Does Butter Really Cause Alzheimer’s?
By biochembelle on August 13, 2012
BlogHer Original Post
Alternatively, owing to either Aβ heterogeneity or other factors of the tissue milieu, the actual structures of "toxic" oligomers in the brain may differ from those of isolated peptides such Aβ42. From my viewpoint, these discrepancies make it difficult to judge whether in vitro differences in Aβ aggregation will hold true in vivo.
Another critical consideration is that dose makes a difference, a principle that is often lost in reporting toxicity studies. The authors of this paper noted that they used concentrations of diacetyl that can be physiologically attained - among workers in food manufacturing factories, specifically those in popcorn factories though diacetyl is used in production of other foods. These individuals are working around vats of diacetyl and are chronically exposed. In the abstract, the authors state (emphasis mine):
In light of the chronic exposure of industry workers to DA, this study raises the troubling possibility of long-term neurological toxicity mediated by DA.
The concentrations of diacetyl needed to affect Aβ42 toxicity could hypothetically be seen in industry workers, based on exposure levels reported in some cases. But would this exposure level be reflected in the brain? We know very little about how diacetyl is metabolized and removed by the human body. This study suggests that diacetyl can cross the blood-brain barrier, but those experiments were conducted using levels of diacetyl much higher than typical industry exposure.
Diacetyl poses a known respiratory health risk for industry workers, but this study is only the first step in characterizing other potential risks. However, these risks concern individuals chronically exposed to industrial quantities of the compound.
The missing ingredient?
At some point, you might have wondered, "What the hell is diacetyl doing in my popcorn?!" Over many decades, scientists have identified the naturally occurring chemicals that give our favorite foods their distinct smells and tastes. Food manufacturers use this knowledge to add desired flavors (or remove wanted ones) to products. Diacetyl -- produced by microorganisms used to make butter, cheeses, and wine -- is one of the elements that provides the products their buttery aroma. So it seemed natural to use diacetyl to replicate the butter flavor in things like popcorn.
But a few years ago, two major manufacturers, ConAgra and PopWeaver, removed diacetyl from their microwave popcorn. Diacetyl continues to be used in other food products, but the exposure levels of consumers are orders of magnitude below those of industry workers.
So, if you find yourself more forgetful after that next bag of popcorn, there's a better chance it's a nocebo effect than the butter.
More, S. S., Vartak, A. P., and Vince, R. The Butter Flavorant, Diacetyl, Exacerbates β-Amyloid Cytotoxicity. Chem. Res. Toxicol. (2012, in press) DOI: 10.1021/tx3001016
Other selected references
Benilova, I., Karran, E., and De Strooper, B. The toxic Aβ oligomer and Alzheimer’s disease: an emperor in need of clothes. Nat. Rev. Neurosci. (2011) DOI: 10.1038/nn.3028
Wang, Q., Rager, J. D., Weinstein, K., Kardos, P. S., Dobson, G. L., Li, J., and Hidalgo, I. J. Evaluation of the MDR-MDCK cell line as a permeability screen for the blood–brain barrier. Int. J. Pharm. (2005) DOI: 10.1016/j.ijpharm.2004.10.007
Mallia, S., Escher, F., and Schlichtherle-Cerny, H. Aroma-active compounds of butter: a review. Eur. Food Res. Tech. (2008) DOI: 10.1007/s00217-006-0555-y
Chemical Information Review Document for Artificial Butter Flavoring and Constituents Diacetyl [CAS No. 431-03-8] and Acetoin [CAS No. 513-86-0] (Supporting Nomination for Toxicological Evaluation by the National Toxicology Program)
Biochem Belle is a biochemist with a PhD in Chemistry. Her first love -- professionally speaking -- is proteins, and she explores how their interactions and organization alter their functions in cells. She writes about life and culture in science at Ever On & On, where this post first appeared. You can follow her on Twitter @biochembelle.
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