Gender - confounder of concern?

Background and clinical characteristics measured at baseline are comparable in the groups of our study. But this doesn't eliminate the need to investigate the impact of confounding. We've already analyzed the effects of age, What about gender as a potential confounder?

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The Anna Karenina Principle: Alloprevotella

"All happy families are alike; each unhappy family is unhappy in its own way", said the great novelist. The Anna Karenina principle (AKP), in the context of metabolic disorders, would mean that an uncompensated deficiency in any one of important enzymes, or presence of any one of pathogenic microorganisms, dooms the person to having the MEBO/PATM symptoms.

... Read more ...

The elusive balance: Epulopiscium

Originally published on Aurametrix site

Diseases and conditions caused by microorganisms could be difficult to diagnose. Even in such seemingly simple case as avian flu there could be many different infectious agents causing it, so  new molecular diagnostic techniques are constantly developed and refined. 

We don't have all our test results yet, but have already started analyzing available data. Regression analyses of 153 gut microbiome samples show that MEBO score (a composite score derived from answers to questions pertaining to odor or PATM symptoms) can be explained by combined levels of several dozen microorganisms. Some of them make symptoms worse, while others neutralize the odors or PATM aura.

Here is one example: Epulopiscium

Discovered in the gut of the brown surgeonfish, Epulopiscium actually means “guest at a banquet of fish.” It's a large bacteria  - the size of a hyphen in a printed text, visible to the naked eye. 

Epulopiscium was found in only 5% of general population that tested with uBiome. But we see a much higher percentage of samples with these bacteria in our dataset, depending on the symptoms reported.  

It could be detected in 50% of the sufferers experiencing the worst symptoms, decreasing as symptoms lessen.  The prevalence of this bacteria in sufferers with strong but rarely manifested symptoms  is about the same as in general population, but we never observed these bacteria in those with mild occasional symptoms or no symptoms at all.

Of course, this is not the only responsible microorganism for odors or PATM. We will be reporting more, along with what seem to help in reducing the levels.

We will also tell about bacteria "neutralizing" the odors, found in remission. Some of them are antiinflammatory, others help with digestion. Interestingly, a number of butyric acid-producing microbes also seem to help, even though butyric acid is not supposed to smell pleasant. We'll talk about it next time.

Chemicals in food affecting body odor

Volatile compounds (complex organic and simple like hydrogen sulfide and ammonia), together with sugars and acids, are the main chemicals determining the characteristic aroma of food, as well as odors related to human body.

The bad smells are generally the result of a combination of odorous sulfur compounds and ammonia.

Volatile sulfur compounds are produced through bacterial metabolism of sulfur amino acids such as cysteine and methionine. High sulfur content in food is another source.

Choline  - a quaternary saturated amine - can lead to increases in the amount of trimethylamine responsible for sweet and sickly, fish-like smell.

How to estimate the amount of choline, sulfur and sulfur-containing aminoacids in your food?
You can do it easily with Aurametrix.
Watch these videos:

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

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

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.

References

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
 

Foods and Smells

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How many flavors are out there? We often hear only about these five - sweet, sour, salty, bitter and savory (umami), but there are so many more and they are important not only to our tastes but also health.

Remember that fresh grassy smell wafting up from the newly sliced tomato? It may be it's way of saying  "I'm good for you".

Stephen A. Goff and Harry J. Klee's article "Plant Volatile Compounds: Sensory Cues for Health and Nutritional Value?" published in a 2006 issue of Science explains why odors from foods may be nutritional or health signals that the human nose has learned to recognize.

Among the things emmigrants from less developed countries miss in USA is the scent of fresh tomatoes. One of the volatile compounds associated with the “grassy” tomato flavor, cis-3-Hexenal, is also an indicator of fatty acids essential to the human diet. Wild tomato contained more than three times the amount of that chemical than the cultivated version in the developed world. Two other contributors to tomato flavor — 2- and 3-methylbutanal — are indicators of the presence of essential amino acids and are also three times more common in the wild tomato. Same applies to commercial apples, strawberries, bread, cheese, even wine and beer.

Flavorful curcumin in tumeric has anti-inflammatory properties, compounds in ginger have antioxidants, and there are antimicrobial chemicals that contribute to the scent of onions, garlic, rosemary, sage, clove, mustard, chili peppers and thyme.

There are hundreds of volatile compounds in foods and beverages, often a major factor in how taste of foods is perceived.

What smells people enjoy the most?

Joanne Camas from Epicurious.com lists these 5 food smells:

1. Fried onions cooking
2. Banana bread baking (extra points if it has chocolate chips in it)
3. A perfectly ripe tomato as you slice into it, especially on a warm, sunny day
4. Coffee brewing
5. Garlic bread, fresh out of the oven
Most people commenting on this post listed baked breads and coffee as their top favorites too. Other choices include pies, spices and meats.

Here are some of the responses pulled from different blogs. What are your top five?

chefrosey 12:23:21 PM on 02/01/10

Chocolate
Fresh brewed coffee
Fresh baked bread
Fresh picked strawberries or an orange being peeled!
Any baked good coming out of the oven!

chef330 12:14:17 PM on 02/01/10

1. Onions sauteeing in butter
2. Chocolate Chip Cookies coming out of the oven
3. Just-picked peaches
4. Hot Apple Pie
5. European Butter - you can smell the flavor

Janet Tue Feb 2, 2010 2:22pm PST

apple pie baking in the oven
tralala311 Tue Feb 2, 2010 2:25pm PST

mmmm... GUMBO!!!

Habanero♥™ Tue Feb 2, 2010 2:32pm PST

Bacon, Baking Bread, Turkey, Pumpkin Pie, Molasses Cookies, Cinnamon Rolls.

Sherri Tue Feb 2, 2010 2:53pm PST

Coffee brewing, Chocolate Chip Cookies, Cinnammon Rolls, Bread, Pumkin Pie
__A_YAHOO_USER__ Wed Feb 3, 2010 9:21am PST
i think there's something about a roast that's been slow cooking all day that smells delicious, it'd be on my top 5 for sure.

Adapted on 2/15/2026 from: https://www.meboblog.com/2008/04/chemical-composition-of-odors-chemical.html

Formatted, and expanded version of Maria de La Torre's post of Friday, April 11, 2008

See also old Aurametrix Notes about this. 

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Chemical Composition of Odors

Sulfur compounds

Chemical	Odor	Origin / Source
Hydrogen sulfide	Rotten eggs	Sulfur metabolism; amino acids (e.g., methionine, cysteine)
Methyl mercaptan (methanethiol)	Rotten cabbage	Sulfur-containing amino acids
Diethyl sulfide	Rotten vegetables	Sulfur compounds from protein breakdown
Methionine	Rancid butter	Sulfur amino acid metabolism

Phenolic & aromatic compounds

Chemical	Odor	Origin / Source
Phenol	Medicinal, sweet	Tyrosine metabolism
p-Cresol	Fecal	Tryptophan, tyrosine degradation
Phenylalanine	Musty / mousy	Amino acid metabolism
2-Aminoacetophenone	Musky, grape-like	Microbial metabolism
Indole + other compounds	“Wet dog” odor	Protein decomposition

Nitrogenous amines

Chemical	Odor	Origin / Source
Methylamine	Fishy, pungent	Nitrogen metabolism
Dimethylamine	Fishy	Protein degradation
Diethylamine	Pungent, ammoniacal	Nitrogen compounds
Trimethylamine	Fishy, ammoniacal	Choline metabolism
Ammonia	Sharp, pungent	Protein breakdown, urea metabolism
Dimethylglycine	Fishy	Choline metabolism
Cadaverine	Rotting corpse	Lysine decomposition

Indoles & related compounds

Chemical	Odor	Origin / Source
Indole	Fecal, mothball-like	Tryptophan breakdown
Skatole	Fecal, pungent	Tryptophan metabolism

Organic acids (short-chain & volatile)

Chemical	Odor	Origin / Source
Acetic acid	Vinegar	Fermentation; carbohydrate metabolism
Butanoic (butyric) acid	Rancid butter, sour meat	Fiber fermentation; amino acids
Caproic / capric acid	Sour, goat-like	Short-chain fatty acid metabolism
Isovaleric acid	Sweaty feet	Leucine metabolism
Methylcrotonic acid	Cat urine	Organic acid metabolism
Branched-chain amino acids	Maple syrup-like	Amino acid disorders/metabolism

Ketones & aldehydes

Chemical	Odor	Origin / Source
Acetaldehyde	Fruity, pungent	Alcohol metabolism; fermentation
Acetone	Sweet, pungent	Fat metabolism; ketosis
2-Nonanone	Fruity	Lipid metabolism

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Notes

• Many odors originate from microbial metabolism of:

  • Amino acids

  • Lipids

  • Carbohydrates

• Common biochemical sources of odor compounds

  • Protein decomposition → amines, indoles, sulfur gases

  • Fat breakdown → ketones, short-chain fatty acids

  • Fermentation → organic acids, aldehydes

• Key amino acid–odor links

  • Tryptophan → indole, skatole

  • Tyrosine → phenol, cresols

  • Lysine → cadaverine

  • Leucine → isovaleric acid

  • Methionine/cysteine → sulfur odors

MAPPING OF ODORS

Described odor	Similar Odor	Why
Rotten eggs	Fecal	Sulfur compounds (e.g., hydrogen sulfide) are common in fecal odors
Rotten cabbage	Fecal	Sulfurous, putrefaction-type smell typical of fecal decomposition
Rotten vegetables	Fecal	Putrid, decomposition odor similar to fecal notes
Rancid butter	Fatty	Classic oxidized-fat smell (butyric/related fatty acids)
“Wet dog”	Foot odor	Microbial, sweaty, slightly sour—similar to foot-associated bacteria
Medicinal	Underarm odor	Sharp, chemical, phenolic notes often linked to apocrine sweat breakdown
Cat urine	Ammonia-like	Strong ammonia/urea breakdown odor
Fruity	Underarm odor	Some underarm bacteria produce sweet/ester-like scents
Pungent	Underarm odor	Sharp, acrid body-odor character typical of armpit sweat compounds
Maple syrup	Fatty	Sweet, warm, lactone/organic-acid notes often grouped with fatty odors