Aspartame is linked to leukemia and lymphoma in humans
As little as one diet soda daily may increase the risk for leukemia in men and women, and for multiple myeloma and non-Hodgkin lymphoma in men, according to new results from the longest-ever running study on aspartame as a carcinogen in humans. Importantly, this is the most comprehensive long-term study ever completed on this topic, so it holds more weight than other past studies which appeared to show no risk. And disturbingly, it may also open the door for further similar findings on other cancers in future studies.
The most thorough study yet on aspartame: over two million person-years
For this study, researchers prospectively analyzed data from the Nurses’ Health Study and the Health Professionals Follow-Up Study for a 22 year period. A total of 77,218 women and 47,810 men were included in the analysis, for a total of 2,278,396 person-years of data. Apart from sheer size, what makes this study superior to other past studies is the thoroughness with which aspartame intake was assessed. Every two years, participants were given a detailed dietary questionnaire, and their diets were reassessed every four years. Previous studies which found no link to cancer only ever assessed participants’ aspartame intake at one point in time, which could be a major weakness affecting their accuracy.
One diet soda daily increases leukemia, multiple myeloma and non-Hodgkin lymphomas
The combined results of this new study showed that those consuming at least one 12-fl. oz. can (355 ml) daily of diet soda experienced:
- 42% higher leukemia risk in men and women
- 102% higher multiple myeloma risk (in men only)
- 31% higher non-Hodgkin lymphoma risk (in men only)
These results were based on multivariable relative risk models, all in comparison to participants who drank no diet soda. The fact that men were more affected by women in this study raises an important point. Men are known to have higher levels of the enzyme alcohol dehydrogenase type 1 (ADH) which breaks down methanol into formaldehyde--a known carcinogen. It has been suspected that aspartame may partially break down into methanol in the body, and that the conversion of this methanol into formaldehyde by ADH could result in increased risk for cancer. A convenient way to test this theory would be to observe if those men drinking higher amounts of alcohol had different levels of cancer risk: since ADH is also used by the body to break down normal alcohol (ethanol), heavier drinkers would have less ADH left over to metabolize methanol and should have less cancer risk. Fascinatingly, that's exactly what is seen in this study. Men who consumed at least two servings daily of diet soda and also drank on average at least six grams of ethanol daily (one standard drink contains 14 grams of ethanol) saw no increased risk for non-Hodgkin lymphomas, whereas those men drinking less than six grams of ethanol daily had more than double the risk of NHL (RR=2.34). The association was even more striking for multiple myeloma for those drinking at least one diet soda daily: low drinking men had nearly quadruple the risk compared to heavier alcohol drinkers. Note that diet soda is the largest dietary source of aspartame (by far) in the US. Every year, Americans consume about 5,250 tons of aspartame in total, of which about 86 percent (4,500 tons) is found in diet sodas.
Confirmation of previous high quality research on animals
This new study shows the importance of the quality of research. Most of the past studies showing no link between aspartame and cancer have been criticized for being too short in duration and too inaccurate in assessing long-term aspartame intake. This new study solves both of those issues. The fact that it also shows a positive link to cancer should come as no surprise, because a previous best-in-class research study done on animals (900 rats over their entire natural lifetimes) showed strikingly similar results back in 2006: aspartame was linked to significantly increased risk for lymphomas and leukemia in both males and females. More worrying is the follow on mega-study, which started aspartame exposure of the rats at the fetal stage. Increased lymphoma and leukemia risk were confirmed, and this time the female rats also showed significantly increased breast cancer rates. This raises a critical question: will future high-quality studies uncover links to the other cancers for which aspartame has been implicated (brain, breast, prostate, etc.)?
There is now more reason than ever to completely avoid aspartame in our daily diet. For those who are tempted to go back to sugary sodas as a “healthy” alternative, this study had a surprise finding: men consuming one or more sugar-sweetened sodas daily saw a 66% increase in non-Hodgkin lymphoma (even worse than for diet soda). Perhaps the healthiest soda is no soda at all.