Bioavailability of vitamin D2 from enriched mushrooms in prediabetic adults: a randomized controlled trial

Background/Objectives: Based on the growing evidence of risk reduction from fresh fruit and vegetable consumption and an inverse relationship between serum 25-hydroxyvitamin D (25OHD) and the risk of type 2 diabetes (T2D), we determined the benefits of regularly consuming vitamin D-enriched mushrooms in a prediabetic cohort. Exposing edible mushrooms to ultraviolet B (UVB) light increases vitamin D 2 (D 2 ) and raises serum 25OHD 2 in healthy young adults; however, their benefit to deficient prediabetics and glucose metabolism remains untested. Subjects/methods: Forty-three prediabetic, D-deficient adults (25OHD≤20 ng/ml), BMI>25 were randomized to four groups consuming daily entrées containing 100 g fresh sliced cooked mushrooms prepared by a chef for 16 weeks. Two groups were fed UVB-treated mushrooms initially containing: 600 IU D 2 or 4000 IU D 2 ; each one also received one capsule of placebo daily. Two control groups were fed untreated mushrooms and D 3 dietary supplements at two label doses: 600 IU D 3 and 4000 IU D 3 . D 2 and D 3 content were analyzed in mushrooms, before and after cooking and in over-the-counter supplements. Results: After 16 weeks, both D 2- UVB-mushroom entrée doses, which were significantly lower after cooking, produced modest or no increases in 25OHD 2 or total 25OHD relative to the positive control subjects who actually consumed about 1242 and 7320 IU per day of D 3 (higher than stated on the label). Conclusions: Unanticipated D 2 cooking loss from fresh UVB mushrooms and probable low absorption and/or hydroxylation may explain the smaller increase in 25OHD 2 in our prediabetic overweight/obese cohort compared with past findings in younger, healthy subjects. Moreover, no dose or vitamin D source was associated with modifying T2D risk factors.