April 24, 2011
Soy Isoflavones Block DNA Repair

Soy isoflavones block DNA repair mechanisms and help radiation kill cancer cells. But you might worry about what blocking the DNA repair mechanism does to your cells if you aren't undergoing treatment for cancer.

"To improve radiotherapy for lung cancer cells, we are studying the potential of natural non-toxic components of soybeans, called soy isoflavones, to augment the effect of radiation against the tumor cells and at the same time protect normal lung against radiation injury," said Dr. Gilda Hillman, an associate professor in the Department of Radiation Oncology at Wayne State University's School of Medicine and the Karmanos Cancer Institute in Detroit.

"These natural soy isoflavones can sensitize cancer cells to the effects of radiotherapy, by inhibiting survival mechanisms which cancer cells activate to protect themselves," Hillman said. "At the same time, soy isoflavones can also act as antioxidants in normal tissues, which protect them against unintended damage from the radiotherapy. In a recent study, published in the Journal of Thoracic Oncology, we demonstrated that soy isoflavones increase killing of cancer cells by radiation via blocking DNA repair mechanisms, which are turned on by the cancer cells to survive the damage caused by radiation."

Soy is very un-paleo. Soy is high in lectins (unless fermented) and for men the soy isoflavone genistein is only appropriate if you want to shrink your prostate and don't mind the feminization.

Soy might not be as harmful as poisonous sugar and high fructose corn syrup. We need to turn back the clock on our diets by about a century.

Share |      Randall Parker, 2011 April 24 10:09 PM  Aging Diet Studies

Dragon Horse said at April 25, 2011 7:23 AM:

Soy has been eaten in East Asia for centuries.

Axel said at April 25, 2011 5:16 PM:

But many say in East Asia soy is consumed fermented as the post reads.

James Bowery said at April 25, 2011 9:55 PM:

Tofu is curdled unless otherwise specified. Forming curds doesn't get rid of the nasties. Tempeh is fermented soy. Tempeh still isn't "paleo" but it has to be better than unfermented tofu.

Andrew Myers said at April 28, 2011 11:53 AM:

Maybe people in East Asia have adapted to soy and aren't as affected by this?

Kevin said at April 28, 2011 12:01 PM:

So you are willing to skip the paleo myth and eat grain? Because they ate a hell of a lot more grains in the 1900s than we did 50 years later or today.

Ben Thompson said at April 28, 2011 12:29 PM:

But a 100 years ago wasn't life expectancy about 48 years? They never lived long enough to see the effects of their diet.

Phil said at April 28, 2011 12:45 PM:

Once you get past infancy life has always been about three score and 10, in other words 70 years, give or take a few. I really wish people would learn that the adjustments to life span mainly reflect improvement in suviving to adulthood, nothing more.

Thomas said at April 28, 2011 5:30 PM:

Err - your link says soy *protects* normal cells against radiation, even as it sensitizes cancer cells to radiation. Did you actually read the link?

djr said at April 28, 2011 6:21 PM:

What is fermented soy - in terms for dopes like me? I eat Kashi GoLean like crazy, to get the fiber & protein. I don't eat meat right now (causes me horrendous problems) and I run a lot (need the extra protein). Am I doing myself in?

Randall Parker said at April 28, 2011 7:40 PM:


Yes, I read the link.

Normal cells divide less often than cancer cells. Therefore they experience less DNA damage when in the presence of mutagens (i.e. chemotherapy drugs). When chromosomes are replicating they are much more susceptible to DNA damage. So the soy compound's interference with DNA repair will exert a greater effect on cancerous cells. It might exert other effects on cells that are more beneficial. But over the long run interference in DNA damage repair will matter more.

Andrew Myers,

Whether they are adapted genetically depends on how long they've been eating soy. Have they experienced enough selective pressure to produce adaptations to soy? Not clear to me.

Kim said at May 2, 2011 5:52 PM:

Soy has been linked to dementia as well. Best to replace it with another vegetable-based protein source. (not tofu) As far as being "unpaleo," that doesn't really matter, because paleo diets haven't been proven to be that great with regard to longevity. The longest-lived peoples in the world eat modest amounts of animal products (very "unpaleo") and lots of veggies...that's the best way to go. See the Blue Zone study.

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