For years I drank Diet Coke like it was water. But after learning that aspartame, which is the artificial sweetener in Diet Coke and most sugar-free beverages, converts into formaldehyde in the body, and has been shown to cause tumors in lab animals, I quit Diet Coke and never looked back. I don't regret it, though I sorely miss that first fizzy sip of my favorite drink. Still, I am convinced Diet Coke is bad for you. The research is strong on both sides (the US says aspartame is safe even as studies have questioned whether it is unsafe) but net-net, I decided it makes sense to listen to my gut and skip the Diet Coke.

Can Diet Coke kill you? Probably not, or at least not unless you are a lab rat, drink a lot of it, or have a rare genetic condition called PKU. But aspartame may be the most controversial food additive ever to have won approval by the FDA, first for use in dry foods in 1981, then in beverages in 1983, and finally as a general-purpose sweetener in 1996. The process was marred with conflicting studies and a long list of characters skipping back and forth between regulatory positions and private industry, with respected scientists making claims that aspartame producer G.D. Searle had withheld and falsified vital safety data.

Aspartame has been linked to cancer in lab animals, migraines in children, and immune issues as well as inflammation and weight gain, among other health woes. Yet the government insists it is safe. So is aspartame safe? That depends on who you ask and what you believe. Do you want to be the experiment? I decided: No thank you.

What is Aspartame?

Aspartame is a low-calorie sweetener that is about 200 times sweeter than sugar and is the active ingredient in NutraSweet, Equal, and most artificially sweetened beverages and gum.

Aspartame consists of two amino acids—aspartic acid and phenylalanine. When ingested, aspartame is broken down into these amino acids, so it should never be consumed by people with phenylketonuria (PKU), a rare genetic disease that makes it impossible to metabolize phenylalanine.

By 2010, one in five Americans drank diet soda regularly,  according to the CDC. By 2014, aspartame was the single largest source of methanol in our diets, and methanol is toxic in large quantities.

Foods that contain aspartame

  • NutraSweet and Equal
  • diet soda
  • chewing gum
  • sugar-free yogurt
  • sugar-free iced tea
  • sugar-free candy
  • reduced-calorie juice
  • sugar-free iced cream

Is aspartame bad for you?

The American Cancer Society does not determine if something "causes" cancer, but instead looks at the research for the most credible findings. Here is the ACS' take on aspartame:

"Some of the concerns about cancer stem from the results of studies in rats published by a group of Italian researchers, which suggested aspartame might increase the risk of some blood-related cancers (leukemias and lymphomas). However, later reviews of the data from these studies have called these results into question. The results of epidemiologic studies (studies of groups of people) of possible links between aspartame and cancer (including blood-related cancers) have not been consistent."

Aspartame and cancer

Then in 2005, an Italian study linked low doses of aspartame, the popular sweetener in NutraSweet, Equal, and thousands of other consumer products, to increased incidents of leukemia and lymphoma in rats. The researchers fed it to a test group of 1,800 rats, from the early age of eight weeks.

They then allowed the rats to live out a full lifetime, or 36 months. They then examined the animals for signs of cancer and found more cancer in the rats fed aspartame. In the female rats, 20 percent of those fed aspartame had lymphoma and leukemia, or more than double the rate in rats not fed the sweetener. They also found that male rats had to consume much more aspartame than females to increase the risk of cancer.

The Italian study linked aspartame to "a wide range of cancers," reports The Center for Science in the Public Interest. Depending on doses, the animals developed an array of cancers including leukemia, lymphoma, and kidney cancer. The researchers concluded that aspartame has the potential to cause cancer in humans at levels far below what is considered safe by the US government.

The Center for Science in the Public Interest called on the FDA to immediately review the study. "If FDA concludes that aspartame does cause cancer in animals, the agency is required by law to revoke its approval for the controversial sweetener." That was about 15 years ago. Nothing happened.

Even before that study, a Virginia Tech review found that during the approval process, the findings of another study that linked lab animals to cancer had been overlooked. the 1977 study of 196 infant mice exposed to aspartame found that 98 of the animals died after exposure. The findings of that study were shared with the Food and Drug Administration and the results were part of a document known as the Bressler Report. Regardless, aspartame got approved.

Artificial sweeteners and weight gain

In America, we are hooked on aspartame, since we think avoiding sugar will help us cut calories and lose weight. But studies have found a connection between artificial sweeteners and weight gain and high blood sugar.

The sugary sweet taste of fake sweeteners can trick your brain and body into thinking "calories are coming, get insulin ready!" When you fool the body into thinking it's receiving a hit of sweet calories, your insulin receptors activate just as when real sugar gets consumed. The result: The next thing you eat or drink gets carted off to fat. This is the finding of a study at the University of Illinois, where professors measured the effect of fake sugar on metabolism and blood glucose.

After eating fake sweets, your body doesn't know the difference, the study found: Simply tasting artificial sweeteners "may affect blood glucose and insulin levels on glucose tolerance tests," scientists at the University of Illinois found in a study done on sucralose.

The findings suggest that artificial sweeteners may have metabolic effects that mimic actual sugar consumption. So your insulin messengers are primed and ready to cart off all those calories for fat storage and when the calories don't come, it acts as a "call" on a stock, it waits. The cookies or chips you eat next get the same treatment that the fake sugars triggered. Insulin is elevated, and off to fat storage, they go.

In a study done at the Medical College of Wisconsin and Marquette University, when artificial sweeteners found in Equal (aspartame and acesulfame potassium) were given to rats and human cell cultures, the researchers saw significant "metabolic changes at the genetic level that could lead to diabetes and obesity," according to biologist Dr. Brian Hoffmann, assistant professor in the Department of Biomedical Engineering.

After three weeks of exposure to aspartame, there was a marked change in "the expression of genes responsible for lipid metabolism in the cells of both rats and humans." As he explained it: Aspartame caused some "significant changes, and one of those was an increase in lipids in the bloodstream and a decrease in a biomolecule that is involved in clearing (lipids) from the bloodstream." So anyone drinking Diet Coke for their health may be doing more harm than good if these studies are any indication.

Aspartame and other health dangers

An unbiased study found that aspartame has been linked to pediatric and adolescent migraines. And in the body, aspartame is broken down, converted, and oxidized into formaldehyde in various tissues.

Authors of a 2017 review concluded that aspartame may affect cell membranes, leading to chronic inflammation and that safety questions should be reviewed. "Data on the safe aspartame dosage is controversial, and the literature suggests there are potential side effects associated with aspartame consumption," the authors wrote. "Since aspartame consumption is on the rise, the safety of this sweetener should be revisited.

"Safety studies are based primarily on animal models, as data from human studies are limited. The existing animal studies and the limited human studies suggest that aspartame and its metabolites ... may disrupt the oxidant/antioxidant balance, induce oxidative stress, and damage cell membrane integrity, potentially affecting a variety of cells and tissues and causing deregulation of cellular function, ultimately leading to systemic inflammation." Their findings suggested that aspartame could affect the cells in a way that can lead to disease.

Aspartame didn't just lead to more fat storage but changes in the cardiovascular system: “We then took those particular sweeteners and put them on endothelial cells (the cells that line the blood vessels) and we detected a marked dysfunction, suggesting why sweeteners and diet soda have been linked to potential cardiovascular problems,” he added.

Conclusion: "Artificial sweeteners appear to contribute to metabolic disorders by altering the activity of certain genes responsible for the breakdown of macromolecules such as fats and proteins," Hoffmann said. "This is different from normal sugars, which contribute to cardiovascular disease through insulin resistance and by damaging the cells lining the body’s blood vessels."

Aspartame formaldehyde connection

Aspartame breaks down into the body as formaldehyde. Remember that formaldehyde, which exists in nature as a gas that is safe at minuscule levels (in the air at less than 0.1 ppm), can be harmful at higher levels, and has been linked to cancer.

Formaldehyde is created when your body breaks down the components of aspartame, which are aspartic acid, phenylalanine, and methanol, which is a naturally occurring gas in fruit juice. But when methanol is ingested in fruit juice, that also contains the antioxidants and phytonutrients to counter oxidative stress on the body.

A study in 2002 found that aspartame breaks down into methanol and formaldehyde when metabolized, yet concluded that nonetheless, aspartame is safe for human consumption.

Aspartame side effects

Aspartame has been linked to metabolic disorders, obesity, and cardiovascular disease, including these conditions, according to critics of its widespread use:

  • possible weight gain
  • migraines
  • methanol in the body
  • formaldehyde in the body
  • Alzheimer's
  • cardiovascular damage
  • inflammation

Aspartame is made from E. coli bacteria

Just on the gross factor alone, aspartame should be avoided. A patent has confirmed that aspartame is made from the feces of genetically modified E. coli bacteria. So whether you want to think of the E. Coli as gross or their poop as gross, either way, aspartame is gross.

According to the patent, genetically modified E. coli are cultivated in tanks and fed so that they can defecate the proteins that contain the aspartic acid-phenylalanine amino acid that is then used to make aspartame. The proteins are then collected and treated in a process called methylation to produce the sweetener.

How aspartame got approved for use in the US

Aspartame's controversial history: Back when aspartame was up for approval, scientists who reviewed the data had major concerns about aspartame's safety, alleging that the initial studies were inadequate or biased. Well after it was on the market, 60 Minutes aired a report on the flawed approval process amid lingering concerns that aspartame could cause brain tumors in humans. The CBS News team stated that "aspartame's approval was one of the most contested in FDA history."

Eventually, aspartame was approved for full use in food and beverages in the US without restriction. That has not stopped the controversy or the conspiracy theorists from believing that aspartame is in fact linked to brain tumors, headaches, and other ailments. But when countries in the EU, as well as Asia, have considered banning aspartame, it wins approval every time. Does that mean it's safe? Or has really good PR people making the case for it. Whichever way you decide, here's what we know about Diet Coke.

The FDA’s own toxicologist, Dr. Adrian Gross told Congress that...aspartame can cause brain tumors and brain cancer and that it violated the Delaney Amendment, which forbids putting anything in food that is known to cause cancer." At the time, doctors and researchers submitted that "aspartame causes headaches, memory loss, seizures, vision loss, coma, and cancer."

"The resulting chronic methanol poisoning affects the dopamine system of the brain causing addiction. Methanol, or wood alcohol, constitutes one-third of the aspartame molecule and is classified as a severe metabolic poison and narcotic."

Canadian scientists have been trying to get aspartame banned in that country, according to Yukon News. "Some of them [are] physicians and PhDs," and have linked "aspartame to brain damage, brain cancer, lymphoma, mood disorders, eye damage and vision loss, migraines, tremors, depression, anxiety attacks, insomnia, Lou Gehrig’s Disease, thyroid disorders, gastrointestinal problems, Chronic Fatigue Syndrome, MS, epilepsy and unusual sudden deaths."

In Europe, aspartame is not allowed to be used in products marketed to children. The risks have been assessed, and even after reviewing the lab studies that showed it is carcinogenic to lab animals, the EFSA has decided not to change its stance that aspartame can be used in food and drinks.

So why is this artificial additive still so politicized? The answer is that it always has been.

Safe for human consumption

On the FDA's site, the government claims that aspartame is safe for human consumption, especially at doses that have been vetted and are within the realm of reason. According to the FDA and the European Food Safely Association, the acceptable daily intake is:

  • FDA: 50 milligrams per kilogram of body weight
  • EFSA: 40 milligrams per kilogram of body weight

That's equivalent to about 18 cans of diet soda a day. It is possible to overdose on aspartame, according to one expert, especially after exercise in hot climates. Under the Freedom of Information Act, the FDA has been forced to release a list of aspartame symptoms reported by thousands of victims. "From 10,000 consumer complaints, the FDA compiled a list of 92 symptoms, including death," according to Dr. Betty Martini, founder of Mission Possible International, which works with doctors to remove aspartame from food, drinks, and medicine. "Aspartame has brought more complaints to the FDA than any other additive and is responsible for 75% of [all] such complaints."

What to drink instead of diet coke

  1. Homemade Arnold palmer
  2. Kombucha
  3. Sparkling water with fruit juice
  4. Coconut water
  5. Freshly squeezed lemonade

Bottom Line: Aspartame has been deemed safe for humans but the choice is yours to make

Is aspartame safe? The FDA and European regulators say yes, but studies have shown a link between aspartame and tumors in lab animals, and have linked it to migraines in children and adolescents. The jury may still be out on whether aspartame only causes cancer in rats, or if it is safe long-term for humans. Until we know for sure, you may want to add good old-fashioned sugar to your iced tea. Or drink carbonated water with a little squeeze of fruit juice.

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