Mushrooms are the only vegetable with vitamin D, which helps bodies absorb calcium, supports bone production, and regulates the immune system. The more a mushroom is exposed to the sun, the more vitamin D it produces.
Eating mushrooms can boost a person's vitamin D as much as, if not more than, taking a vitamin D supplement, according to researchers at the Boston University School of Medicine. They also found that exposing mushrooms to ultraviolet light increases their vitamin D production.
How much vitamin D a mushroom has depends on how long it is exposed to the sun, before or after it is harvested. Even putting cut mushrooms in direct sunlight for two days can boost their vitamin D content for up to one year. Eating four handfuls of vitamin D-enriched mushrooms a week can naturally boost vitamin D levels.
Most people get some vitamin D through exposure to the sun, because very few foods naturally contain it. Tuna, salmon and mackerel are good sources of vitamin D, and beef liver, cheese and egg yolks have small amounts. Vitamin D is often added to milk, soy beverages, some breakfast cereals, orange juice, yogurt and margarine. Some people opt to take vitamin D supplements to make sure they get enough. Vegetables such as carrots and broccoli are not good sources of vitamin D, but they do provide healthy amounts of vitamins A, B and C and also contain carbohydrates and minerals.