Brief Primer on the LNT Model and Radiation Hormesis Version 1.0 Aug 8, 2018 LNT Model (simplistic, easy to understand and so popular, but is wrong, i.e. not consistent with evidence): 1. Low-dose radiation causes some DNA damage and mutations. 2. Increased mutations mean increased cancers. Radiation Hormesis (realistic, requires more thinking to understand, and is correct, i.e. consistent with evidence) 1. Low-dose radiation causes some DNA damage. 2. Even in the absence of the low-dose radiation, DNA damage does occur due to natural causes. This damage is much more than the damage due to low-dose radiation. 3. Our body responds to the additional DNA damage due to low-dose radiation by increasing defenses such as antioxidants and DNA repair enzymes. These elevated defenses last for some time. 4. The elevated defenses not only repair the damage caused by low-dose radiation but also repair and prevent some of the damage that would have occurred due to natural causes in the subsequent period. 5. The net result is that there would be reduced DNA damage and mutations following the exposure to low-dose radiation, in comparison to having no radiation exposure. 6. The primary cause of cancer is not cancerous mutations. (Almost all of us have cancerous mutations within us but only a small percentage of us have cancer.) 7. The primary cause of cancer is the suppression of the immune system. (There is plenty of data showing that when the immune system is suppressed, cancer risk increases, and when the immune system is boosted, cancer risk decreases.) 8. Low-dose radiation causes some DNA damage. The damaged cells up-regulate RAE-1 and other ligands of the NKG2D receptor activating natural killer cells. (This is the mechanistic reason for the radiation hormesis). 9. Natural killer cells eliminate cancer cells, and so there would be less cancers following exposure to low-dose radiation.
Radiation Hormesis (simpler explanation – omitting the discussion of DNA damage and mutations): 1. Low-dose radiation increases activation of natural killer cells. 2. Natural killer cells eliminate cancer cells, and so there would be less cancers following exposure to low-dose radiation.
Mohan Doss, PhD, MCCPM, Diagnostic Imaging, Fox Chase Cancer Center, Philadelphia, PA, E-mail: mohan.doss@fccc.edu