations in overweight and obese vitamin D deficient women with polycystic ovarian syndrome. Clin Nut 2014;DOI: dx.doi.org/10.1016/j.clnu.2014.09.015. [Abstract]
- Karlsson T, Andersson L, Hussain A, et al. Lower vitamin D status in obese compared with normal-weight women despite higher vitamin D intake in early pregnancy. Clin Nutr 2014;DOI: 10.1016/j.clnu.2014.09.012. [Full Text]