Does dark chocolate (epicatechin) boost strength?

Short answer

No. Strength rose more only in one study of 62 people with sarcopenia (age-related muscle loss). In 603 people taking cocoa extract for 2 years, grip strength did not change, and in 20 people doing cycling training, aerobic fitness actually improved less.

Does dark chocolate (epicatechin) boost strength?
'Epicatechin → less muscle-blocking protein → more strength' — does this formula hold?
The claim is that epicatechin, found in dark chocolate, lowers a protein that holds back muscle growth (myostatin) and so raises strength. It is also sold as a supplement. We checked this formula against human studies.
It started with mice and a 7-day test
The blocking protein fell in mice, and grip strength rose in people
When mice were given epicatechin, the protein that blocks muscle growth went down and growth signals went up. When people took it for 7 days, grip strength rose, as did the ratio of a growth-promoting protein to the blocking one in the blood. It was a short test with no exercise.
What about with strength training?
Strength rose more in a study of 62 people with sarcopenia
62 people with sarcopenia (a condition of age-related muscle loss) did strength training for 8 weeks with epicatechin (70 mg a day for a 70 kg person). Their leg press and chest press strength rose more than with training alone. Muscle mass improved in the training-only group as well.
What about people who exercise?
Aerobic fitness actually improved less
20 people did 4 weeks of cycling training while taking 200 mg of epicatechin a day or a placebo. Peak oxygen uptake (aerobic fitness) rose in the placebo group but not in the epicatechin group. The muscle-blocking protein did not change in either group.
Same story with cocoa
Body fat dropped, but performance stayed the same
In a study where people took 5 g of cocoa (425 mg of flavanols) every day for 10 weeks, body fat percentage dropped but exercise performance did not change. A review of 13 cocoa studies also found no boost in performance for people who exercise.
What did a large, long trial show?
603 people, 2 years, no difference in grip strength
603 people took cocoa extract or a placebo for 2 years. There was no difference in grip strength, walking speed, standing up from a chair, or balance.
Pooling strength training + polyphenol trials
No meaningful difference in strength or muscle mass
A 2026 analysis pooled 11 trials (360 people) in which polyphenols such as epicatechin, green tea, and curcumin were taken with strength training. Neither strength nor muscle mass differed meaningfully from training alone.
Summary: no result showed a strength boost
Getting 200 mg from chocolate takes 31-214 g
Strength rose more only in the study of 62 people with sarcopenia; the 603-person, 2-year trial and the 11-trial analysis showed no difference. Flavanols in 12 dark chocolates ranged from 93.5 to 651.1 mg per 100 g, so reaching 200 mg takes 31-214 g.