By Peter Montague
In the United States, brain cancer has been steadily increasing about 0.7% per year since 1973. This steady increase is noteworthy by itself. However, among people over age 65, brain cancer has been increasing 2.9% each year, an astonishingly rapid rise in a cancer that is almost always fatal in the elderly. At this rate, the disease is doubling every 23 years among the elderly.
Today roughly 17,500 people in the US (9600 males, 7900 females) are diagnosed with new brain cancers each year. During the period 1973-1990, brain cancer steadily increased in other industrialised countries as well, especially among the elderly.
Are these increases real or do they simply reflect better diagnosis? Several careful studies of this question have concluded that much of the increase in brain cancer is real, and does not merely reflect better diagnosis.
For one thing, the steady increases began before the invention of modern diagnostic equipment. New imaging techniques (CAT scans in the mid-1970s, and magnetic resonance imaging [MRI] in the 1980s) did make the diagnosis of brain tumours easier and more accurate. When CAT scans and MRI became available, brain tumours formerly missed were found; on the other hand, non-cancer brain problems formerly misdiagnosed as brain tumours could now be properly identified as something besides cancer.
Furthermore, analysis has determined that the AIDS epidemic is not the cause of the observable brain cancer increases.
Although the causes of brain cancers remain a mystery, in all likelihood the problem has multiple sources, including dental X-rays; occupational exposure to chlorinated hydrocarbons, organic solvents, paints and oils; pesticides; electromagnetic fields; hormonal status in women; and N-nitroso compounds.
Because brain cancers are increasing in both men and women, occupational exposures are unlikely to be a major cause. A new study published in November (Journal of Neuropathology and Experimental Neurology Vol. 55, No. 11, pp. 1115-1123) suggests that the artificial sweetener aspartame (marketed as Nutrasweet and Equal), may be implicated. At least half of US people —knowingly or not —now expose themselves to aspartame in "diet" food products and soft drinks.
Initial controversy
When G.D. Searle, the pharmaceutical manufacturer, sought approval for aspartame from the US Food and Drug Administration (FDA) in 1973, a long controversy ensued. Some scientists within the FDA suspected that aspartame might cause brain cancer in laboratory animals. If this were shown to be true, aspartame would have been banned under federal law.
FDA initially approved aspartame for certain food uses in 1974, but two citizens —John W. Olney, MD, and James S. Turner — challenged that decision and requested a full hearing. To settle the controversy and avoid the expense of a full hearing, FDA commissioner Donald Kennedy established an independent public board of inquiry (PBOI), consisting of three qualified scientists from outside the agency.
The PBOI reviewed the available data and on October 1, 1980, issued its decision, saying, "the evidence suggested that aspartame might induce brain tumours" in laboratory rats. Accordingly, the PBOI concluded that aspartame should not be approved until further animal testing was conducted to resolve the brain tumour issue. In response to the PBOI's findings, FDA revoked Searle's licence to sell aspartame.
However, in 1981 a new FDA commissioner, Arthur Hull Hayes, Jr, appointed by President Ronald Reagan, simply reversed the decision of the PBOI and licensed aspartame for "dry" uses as a substitute for sugar. No new studies were initiated on the question of brain cancer. Under the guidance of Dr Hayes, FDA simply reinterpreted the old data and asserted that the reinterpreted data showed that brain cancer was not a problem. Thus aspartame became a legal food additive.
In 1983, Hayes extended Searle's aspartame licence to include its use as a sweetener in "diet" soft drinks, and aspartame sales took off. In 1985 Monsanto bought Searle, and Monsanto now aggressively markets Nutrasweet for "diet" sweeteners, selling roughly 9 million kilograms of aspartame for use in the US each year at US$198 per kg, plus unknown quantities overseas. On average, people in the US ingest 38 grams of aspartame per person per year.
New study
The aspartame study published in November, by John W. Olney of Washington University in St Louis, suggests that the steep increases in brain cancer in the US in the 1980s and 1990s may have been caused by exposure to aspartame.
Olney offers three reasons for concern:
(1) The kinds of cancer rising most rapidly in people (glioblastomas) are the same kind found in 3.8% of aspartame-fed rats in one of Searle's studies.
(2) Monsanto asserts that aspartame could not cause cancer because it breaks down into harmless constituents in the human stomach, but Olney points to a 1993 study showing that aspartame can be nitrosated and therefore might be expected to become an N-nitroso compound in the human stomach. N-nitroso compounds are potent carcinogens, some linked to brain tumours.
(3) Olney analyses the National Cancer Institute's (NCI) data and finds two sharp increases in brain cancers. He believes aspartame might have caused these increases because it was introduced rapidly, whereas other suspected causes of brain cancer were introduced gradually and would not be expected to cause sharp increases.
Olney says cancer requires several cell injuries, and older people may acquire many such injuries during their lives and may thus be ready to be "pushed over the edge" by exposure to aspartame. This could explain the short delays between introduction of aspartame to the US diet and the rapid rises in brain cancer that Olney points to in the NCI data. (Cancers are usually delayed by a decade or more after exposure to a cancer-causing agent, but Olney points to brain cancer increases only a couple of years after FDA approved aspartame.)
Wherever the truth lies, FDA is unlikely at this point to re-examine the safety of aspartame. To do so would be, in some sense, to admit the haste —perhaps it could even be termed foolhardiness — of its earlier decision.
The issue back in 1980 was this: in one Searle study, 3.8% of aspartame-fed rats got brain tumours. What was the "normal" rate of brain tumours in this strain of rat? Commissioner Hayes acknowledged that all of the data available to answer this question had "flaws" (his word) because the "normal" animals had all been exposed to experimental chemicals or drugs, or had been fed irradiated food. However, instead of ordering new studies that would avoid such flaws, to answer this important question Dr Hayes simply asserted that a 3.8% rate of brain tumours in aspartame-fed rats was not significantly different from the rate of brain tumours in "normal" rats.
Furthermore, when the commissioner applied two statistical tests (of his own choosing) to the data in this study, those tests showed significant increases in brain cancers among female rats fed aspartame. The commissioner then removed one of the aspartame-fed rats from the study, asserting that its brain tumour had not been caused by aspartame. After the removal of this rat, the cancer increases were no longer statistically significant. Thus FDA approval of aspartame appears to have been tainted by decisions based on something other than science.
Nevertheless, FDA has dug in its heels on this issue, and it apparently will be left to independent researchers to examine the health consequences of exposing half (or more) of the population to aspartame. Given that funding for scientific research in the US —including research at academic institutions — is increasingly controlled by private corporations, and not by government or other independent sources, it is difficult to see where the necessary research funds could come from. In any case, a huge experiment is being conducted now on more than 100 million people.
[From Rachel's Environment & Health Weekly. Like Â鶹´«Ã½ Weekly, Rachel's Environment & Health Weekly is a non-profit publication which distributes information without charge on the internet and depends on the generosity of readers to survive. If you are able to help keep this valuable resource in existence, send your contribution to Environmental Research Foundation, PO Box 5036, Annapolis, Maryland 21403-7036, USA. In the United States, donations to ERF are tax deductible.]