Somatotropin is a peptide hormone that is secreted in the anterior pituitary gland. STH helps to establish a positive balance of protein metabolism in the skeletal muscles by stimulating synthesis and presumably suppressing protein breakdown. These results are somewhat contradictory, since it is difficult to separate the effects of stimulating IGF-I production in the liver and skeletal muscles. How food we eat and diet we have influences the growth hormone production?
STH stimulates lipolysis in adipose tissue cells; in this regard, the C-terminal fragment of STH is of particular interest, which has pronounced lipolytic and anti-lipogenic activity in vitro and when administered to animals. Somatotropic hormone significantly reduces the effectiveness of lipogenesis along with a parallel increase in muscle mass, which indicates a powerful effect on the redistribution of nutrients in the body.
Changes due to food intake
Changes in STH caused by food intake can be quite diverse, which to some extent can be explained by the periodic nature of somatotropin secretion. Studies have shown that proteins, fats, and carbohydrates have an independent effect on the regulation of STH secretion.
Consumption of carbohydrates (0.7g per kg per hour) in pure form or in combination with proteins (0.35g per kg per hour) leads to a reduction in GH levels for up to two hours. The oral glucose tolerance test (75g of glucose) results in a slight gradual decrease in the GH level for about two hours, followed by a marked increase in its concentration in the blood, which peaks at the 240th minute.
Thus, hyperglycemia is associated with a decrease in STH, followed by hypoglycemia and subsequent increase in STH. These data are consistent with the results of work where hypoglycemia has been shown to be a powerful STH stimulant. Thus, when exposed to carbohydrates, their intake leads to GH reduction after a meal and its increase after some time.
Injections and, in some cases, oral administration of certain amino acids, namely arginine, lysine and ornithine, can increase the level of STH. This effect is characterized by a high variability of the response, which is suppressed during workouts or in the case of a protein-rich diet.
The growth hormone level increases after consumption of beef chop, presumably due to the significant content of amino acids, however, such an increase is prevented by injection of heparin, which stimulates an increase in the level of free fatty acids in the blood. The discovered inhibitory effect of free fatty acids is confirmed by the results of another study, which revealed suppression of the GH secretion by free fatty acids, but not by triglycerides circulating in the blood.
The dynamics of groцер hormone changes due to food intake are not fully understood. The intake of a liquid energy supplement (520kcal) rich in fats or carbohydrates does not affect the GH level measured 35 minutes after that, and the intake of food containing proteins and carbohydrates (216 kcal) does not change the level of STH measured after 90 min.
Alcohol consumption (0.45g of ethanol per 1 kg of body weight) every hour for three hours had no effect on the level of GH compared to water.
Growth hormone and diet: changes caused by food intake when exposed to physical activity
Consumption of carbohydrates and proteins affects changes in growth hormone levels induced by exercise. The use of protein and carbohydrate supplements immediately or 2 hours after weight training increased the level of STH in the later stages of the recovery period, while the glucose level was lower than after taking a placebo, which is consistent with the known effect of hypoglycemia on STH.
Taking protein and carbohydrate supplements before and after weight training sessions led to an increased acute STH response in the period 0-30 minutes after the session compared to a non-calorie placebo, despite the absence of differences in glucose levels in the experimental and control groups. Another study showed that taking protein- and carbohydrate-rich supplements had no effect on changes in STH after weight training.
Diet also affects changes in the STH level when performing exercises and workouts with submaximal loads. The effects of physical activity, fasting, and intake of isoenergetic foods rich in fats (71%) and carbohydrates (86%) were compaired with changes in STH levels 4 hours before exercise on a bicycle ergometer lasting 90 minutes. Changes in GH levels during fasting and intake of carbohydrate foods were the same and significantly higher than when taking fatty foods.
In accordance with the peculiarities of the glucose and fatty acids influence on the level of STH secretion, after eating a diet rich in fats, a lower level of the hormone during exercise correlated with a higher level of glucose and fatty acids in the blood.
The scientists also conducted a comparative analysis of the effect of isoenergetic (520 kcal) drinks consumption with a high content of fats or carbohydrates 45 minutes before intensive sports for 10 minutes on changes in STH levels after exercise.
After eating a meal rich in fats, an increase in the level of somatostatin was observed, which indicates a possible relationship between the fat content in food, the level of somatostatin and somatotropic hormone.
In addition, somatostatin lowers the level of ghrelin, a peptide that is produced primarily in the stomach and has a powerful stimulating effect on the secretion of STH. This allows us to conclude that there is an alternative mechanism for reducing GH levels under the influence of fats rich in food.
The fact that eating fat-rich foods reduces STH more than carbohydrate-rich foods is somewhat contrary to common sense, since carbohydrate intake will be accompanied by an increase in glucose levels, which in turn will inhibit the secretion of STH.
The consumption of carbohydrate drinks before, during and after training leads to an increase in blood glucose and a decrease in the level of STH changes induced by physical activity. Consumption of a carbohydrate drink during exercise on a bicycle ergometer lasting 2 hours weakens STH changes after exercise compared to consumption of skim milk and non-nutritive placebo, despite the absence of differences in blood glucose in all three cases.
These data indicate that STH changes under the influence of physical activity are not mediated by glucose, but by other factors. Studies have also shown that carbohydrate intake before or during exercise on a 2-hour exercise bike or rowing does not affect STH levels, despite differences in glucose levels.
In one of these studies, nicotinic acid, a lipolysis inhibitor, was included in energy drinks. Consumption of nicotinic acid with water or in combination with carbohydrates prevents an increase in the content of fatty acids in the blood and leads to an increase in the level of GH compared with water or a carbohydrate drink without nicotinic acid. Thus, changes in GH induced by physical activity to a certain extent depend on the level of glucose and the content of fatty acids in the blood.
An increase in the GH level induced by physical activity, in the case of a fat rich diet or fasting, is accompanied by a more rapid decrease in insulin levels and plasma glucose concentration during exercise. This indicates the possible participation of glucose-sensitive receptors in the regulation of STH changes due to physical activity.
Glucose injection at the end of the session does not particularly affect the change in the growth hormone level that occurs with a meal rich in fats, which also indicates the possible participation of other substrates (e.g. glycogen, ketones, fatty acids) or hormones (e.g. insulin or catecholamines) in the regulation of secretion of STH. That was the minimum you should know about growth hormone and diet.