Middle-aged men doing strength training don't change their protein intake whether they take collagen, whey, or a placebo.

For middle-aged men doing strength training, whey protein and this collagen supplement have similar effects on muscle gain and fat loss.

For young guys lifting weights, eating 1.8 grams of protein per kilo of body weight each day is enough to gain muscle and get stronger in 10 weeks — it doesn’t matter if they take a 35g casein protein shake during the day or before bed.

If guys who already lift weights drink a 20g protein shake after working out for 9 weeks, they’ll gain more muscle and get stronger—even if the protein is a mix of fast- and slow-digesting types.

If you're a young man who already lifts weights and eats enough protein, doing strength training twice a week for 12 weeks will make you stronger and build more muscle — and taking leucine supplements won't make any extra difference compared to taking a sugar pill.

If young adults who aren't used to working out eat a bit more protein—especially from whey or soy—and lift weights 3 times a week for 3 months, they’ll likely gain more muscle and get stronger, even if they weren’t eating enough protein to start with.