Showing posts with label Food. Show all posts
Showing posts with label Food. Show all posts

Saturday, September 7, 2013

Body Odor and Skin Bacteria

Our bodies are rainforests of microbes feeding off the leftovers from our meals and contributing to a variety of body odors. 

Human skin is inhabited and re-populated depending on health conditions, age, genetics, diet, the weather and climate zones, occupations, cosmetics, soaps, hygienic products and moisturizers. All these factors contribute to the variation in the types of microbes. Population of viruses, for example, can include a mixture of good ones - like bacteriophages fighting acne-causing Propionibacterium  - and bad ones  - as highly contagious Mesles. Bacterial communities include thousands of species of Actinobacteria, Bacteroidetes, Cyanobacteria, Proteobacteria, and fungi Malassezia.
Nat Rev Microbiol. 2011 April; 9(4): 244–253.
Nat Rev Microbiol. 2011 April; 9(4): 244–253.
These microbes form communities and have active social lives, cooperating to our good and bad experiences. They converse chemically - in many specific dialects and in universal Esperanto-like languages some of which even we could listen to  - by sampling and understanding smells. 
Humans are among the smelliest animals. And very capable in telling smells apart,  even if the only difference in two molecules is that their structures are mirror images of one another. But unlike dogs that appreciate a garbage bin as much as we appreciate the smell of fresh flowers, we don't properly interpret smells and like to complain about body odors. As we don't know all that much about chemical nature of our surroundings and rely on context and psychological factors, like feeling an intrusion in our experiences of the world. 

Maybe we have something to learn from the science of smells? 

In  a recent review of axillary microbiota, German researchers gave a good lesson in organic chemistry, listing major chemicals, enzymes and microbes responsible for body odor. Let's take a look. 

As was also shown in previous studies, Staphylococcus and Corynebacterium spp. are the most abundant organisms colonizing moist areas and emitting chicken-sulfury, onion-like and clary-sage like odors. The strain of Staphylococcus haemolyticus is producing some of the most offensive sulfury smells. Corynebacterium jeikeium K411 is another species that can compete on the strength of the odor. 

The major odor-causing substances are sulphanyl alkanols, steroid derivatives and short volatile branched-chain fatty acids. 

Most common sulphanyl alkanol in human sweat, 3-methyl-3-sulfanylhexan-1-ol is produced by bacteria in several ways, particularly in glutathione biodetoxification pathway, from molecules synthesized after consuming proteins (due to aminoacids L-cysteine, L-glutamic acid and glycin). This chemical,  besides being a major descriptor of human sweat odor,  is also present in beers. Its S-enantiomer (75%) is described as a classical body odor (sweat) with onion-like tones. Interestingly, the opposite enantiomer, (R)-3-methyl-3-sulfanylhexan-1-ol, is fruity and grapefruit-like. 

Another set of molecules produced by Corinebacterium are most prominent in Caucasian men and some Asians. The odor is hircine - resembling of goats with fatty and cheesy notes or cumin-spice like. The food sources contributing to this odor are proteins and animal fats. 

Pheromones androstenol and androstenone, metabolites of sexual hormones, are also odorous. The latter is especially interesting as to some of us it smells like vanilla while to others is smells like urine.

Sweaty-feet and cheesy smelling isovaleric and propionic acids and sour-vinegary acetic acid are also adding to the spectrum of human odors.  They can smell different to different people too - some people have genetic makeup making them hypersensitive to these smells, but others are much more tolerant and forgiving. The food sources of sourish smells are protein-rich. Lactic acid is found in cheeses, yogurt, soy sauce, sourdough, meats and pickled vegetables. It can be also produced from the breakdown of carbohydrates during exercise and used as additional fuel. Glycerol is created from triglycerides found in fats and oils.  


So next time you are exposed to body odor, try to understand what could be causing it. It is not easy as it is a combination of many factors such as hormonal fluctuations, mental or physical stress, metabolism and microbes. It could be perfectly normal or result from a medical condition of the person who has the smell and your own olfactory abilities. But the smells are fascinating clues to health and  the basics can be learned by most everyone.
REFERENCES

Fredrich E, Barzantny H, Brune I, & Tauch A (2013). Daily battle against body odor: towards the activity of the axillary microbiota. Trends in microbiology, 21 (6), 305-12 PMID: 23566668

Grice EA, & Segre JA (2012). The human microbiome: our second genome. Annual review of genomics and human genetics, 13, 151-70 PMID: 22703178

Stevenson, R., & Repacholi, B. (2005). Does the source of an interpersonal odour affect disgust? A disease risk model and its alternatives. European Journal of Social Psychology, 35 (3), 375-401 DOI: 10.1002/ejsp.263

Troccaz M, Starkenmann C, Niclass Y, van de Waal M, Clark AJ.  ( 2004) 3-Methyl-3-sulfanylhexan-1-ol as a major descriptor for the human axilla-sweat odour profile.Chem Biodivers. 2004 Jul;1(7):1022-35. PMID: 17191896

Lenochová P, Vohnoutová P, Roberts SC, Oberzaucher E, Grammer K, Havlíček J (2012) Psychology of fragrance use: perception of individual odor and perfume blends reveals a mechanism for idiosyncratic effects on fragrance choice. (PMID:22470479) Free full text article  PLoS One [2012, 7(3):e33810]
Barzantny H, Brune I, Tauch A. (2012) Molecular basis of human body odour formation: insights deduced from corynebacterial genome sequences. Int J Cosmet Sci. 2012 Feb;34(1):2-11. doi: 10.1111/j.1468-2494.2011.00669.x. Epub 2011 Jul 25.  PMID: 21790661

Friday, June 28, 2013

I Know What You Ate This Summer

Despite active foodstagramming and foodteresting, and eagerness to show pictures of meals and diet reports to friends on social media, we don't really want others to know everything we eat. But they might know anyway.

Why worry about NSA, when Google, Facebook, Amazon and many others know what we might be eating. Cameras record our ways to groceries and restaurants, credit cards record our purchases, food chains know our weaknesses, clothes shops know how, as a result, our pant sizes change over time. One day phones will know what we ate too.  As both short- and long-term diets change our breath-prints - creating signature metabolites in exhaled breath.

A recent Dutch study actually looked at what gluten-free eating does to our breath. Just 4 week of dieting lead to remarkable - though reversible -  differences. (As detected in 20 healthy individuals by gas chromatography coupled with mass spectrometry (TD-GC-tof-MS) in combination with chemometric analysis ). A set of twelve volatile compounds that distinguish gluten-free eaters along with information from Aurametrix knowledgebase is listed in the table below.


Compound Odor Notes
2-butanol strong alcoholic 1-Butanol smells like permanent marker (Sharpie) 
octane Gasoline-like, car exhaust octyl chloride smells faintly of oranges
2-propyl-1 pentanol green banana 1-Pentanol smells like paint thinner 
nonanal strong fruity or floral attracts mosquitoes
dihydro-4-methyl-2(3H)-furanone strong coconut aroma 5-butyl-4-methyloxolan-2-one is known as "whisky lactone"
nonanoic acid rancid beer, old cooking oil armpits of males over 30
dodecanal Soapy, waxy, aldehydic, citrus, orange rindy with floral nuances Pure, synthetic qualities of this fatty aldehyde are used in traces in perfumery for "fresh laundry"-like effects.


Reference
Baranska A, Tigchelaar E, Smolinska A, Dallinga JW, Moonen EJ, Dekens JA, Wijmenga C, Zhernakova A, & van Schooten FJ (2013). Profile of volatile organic compounds in exhaled breath changes as a result of gluten-free diet. Journal of breath research, 7 (3) PMID: 23774130

Monday, February 1, 2010

Foods and Smells

Kagome started as a tomato grower, and its mai...Image via Wikipedia
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.
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