Does Aspartame Cause Lymphoma?

The approval of aspartame has a controversial history. The Commissioner of the U.S. Food and Drug Administration (FDA) concluded that “there is a reasonable certainty that human consumption of aspartame: (1) …will not pose a risk of brain damage resulting in mental retardation, endocrine [hormonal] dysfunction, or both; and (2) will not cause brain tumors.” However, the FDA’s own Public Board of Inquiry withdrew their approval over cancer concerns. “Further, several FDA scientists advised against the approval of aspartame, citing…[the aspartame company’s] own brain tumor tests…” Regardless, the Commissioner approved aspartame before he left the FDA and went on to enjoy a thousand-dollar-a-day consultancy position with the aspartame company’s PR firm. Then, the FDA actually prevented the National Toxicology Program (NTP) from doing further cancer testing. As I discuss in my video Does Aspartame Cause Cancer? we were then left with people battling over different rodent studies, some of which showed increased cancer risk, while others didn’t.

This reminds me of the saccharin story. That artificial sweetener caused bladder cancer in rats but not mice, leaving us “to determine whether humans are like the rat or like the mouse.” Clearly, we had to put the aspartame question to the test in people, but the longest human safety study lasted only 18 weeks. We needed better human data.

Since the largest rat study highlighted lymphomas and leukemias, the NIH-AARP study tracked blood cancer diagnoses and found that “[h]igher levels of aspartame intake were not associated with the risk of…cancer.” Although the NIH-AARP study was massive, it was criticized for only evaluating relatively short-term exposure. Indeed, people were only studied for five years, which is certainly better than 18 weeks, but how about 18 years?

All eyes turned to Harvard, where researchers had started following the health and diets of medical professionals before aspartame had even entered the market. “In the most comprehensive long-term [population] study…to evaluate the association between aspartame intake and cancer risk in humans,” they found a “positive association between diet soda and total aspartame intake and risks of [non-Hodgkin’s lymphoma] and multiple myeloma in men and leukemia in both men and women,” as you can see at 2:12 in my video. Why more cancer in men than women? A similar result was found for pancreatic cancer and diet soda, but not soda in general. In fact, the only sugar tied to pancreatic cancer risk was the milk sugar, lactose. The male/female discrepancy could have simply been a statistical fluke, but the researchers decided to dig a little deeper.

Aspartame is broken down into methanol, which is turned into formaldehyde, “a documented human carcinogen,” by the enzyme alcohol dehydrogenase.The same enzyme that detoxifies regular alcohol is the very same enzyme that converts methanol to formaldehyde. Is it possible men just have higher levels of this enzyme than women? Yes, which is why women get higher blood alcohol levels than men drinking the same amount of alcohol. If you look at liver samples from men and women, you can see significantly greater enzyme activity in the men, so perhaps the higher conversion rates from aspartame to formaldehyde explain the increased cancer risk in men? How do we test this?

Ethanol—regular alcohol—competes with methanol for this same enzyme’s attention. In fact, regular alcohol is actually “used as an antidote for methanol poisoning.” So, if this formaldehyde theory is correct, men who don’t drink alcohol or drink very little may have higher formaldehyde conversion rates from aspartame. And, indeed, consistent with this line of reasoning, the men who drank the least amounts of alcohol appeared to have the greatest cancer risk from aspartame.

A third cohort study has since been published and found no increased lymphoma risk associated with diet soda during a ten-year follow-up period. So, no risk was detected in the 18-week study, the 5-year study, or the 10-year study—only in the 18-year study. What should we make of all this?

Some have called for a re-evaluation of the safety of aspartame. The horse is kind of out of the barn at this point with 34 million pounds of aspartame produced annually, but that doesn’t mean we have to eat it, especially, perhaps, pregnant women and children.


For more information on the effects of aspartame, watch my videos Aspartame and the Brain and Aspartame-Induced Fibromyalgia. Interested in learning more about the effects of consuming diet soda? See, for example:

What about Splenda? Or monk fruit sweetener? I have videos on those, too—watch Effect of Sucralose (Splenda) on the Microbiome and Is Monk Fruit Sweetener Safe?.

I also do a comparison of the most popular sweeteners on the market, including stevia and xylitol, in my video A Harmless Artificial Sweetener.

Perhaps the best candidate is erythritol, which you can learn about in my video Erythritol May Be a Sweet Antioxidant. That said, it’s probably better if we get away from all intense sweeteners, artificial or not. See my video Unsweetening the Diet for more on this.

In health,
Michael Greger, M.D.

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The Difference Between Alpha and Beta Receptors Explain Soy’s Benefits

“[S]oyfoods have become controversial in recent years…even among health professionals…exacerbated by misinformation found on the Internet.” Chief among the misconceptions is that soy foods promote breast cancer because they contain a class of phytoestrogen compounds called isoflavones, as I explore in my video, Is Soy Healthy for Breast Cancer Survivors? Since estrogens can promote breast cancer growth, it is natural to assume that phytoestrogens might, too, but most people do not realize there are two different types of estrogen receptors in the body, alpha and beta. Unlike actual estrogen, soy phytoestrogens “preferentially bind to and activate ERβ,” estrogen receptor beta. “This distinction is important because the [two types of receptors] have different tissue distributions within the body and often function differently, and sometimes in opposite ways. This appears to be the case in the breast,” where beta activation has an anti-estrogenic effect, inhibiting the growth-promoting effects of actual estrogen—something we’ve known for more than ten years.

The effects of estradiol, the primary human estrogen, on breast cells are “completely opposite” to those of soy phytoestrogens, which have “antiproliferative effects on breast cancer cells…even at [the] low concentrations” we get in our bloodstream after eating just a few servings of soy. This makes sense, given that after eating a cup of soybeans, the levels in our blood cause significant beta receptor activation, as you can see at 1:27 in my video.

Where did this outdated notion that soy could increase breast cancer risk come from? The concern was based largely on research that showed that the main soy phytoestrogen, genistein, stimulates the growth of mammary tumors in a type of mouse—but, it turns out, we’re not mice. We metabolize soy isoflavones very differently from rodents. As you can see at 2:00 in my video, the same soy phytoestrogens led to 20 to 150 times higher levels in the bloodstream of rodents. The breast cancer mouse in question had 58 times higher levels. What does this mean for us? If we ate 58 cups of soybeans a day, we could get some significant alpha activation, too, but, thankfully, we’re not hairless athymic ovariectomized mice and we don’t tend to eat 58 cups of soybeans a day.

At just a few servings of soy a day, with the excess beta activation, we would assume soy would actively help prevent breast cancer. And, indeed, “[s]oy intake during childhood, adolescence, and adult life were each associated with a decreased risk of breast cancer.” Those women who ate the most soy in their youth appeared to grow up to have less than half the risk. This may help explain why breast cancer rates are so much higher in the United States than in Asia, where soy foods are more commonly consumed. Yet, when Asians come to the United States and start eating and living like Americans, their breast cancer risk shoots right up. Women in their 50s living in Connecticut, for example, are way at the top of the breast cancer risk heap, as you can see at 3:00 in my video, and have approximately ten times more breast cancer than women in their 50s living in Japan. It isn’t genetic, however. When Japanese women move to the United States, their breast cancer rates go up generation after generation as they assimilate into American culture.

Are the anti-estrogenic effects of soy foods enough to actually change the course of the disease? We didn’t know until the first human study on soy food intake and breast cancer survival was published in 2009 in the Journal of the American Medical Association, suggesting that “[a]mong women with breast cancer, soy food consumption was significantly associated with decreased risk of death and [breast cancer] recurrence.” That study was followed by another study, and then another, each with similar findings. That was enough for the American Cancer Society, which brought together a wide range of cancer experts to offer nutrition guidelines for cancer survivors, concluding that, if anything, soy foods should be beneficial. Since then, two additional studies have been published for a total of five—five out of five studies that tracked more than 10,000 breast cancer patients—and they all point in the same direction.

Pooling all of the results, soy food intake after breast cancer diagnosis was associated with both reduced mortality and reduced recurrence—that is, a longer lifespan and less likelihood that the cancer comes back. This improved survival was for women with estrogen receptor negative tumors and estrogen receptor positive tumors, and for both younger women and for older women.

Pass the edamame.


Flaxseeds are protective for likely the same reasons. For more on this, see my videos Flaxseeds and Breast Cancer Survival: Epidemiological Evidence and Flaxseeds and Breast Cancer Survival: Clinical Evidence.

What about women who carry breast cancer genes? I touched on that in BRCA Breast Cancer Genes and Soy and Should Women at High Risk for Breast Cancer Avoid Soy?.

What about genetically modified soy? See GMO Soy and Breast Cancer.

Who Shouldn’t Eat Soy? An excellent question I answer in that video.

For even more information on soy, see:

Not all phytoestrogens may be protective, though. See The Most Potent Phytoestrogen Is in Beer and What Are the Effects of the Hops Phytoestrogen in Beer?.

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:

What Not to Do When You Handle Receipts

The plastics chemical bisphenol A, commonly known as BPA, was banned for use in baby bottles in Canada in 2008, in France in 2010, in the European Union in 2011, and in the United States in 2012. Then, in 2015, France forbade the use of BPA in any food or beverage packaging, something the U.S. Food and Drug Administration had decided was not warranted. But, what about the more than 90 studies “reporting relationships between total BPA in [people’s] urine and a wide array of adverse health outcomes, including a significant increase in the likelihood of developing cardiovascular disease and type 2 diabetes, obesity, impaired liver function, impaired immune and kidney function, inflammation, reproductive effects in women…[and] in men…, altered thyroid hormone concentrations, and neurobehavioral deficits such as aggressiveness, hyperactivity, and impaired learning”?

Only a very small minority of studies appear to support the U.S. government’s assertions that there were no effects of BPA at low doses. Where is the disconnect? Governmental regulatory agencies determine safety levels of chemicals by sticking tubes down into the stomachs of lab animals. In these types of tests, BPA is released directly into the stomach, where it goes to the liver to be detoxified into an inactive form called BPA-glucuronide. So, very little active BPA gets into the bloodstream. But, that’s not what studies on humans show. People have active BPA in their blood. How did the FDA respond? By rejecting all such human studies as implausible.

The problem with a “blanket rejection” of human data is that there may be sources of BPA exposure that are not modeled by stomach tube exposure in rats. After all, “[t]his isn’t how food actually enters our bodies. We chew it, move it around in our mouths…before it enters the stomach.” It turns out “that BPA can be completely absorbed directly into the bloodstream from the mouth,” thus bypassing instant liver detoxification. The same would be the case for BPA absorbed through the skin, which you can see at 2:08 in my video BPA on Receipts: Getting Under Our Skin.

Thermal paper, often used for cash register receipts, luggage tags, and many bus, train, and lottery tickets, is 1 to 2 percent BPA by weight. Taking hold of a receipt can transfer BPA to our fingers, especially if they’re wet or greasy. Does the BPA then get absorbed into our system through the skin? Cashiers were found to have more BPA flowing through their bodies “[c]ompared with other occupations,” but that was based on only 17 people. “Strict vegetarians had lower urinary BPA concentrations compared with nonvegetarians,” but, once again, the sample size was too small to really make a conclusion. It’s been estimated that even cashiers handling receipts all day may not exceed the “tolerable daily intake” of BPA—however, that could change if they were using something like hand cream.

Indeed, “many skin-care products, including hand sanitizers, lotions, soaps and sunscreens,” contain chemicals that enhance skin penetration. So, using a hand sanitizer, for example, before touching a receipt could cause a breakdown of the skin barrier.

What’s more, we now know that “using hand sanitizer and handling a thermal receipt…prior to picking up and eating food with [our] hands” results in high blood levels of active BPA. Researchers at the University of Missouri, conducting a study to mimic aspects of the behavior of people in a fast-food restaurant found that when people handled a receipt right after using the hand sanitizer Purell, BPA was transferred to their fingers. Then, BPA was transferred from their fingers to their fries, and the combination of absorption through the skin and mouth led to significant levels of active BPA in their blood, as you can see at 3:45 in my video.

We can hold a receipt in our hand for 60 seconds and only come away with 3 micrograms of BPA in our body. In contrast, if we pre-wet our hands with hand sanitizer, we can get 300 micrograms in just a few seconds—a hundred times more BPA, as you can see at 4:05 in my video. “These findings show that a very large amount of BPA is transferred from thermal paper to a hand as a result of holding a thermal receipt for only a few seconds immediately after using a product with dermal penetration enhancing chemicals,” like hand lotion. This could explain why dozens of human studies show active BPA in people’s systems, contrary to the assumptions based on stomach tube studies in rodents.

When actual evidence contradicts your assumptions, you reject your assumptions. The FDA, however, rejected the evidence instead.


Watch my video to learn Why BPA Hasn’t Been Banned.

For more on BPA, see:

Interested in other examples of Food and Drug Administration failings? Check out:

Phthalates are another class of concerning plastics compounds. For more, 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: