Showing posts with label Chemistry. Show all posts
Showing posts with label Chemistry. Show all posts

Saturday, November 5, 2011

What's that fatty odor?

Body odor is closely associated with diet. Deciphering the chemistry of human odor is not an easy task - only about 5% of odorous molecules are usually recovered from collection containers, and not all of the molecules are identified in complex spectra. Volatile fatty acids, alcohols, and aromatic ring compounds comprise a substantial fraction of smelly molecules, yet very little is known about the origin and factors controlling their production in humans. Fortunately for some (and not so fortunately for others), the human nose can capture and discriminate many smell signatures. Could this discrimination be used to connect the dots between diet and body odor? MEBO Research has just started an anonymous study using the Aurametrix health analysis tool to find out.

Aurametrix's knowledge base provides a wide selection of foods and symptoms, including different types of odors recognizable by the human nose. Participants in the study have been recording some of their food intake and activities on days when their symptoms are better or worse than average, entering items they suspect might be contributing to or alleviating their body odor on those days. The tool's analysis engine then lets them explore all the possible cause-effect relationships. In addition, Aurametrix performs automated analyses across the entire user community and displays cumulative results as "aggregate correlations." The figure on the right is an excerpt from these results.

Although the study has only just begun, the preliminary results already look very interesting. One example is fatty odor. Aurametrix linked several dietary chemicals to unpleasant "fatty odor" emanating from skin based on Aura entries of several participants. The top chemicals so far are:  Vitamin K1 (phylloquinone), Octadecanoic acid, FODMAPs, Beta-carotene,  Carbohydrates and Monosaccharides. Another interesting result (although there were fewer observations) is that Vitamin B12 obtained from diet seemed to help prevent fatty body odor.
  • Could Vitamin K1 really contribute to "fatty" odor?  Could 6 observations derived from different users' Auras be just a coincidence? Vitamin K is proposed to increase production of alkaline phosphatase in intestines. This enzyme produces a number of different substances, some of which have a peculiar sweetish smell.  Chlorophyll, usually recommended to combat body odor and supposedly makes odor "sweeter," is an excellent source of vitamin K1. And so is Asparagus that gives urine a disagreeable odor.
  • Octadecanoic (Stearic) acid was also linked to fatty odor in 6 observations. This saturated fatty acid is most abundant in animal fats and cocoa butter, and also in nuts and seeds (peanuts, flax), cheese, cookies and candies. Its smell is fairly mild, yet can be detected by the human nose (Bolton and Halpern, 2010). Besides, it slowly converts in the liver to heart-healthy oleic acid which has a faintly fatty odor with a hint of dead insects. It could also metabolize into other compounds and incorporate into liver lipids or follow alternative routes.
  • FODMAPs, highly fermentable but poorly absorbed short-chain carbohydrates and polyols, were found to be an important dietary factor contributing to gastrointestinal symptoms. Perhaps FODMAPs, carbohydrates and monosacharides in particular could also contribute to odor in the absence of GI discomfort?
  • Beta-carotene is another heart-healthy chemical with anticancerous properties important in human nutrition as a source of Vitamin A. Tobacco, tea, many spices and flowers owe their flavors to chemicals metabolized from beta-carotene. One of such chemicals is warm and woody beta-Ionone that smells of blackberry at lower concentrations and fatty-cheesy at higher concentrations.

The chemistry of odors and their origins is undoubtedly very complex. Yet, these preliminary results show that together we may find the answers to many health-related questions. With more participants, we'll soon connect the dots between diet and body odor. Want to participate? Write to:


Bolton B, & Halpern BP (2010). Orthonasal and retronasal but not oral-cavity-only discrimination of vapor-phase fatty acids. Chemical senses, 35 (3), 229-38 PMID: 20100787

Dunkel M, Schmidt U, Struck S, Berger L, Gruening B, Hossbach J, Jaeger IS, Effmert U, Piechulla B, Eriksson R, Knudsen J, & Preissner R (2009). SuperScent--a database of flavors and scents. Nucleic acids research, 37 (Database issue) PMID: 18931377

Wednesday, July 28, 2010

Hormonal Manipulation of Olfactory Cues, or How to Lose a Guy in 10 days

This post was chosen as an Editor's Selection for
Ring-tailed Lemur (Lemur catta) at Berenty Pri...Image via Wikipedia
Body odors are important cues used for social and sexual discrimination. As was shown many times, animals can easily smell age-, health- and genetics-related  differences.  Recent study of our large-eyed relatives, ring-tailed lemurs, demonstrate that drugs can alter body scents and change behavior.

Researchers examined changes in endocrine and  semiochemical profiles of sexually mature female lemurs treated with hormonal contraceptives during their breeding season. Genetic diversity and kinship were estimated using 11–14 microsatellite loci and pairwise genetic distances. Gas chromatography-mass spectrometry (GCMS) was used to detect the volatile compounds in odor. A rater blind to the treatments scored lemur male behavior in regards to female odors. 

The conclusion? Contraceptives change chemical ‘signature’, minimizing distinctiveness and genetic fitness cues. No more can the males determine which females are genetically and physically beautiful. All contracepted females lost their individuality and started to smell funny.  

What about hormones and chemicals in our food?  Maybe one day humans will wake up and realize that something is lost? May it will happen  sooner rather than later...

For those interested in helping with our research of human environmental malodor - check our studies or this call for collaboration.

Jeremy Chase Crawford,, Marylène Boulet,, & Christine M. Drea (2010). Smelling wrong: hormonal contraception in lemurs alters critical female odour cues Proc. R. Soc. B published online before print July 28, 2010

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Thursday, July 15, 2010

Odor-prints: individual but genetic connections unclear

Odor is like fingerprints or facial features - it's unique.  Yet no single measurement could be easily applied to recognize an individual.

GC/MS measurements can be used to analyze mixtures of acids, alcohols, aldehydes, hydrocarbons, esters, ketones, and nitrogenous molecules in human odor. Complex algorithms mining patterns help to pinpoint the signatures. But could these signatures be easily derived from genetic makeups?

Recent article published in the Journal of Chemical Ecology looked at the usual suspects -  major histocompatibility locus (MHC) and found that these genes do not determine major patterns. 

Volatile carboxylic acids are the most diverse class of known axillary odorants, and the pattern of these acids is genetically determined. These acids  - like vast majority of human odorous compounds - are produced by human microbiome, in this case by skin bacteria. Odors of 12 families, comprising 3 to 6 siblings,were analyzed with comprehensive two-dimensional gas chromatography (GC x GC) and time-of-flight mass spectrometry (ToF MS). the analysis onfirmed the presence of individual signatures. but failed to find odors specific to HLA genes.

Even though paternally inherited HLA-associated odors were proposed to influence women odor preferences, genetic basis of odors may be more complicated than previously thought.

Natsch A, Kuhn F, & Tiercy JM (2010). Lack of Evidence for HLA-Linked Patterns of Odorous Carboxylic Acids Released from Glutamine Conjugates Secreted in the Human Axilla. Journal of chemical ecology PMID: 20623248

Thompson EE, Haller G, Pinto JM, Sun Y, Zelano B, Jacob S, McClintock MK, Nicolae DL, Ober C. (2010) Sequence variations at the human leukocyte antigen-linked olfactory receptor cluster do not influence female preferences for male odors. Hum Immunol. 2010 Jan;71(1):100-3. PMID: 19833159 
Jacob S, McClintock MK, Zelano B, Ober C (2002) Paternally inherited HLA alleles are associated with women's choice of male odor. Nature Genet 30: 175-179  PMID: 11799397  PDF

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