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[Definitie:] "An ergogenic aid is any substance or phenomenon that enhances performance."
(Wilmore and Costill) 
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2 2 - 1 1 - 2 0 0 4 Increased aggressive behavior and decreased affiliative behavior in adult male monkeys after long-term consumption of diets rich in soy protein and isoflavones
Horm Behav. 2004 Apr;45(4):278-84
We studied the effects of long-term (15 months) consumption of diets rich in soy isoflavones on spontaneous social behavior among adult male cynomolgus macaques (Macaca fascicularis) (n = 44) living in nine stable social groups.
There were three experimental conditions which differed only by the source of dietary protein: casein and lactalbumin (no isoflavones), soy protein isolate containing 0.94 mg isoflavones/g protein, and soy protein isolate containing 1.88 mg isoflavones/g protein.
In the monkeys fed the higher amount of isoflavones, frequencies of intense aggressive (67% higher) and submissive (203% higher) behavior were elevated relative to monkeys fed the control diet (P's < 0.05).
Fig. 1. Frequencies (mean F SEM) of episodes of intense aggression and submission among male cynomolgus monkeys fed an isoflavone-free casein and lactalbumin-based diet (C/L) (n = 14), a diet based in soy protein isolate containing 0.94 mg/g of isoflavone (Lo Iso) (n = 15), and a diet based in soy protein isolate containing 1.88 mg/g isoflavone (Hi Iso) (n = 15). *P < 0.05 relative to C/L group.
Fig. 2. Frequencies (mean F SEM) of episodes of mild aggression and submission among male cynomolgus monkeys fed an isoflavone-free casein and lactalbumin-based diet (C/L) (n = 14), a diet based in soy protein isolate containing 0.94 mg/g of isoflavone (Lo Iso) (n = 15) and a diet based in soy protein isolate containing 1.88 mg/g isoflavone (Hi Iso) (n = 15). Although there was a tendency toward a main effect of treatment on mild submission ( P < 0.07), differences among groups were not significant statistically.
In addition, the proportion of time spent by these monkeys in physical contact with other monkeys was reduced by 68%, time spent in proximity to other monkeys was reduced 50%, and time spent alone was increased 30% (P's < 0.02).
Fig. 3. Percentage of time spent (mean F SEM) close to another monkey, in body contact with another monkey and alone among male cynomolgus monkeys fed an isoflavone-free casein and lactalbumin-based diet (C/L) (n = 14), a diet based in soy protein isolate containing 0.94 mg/g of isoflavone (Lo Iso) (n = 15), and a diet based in soy protein isolate containing 1.88 mg/g isoflavone (Hi Iso) (n = 15). *P < 0.02 relative to C/L group.
There were no effects of treatment on serum testosterone or estradiol concentrations or the response of plasma testosterone to exogenous gonadotropin-releasing hormone (GnRH).
[Ahum. Als je de tabellen uit het artikel erbij pakt, dan zie je toch iets anders. De veranderingen vanaf baseline zijn dan wel niet significant, maar wel interessant.] [Tabel]
Discussion [De onderzoekers speculeren dat de fyto-oestrogenen in soja koppelen aan de b-receptor voor estradiol. Daar werken ze als een zwak oestrogeen, en verhinderen ze dat het echte estradiol een koppeling aangaat met de receptor. Daardoor komt het signaal van de a-receptor krachtiger door - en dat veroorzaakt de agressie. Dat lijkt niet te sporen met fundamenteel onderzoek.] [ErGs]
[Een andere theorie:] The third potential mechanism for contributions of phytoestrogen– ERh complexes to the increased agonistic behavior involves effects in target cells that express only ERh. The modulation of serotonergic tone in the rhesus monkey provides an example of this hypothesized process. In nonhuman primates, only ERb are found in 5-HT neurons (Bethea et al., 2002b; Gundlah et al., 2001). Estradiol normally acts in these cells to enhance serotonergic tone by increasing tryptophan hydroxylase synthesis and decreasing 5-HT transporter expression (Lu and Bethea, 2002; Lu et al., 2003). The level of isoflavones from the high-dose diet could result in competition for ERb binding. Because genistein, daidzein, and equol are weaker agonists and exhibit reduced transactivation effects compared to estradiol (An et al., 2001; Jefferson et al., 2002; Yi et al., 2002), a consequence of the high-isoflavone diet would be reduced serotonergic function, which is associated with increased agonistic behavior in mammals from rodents to humans (Simon, 2002).
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