Is Coke Zero A Refreshing, Healthy Beverage or a Mass Killer?
We often fear things we should not while ignoring clear and present dangers. Coke Zero falls in the former category.
Careful review of the research on Coke Zero (and diet soda in general) undermines the wildest claims made by its detractors (who are often, but not always, allied with critics of vaccines, medications (except of course, "alternative" or "natural" ones), microwaves, cell phones, and power lines). There is scant evidence that Coke Zero is harmful and much theoretical evidence that it could be quite helpful.
Of course, the absence of proof of harm does not prove safety, but this is true for everything. Decades of exposure to trace chemicals in anything we consume might harm us at some remote future date. But any theoretical risk must be weighed against known, proven risks that the theoretical risk displaces.
Your car's airbag might break your nose. But that theoretical risk must be weighed against the known risk airbags reduce - death from a sudden deceleration. The theoretical danger of a broken nose must not only be real but overwhelming before a rational person avoids using air bags.
Coke Zero also attempts to reduce a risk – that of obesity – by substituting a sweet-tasting but zero-calorie beverage for a high-calorie drink that would trigger a surge of insulin and the metabolic cascade involved in digesting sugar-rich foods that leads inexorably to obesity. The evidence that Coke Zero's risks overwhelm its potentially enormous benefits is either weak or nonexistent.
The evidence that obesity shortens your life and decreases its quality is overwhelming. We should therefore welcome anything that decreases this risk even marginally.
In fairness, it's very hard to prove that Coke Zero makes you thinner. However, this is true of virtually every diet regimen, but we don't conclude the dieting is bad. In fact, I think that Coke Zero is a victim here of what I call the Ambulance Effect: If you measured the mortality rate of people brought to the hospital by ambulance versus those who walked in, you would find no doubt that those arriving by ambulance were far more likely to die in the hospital. But does this mean that ambulances kill people? Of course not. Ambulances simply identify a group of people at higher risk of death.
Diet Coke, consumed disproportionately by people trying to lose weight, is similarly identifying a group of people at higher risk of obesity.
But if 16% of the excess calories in the typical American's diet come from regular soda, would not a shift to diet colas be healthier?
What the research shows
While in medical school and residency, we often fueled ourselves with massive amounts of caffeine. So naturally we were quite interested in surveying the literature to determine if there were any horrible long-term consequences of caffeine ingestion.
The answer, no matter how you sliced and diced it, seemed to be no, certainly nothing on the order of nicotine and alcohol, the chemicals that seemed to be killing most of our patients. To this day, I have never had a patient admitted for caffeine toxicity much less any long term consequences of caffeine use.
Caffeine can cause a fine tremor, headaches in some people, and of course irritability and insomnia if consumed too close to bedtime. It can cause physiological dependence with a wicked headache if stopped suddenly. But all of these side effects are self-limited. None is life-threatening.
As a side note, the sleep deprivation the caffeine is attempting to self-medicate is a much bigger problem and has been associated with everything from higher rates of motor vehicle accidents to obesity to cancer, so the answer is to sleep more, not to avoid caffeine per se.
So when a horrified social worker with whom I was working once saw me drinking Diet Coke and begged me never to let such a horrid beverage touch my lips again, I gave her my summary of the literature on caffeine.
No, she said. It wasn't the caffeine. It was the aspartame.
It turns out that there is a vocal anti-aspartame lobbying group out there, committed to ridding our land of the scourge of artificial sweeteners. With generous funding from the Florida sugar industry (which has some understandable skin in this game), they produce websites and books making their case that aspartame is linked to everything from headaches to brain cancer. She brought in one such book, Apartame Disease: An Ignored Epidemic, by H.J. Roberts, MD (Sunshine Sentinel Press, West Palm Beach, FL, 2001) the next day.
Out of morbid curiosity, I waded through it, mostly a collection of anecdotes, theoretical speculations, and some rather glaring misrepresentations of national cancer data. And that is when I became and anti-anti-aspartame activist.
What's In Coke Zero?
Let's back up a moment and examine what is in Coke Zero.
Water mostly. If you were to extract the sweeteners and caffeine and artificial coloring from Coke Zero, you would end up with a glass of water. Those in the "drink 5 glasses of water a day or DIE! of dehydration" movement (another lay health movement that makes up with enthusiasm and passion what it lacks in evidence) seem to forget that water makes up the bulk of most of our foods and our body cares not at all as to the source of the water we feed it. When you are drinking Coke Zero, you are drinking water with a little something added to it.
That little something, by the way, is far less proportionally than the sugar in a glass of sweetened ice tea or fully-loaded soda.
Coke Zero has zero calories. It's essentially carbonated water with a small amount (34 mg) of caffeine added. The caffeine content is low – you must drink three Coke Zeros to get the same caffeine intake as a cup of coffee (110-150 mg for percolated coffee) or an energy drink (144 mg for a Full Throttle beverage).
For a variety of health reasons, Coke Zero is infinitely preferable to either fully loaded soda, juices, or even coffee itself (which is more likely to discolor your teeth, upset your stomach, and – if sweetened or mixed with cream or milk – adds needless calories).
Why not just drink water?
I don't know. Because I like a little caffeine and the taste of Coke Zero is preferable to the taste of water. Because the carbonation helps me digest my food. Because I want to.
The case against drinking water is a hard one to make and ultimately boils down to personal preference, but over 99% of Coke Zero is water, so in essence this is what you are doing.
But those in the Coke Zero Is Murder camp are not making an aesthetic argument. They are making some very specific health claims that are simply not supported by the medical literature.
The Great Aspartame Experiment
Americans may not realize it, but they have been part of a giant naturalistic experiment constituting billions of patient-years of exposure since the early 1980s to aspartame. If even a tiny fraction of what the aspartame abolitionists said were true, it would by now be overwhelmingly clear and aspartame, like a host of harmful products once thought to be safe, would have been yanked from the market.
Aspartame is actually one of the most studied chemical additives in human history. The FDA website gives a wealth of peer-reviewed studies supporting their conclusion that aspartame is safe.
Aspartame was first approved in the United States in 1981 and is one of the most widely used artificial sweeteners. When metabolized by the body, aspartame is broken down into two common amino acids, aspartic acid and phenylalanine, and a third substance, methanol. These three substances are available in similar or greater amounts from eating common foods.
FDA reviewed the study data made available to them by ERF and finds that it does not support ERF's conclusion that aspartame is a carcinogen. Additionally, these data do not provide evidence to alter FDA's conclusion that the use of aspartame is safe.
But the FDA isn’t alone.
Organizations who reviewed aspartame and deemed it safe as a dietary supplement include the World Health Organization, the FDA (Dec, 1980; then 1983 for carbonated beverages), the Centers for Disease Control (November, 1984), and the American Medical Association (July, 1985).
The organizations who oppose aspartame and believe it is unsafe: H.J. Roberts, M.D., the Aspartame Victims and Their Friends (295 people), and Mission Possible, a volunteer organization.
Now this isn't to say that aspartame is entirely risk-free. Nothing is. By April, 1995, the FDA received 7,232 consumer complaints regarding aspartame. That sounds like a lot but it represented .000026% of the American population, or, more generously, .000038% if one uses 70% as the proportion of the population exposed to aspartame. Assuming that these complaints are cumulative, correcting for the number of years of exposure reveals that about .000004% of the American population has complained about an alleged aspartame to the FDA each year. Assuming that the adverse effect would have to affect .1% of the population to be significant, the ratio of those who experienced adverse effects and wrote to the FDA to those who experienced adverse effects and did not would have to be 1: 26,315 (meaning that over 26,000 people experienced adverse effects and didn't contact the FDA for everyone who did).
The vast majority (89.4%) of those who complained to the FDA were classified as having a "mild to moderate" reaction. Only 10.6% were classified as having a "severe" reaction. This means that only .0000038% of the American population exposed to aspartame had a severe reaction and wrote to the FDA.
The most common FDA-reported symptom was headache (28%) followed by dizziness (11%) and change in mood (10%). No control data are given for the background rates of these complaints in the general age-adjusted population.
Note that these data do NOT indicate that 28% of those exposed to aspartame develop headache, only that 28% of those who reported to the FDA about side effects (.000038% of the American population exposed to aspartame) experienced headache. One can assume of course that the rate of headache among aspartame-consumers in the general population is higher or lower, but since we do not have controlled data, we can only speculate. We could reason that those who complain in general would have a higher complaint rate about any specific symptom than the general population.
If You Don't Like Aspartame, Don't Use It
A minority of people are sensitive to aspartame. If you're one, you will know shortly after ingesting products containing it. The most common response is headache. Rarely, you can develop flushing or even some cognitive clouding.
All of these symptoms are entirely reversible upon discontinuation of the aspartame. It is a harmless exercise to discontinue the exposure, which gives an answer within hours or days.
According to the Dr. Robert's 2001 book denouncing aspartame as a public health menace, 70% of Americans are exposed to aspartame in some form on a daily basis. If as many as 1,200 develop some adverse reaction, this translates to only .000436% of the population (of 275 million in 2001). By contrast, at least 1-2% of the population has an allergy to some food.
Flaws With The Anti-Aspartame Literature
None of the most dramatic writings about aspartame were peer-reviewed. A professional scholarly editor at least could have pointed out obvious flaws and identified potential errors.
Those who claim to have information suppressed by organizations as diverse as the FDA, the WHO, the CDC, and the American Medical Association must explain not only why their case was dismissed by medical professionals internationally but why so many professionals would be engaged in such a massive conspiracy. In general, I mistrust conspiracy theorists because conspiracies are quite rare whereas our propensity to believe in them is not.
The good Dr. Roberts cited above asserted throughout his book that he was "corporate-neutral." He never disclosed, however, his own personal stake in promoting his theories, either by selling more copies of his book, being invited to more television appearances, or recruiting more patients for his practice. He also has an agenda, one that no doubt is positively reinforced. This does not per mean his ideas are without merit, but it also does not mean that the corporate-sponsored research he dismisses is worthless. Biased, yes, worthless, no. The FDA is far from perfect, but aspartame had substantially more review than did his book.
The anti-aspartame case is based almost entirely on anecdotal evidence. Although, as his quotations indicate, case reports almost always open the door to more research so should not be dismissed out of hand, the key here is that in other examples (such as with digitalis, for example), rigorous, controlled trials followed initial observations. Those trials done with aspartame failed to support the more breathless claims of the anti-aspartame movement.
Those who advance anti-aspartame theories view the Internet as some kind of propagator of truth, of the little guy winning out over corporate interests. Their opinion of the Internet as a source of legitimate information is much higher than mine. Anyone with an Internet connection and a browser can throw up a web site and it is impossible to verify anyone's credentials or background. The propagation of misinformation is much easier. There is no peer review, no checks and balances, no quality assurance. Anyone who uses the Internet as the primary source of medical information is being reckless.
One cannot reason that because some of the population abuses or is sensitive to alcohol that it should be banned or that it poses a major public health risk to all Americans, although that, it seems, is what the author is trying to do with aspartame. We know that about 20,000 Americans die each year on the highway from alcohol-related deaths. We have no such data on aspartame; all we know is that a small proportion of those exposed report headaches and mild, reversible symptoms, and that a much tinier proportion report more severe symptoms that appear idiosyncratic and dose-independent (by his description). If the substance should be banned based on this, then so too should Tylenol, aspirin, and ibuprofen, all of which are associated with much more prevalent health risks. Also, a strong argument could be made for the banning of fresh fruits and vegetables or poultry and meat since thousands of Americans die each year from food poisoning.
Those opposed to aspartame point out correctly that powerful, wealthy corporations have a vested interest in insuring that aspartame is not yanked from the market. We certainly have many examples of corporations minimizing the public health risks of a product they manufacture or use.
But it takes more than a motive to establish a crime. You must also demonstrate that a crime has been committed (i.e, that there is demonstrable harm that rises to the challenge of a public health risk), and explain why so many disinterested third parties, such as the FDA, the WHO, and the CDC, would sign off on such a deal. Why would a salaried government official approve something that might theoretically benefit a distant CEO? Is he asserting that there was outright bribery? If so, where is the smoking gun, and why has no one "blown the whistle"? It takes only one informant to ruin a conspiracy and he posits that this conspiracy involves multiple agencies in multiple countries.
Also, if the federal government is so corrupt (or inept) then why did this conspiracy succeed when others failed (the list of medications and food additives that do not get FDA approval or are yanked from the market is much longer than the short list of those that do make it, and those that do are subjected to critical ongoing scrutiny. If anything, the government overreacts in a draconian fashion, pulling products that have merit and save lives (such as DDT in the developing world where far more people die of malaria than of pesticide toxicity)).
Life Expectancy
Dr. Roberts cited the swine flu epidemic of the early 20th century, a disease then killed millions, more than died in World War I (whose final year overlapped with the epidemic and probably helped spread it). Even if the author's worst concerns are true, all we know is that aspartame may induce uncomfortable symptoms in a subset of those exposed; he most certainly does not establish the case for millions of deaths. If so, then why is life expectancy rising in a linear fashion since the introduction of aspartame?
Teen Suicide
Roberts makes some rather loose associations between aspartame and the rise in teen suicide. He does not discuss the role of substance abuse or alcohol, which we know are independent risk factors for suicide, or why he feels a Diet Coke would be more likely to disrupt mood than crack cocaine or alcohol. In refutation he offers an anecdote about 1 of his respondents who said it was subjectively harder to wean himself off of aspartame than alcohol. No vital signs or objective evidence of withdrawal was offered.
Eating Disorders
Although I agree strongly that the "cult of thinness" is overdone in this country, obesity poses a far greater risk to the population (about 30% of Americans are obese) than does anorexia (an illness that affects less than 5% of the population, and usually transiently). I agree that bouncing your weight up and down is probably associated with long-term health consequences, but do not agree that aspartame exposure leads to weight gain. His own sample data do not support this assertion. As many respondents (3%) had severe weight gain as weight loss, and we do not know if either is statistically significant.
Diabetes
The vast majority of new cases of diabetes the author cites on page 756 are Type II diabetes (adult onset) secondary to obesity and a sedentary lifestyle. The role, if any, of aspartame seems remote and theoretical.
Some studies since the publication of the book have shown a weak association between diet soda ingestion and metabolic syndrome, but this is all part of the Ambulance Effect at work again. The cycle of obesity and metabolic syndrome and diabetes is well-established and it seems damn hard to break it up, but blaming it all on diet sodas is simply not supported by the research.
Osteoporosis
Young women who eat a "normal" diet in America get far too little calcium; those who diet are much more likely to get even less calcium. Obviously, as he admits, most of those who consume aspartame-containing foods are dieting (calorie-restricting), so how can he assume that of all the variables at play aspartame is the causative agent of osteoporosis? It defies logic to leap to this conclusion.
Seizures
Dr. Roberts accuses aspartame of causing seizures, yet fails to note that caffeine potently lowers seizure threshold (and is therefore used in ECT to help induce seizures).
I must agree with Dr. Arturo R. Rolla, who slammed the author's 1988 book on Aspartame in the NEJM: "This type of book… only adds to public misinformation, confusion, and mistrust" (p. 875). It is hard enough to get patients to make good, sensible decisions about reducing risk factors to illness and death that have been unquestionably demonstrated, such as:
• avoiding tobacco, especially cigarette smoking;
• avoiding excess alcohol and substance abuse;
• avoiding drinking while driving;
• maintaining a healthy, balanced lifestyle with a sensible diet and reasonable exercise regimen;
• treating chronic conditions such as diabetes, hypertension, and major depression.
We know that heart disease, drunk drivers, and tobacco kill hundreds of thousands each year in total just in this country alone. With limited clinical resources, we should be focusing on the many barriers to people modifying their exposure to these known and overwhelming risk factors (clear and present danger, if you will). As mental health professionals, we should be helping clients overcome the extraordinary stimgatizing and mistrust that prevents people from seeking the latest in treatment, both psychotherapeutic and psychopharmacological. This is a tall order without throwing in additional tasks over less demonstrable, but arguably important risks. In an ideal world, we could do it all, but our time and energy is limited, and the attention span of our patients is also limited. Focusing compliance on a few key areas probably would be much more helpful than trying to do too much, especially if it threatens to undermine our credibility as clinicians and scientists. We may have strong, personal convictions about the choices we make, but I think we have an ethical duty from imposing those personal convictions on our patients unless we can demonstrate empirically that they are significant and evidence-based.
Methyl alcohol
The author states that the average daily intake from natural sources is < 10 mg; aspartame beverages contain 55 mg/ liter (no source is given). Therefore a can of Diet Coke (240 cc or 8 fluid oz.) would contain roughly 13 mg of methanol, or about 30% more than the average daily methanol intake.
Weight gain
Roberts notes (p. 389) that 3% of his sample of positive responders gained excessive weight; however this number (40) was identical to the 3% who LOST excessive weight. After spending some time explaining why at the theoretical level aspartame might cause anorexia, he then turns around and explains why it may cause weight gain.
Bottom Line
If you are a typical non-smoking American, your biggest killer is obesity (if you smoke, tobacco is the culprit you must eliminate from your life). However you get to a lower BMI is up to you, but if diet colas including Coke Zero help, then the weight of evidence suggests that they are safe and effective as part of an overall regimen of diet and exercise.
