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Too much fructose reduced both serum and active vitamin D in rats – April 2013

Excessive fructose intake causes 1,25-(OH)2D3-dependent inhibition of intestinal and renal calcium transport in growing rats.

Am J Physiol Endocrinol Metab. 2013 Apr 9.
Douard V, Sabbagh Y, Lee J, Patel C, Kemp FW, Bogden JD, Lin S, Ferraris RP ferraris at umdnj.edu
1 UMDNJ-New Jersey Medical School.

We recently discovered that chronic high fructose intakes by lactating rats prevented adaptive increases in rates of active intestinal Ca2+ transport and in levels of 1,25-(OH)2D3, the active form of vitamin D. Since sufficient Ca2+ absorption is essential for skeletal growth, our discovery may explain findings that excessive consumption of sweeteners compromises bone integrity in children.

We tested the hypothesis that 1,25-(OH)2D3 mediates the inhibitory effect of excessive fructose intake on active Ca2+ transport. First, compared with those fed glucose or starch, growing rats fed fructose for 4 wk had a marked reduction in intestinal Ca2+ transport rate as well as in expression of intestinal and renal Ca2+ transporters that was tightly associated with decreases in circulating levels of 1,25-(OH)2D3, bone length, and total bone ash weight but not with serum PTH.

Dietary fructose increased the expression of 24-hydroxylase (CYP24A1) and decreased that of 1α-hydroxylase (CYP27B1), suggesting that fructose might enhance the renal catabolism and impair the synthesis, respectively, of 1,25-(OH)2D3. Serum FGF23, which is secreted by osteocytes and inhibits CYP27B1 expression, was upregulated, suggesting a potential role of bone in mediating the fructose effects on 1,25-(OH)2D3 synthesis. Second, 1,25-(OH)2D3 treatment rescued the fructose effect and normalized intestinal and renal Ca2+ transporter expression. The mechanism underlying the deleterious effect of excessive fructose intake on intestinal and renal Ca2+ transporters is a reduction in serum levels of 1,25-(OH)2D3. This finding is significant because of the large amounts of fructose now consumed by Americans increasingly vulnerable to Ca2+ and vitamin D deficiency.

PMID: 23571713

Had wondered since 2010 how sugary drinks could reduce Calcium levels.
Now it appears that fructose decreases the Calcium in two ways

  1. Decreasing the vitamin D processed by the liver - which is measured by a Vitamin D blood test
  2. Decreasing the active vitamin D produced by the Kidneys - which is NOT measured by a blood test

See also VitaminDWiki