Coca-Cola claims diet drinks promote weight loss, but studies show that artificial sweeteners actually contribute to weight gain.

In response to a plunge in sales of artificially sweetened sodas last week, Coca-Cola announced plans to roll out an ad campaign to win back popular favor for its aspartame-containing beverage, Diet Coke. (Diet Pepsi, which also contained aspartame, saw its sales fall 6.2 percent in 2012 while regular Pepsi sales fell little more than half that amount.)


The safety of aspartame, which the FDA approved for human consumption in 1981, has long been in dispute, before, during, and after its approval by the FDA. The simmering controversy is notable for the parallels between aspartame's safety and regulatory history, and that of another controversial industrial food product - genetically modified foods also known as GMOs.

Aspartame, developed by Searle, was approved for public consumption despite the strong concerns of FDA scientists, who were over-ruled by Dr. Arthur Hull Hayes, Jr. then the newly appointed FDA Chief - handpicked by Donald Rumsfeld, the former CEO of Searle, and the Secretary of Defense in two Republican administrations. Hayes pushed through the approval, and then returned to the same industry (at Searle's public relations firm.) Upon aspartame's approval, Searle gained two things:
  1. The ability to market and profit from this product (sold as NutraSweet or Equal)
  2. The upper hand in science
Since then, industry sponsored science has sustained the FDA decision, opposing both independent scientific findings, as well as citizen reports of adverse reactions. After a profitable three decades, first for Searle, soon thereafter for Monsanto, which bought Searle in 1985, the vestiges of the former company are now owned by Pfizer. But public confidence in aspartame has steadily eroded. Coca-Cola's ad campaign seeks to restore that confidence.

Following a similar pattern, the 1992 FDA declaration that GMO seeds and plants were "substantially equivalent" to regular seeds and plants, also occurred despite the concerns of FDA scientists, who were over-ruled by a policy maker (Michael R. Taylor) who came in to the FDA (as Deputy Commissioner of Policy) from industry (Monsanto's law firm), got GMOs approved, and then returned to the same industry (serving as a Monsanto Vice President for Public Policy.) Note: Taylor is currently Commissioner for Food at the FDA. This time the Searle/Monsanto playbook gave Monsanto three things:
  1. The ability to develop, market, and profit from its products
  2. The upper hand in science, AND
  3. The right to patent its seeds and products and to protect its patents.
With many open questions about the long-range health and environment impacts of GMOs, today over twenty years after FDA approval, public discomfort with GMOs continues to rise. According to a recent New York Times poll, ninety-three percent want GMO foods to be labeled. While industry science supports use, other evidence (and many more concerns not addressed by industry science) continue to emerge. Glyphosate, the key ingredient in Roundup, the Monsanto herbicide, integral to GMO agriculture, increases the proliferation of breast cancer, even at exposures at low concentrations of parts per trillion, 2013 research found. Glyphosate decreases the body's ability to detoxify from other toxic exposures, thus increasing the potential for diseases arising from other toxic chemicals, a second study found.

According to Dr. Charles Benbrook, a Washington State University professor and researcher, GMO agriculture's dramatic increases in the use of fungicides and pesticides (principally Roundup) could outstrip earlier scientific projections of safe exposure levels. Based on current use and exposure rates, risk assessment faces a multiplex of
testing challenges arising from the likely presence of multiple transgenes, DNA fragments, promoters, regulatory sequences and chemicals from pesticides (active ingredients, metabolites, surfactants, adjuvants...)

But how well can the needed risk assessment be conducted (and acted upon) in a climate where science gets mired in debate between independent researchers and pro-industry factions? If we lack the science to inform policy, both environmental risks (like honeybee collapse) and health risks will only become apparent over time. Accurate assessment is further hampered when patent laws permit Monsanto to limit seed access for study. Aspartame is freely available, yet it still took thirty years for concerns over aspartame's health risks to amplify to levels that would significantly dent sales. We can learn a lot about the risks from GMOs by taking a look at aspartame.

Conflicting Studies

In its ads, and media messaging, Coke plans to tout the benefits of its aspartame-containing soft drinks as a weight loss aid. Its print ad, rolling out in Atlanta and Chicago this week will say that, "diet drinks can help people manage their weight." Despite Coke's claim, several studies found that artificial sweeteners fail to promote weight loss, and instead contribute to weight gain.

According to one of the researchers, the San Antonio Heart Study, which studied over 1,100 participants found that,
"On average, for each diet soft drink our participants drank per day, they were 65 percent more likely to become overweight during the next seven to eight years, and 41 percent more likely to become obese."
The Multi-Ethnic Study of Atherosclerosis (MESA) confirmed these findings when it found that, "Daily consumption of diet drinks was associated with a 36% greater risk for metabolic syndrome and a 67% increased risk for type 2 diabetes."

One mechanism for weight gain could be that the "Overstimulation of sugar receptors from frequent use of these hyper-intense sweeteners may limit tolerance for more complex tastes," says Dr. David Ludwig, MD, PhD, a leading Harvard clinician and researcher into the causes and treatment of the obesity epidemic. As a result, less sweet or non-sweet foods may become unpalatable, driving people to avoid healthy foods and eat unhealthy ones.

Given this evidence, Coke's boast that diet drinks produce weight loss may be a fib, but nowadays, industries wooing the public back to their product, can also bolster their claims with science. Though confusing to a public seeking answers, for every scientific finding, there is often an opposite scientific finding.

For example, a 2012 study published in The Journal of Nutrition concluded that,
"There is no evidence that low calorie sweeteners can be claimed to be a cause of higher body weights in adults."
What explains these opposite findings? Well, the thrust of the JN study is that with so many egregious foods on the nutritional landscape, it's hard to single out just one. Point taken. Surprisingly, this implied critique of the industrial food system comes from the four study authors, three of whom had "received consulting fees, honoraria, donations, and unrestricted grants from food, beverage, and pharmaceutical companies."

The Double-Faced Role of Science

If only all science were as unanimously agreed to as is climate science. Despite a lack of political will to address climate change, and public bafflement about how to tackle it, there is no uncertainty in the science.

But that's harder to locate in other regulatory realms, due to opposing claimants. When assessing the health and safety of products and practices, government regulators default to industry sponsored scientific research. It's up to independent scientists, (or members of the general public) to uncover evidence of harm - all too often after governmental approval.

Sometimes the shoe winds up on the other foot: Industry sponsored scientists question the safety of their competitors' products. Exaggerated concerns over artisanal jams, or locally grown lettuce come from the pesticide-ridden ag industry. Drug companies fret that someone will reject pharmaceuticals because they take vitamin C. In such cases, independent scientists, farmers, or regular people counter health concerns with evidence of no to low-harm for non-industrial products.

Beyond aspartame's benefits (or lack thereof) for weight loss, over the last three decades, public health gatekeepers, reliant on industry research, consistently affirm that aspartame (marketed as NutraSweet and Equal) is safe. This past week, both the FDA and the American Cancer Society were cited in the COMMENT NOW! following Coke's campaign launch. The American Cancer society noted that: "Most (italics mine) studies using people have found that aspartame is not linked to an increased risk of cancer..."

The same language appears on the ACS on-line information page on aspartame's cancer risk. "Most (italics mine) studies in people have not found that aspartame use is linked to an increased risk of cancer."

This is misleading because when scientists consider evidence, they don't merely count the number of studies, a la the Electoral College, in which a majority vote wins. They evaluate the weight of the evidence, and damning evidence on aspartame goes back to the mid-1960's. The phrase "most studies" likely refers to the many industry-sponsored studies, but certain significant independent studies find that there are health concerns.

The ACS aspartame web page was created in February 2011, and never revised to include significant 2012 findings on aspartame cancer risks. When this past week, the ACS (and the FDA) weighed in with Coke on the safety of aspartame, both the agency and the premiere cancer organization politely omitted mention of a well-regarded December 2012 Harvard study which found that a daily serving of diet soda increased the risks of non-Hodgkin's lymphoma and multiple myeloma in men.

Nor was this the first warning of health risks with aspartame. As is often the case with science, first there were animal studies.

The Animal Studies

As early as 1967 and again in 1971, animal study outcomes provoked questions about aspartame health risks. In 1980, a Public Board of Inquiry (PBOI) convened by the FDA, revoked an earlier approval of aspartame because of a study indicating it caused brain tumors in rats.

More recently, a 2007 study conducted by Dr. Mirando Soffritti, MD, the Scientific Director of the Ramazzini Foundation of Oncology and Environmental Sciences, (located in Bologna, Italy) found high rates of lymphomas, leukemias and other cancers in rats consuming aspartame. As in the Harvard study, this similar constellation of cancers was more pronounced in males.

Soffritti, a prominent and highly regarded international scientist, designed his research to correct design flaws he identified in the original Searle research. Searle scientists followed rats for only two years, which roughly equates to age fifty-three in the human life span. The Ramazzini study used a larger cohort of rats (1,900 vs. 300-700 animals) and followed them throughout their natural life cycle. Soffritti's rationale for the study design was that:
Cancer is a disease of the third part of life. You have 75 percent of cancer diagnoses for people who are 55 years old or older. So if you truncate the experiments at 110 weeks and the rats are supposed to survive until 150 to 160 weeks, it means you avoid the development of cancer at the time when cancer would be starting to arise.
When independent, international, or even mainstream Harvard scientists find post-approval evidence of health risks from ingredients (like aspartame or GMOs), they are in effect acting as scientific whistleblowers, but scientific whistleblowers all too easily get dismissed or marginalized as cranks or quacks.

Yet over time, the evidence mounts. As aspartame research continues to emerge, the history of aspartame science and its suppression confers key lessons for the scientific assessment of GMOs.


First, GMOs were introduced a decade later than aspartame, and have much less science, and consumer report. Second, GMOs are difficult for independent scientists to study because Monsanto (via patent law) limits access to its seeds. Nevertheless, two animal studies done in Europe, found evidence of tumor growth in mice consuming GMO ingredients. A storm of protest erupted over the study design both for the earlier English study and the recent French study. But while study designs can often be improved, and independent research merits better funding, it's vital that critiques not end by suffocating all independent research into industrial food products.

A 2009 position paper published by the American Academy of Environmental Medicine, surveyed animal studies on GMO health effects, and found:
  • Immune dysregulation of inflammatory markers associated with increases in asthma, allergy, and inflammation.
  • Functional and structural changes of the liver, which can alter fat and carbohydrate metabolism
  • Intestinal and immune system damage, including proliferative cell growth
  • Changes in the kidney, pancreas and spleen have also been documented
  • Links to infertility and low birth weight
  • Changes in the expression of four hundred genes that "control protein synthesis and modification, cell signaling, cholesterol synthesis, and insulin regulation
This review of animal studies is a strong indicator of areas of health concern entailed by GMO consumption.

The Public Trust

What people find so hard to wrap their minds around is this: How can major gatekeeping organizations, trusted by the public, lay claim to scientific validation of product safety while selectively ignoring animal studies and other meaningful science?

First, it's obvious that institutional loyalties, economic pressures, and reputations make it hard for organizations like the FDA and the ACS to shift their stance on nearly three decades of safety claims.

Second, we, the public allow it. Apart from climate science, in most cases where there is scientific debate, there is complexity. As the breakdown in traditional journalism eats away at traditional scientific reporting, people seek simple answers and lack time for nuanced analysis.

Most of the educated public wants to trust science, without having to evaluate its credibility, and industry takes advantage of that.

"If at the outset, agencies like the FDA confer scientific validation on an industrial food product or ingredient, going forward, industry can more readily maintain the scientific upper hand," says James S. Turner, Chairman of Citizens for Health, a health and science policy organization.

The studies industry commissions will be cited. Contending studies will be invalidated. Typically corporate funded science has more generous budgets for larger cohorts of participants in a study than independent researchers. This can translate into a seemingly "scientific" basis for rejecting independent research, because "most studies" are funded by industry and support industry claims.

Because it takes time and money to progress up the chain of proof from animal to human studies, it may take decades for independent science to reverse the initial advantage conferred by a government agency like the FDA, the USDA, or the EPA. By then the product or ingredient is in wide use, making its risks "impossible" to accept (even with scientific proof) given that by then millions have been exposed to its dangers. Moreover, there is heavy economic vestment in the use of even a nutritionally valueless ingredient like aspartame. Finally, since our medical treatment and research model focus on treatments of disease, rather than the causes of disease, it will be harder after the fact to ascertain whether a person's illness was caused by aspartame or GMOs or other exposure to chemicals, like in plastic bottles and containers containing bisphenol-A (BPA), or chemicals used in fracking oil and gas wells, which are becoming more common, or myriad other chemicals or combinations of chemicals.

Soffritti defined the bottom line when he spoke to The New York Times back when his animal study was first published, "If something is a carcinogen in animals, then it should not be added to food, especially if there are so many people that are going to be consuming it." When it comes to the novel ingredients in the food supply, independent study is a must.

About the author

Alison Rose Levy writes on health, food and the environment. Her Web site is healthjournalistblog.com and her weekly radio program on Progressive Radio is Connect the Dots.