While there is not enough research on human odors, there are plenty of studies that can be related to this topic. Scientific papers published in January are about goats, fish, fermented food and biological waste.
It is worth examining some of the latest findings and how they may be translated into take-home messages for humans.
1. Intermittent fasting could improve body odor.
At least for fish. The study aimed to investigate the response of intestinal microbiota during 3 weeks’ starvation of largemouth bass (Micropterus salmoides), found that food deprivation helped to improve the odor of an economically important freshwater fish by reducing earthy-musty off-flavor compounds such as geosmin and 2-methylisoborneol. The study revealed that certain actinobacteria such as Microbacterium and Nocardioides were able to grow better than Mycoplasma, Pseudomonas, Acinetobacter, and Microbacterium when the fish were in a fasted state. This suggests that intermittent fasting may help to improve body odor by promoting the growth of beneficial bacteria and reducing the growth of odor-causing bacteria. However, more research is needed to confirm these findings in human studies. Besides, our own data show that people smell worse when starving themselves and it is a good idea to not go overboard.
2. Adding fiber to diet and reducing stress levels can improve body odor.
Korean native black goats (KNBG) are able to adapt to a wide variety of climatic conditions and foraging preferences. Twenty-four KNBG (48.6 ± 1.4 kg) were randomly allocated to one of four treatments featuring different dietary forage (high in fiber) to concentrate ratio (high forage [HF, 80:20] and low forage [LF, 20:80]), and a castration treatment (castration [CA] vs. non-castration [NCA] - aka higher levels of sex hormones, stress hormones). The animals were maintained on a free-choice feed and water regimen.
A healthy gut microbiome may positively influence sex hormones by regulating the appetite and reducing insulin resistance. Acute psychosocial stress, on the other hand, causes unhealthy fluctuations in sex hormone levels.
Here are a few tables compiled from the goat diet/hormones article:
| Microbe Genus | Compounds positively correlated | Compounds negatively correlated. |
|---|---|---|
| Flexilinea | C16:0 (Palmitic acid, oily smell) | C18:2n6 (Methyl linoleate, oily odor), C18:3n3 (Linoleic acid, oily, low odor), PUFA |
| Ihubacter | C16:0 (Palmitic acid, oily smell) | C18:2n6, C18:3n3 (Linoleic acid), PUFA |
| Ruminococcus | - | C16:0 (Palmitic acid, oily smell) |
| Christensenella | C18:0 (Stearic acid), PUFA | C16:1n7 (Palmitoleic Acid, Cardioprotective - smells like Old Books) |
| Lachnoclostridium | C18:1n9 Oleic acid) | C18:2n6, C18:3n3 (Linoleic acid),, PUFA |
| Treponema | - | C18:0 (Stearic acid), C18:3n3 (Linoleic acid), C20:4n6 (Arachidonic acid: from marine, at low concentrations, to intense orange-citrus and animal-like odor) |
| Succiniclasticum | C18:1n7 (Vaccenic acid), C18:3n3 (Linoleic acid) | - |
| Desulfovibrio | C18:1n7 (Vaccenic acid) | - |
| Blautia | - | C18:2n6 (Linolelaidic acid) |
| Rhabdanaerobium | - | C18:3n3 (Linoleic acid) |
| Gracilibacter | - | C18:3n3 (Linoleic acid) |
| Butyrivibrio | - | C18:3n3 (Linoleic acid) |
| Paraprevotella | C20:4n6, C22:4n6 | - |
| Intestinimonas | C22:4n6 | - |
This table summarizes the relationship between meat fatty- composition and rumen bacteria at the genus level.
Higher levels of carbohydrates may promote the persistence and flavor formation of Z. rouxii (Zygosaccharomyces, a genus of yeasts in the family Saccharomycetaceae) in the moromi soy sauce, and it changes its aroma profile. Not sure if it is to the better or worse.
3. Acinetobacter is associated with fish odor and the odor of biowaste. It is also associated with odor in MEBO and PATM populations - this is one of not yet published results of our microbiome study (in addition to skin bacteria)
A study to be published in print in the February issue of "Science of The Total Environment", examined odor profiles of cooked and uncooked food waste.
Odor pollution often occurs in the initial decomposition stage of municipal biowaste, including throwing/collection and transportation. However, this aspect of odor impact from municipal biowaste has not been well studied. In Nie and colleagues' experiments, a practical dustbin (120 L) equipped with flux chamber and filled with three types of municipal biowaste was used to simulate garbage storage conditions. The result indicated that the emission rate of odor pollutants for uncooked food waste (UFW) represented a nearly linear growth trend, reaching the maximum (3963 ± 149 μg kg−1 DM h−1) at 72 h. Cooked food waste (CFW) increased rapidly from 8 h to 24 h, and then remain fluctuated, reached the maximum (2026 ± 77 μg kg−1 DM h−1) at 72 h. Comparatively, household kitchen waste (HKW) reached the maximum emission rate (10,396 ± 363 μg kg−1 DM h−1) at 16 h. Sulfide and aldehydes ketones were identified as dominant odor contributor to UFW and CFW, respectively. While aldehydes ketones and sulfides were both dominant odor contributor to HKW. Moreover, the microbial diversity analysis suggests that Acinetobacter was the dominant genus in UFW, and Lactobacillus was the dominant genus in CFW and HKW. In addition, it was evident that each odorous pollutant was significantly associated with two or more bacterial genera, and most bacterial genera such as Acinetobacter, were also significantly associated with multiple odorous pollutants. The variation of odorants composition kept consistent with microbial composition. The present study could provide essential evidence for a comprehensive understanding of odorant generation in the initial decomposition stage of municipal biowaste. It could contribute to setting out strategies for odor control and abatement in municipal biowaste management systems.
The highest emission was observed in household kitchen waste with alcohol esters.
The highest total odor activity values were observed in uncooked food waste.
Lactobacillus was the dominant genus in household kitchen waste and cooked food waste.
Acinetobacter was the dominant genus in uncooked food waste.
The variation of odorants composition kept consistent with microbial composition.
REFERENCES
Lee J, Kim HJ, Lee SS, Kim KW, Kim DK, Lee SH, Lee ED, Choi BH, Barido FH, Jang A. Effects of diet and castration on fatty acid composition and volatile compounds in the meat of Korean native black goats. Anim Biosci. 2023 Jan 11. doi: 10.5713/ab.22.0378. Epub ahead of print. PMID: 36634653. download pdf
Zou S, Ni M, Liu M, Xu Q, Zhou D, Gu Z, Yuan J. Starvation alters gut microbiome and mitigates off-flavors in largemouth bass (Micropterus salmoides). Folia Microbiologica. 2023 Jan 13:1-2.
Lülf RH, Selg-Mann K, Hoffmann T, Zheng T, Schirmer M, Ehrmann MA. Carbohydrate Sources Influence the Microbiota and Flavour Profile of a Lupine-Based Moromi Fermentation. Foods. 2023 Jan 2;12(1):197. doi: 10.3390/foods12010197. PMID: 36613413; PMCID: PMC9818829.
Nie E, Wang W, Duan H, Zhang H, He P, Lü F. Emission of odor pollutants and variation in microbial community during the initial decomposition stage of municipal biowaste. Sci Total Environ. 2023 Feb 25;861:160612. doi: 10.1016/j.scitotenv.2022.160612. Epub 2022 Nov 29. PMID: 36455726.
Shi Q, Tang X, Liu BQ, Liu WH, Li H, Luo YY. Correlation between microbial communities and key odourants in fermented capsicum inoculated with Pediococcus pentosaceus and Cyberlindnera rhodanensis. J Sci Food Agric. 2023 Feb;103(3):1139-1151. doi: 10.1002/jsfa.12321. Epub 2022 Nov 24. PMID: 36349455.
Gabashvili IS Cutaneous Bacteria in the Gut Microbiome as Biomarkers of Systemic Malodor and People Are Allergic to Me (PATM) Conditions: Insights From a Virtually Conducted Clinical Trial JMIR Dermatol 2020;3(1):e10508 doi: 10.2196/10508
Search Odors (cdc.gov) - database of toxic chemicals
