The Effect of Meat Consumption on Body Odor Attractiveness
 Abstract
 
 Axillary body odor is individually specific and potentially a rich source of information about its producer. Odor individuality partly results from genetic individuality, but the influence of ecological factors such as eating habits are another main source of odor variability. However, we know very little about how particular dietary components shape our body odor. Here we tested the effect of red meat consumption on body odor attractiveness. We used a balanced within-subject experimental design. Seventeen male odor donors were on “meat” or “nonmeat” diet for 2 weeks wearing axillary pads to collect body odor during the final 24 h of the diet. Fresh odor samples were assessed for their pleasantness, attractiveness, masculinity, and intensity by 30 women not using hormonal contraceptives. We repeated the same procedure a month later with the same odor donors, each on the opposite diet than before. Results of repeated measures analysis of variance showed that the odor of donors when on the nonmeat diet was judged as significantly more attractive, more pleasant, and less intense. This suggests that red meat consumption has a negative impact on perceived body odor hedonicity.
 
 
 Human body odor is individually specific, similar to our appearance. Odor individuality is established very early in life as was clearly shown by Porter’s team and other researchers (for review, see Winberg and Porter 1998). Newborn babies are able to distinguish their mothers’ breast and axillary odor within several weeks after delivery (Russell 1976; Cernoch and Porter 1985). Simultaneously, mothers can recognize the odor of their offspring 2 days after delivery (Porter et al. 1983). Fathers can also distinguish their own baby’s smell from the smell of a strange baby when babies are aged 3 weeks (Porter et al. 1986). Individual odor recognition is not restricted to early parent–offspring relationships, occurring also in adulthood in sibling recognition for instance (Porter and Moore 1981). In addition, body odor plays a significant role in mate choice (Herz and Cahill 1997; Herz and Inzlicht 2002) and in sexual partners’ recognition once the relationship is established (Hold and Schleidt 1977). Based on all the above-mentioned empirical findings, body odor emitted by a specific individual was therefore labeled an “odor signature” (Porter et al. 1985).
 The odor signature is to some extent genetically inherited. This view is supported by 3 lines of evidence. First, odors of parents and offspring can be correctly matched by subjects not acquainted to odor donors (Porter et al. 1985). On the other hand, the raters were not able to match odors of spouses, who are not genetically related. This result also excluded the possibility that matching of parents and offspring was due to shared home odor. Second, odors of monozygotic twins are more difficult to distinguish than dizygotic twins (Wallace 1977), and monozygotic twins are matched at rates better than chance, even when they live apart (Roberts et al. 2005). Third, odor preferences are correlated with genes in the major histocompatibility complex (MHC). Products of MHC genes are crucial elements of the immune system, particularly in self/nonself recognition. It was found that women rate the odor of MHC dissimilar men as most attractive (Wedekind et al. 1995; Wedekind and Füri 1997). Such preference may potentially result in more MHC heterozygous, and therefore also more viable, offspring (Penn 2002).
 However, not only is body odor preprogrammed by genetic factors but also much variability is due to psychophysiological and ecological influences. For instance, it has been shown repeatedly that body odor changes across women’s menstrual cycle, peaking in attractiveness around the time of ovulation (Thornhill et al. 2003; Kuukasjärvi et al. 2004; Havlicek et al. 2006). Other studies found that mood (e.g., fear) of a target person may influence hedonic perception of his/her axillary odor (Chen and Haviland-Jones 2000; Ackerl et al. 2002). Eating habits also may have a crucial impact on body odor composition. However, very little is known about the effect of individual alimentary components on human body odor. Some folk beliefs connect odor hedonicity with meat consumption. For instance, Hindu Indians who are usually vegetarian say that people who eat meat smell bad because of it (S Komarek, personal communication). To our knowledge, however, this effect has not yet been tested under controlled conditions.
 The aim of this study was to test the effect of red meat consumption on axillary odor hedonicity. For this purpose, we used a balanced within-subject design with a relatively long period (2 weeks) of diet control. The results may improve our rather poor understanding of how axillary odor is determined and also may be of methodological importance for dietary control in olfactory studies.
 
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 -n&m