Diet & Fitness

Adding protein to carbohydrate intake immediately after exercise may be helpful for improving recovery of glycogen (carbohydrate) stores after exercise, according to some,^1,2,3 though not all,^4,5,6,7,8 controlled studies. Preliminary studies have suggested that protein supplements may have biological effects that could improve muscle growth resulting from strength training, especially if liquid supplements (typically containing at least 10 grams of protein in addition to varying amounts of carbohydrate) are taken immediately after exercise.^9,10,11 However, controlled studies have found no advantage of protein supplementation (up to about 100 grams per day or about 14 grams immediately following exercise) for improving strength or body composition as long as the diet already supplies typical amounts of protein and calories.^12,13,14 In one preliminary study, elderly men participating in a 12-week strength training program took a liquid supplement containing 10 grams of protein (part of which was soy protein), 7 grams of carbohydrate and 3 grams of fat either immediately following exercise or two hours later.¹⁵ Men taking the supplement immediately following exercise experienced significantly greater gains in muscle growth and lean body mass than those supplementing two hours later, but strength gains were no different between the two groups. A controlled study of female gymnasts found that adding 0.45 grams of soy protein to a diet that was adequate in protein during an 8-week training program did not improve lean body mass compared to a placebo.¹⁶ No research has compared different sources of protein to see whether one source, such as soy protein, has a better or more consistent effect on exercise recovery or the results of strength training.