Researchers out of South Korea have recently reported that omega-3 fatty acid supplementation increases activated vitamin D levels in dialysis patients.
The researchers, led by Professor Won Suk An, conducted an open-label randomized controlled trial administrating omega-3 fatty acids to dialysis patients treated with either hemodialysis or peritoneal dialysis for at least one year due to kidney failure.
Dialysis patients with kidney failure are of interest to vitamin D researchers because they cannot produce adequate activated vitamin D [1,25(OH)₂D, not 25(OH)D] from their kidneys like healthy people, but can still produce activated vitamin D in tissues all over the body outside the kidney. Therefore, in theory, when researchers measure activated vitamin D in kidney failure subjects, they are possibly measuring production from tissues all over the body, and not just what the kidney may or may not be doing.
The kidney’s production of vitamin D plays a large role in calcium homeostasis, while other tissue’s production may play a hand in some of the more recent research areas, like cancer and cardiovascular disease. When you measure activated vitamin D in healthy subjects, it is predominantly a measure of what the kidney is doing in regards to calcium homeostasis, and not what other tissues are doing throughout the body.
Here, the researchers wanted to see if 3 grams of omega-3s per day (containing 1380mg of EPA and 1140 of DHA) affected activated vitamin D levels in dialysis patients with kidney failure. Twenty five patients received the omega-3s for 6 months, while twenty-two patients acted as a control group, though they did not receive a placebo.
They found that 1,25(OH)₂D concentrations increased from 17.4 pg/ml to 26.0 pg/ml after three months and to 28.3 pg/ml after sixth months. In the control group, 1,25(OH)₂D levels changed from 22.2 pg/ml to 20.8 pg/ml after sixth months. Neither the control group nor the omega 3 group’s 25(OH)D levels changed significantly, both hovering around 20 ng/ml.
To the researchers’ knowledge, this is the first report to show increased vitamin D activation caused by omega-3 fatty acid supplementation in dialysis patients.
The researchers note that they believed the elevated 1,25(OH)₂D levels are due to activity outside the kidney. What is peculiar is that 25OHD levels did not change in the omega-3 group.
There are two hypotheses:
- One, that the omega-3s had 25(OH)D content in them, and that the body used that new 25(OH)D to convert to 1,25(OH)₂D, but did not have enough over the sixth month period to raise 25(OH)D levels.
- Or, the enzyme that breaks down 1,25(OH)₂D (24-hydroxylase) is suppressed by omega 3 fatty acids.
The authors state:
“Omega-3 supplementation has been shown to reduce the risk of cardiovascular disease. In addition, the biologically active metabolite 1,25(OH)D has anti-inflammatory, antiproliferative, and antifibrotic effects in both the endothelial and smooth muscle cells of the vascular wall. Therefore, based on our present study, the cardioprotective effect of omega-3 fatty acids can be partially explained by vitamin D activation.”
Further studies in general populations as well as kidney failure patients will be needed to clarify the effect of omega-3s on activated vitamin D.