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:



References

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

1 comment:

  1. East Asians have predominantly dry earwax, as opposed to the sticky kind that most other people have; the gene encoding for this is strongly linked to reduce body odor, whereas those with wet, sticky earwax (such as Europeans and Africans) are prone to more body odor.

    Apocrine and/or eccrine glands in the human body cause odor, especially from the axillary and pubic apocrine glands. As in other mammals, the odor may have a pheromone-like effect on the opposite sex. This odor does not affect health; however, many individuals feel uncomfortable with their axillary odor, regardless of its strength and often do their best to reduce such orders; some people even elect to have surgery to remove one or more of such glands.

    http://blogs.discovermagazine.com/gnxp/2010/10/east-asians-dry-earwax-and-adaptation/

    These glands secrete an oily fluid with proteins, lipids, and steroids which are odorless before microbial activity. They appear on the skin surface mixed with sebum, as sebaceous glands open into the same hair follicle. Unlike eccrine sweat glands, which secrete continuously, the apocrine glands secrete in periodic spurts.

    Myoepithelial cells form a smooth muscle lining around the secretory cells; when the muscle contracts, they squeeze the secretory ducts and push out the accumulated fluid into the hair follicle. Sweat and sebum are mixed in the hair follicle and arrive mixed at the epidermal surface. The apocrine sweat is cloudy, viscous, initially odorless, and at a pH of 6–7.5. It contains water, protein, carbohydrate waste material, and NaCl. The sweat only attains its characteristic odor upon being degraded by bacteria, which releases volatile odor molecules. More bacteria (especially corynebacteria) leads to stronger odor. The presence of axillary hair also makes the odor worse, as secretions, debris, keratin, and bacteria accumulate on the hairs.

    http://en.wikipedia.org/wiki/Apocrine_sweat_gland

    This would also explain why SOME people can get away without wearing deorderant without other people noticing.

    http://www.theguardian.com/science/sifting-the-evidence/2013/feb/14/wasting-money-deodorant-ears
    http://www.reddit.com/r/todayilearned/comments/1h7rtx/

    ReplyDelete