What’s the Best Ferritin Level to Lower Cancer Risk?

If cancer is indeed a so-called ferrotoxic disease, a consequence, in part, of iron toxicity, that would explain not only the dramatic drop in cancer rates after blood donations, but also why people with higher levels of iron in their blood have an increased risk of dying from cancer, why women who bleed into their ovaries are at high risk for ovarian cancer, and why those suffering from hemochromatosis (an iron overload disease) have up to 200 times the risk of cancer. There has even been a call to go back and look at some of the chemotherapy trials that kept taking blood from the chemo group to check for side effects. Perhaps just the iron removal from the blood draws accounted for some of the apparent chemo benefits.

Iron may be a double-edged sword, as I explore in my video Donating Blood to Prevent Cancer?. Iron deficiency causes anemia, whereas excessive iron may increase cancer risk, presumably by acting as a pro-oxidant and generating free radicals. Iron-deficiency anemia is a serious problem in the developing world. “In meat-eating countries, however, iron excess may be more of a problem than iron deficiency…Body iron stores accumulate insidiously with ageing due to the fact that intake exceeds loss,” and our body has no good way of getting rid of excess iron.

Ferritin is a blood test measure of our backup iron stores. As you can see at 1:31 in my video, the normal range is about 12 to 200 ng/mL—but just because it’s normal doesn’t mean it’s ideal. In the blood donor study discussed earlier, those who developed cancer had ferritin levels around 127.1 ng/mL. The average for men may be over a hundred.

This suggests that so-called normal, “ambient levels of iron stores may be noxious and constitute a ‘public’ problem that affects large segments of the population.” As such, “[t]here may be a need to redefine the normal range…based on associated disease risk” rather than following a bell curve. “Thus, iron deficiency may exist when ferritin levels decline to less than about 12 ng/mL, whereas ferrotoxic disease may occur with levels greater than about 50 ng/mL.”

Harvard recently looked at blood donations and colorectal cancer, and found no connection, but the range of ferritin levels the researchers looking at was roughly 100 to less than 200 ng/mL, as you can see at 2:28 in my video. What’s more, those were from individuals who reported giving blood 30 or more times. So, perhaps instead of draining our blood to reduce excess iron stores, why not prevent the iron overload in the first place? If we measure the iron stores of men who stay away from heme iron and, instead, get all of their iron from plants, their iron levels are right around where the cancer-free donor group came in, as you can see at 2:54 in my video. This may help explain why those eating plant-based diets tend to have less cancer and other diseases associated with iron overload. Indeed, they may also have less pre-diabetes, as well as have less diabetes.


For more on the blood donor study I discussed, see Donating Blood to Prevent Heart Disease?.

For more on diet and iron levels, see The Safety of Heme vs. Non-Heme Iron and Risk Associated with Iron Supplements.

Interested in other examples of normal lab values not being necessarily ideal? Check out:

Even though a plant-based diet may be preferable for personal disease risk, that doesn’t mean we shouldn’t all give blood. Join me in supporting the Red Cross.

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:

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:

Do Poultry Viruses Cause Human Cancers?

The incidence of cancers has been rising for the last half century, and the question is why? Up to 20 percent of all cancers are caused by infectious agents, chiefly viruses. We’ve known this was possible for a century, when a cancer-causing virus was discovered in chickens. The idea was considered such heresy that Dr. Peyton Rous, the man who made this landmark discovery, wouldn’t get his Nobel Prize until 55 years later.

If there are cancer-causing chicken viruses, might they have any effect on people who handle or eat poultry? Concern has been raised about the potential infectivity of cancer-causing farm animal viruses for decades. The first question was whether there was any evidence of human exposure, and, indeed, people do have antibodies to these cancer-causing chicken viruses in their bloodstream. This indicates that the virus is no stranger to our immune systems. Is there any evidence, though, that the virus itself can get into our blood? There wasn’t any such evidence…until 2001.

As I explain in my video The Role of Poultry Viruses in Human Cancers, there is a cancer-causing herpesvirus in poultry, but does it pose a public health hazard? Researchers used DNA fingerprinting techniques to test the blood of 202 people and found that 20 percent, or one in five individuals, had viral DNA in their bloodstream. Testing positive for avian herpesvirus doesn’t mean these diseases can necessarily infect human cells, however. But, as it turns out, they can indeed.

But do they cause human disease? How can that be figured out? Since we can’t just inject people, researchers looked at poultry workers, which is the way we figured out how other farm animal diseases, such as brucellosis and anthrax, jumped to humans. In fact, studying workers is also how we discovered the carcinogenic nature of things like asbestos and benzene. If the poultry workers, who are exposed day in and day out, don’t have higher cancer rates, then presumably the viruses are harmless. Unfortunately, they do have higher rates. In fact, those with high exposure to cancer-causing poultry viruses have “increased risk of dying from several cancers.”

As such, “the relative ease” with which some of the viruses can infect human cells, as well as infect and cause tumors in primates in laboratories, “may be of public health significance, particularly because of the…increased risk of cancer in meat workers” and the evidence that we may become infected with these viruses. However, even if poultry workers are at risk, it doesn’t mean people who merely eat chicken or eggs are. For example, workers who kill chickens were found to be six times more likely to die from brain cancer compared to workers who do not kill poultry, but the slaughterers have live birds flapping in their faces. The “intensity of exposure to these viruses in the general population cannot be expected to be as high as those experienced by poultry workers…[but] the general population is nevertheless widely exposed” to the viruses simply because we eat so many chickens and eggs.

This is supported by data showing that it’s not only the factory farm workers who are at higher risk for brain tumors, but also butchers and meat cutters who have no exposure to live birds, particularly those who don’t wear gloves and frequently have cuts on their hands. These workers are at higher risk for other cancers, as well.

Those who handle meat for a living also have higher rates of non-cancer mortality, such as increased death from heart disease and other health concerns outlined at 3:32 in my video. Some of the poultry viruses not only cause cancer in chickens, but also atherosclerosis. Indeed, that cancer-causing poultry herpesvirus also triggers the buildup of cholesterol crystals in chickens. But, what about in people? “Because chickens infected with Marek disease virus, a herpesvirus, develop atherosclerotic lesions after infection, [researchers] looked for the presence of herpesvirus or parts thereof in human artery wall tissue…” Evidence of the virus was found, though any role they play in human heart disease remains speculative.

“Considerable attention has been paid to substances present in animal food before and after cooking as risk factors for human diseases such as heart disease, diabetes, and various cancers…[and] exposures have included heme [iron], fat or cholesterol, dioxins,” and the cooked meat carcinogens. We didn’t think, however, about the animal viruses, which “are important not only for supermarket workers and other workers in the meat and poultry industries, but also because the general population is exposed.” Indeed, the study that found chicken virus DNA circulating in people’s bloodstreams also found about the same rates in office workers as they did in chicken slaughterhouse workers, which you can see at 4:42 in my video.


Other viruses may actually play a role in the obesity epidemic. See, for example, Infectobesity: Adenovirus 36 and Childhood Obesity

For other potential microbiological hazards in poultry, check out:

And, for potential chemical hazards in poultry, see:

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: