Higher Carb To Protein Ratio Results In Higher Testosterone And Lower Cortisol In Men (1987)

[Comstock]

https://www.researchgate.net/public...and_their_respective_binding_globulins_in_man

The aim of this study was to determine if a change in protein/carbohydrate ratio influences plasma steroid hormone concentrations. There is little information about the effects of specific dietary components on steroid hormone metabolism in humans. Testosterone concentrations in seven normal men were consistently higher after ten days on a high carbohydrate diet (468 +/- 34 ng/dl, mean +/- S.E.) than during a high protein diet (371 +/- 23 ng/dl, p less than 0.05) and were accompanied by parallel changes in sex hormone binding globulin (32.5 +/- 2.8 nmol/l vs. 23.4 +/- 1.6 nmol/l respectively, p less than 0.01). By contrast, cortisol concentrations were consistently lower during the high carbohydrate diet than during the high protein diet (7.74 +/- 0.71 micrograms/dl vs. 10.6 +/- 0.4 micrograms/dl respectively, p less than 0.05), and there were parallel changes in corticosteroid binding globulin concentrations (635 +/- 60 nmol/l vs. 754 +/- 31 nmol/l respectively, p less than 0.05). The diets were equal in total calories and fat. These consistent and reciprocal changes suggest that the ratio of protein to carbohydrate in the human diet is an important regulatory factor for steroid hormone plasma levels and for liver-derived hormone binding proteins.

 

[orewashin]

IIRC, high protein diets reduce blood testosterone because they increase its uptake into tissues and binding to androgen receptors.

If the men on the high-protein diet had hypoglycemia, testosterone production may have been inhibited due to a stress response. It would have been useful to know their blood sugar and LH levels.

 

[julcreutz]

I mean, 44% energy from protein is really high.. I wonder what would happen at like 20-30 vs 10

 

[reality]

I think excess protein stimulates cortisol as it gets converted to carbs (gluconeogenesis)

 

[BearWithMe]

I can't find the paper right now but I remember a Russian study, where increasing protein intake up to 40% led to increased muscle mass compared to 30, 20 and 10% protein intake. If high protein would increase cortisol and lower testosterone, this would not be possible.

 

[BearWithMe]

From the study linked by OP:
"The first diet contained foods rich in protein, such as meat, fish, poultry, egg white, and a liquid dietary supplement (Sustacal, Mead Johnson and Company, Evansville, IN); in this diet 44% of total calories were protein, 35% were carbohydrate, and 21% were fat. The second diet contained carbohydrate-rich foods such as bread, vegetables, fruit, juices, pastry, and candy~ in this diet 10% of total calories were protein, 70% were carbohydrate, and 20% were fat."

It might have been something else in the high carb diet that caused the testosterone increase in the low protein group. Maybe they got more of some vitamin/mineral from the fruits/juices? Maybe they got more sugar, while the high protein group was getting just complex carbs? I would be really curious what kind of carbohydrates were served to the high protein group.