Protein powders mixed with milk do contain more protein than if you were to mix the powder with juice or water. Milk is a rich source of protein, at about 8 g per cup. It may also provide a more satisfying mixture with a creamier texture similar to a milkshake. However, more protein isn’t always a good thing. Too much protein in your diet can lead to increased body fat or strain on your kidneys. Consult your doctor to see if protein supplements can benefit you and to receive dosing instructions.
The two main proteins found in milk are whey and casein. Both proteins contain all of the essential amino acids your body needs. Amino acids are the building blocks of proteins, and essential amino acids are the ones your body can’t produce. Whey is a fast-absorbing protein, while casein absorbs at a much slower rate in your body, but both milk proteins stimulate a boost in blood amino acid levels once ingested.
Liquid sources of protein can add to your daily protein totals without you even realizing it. Consider the recommended dietary allowance, or RDA, of protein for a 150-lb., sedentary individual. According to the University of California-Los Angeles, this person needs 54 g of protein per day. A single protein shake mixed in milk can easily top 30 to 40 g of protein, which is more than half of the RDA for protein. So use caution when mixing protein powders with milk to ensure you don’t exceed your daily need for protein.
Mixing protein powders with milk may affect the absorption rate of the protein supplement. According to Eric Satterwhite of Bodybuilding.com, combining whey protein powder with milk significantly slows the absorption of whey. The milk coagulates in your stomach, causing the whey to stick around longer in your stomach than it would if mixed with water. This can be a good or a bad thing. On one hand, it prolongs the delivery of amino acids into your blood stream, but it also diminishes the main benefit of whey powder, which is fast delivery of amino acids to your muscles.
The main thing to consider when mixing milk and protein powders is to make sure and count the extra grams of protein in your daily totals. If you’re taking protein supplements, you’re most likely trying to lose weight or put on muscle. Too much protein in your diet can hinder both of these fitness goals. Consider mixing with water in certain circumstances and milk in others. For example, when you need amino acids quickly, such as after each workout, mix the supplement with water. If you need to prolong the effects of protein supplements, such as during the night while you sleep, consider mixing the protein supplement with milk to slow its absorption.