This evidence of radiogenic metabolism (metabolism promoted by ionizing radiation) includes enzyme induction, photosynthesis, respiration and growth. Radiation hormesis in immunity decreases infection and
premature death in radiation exposed populations. Increased immune competence is a major factor in the increased average life-span of populations exposed to low-dose irradiation.

This article is very accurate and it is demonstrated here radiationhormesis.com

I second Glen’s answer. Additional insight into this issue is the battle between different groups on whether radiation hormesis exists. At stake is an issue of very large economic consequences. See, if this hypothesis is not verified then any level of radiation is harmful and therefore regulations are working to reduce any radiation output to zero (as they should), a cost that no society can really bear (there is natural radiation everywhere). If the hypothesis is true, then the linear hypothesis is wrong at very very low dose and regulations need to take that into account so as to not burden technologies that in fact are doing no harm when there are releasing very very low doses. However, if the latter is true, the journalistic treatment on any information linked to nuclear subjects cannot really be unbiased: Fear backed up by so called specialists always sells.

Igor.

Unfortunately, the reflexive tendency to associate hormesis with homeopathy has probably resulted in it receiving much less atttention than it deserves.

I doubt the damage-repair system would be stimulated by benign bacteria though.

Too little is bad. Too much is just as bad. The optimal is somewhere in the middle.

Glen, when I stop eating fermented food or eat much less of it the effects seem to wear off in about a day. Along the same lines, I met a woman whose health greatly improved when she switched from eating yogurt once/week to once/day. This observations support a once/day rule over a once/week rule.

We know that most substances which are dangerous in large amounts (say, arsenic) are beneficial in smaller amounts. It’s even true with things we think of as necessary and good for you such as water: too little and you die of thirst, but too much and you drown. There’s a U-shaped or inverted-U-shaped dose-response curve for almost everything people have studied and we don’t yet really know *why* this is, though there are some half-baked, untested theories about it.

The logical application of that principle to the question of bacteria in the diet would be to assume that that, too, has an inverted-U-shape dose-response curve. The notion of hormesis implies there’s some *optimum* nonzero amount of bacteria in the diet to achieve maximally beneficial health effects and if you consume less *or more* than that amount it will be less beneficial. And if you take way too much it might hurt or kill you.

Even if it’s clear that *some* bacteria in the diet is much better than *no* bacteria in the diet, it does not logically follow that more still is better, or that stuff past its “sell-by date” is better for you than “fresher” food.

Determining the optimum amount of bacteria in the diet seems like an empirical question rather than something you could answer on principle. Might we all be better off eating natto/miso/kombucha once a week than once a day?