Vitamin D, & some use mushrooms as a way to stretch hamburger meat...

"Farmworkers march to Ostrom Mushroom Farms, announce vote for unionization" | Local | yakimaherald.com

https://www.yakimaherald.com/news/local/farmworkers-march-to-ostrom-mushroom-farms-announce-vote-for-unionization/article_a7e76158-3786-11ed-90ed-5336c4977bd8.html