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Whey protein, one of the main proteins found in milk, may modestly lower blood pressure, according to a small study in the December 2016 American Journal of Clinical Nutrition.
Whey is the liquid that's left over after milk is curdled and strained to make cheese. Evaporating this liquid creates whey protein powder, a supplement popular among athletes and bodybuilders for building muscle mass (despite insufficient evidence for this claim).
For the study, researchers recruited 42 volunteers with slightly elevated blood pressure. The participants drank two shakes a day that contained whey, casein (another milk protein), or maltodextrin (a carbohydrate that served as a control). They all consumed each of the three supplements for eight weeks each, in random order. Thirty-eight people completed the entire study.
Consuming 56 grams per day of whey protein led to about a 3-point drop in systolic blood pressure (the first number in a blood pressure reading) and a 2-point drop in diastolic blood pressure (the second number) compared with the control. Both whey and casein also led to better blood vessel function as well as small improvements in blood cholesterol levels.