Mushrooms and Vitamin D

There are few naturally occurring sources of vitamin D, especially ones suitable for vegetarians and vegans. Mushrooms harvested from the wild have historically contained higher amounts of vitamin D in comparison to those grown commercially. This is owed in part to the cultivation of commercial mushrooms in dark growing rooms. However, research has found that exposing mushrooms to ultraviolet (UV) light after harvesting increases the amount of vitamin D. Despite this advantage, some discrepancies have been found in the amount of vitamin D among -mushrooms of both the same and different varieties. As a result, commercially available mushrooms may or may not provide a significant amount of vitamin D, requiring consumers to refer to the Nutrition Facts, if available, or their source for more information.

In addition to the difference of sun exposure compared to commercial cultivation, other factors may also play a role in the vitamin D content of mushrooms. The type of mushroom under consideration (button, oyster and shiitake have been the most widely studied), whether it is fresh or dried (including the type of drying method used), the length of time spent in storage, and the cooking procedures used may all impact vitamin D content. Additional factors can also impact the amount of vitamin D when the mushrooms are exposed to UV light post-harvest, including: whether they are whole or sliced and which part of the surface area receives the UV light (the dome, stalk or gills).

In addition to the vitamin D content of various mushrooms, the bioavailability of vitamin D from these sources has been another area of interest. Bioavailability from both wild mushrooms and those treated with UV light has been well demonstrated, yet its effectiveness in raising serum 25-hydroxyvitamin D (25(OH)D) levels is still an area of study. A previous systematic review and meta-analysis confirmed that the number of randomly controlled trials have been few and findings have been inconsistent.

Although, serum 25(OH)D levels are used to assess vitamin D status in trials, this measure may be confounded by any additional dietary sources, supplements, as well as the amount of vitamin D obtained through sunlight. Other considerations include the dose and frequency of vitamin D administered, the latitude in which participants reside, and baseline serum levels of 25(OH)D.

While it is evident that some varieties of mushrooms could be regarded as good sources of vitamin D, not all types will meet these criteria. Fortunately, mushrooms provide other valuable nutrients, like some of the B-vitamins and trace minerals, and are naturally low in calories. They are extremely versatile in the kitchen and can be used to complement other good sources of vitamin D in helping people meet the recommended amount.

References:

• O'Mahony L, Stepien M, Gibney MJ, Nugent AP, Brennan L. The Potential Role of Vitamin D Enhanced Foods in Improving Vitamin D Status. Nutrients. 2011;3(12)1023-1041.
• Keegan RH, Lu Z, Bogusz JM, Williams JE, Holick MF. Photobiology of vitamin D in mushrooms and its bioavailability in humans. Dermatoendocrinol. 2013;5(1):165-176.
• Cashman KD, Kiely M, Seamans KM, Urbain P. Effect of Ultraviolet Light-Exposed Mushrooms on Vitamin D Status: Liquid Chromatography-Tandem Mass Spectrometry Reanalysis of Biobanked Sera from a Randomized Controlled Trial and a Systematic Review plus Meta-Analysis. J Nutr. 2016;146(3):565-575
• Cardwell G, Bornman JF, James AP, Black LJ. A Review of Mushrooms as a Potential Source of Dietary Vitamin D. Nutrients. 2018; 10(10):1498.
• Stepien M, O’Mahony L, O'Sullivan A, et al. Effect of supplementation with vitamin D2-enhanced mushrooms on vitamin D status in healthy adults. J Nutr Sci. 2013;2(e29):1-9. doi: 10.1017/jns.2013.22.