Mehrotra A., Calvo M.S., Beelman R.B., Levy E., Siuty J., Kalaras M.D., Uribarri J. Bioavailability of vitamin D2 from enriched mushrooms in prediabetic adults: a randomized controlled trial. Eur J Clin Nutr. 2014;68(10):1154–1160.
Rationale
UV-exposed mushrooms are sold as a "natural vitamin D source." The Urbain 2011 trial showed mushroom D2 raises 25(OH)D like a tablet — but used soup with a known dose. This study tested the real-world version: UV-B-enriched mushrooms cooked into actual dishes for people who need D most (prediabetic, deficient, overweight adults).
Methods
A randomized controlled trial: 43 adults with prediabetes, vitamin D deficiency and BMI>25 were assigned to four arms — including 600 or 4000 IU/day of D2 delivered as UV-B-treated mushroom slices in a 100 g chef-prepared dish — for 16 weeks. Serum 25(OH)D tracked the response.
Results
The 25(OH)D response was modest or absent — far below what the nominal D2 doses predicted. Analysis showed part of the D2 was lost in cooking, and the actual doses in the D3-supplement control arm turned out higher than labeled — compressing the contrast.
Conclusions
Mushroom-derived D2 does work, but a laboratory dose does not equal a dinner plate: cooking losses and dosing reality dominate. "Eat UV mushrooms for vitamin D" requires getting the kitchen chemistry right.
Worth noting
The instructive failure: this study is more useful than a clean positive because it shows where the food-based D2 strategy breaks — preparation method, matrix effects, real vs labeled dose. Pair with Urbain 2011 for the full picture: same molecule, different delivery, opposite outcomes.