Lowering Your Cancer Risk by Donating Blood

Back in the early 1980s, a pathologist in Florida suggested that the reason premenopausal women are protected from heart disease is that they have lower stores of iron in their body. Since oxidized cholesterol is “important in atherosclerosis, and oxidation is catalyzed by iron,” might the lower iron stores of menstruating women reduce their risk of coronary heart disease? “The novel insight suggesting that the longevity enjoyed by women over men might relate to the monthly loss…of blood is remarkable,” but is it true? I discuss this in my video Donating Blood to Prevent Heart Disease?.

The consumption of heme iron—the iron found in blood and muscle—is associated with increased risk of heart disease. Indeed, “an increase in heme iron intake of 1 mg/day appeared to be significantly associated with a 27% increase in risk of CHD,” coronary heart disease. But, heme iron is found mainly in meat, so “it is possible that some constituents other than heme iron in meat such as saturated fat and cholesterol are responsible” for the apparent link between heme iron and heart disease. If only we could find a way to get men to menstruate, then we could put the theory to the test. What about blood donations? Why just lose a little blood every month when you can donate a whole unit at a time?

A study in Nebraska suggested that blood donors were at “reduced risk of cardiovascular events,” but another study in Boston failed to show any connection. To definitively resolve the question, we would really have to put it to the test: Take people at high risk for heart disease, randomly bleed half of them, and then follow them over time and see who gets more heart attacks. Maybe it could turn “bloodletting” from the past into “bleeding-edge technology.” In fact, that was actually what was suggested in the original paper as a way to test this idea: “The depletion of iron stores by regular phlebotomy could be the experimental system for testing this hypothesis…”

It took 20 years, but researchers finally did it. Why did it take so long? There isn’t much money in bloodletting these days. I suppose the leech lobby just isn’t as powerful as it used to be.

What did the researchers find? It didn’t work. The blood donors ended up having the same number of heart attacks as the non-donor group. Something extraordinary did happen, however: The cancer rates dropped. There was a 37 percent reduction in overall cancer incidence, and those who developed cancer had a significantly reduced risk of death. An editorial in the Journal of the National Cancer Institute responded with near disbelief, saying the “results almost seem to be too good to be true.” “Strikingly,” they started to see cancer reduction benefits within six months, after giving blood just once. As the study progressed, the cancer death rates started to diverge within just six months, as you can see at 2:46 in my video, but this is consistent with the spike in cancer rates we see within only six months of getting a blood transfusion. Is it possible that influx of iron accelerated the growth of hidden tumors?


I continue this wild story in my video Donating Blood to Prevent Cancer?.

What if you feel faint when you give blood? Don’t worry. I’ve got you covered. Check out How to Prevent Fainting.

What might iron have to do with disease? See The Safety of Heme vs. Non-Heme Iron and Risk Associated with Iron Supplements.

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live presentations:

Comparing Pollutant Levels Between Different Diets

The results of the CHAMACOS (Center for the Health Assessment of Mothers and Children of Salinas) study were published recently. This study of a California birth cohort investigated the relationship between exposure to flame retardant chemical pollutants in pregnancy and childhood, and subsequent neurobehavioral development. Why California? Because California children’s exposures to these endocrine disruptors and neurotoxins are among the highest in the world.

What did they find? The researchers concluded that both prenatal and childhood exposures to these chemicals “were associated with poorer attention, fine motor coordination, and cognition” (particularly verbal comprehension) by the time the children reached school age. “This study, the largest to date, contributes to growing evidence suggesting that PBDEs [polybrominated diphenyl ethers, flame retardant chemicals] have adverse impacts on child neurobehavioral development.” The effects may extend into adolescence, again affecting motor function as well as thyroid gland function. The effect on our thyroid glands may even extend into adulthood.

These chemicals get into moms, then into the amniotic fluid, and then into the breast milk. The more that’s in the milk, the worse the infants’ mental development may be. Breast milk is still best, but how did these women get exposed in the first place?

The question has been: Are we exposed mostly from diet or dust? Researchers in Boston collected breast milk samples from 46 first-time moms, vacuumed up samples of dust from their homes, and questioned them about their diets. The researchers found that both were likely to blame. Diet-wise, a number of animal products were implicated. This is consistent with what’s been found worldwide. For example, in Europe, these flame retardant chemical pollutants are found mostly in meat, including fish, and other animal products. It’s similar to what we see with dioxins—they are mostly found in fish and other fatty foods, with a plant-based diet offering the lowest exposure.

If that’s the case, do vegetarians have lower levels of flame retardant chemical pollutants circulating in their bloodstreams? Yes. Vegetarians may have about 25% lower levels. Poultry appears to be the largest contributor of PBDEs. USDA researchers compared the levels in different meats, and the highest levels of these pollutants were found in chicken and turkey, with less in pork and even less in beef. California poultry had the highest, consistent with strict furniture flammability codes. But it’s not like chickens are pecking at the sofa. Chickens and turkeys may be exposed indirectly through the application of sewer sludge to fields where feed crops are raised, contamination of water supplies, the use of flame-retarded materials in poultry housing, or the inadvertent incorporation of fire-retardant material into the birds’ bedding or feed ingredients.

Fish have been shown to have the highest levels overall, but Americans don’t eat a lot of fish so they don’t contribute as much to the total body burden in the United States. Researchers have compared the level of PBDEs found in meat-eaters and vegetarians. The amount found in the bloodstream of vegetarians is noticeably lower, as you can see in my video Flame Retardant Pollutants and Child Development. Just to give you a sense of the contribution of chicken, higher than average poultry eaters have higher levels than omnivores as a whole, and lower than average poultry eaters have levels lower than omnivores.

What are the PBDE levels in vegans? We know the intake of many other classes of pollutants is almost exclusively from the ingestion of animal fats in the diet. What if we take them all out of the diet? It works for dioxins. Vegan dioxin levels appear markedly lower than the general population. What about for the flame retardant chemicals? Vegans have levels lower than vegetarians, with those who’ve been vegan around 20 years having even lower concentrations. This tendency for chemical levels to decline the longer one eats plant-based suggests that food of animal origin contributes substantially. But note that levels never get down to zero, so diet is not the only source.

The USDA researchers note that there are currently no regulatory limits on the amount of flame retardant chemical contamination in U.S. foods, “but reducing the levels of unnecessary, persistent, toxic compounds in our diet is certainly desirable.”

I’ve previously talked about this class of chemicals in Food Sources of Flame Retardant Chemicals. The same foods seem to accumulate a variety of pollutants:

Many of these chemicals have hormone- or endocrine-disrupting effects. See, for example:

In health,

Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: