Article written and contributed by Mike O’Sullivan, Watsonia General Practice Dietitian.
Mushrooms have the potential to be great sources of Vitamin D. Here in Melbourne we do go through quite a long period where there is little sun. Also many of us are not getting enough vitamin D due to working indoors. Here are some interesting facts in regards Vitamin d and mushrooms:
- All mushroom have a compound called ergosterol that becomes vitamin D when exposed to UV light (eg sunlight). Changes to ergocalciferol (vitamin D2).
- Eating mushrooms containing vitamin D2 can be as effective at increasing and maintaining vitamin D levels as taking supplemental vitamin D2 or D3.
- Just 1 hour of sun exposure stimulate mushrooms to provide at least 10mg of Vit D (3 medium sized mushrooms) – 10mg is 400 IU. Further exposure yielded higher Vit D, in some cases 3 white mushrooms can yield 890IU vitamin d – this is close to the quantity of one vitamin D capsule.
- Vitamin D is very stable in mushrooms even after cooking.
- Vit D is fat soluble so cooking mushroom in some olive oil would be recommended
- Shiitake mushrooms are probably one of the highest sources. One researcher found that shiitake mushrooms that had been grown inside increased their vitamin D content from 110 IU to 46000 IU after being put outside in the sun for 6 hours gills facing up.
- Vit D supplementation recommendation is 600IU per day for those under 70, 800IU of those over 70 and sun avoiders 1000-2000IU
- Toxicity levels for Vit D – 10000IU/day every day for 3 months or 300000IU in a 24hr period.
- Mushrooms tested showed that nearly a year after exposure, they preserved significant amounts of vitamin D2.
- Sun dried mushrooms have this capacity too and because they are dried; their shelf life is much improved
Summary: Mushrooms either exposed to at least 1 hour direct midday sun or sun dried for 5-6 hour for two days are a great source of Vit D. It appears that 3-4 medium sized, UV exposed white mushroom would be sufficient to supplement for Vit D difficiency = 400-1000IU (dependent on size and exposure length). Shitake Mushroom seem to be by far the greatest yielder of Vit D when exposed to UV. Just half of one of these mushrooms would provide enough Vit D for supplementation purposes. Vit D in UV exposed mushrooms remain stable after cooking but begin to decrease after a few minutes. Toxicity level for Vit D would be difficult to achieve.
