This research indicates some good news
In a time when radiation exposure from a number of sources, including air travel, nuclear power, and former testing grounds seems unavoidable, any news of radio-protective substance is good news. Fortunately, emerging research is indicating that melanin in fungi, which is also the pigment responsible for skin color in humans, may not only enable some fungi to survive ionizing radiation, but also to feed off of it.
An early report of this possibility came from Russia in 2001 on the discovery of a melanin-rich species of fungi seeming to thrive within the walls of the Chernobyl meltdown reactor site. Three years later, the same observation was made for the surrounding soils. 
In 1961, another study found that melanin-rich fungi were growing in a Nevada nuclear test site, surviving doses of up to 6,400 Grays (Gy)! That is around 2,000 times the lethal dose for humans. 
Amazingly, a study published in PLoS from 2007 revealed that melanized fungal cells showed increased growth relative to non-melanized cells after ionizing radiation exposure. The electronic properties of the melanin also changed, raising questions about a role for melanin in energy use.
If melanin could protect fungi from radiation, could consumption of mushrooms containing it protect humans and animals?
Research published in 2012 found that melanin isolated from the fungus Gliocephalotrichum simplex and administered at a dose of 50mg/kg of body weight increased the 30-day survival of mice by 100%! Melanin up to a dose of 100mg/kg had no adverse effects.
Additionally, a second 2012 study on another species of fungus, Auricularia auricula-judae (Jelly ear), suggests that these radio-protective abilities may be mostly melanin-specific. This time, mice were fed jelly ear, a part of East Asian cuisine, an hour before receiving a 9 Gy dose of radiation from Cesium-137. In comparison, anything over 0.1 Gy is dangerous for humans.
All control mice died within 13 days, but 80-90% of the mice that ate jelly ear survived. Those fed white porcini mushrooms died nearly as fast as the controls, but had similar survival rates to the mice fed jelly ear if the white mushrooms were supplemented with melanin.
How Does Melanin Work?
In one study, ionizing radiation was found to alter the oxidation-reduction potential of melanin, not causing destruction, but instead keeping the melanin intact. The only difference was that melanin was then able to produce a continuous electric current, which may produce energy in living cells. This could explain the increased growth of some gamma irradiated fungi, even in low nutrient conditions.
However, this does not mean that it is safe to have radioactive material inside the body. Apple pectin is one substance that can aid in removing radionuclides, with one study showing an over 62% reduction in radionuclides in treated children from the Chernobyl area. Another showed a 28-39% reduction after just 16 days, improving cardiovascular health in the children.
It’s possible that if used alongside each other, both melanized mushrooms, such as Chaga mushrooms, and apple pectin, and possibly other radio-protective natural medicines, may be a highly effective treatment for radiation poisoning.
 L.M. Shields, L.W. Durrell Preliminary observations on radiosensitivity of algae and fungi from soils of the Nevada test site. Ecology, 42 (1961), pp. 440–441
Featured image sourced and modified from: Panoramio / ian.r