I found an article about Diet Coke on John McManamy’s website. What was particularly interesting to me was the relationship between aspartame and depression and bipolar disorder.

Says John:

In 1993, Dr Walton, who is a psychiatrist, conducted a study of 40 patients with unipolar depression and a similar number without a psychiatric history. The subjects were given 30 mgs per kg of body weight a day of aspartame or a placebo for 20 days (about equal to daily consumption if it completely replaced sugar).

Thirteen individuals completed the study, then an institutional review board called the project to a halt “because of the severity of reactions within the group of patients with a history of depression.” In a smaller, shorter crossover design, “again there was a significant difference between aspartame and placebo in number and severity of symptoms for patients with a history of depression, whereas for individuals without such a history there was not.”

Accordingly, the author concluded that “individuals with mood disorders are particularly sensitive to this artificial sweetener and its use in this population should be discouraged.”

As to further particulars of the study, based on the eight depressed subjects and five healthy subjects who completed it:

Three quarters of the patients with a history of depression taking aspartame reported feeling depressed vs none of the healthy subjects taking aspartame and about 40 percent of both groups taking a placebo. The 40 percent is probably a statistical aberration owing to the small numbers who completed the study. Nevertheless, the figures consistently show the depressed/aspartame group experiencing an array of symptoms in far greater numbers and severity, including: fatigue, nausea, headache, trouble remembering, insomnia, and other symptoms.

The depressed/placebo group showed almost none of these symptoms, along with the healthy/aspartame and healthy/placebo groups Dr Walton told this writer he believes aspartame inhibits serotonin synthesis by decreasing the availability of the precursor L-tryptophan, a finding borne out in another research team’s 1987 experiment on rats.

Remarkably, Dr Walton’s study is the only one we have related to both mood and aspartame. It would be helpful to get a second opinion, but no one else since, apparently, has tried to either replicate or refute his results. This may be due to the political and funding climate. “The NutraSweet company,” Dr Walton told this writer, “clearly tried to block our study.”

So we are left contemplating the fridge, where our Diet Coke is being chilled, with but one aging study to either guide us or confuse us. Once again, like the trial and error of our meds, we find ourselves human guinea pigs, this time experimenting with our diet. For many, aspartame may turn out to be a life-saving alternative to that well-documented sweet poison, sugar. Others who continue to experience depression, fatigue, and other symptoms, however, may want to moderate their aspartame consumption and see what happens.