Right now silk peptides are mainly found in cosmetics, but sooner or later you’ll start coming across them in sports supplements. At least, that’s our prediction. We’ve been reading Asian studies on silk peptides, and we’re impressed: they boost fat burning, oxygen uptake and improve endurance capacity during rest and exertion.
Silk peptides are found in the cocoons of the caterpillar of the Bombyx mori butterfly [see right]. Their amino-acid composition is unique: silk peptides consist mainly of glycine (about 30-45 percent), alanine (30-35 percent) and serine (10-15 percent).
Asians have been eating the proteins from these cocoons, or cut-up versions of them, for centuries, and in South Korea scientists at Konkuk University have been studying whether silk-peptide supplements can improve athletes’ performance. One of their discoveries is that mice swim for longer if they are given silk peptides, and that supplementation prevents their testosterone levels from dropping as a result of the exertion. [Biol Pharm Bull. 2010;33(2):273-8.] In 2013 they published a study in which silk peptides boosted fat burning during periods of rest and during periods of exertion. [J Nutr Sci Vitaminol (Tokyo). 2013;59(3):250-5.]
VO2 max, fat burning
In July 2014 the Koreans published the results of an animal study in which they got mice to run on a treadmill almost every day for two weeks. Half of the mice were given silk peptides daily as well [SP]. The human equivalent of the dose they used would be 5-8 g silk peptides per day.
Supplementation boosted the animals’ oxygen uptake capacity.
In addition, the animals burned more fat during a 60-minute running session after two weeks of supplementation plus training than the mice in the control group did. The figure above shows this. The figure below shows that silk peptides boosted fat burning throughout the whole session.
Although the experiment only lasted two weeks, the supplementation resulted in a ten-percent loss of fat reserves.
“These results suggest that silk peptides intake can improve exercise performance”, the Koreans write. “Therefore, silk peptides are considered to confer beneficial effects upon athletes, in whom an exercise ability and fat loss are required. It will be necessary to clarify the effect of silk peptides on endurance capacity in trained human athletes and also to understand the mechanism that underlies the effect of silk peptides on fat and carbohydrate metabolism-related gene expression in the skeletal muscles in future studies.”
Silk peptide treatment can improve the exercise performance of mice
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We previously reported that silk peptide (SP) treatment led to increased resting fat oxidation in exercised mice. However, it was not known whether SP treatment could effectively increase exercise capacity. Accordingly, this study aimed to examine whether SP treatment affected energy metabolism during exercise in addition to exercise performance.
We randomized 36 7-week-old male ICR mice into 2 groups: the control (n?=?18) and SP (n?=?18) groups. All mice were trained by treadmill running 5 times per week for 2 weeks. SP was dissolved in distilled water and daily 800-mg/kg body weight doses before the running exercise were oral administered intraperitoneally to the SP group for 2 weeks. V?O2max was measured before and after the 2 weeks training period. We also assessed energy metabolism during exercise for 1 h after the 2 week training period. In addition to blood samples, liver glycogen and gastrocnemius-white and gastrocnemius-red muscle was obtained at the following 3 time points: at rest, immediately after exercise, and 1-hour post exercise.
The V?O2 max after 2 weeks of training was significantly increased (8%) in the SP group compared to the baseline; a similar result was not observed in the CON group. The sum of fat oxidation during a 1-h period tended to be 13% higher in the SP group than in the CON group (P?< ?0.077). In particular, the sum of fat oxidation was significantly higher in the SP group during the initial 20-min phase than that in the CON group (P?0.05). The glycogen concentration in the white gastrocnemius muscle did not differ between the groups either rest or after 1 h of exercise but was significantly higher in the SP group than in the CON group during the recovery period (1 h post-exercise completion).
These results suggest that SP treatment can improve the exercise performance. Therefore, SP is considered to confer beneficial effects upon athletes, in whom exercise abilities are required.