Protein powders have become increasingly popular as a convenient way to supplement protein intake, particularly for those aiming to lose weight, build muscle, or enhance athletic performance. While protein is an essential nutrient that supports various bodily functions, including weight management, it's important to understand the potential benefits and side effects associated with protein powder consumption.
The Role of Protein in Weight Loss
Protein plays a crucial role in weight loss due to its impact on metabolism, appetite, and muscle mass.
Increased Satiety and Reduced Appetite
Protein has been shown to help decrease hunger and appetite, primarily because it promotes feelings of fullness for longer periods. This effect is partly attributed to the release of fullness hormones like GLP-1 and PYY. Studies suggest that higher protein intake may lead to reduced hunger throughout the day.
For example, a small 2015 study found that older women who consumed a high-protein breakfast ate up to 135 fewer calories later in the day compared to those who had a low-protein breakfast or skipped breakfast altogether. A 2016 meta-analysis of five studies also linked high protein intake to increased fullness. However, it's important to note that factors such as body weight, eating behavior, and other health issues can influence sensations of fullness.
Research indicates that consuming more than 35 grams of protein at once may be most effective for reducing hunger, decreasing the desire to eat, and promoting greater feelings of fullness. While limited studies have specifically examined protein shakes and appetite, a 2019 study involving young women with obesity found that a whey protein drink actively reduced appetite. Additionally, a 2021 study showed that participants who consumed a high-protein shake before their workout reported feeling less hungry after exercising compared to those who had a lower protein shake with the same number of calories.
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Muscle Building and Metabolism
A high-protein diet, especially when combined with strength training, can help build muscle. Muscle aids metabolism and energy production, making muscle building an effective way to maintain a healthy metabolism.
When following a calorie-restricted diet for weight loss, the body may lose both muscle and fat. This loss of lean muscle can slow down metabolism, making it easier to regain weight after the diet. However, consuming sufficient protein along with strength training can help prevent muscle loss and the resulting metabolic slowdown.
A 13-week study involving older adults with obesity found that those who consumed an extra 20 grams of protein weekly (in the form of a shake) gained 2.8 pounds more muscle mass than those who ate less protein. Furthermore, a 6-week study demonstrated that participants on a higher protein, calorie-restricted diet gained 2.4 pounds more muscle and lost 2.9 pounds more fat compared to those on a low protein diet.
Thermic Effect of Protein
The body uses more energy to digest protein than it does to digest fats or carbohydrates, meaning that it burns more calories in the process. This effect, known as the thermic effect of protein, may provide a slight metabolism boost.
While few studies have specifically focused on protein shakes, researchers generally agree that high-protein diets are an effective way to lose weight and body fat. A 14-week study showed that women with overweight or obesity who followed a resistance exercise program and a high-protein, calorie-restricted diet lost 1.7 times more body fat than those on a high-carbohydrate diet. Similarly, a 12-week study found that women with a moderate weight but high body fat percentage lost an additional 3 pounds of body fat and around 1 inch in waist circumference on a high-protein diet. They also retained significantly more muscle mass than those on a standard protein diet.
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A 2020 review suggests that following a high-protein diet in the first 3-12 months after losing weight can minimize weight regain. However, long-term studies are needed to confirm whether this effect lasts beyond the first year. A small 2017 study found that participants with excess weight who drank low-sugar protein shakes as part of a diet program experienced improved weight loss.
Protein Shakes: A Convenient Protein Source
Protein shakes are a convenient way to add more protein to the diet, especially for those with limited access to high-protein foods or who have trouble meeting their protein needs through food alone. They are made by mixing protein powder with water or another liquid, with the option to add other ingredients.
While most people can meet their daily protein requirements through food sources, protein shakes can be a beneficial supplement. Protein's effects on metabolism, appetite, and muscle mass may also help prevent weight regain after weight loss, whether the protein comes from shakes or whole foods.
One 2015 review suggests that higher protein intakes of 25-30 grams per meal improve both weight loss and weight management. However, researchers emphasize that adherence to a high-protein diet and other lifestyle factors are typically necessary. Studies also suggest that high-protein diets result in less short-term weight regain after significant weight loss, although more studies are needed.
Types of Protein Powder
Different types of protein powders contain different nutrients and may affect the body in distinct ways:
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- Whey protein: Quickly absorbed, dairy-based, and contains all nine essential amino acids.
- Casein protein: Slowly absorbed, dairy-based, and provides all essential amino acids.
- Soy protein: Plant-based and offers all essential amino acids, plus soy isoflavones that may provide some health benefits.
- Hemp protein: Plant-based, contains all essential amino acids, rich in omega-3 and omega-6 fatty acids, and has a high arginine content.
- Rice protein: Plant-based but lower in the essential amino acid lysine.
- Pea protein: Plant-based and less allergenic alternative to soy and whey protein, but lower in the essential amino acids cysteine and methionine.
Certain protein powders and drinks contain a mix of protein types to diversify the amino acid profile. For example, many plant-based brands combine different types of protein. Some dairy-based protein powders combine whey and casein to provide immediate and longer-lasting effects on muscle synthesis.
Which Type of Protein Is Best for Protein Shakes?
The best type of protein for protein shakes depends on individual needs and preferences. Whey protein is typically absorbed more quickly than casein, making it optimal for promoting muscle protein synthesis after exercise and potentially helping to reduce hunger in the short term.
While some small studies have shown whey protein to be more effective for weight loss than soy and other plant-based proteins, others have found no significant difference. Individual lifestyle factors may be more important than the type of protein regarding weight loss or other desired outcomes.
It's important to consider the quality of the protein. Whey, casein, and soy are considered complete proteins, meaning they contain sufficient amounts of all the essential amino acids the body needs. However, these three may cause allergic reactions in some people. Rice and pea protein are often considered less allergenic, although rice protein is low in lysine, and pea protein is low in cysteine and methionine. Hemp protein is also considered less allergenic and contains sufficient levels of all essential amino acids, making it a complete source of protein.
Consuming a variety of protein sources regularly makes it unlikely that opting for incomplete proteins in protein shakes will be a problem. However, it's always best to consult a doctor or registered dietitian before adding new supplements to the diet.
Whole Food Alternatives to Protein Powder
Protein powders aren’t the only way to add protein to shakes. Whole food alternatives include:
- Greek or plant-based yogurt: Greek yogurt is naturally rich in protein, as are plant-based alternatives made from soy. Each provides around 6-10 grams of complete protein per 3.5 ounces (100 grams).
- Nuts and seeds: Most nuts and seeds pack around 5-7 grams of protein per 1 ounce (28 grams). Combine with soy or hemp milk for a complete source of plant-based protein.
- Spirulina: This blue-green algae offers around 8 grams of complete protein per 2 tablespoons (14 grams). This serving also covers 95% of the Daily Value (DV) for copper and 22% of the DV for iron.
- Tofu: This popular soy food contains around 5-13 grams of complete protein per 3.5 ounces (100 grams), depending on the variety. It has a naturally mild flavor, so it can be blended with frozen fruit and liquid to yield a protein-rich shake.
- Puffed quinoa: This pseudocereal provides around 10 grams of complete protein per 2.5 ounces (70 grams). It thickens and adds a slightly nutty flavor to shakes.
- Oats: This grain offers around 5 grams of protein per 1.5 ounces (40 grams). Combine with cow’s milk or hemp milk to get a complete source of protein.
These protein-rich ingredients are easy additions to homemade shakes. Simply combine them with dairy or plant-based milk, fruit, and leafy greens for a nutrient-rich, whole-food alternative to protein powder-based shakes.
Potential Risks and Side Effects
While protein powders can be a convenient way to increase protein intake, it's important to be aware of potential risks and side effects.
Lack of Regulation and Potential Contaminants
The Food and Drug Administration (FDA) doesn’t typically review supplements for safety and effectiveness before they hit the shelves. Therefore, it’s important to research the ingredients in protein powders and the brand’s trustworthiness. When possible, choose a protein that has undergone third-party testing.
A report by the Clean Label Project found that many protein powders contained heavy metals (lead, arsenic, cadmium, and mercury), bisphenol-A (BPA), pesticides, or other contaminants with links to cancer and other health conditions. Some toxins were present in significant quantities.
Digestive Issues
If lactose intolerant, drinking protein shakes made with whey or casein may cause side effects such as bloating, cramps, gas, and diarrhea. Switching to protein powders not derived from dairy, such as those made with protein from eggs, peas, soy, or hemp, can help avoid these symptoms.
Consuming very high doses of whey protein may also cause digestive symptoms, such as cramping or nausea.
Kidney Issues
While most research suggests that high-protein diets are safe, people with underlying kidney issues may need to avoid them. High-protein intake can cause a sudden increase in glomerular filtration rate (GFR) and renal blood flow, potentially accelerating renal function decline in those with preexisting chronic kidney disease (CKD). If you have kidney complications, talk with your doctor before increasing your protein intake.
Other Potential Side Effects
High doses of whey protein can cause side effects such as increased bowel movements, acne, nausea, thirst, bloating, reduced appetite, tiredness, and headache.
Some studies have shown that chronic protein supplementation may increase the expression of anger and acne in athletes. Whey protein containing insulin-like growth factor-1, associated with promoting cell growth and division, sebum production, and increased estrogen factors, could explain the association between high consumption of whey protein products and acne.
Whey protein contains components like beta-lactoglobulin that can cause allergies, particularly in children who are intolerant to cow’s milk. Symptoms of whey protein allergy may include atopic dermatitis, respiratory problems such as asthma and coughing, gastrointestinal discomfort, and even life-threatening anaphylactic reactions in infants.
High-protein diets can significantly influence the composition and function of the microbiota by causing amino acid fermentation in the colon. This fermentation process leads to the production of potentially harmful metabolites, including ammonia, amines, phenols, and sulfides.
Added Sugars and Calories
Some protein powders have little added sugar, while others have a lot (as much as 23 grams per scoop). Some protein powders can turn a glass of milk into a drink with more than 1,200 calories, potentially leading to weight gain and an unhealthy spike in blood sugar.
General Recommendations
Most adults can easily get enough protein through food sources without drinking protein shakes. Aim for the Recommended Dietary Allowance for protein intake: 46 grams per day for women and 56 grams for men.
Protein shakes can be a convenient way to add extra protein to your diet. If trying to lose or manage weight, extra protein from shakes may help you feel less hungry.
When using protein powders, it's important to research the ingredients and the brand's trustworthiness, choose products that have undergone third-party testing, and be mindful of serving sizes and nutrient labels.
It's also important to discuss with your physician before you start taking protein supplements.
Whey Protein: A Closer Look
Whey protein is derived from whey, the watery portion of milk that separates from the curds when making cheese. It is a nutritionally complete protein, containing all essential amino acids.
Types of Whey Protein
Whey protein undergoes further processing to create three main types:
- Whey protein concentrate (WPC): Contains low levels of fat and carbohydrates. The percentage of protein in WPC depends on how concentrated it is, with higher concentrations reaching 89% or more.
- Whey protein isolate (WPI): Further processed to remove all the fat and lactose, typically resulting in a protein content of 90% or greater.
- Whey protein hydrolysate (WPH): Considered the "predigested" form of whey protein, having undergone partial hydrolysis to improve digestibility and reduce allergen potential.
Benefits of Whey Protein
Research suggests that whey protein may have several health benefits, including:
- Muscle growth: Whey protein is a popular supplement for those trying to gain muscle due to its high leucine content, an amino acid that helps build and repair muscle. Using whey protein alongside resistance training can help maximize muscle growth.
- Lowering cholesterol: A 2025 review and meta-analysis found evidence that whey protein may help improve cholesterol levels by reducing triglyceride levels and increasing high-density lipoprotein (HDL).
- Cardiovascular health: Whey proteins and the peptides they contain may have numerous benefits for cardiovascular health, such as lowering blood pressure, reducing inflammation, improving vascular stiffness, and increasing nitric oxide.
- Anticancer effects: Some studies suggest whey protein may have anticancer properties by triggering apoptosis, the death of atypical cells, and helping to reduce muscle atrophy during cancer treatment.
- Nutritional support: Whey protein can be a suitable supplement for individuals who cannot get enough protein from other sources, such as those with low body weights or a loss of appetite.
Potential Side Effects of Whey Protein
While whey protein has several benefits, it also has potential risks and side effects:
- Acne: Whey protein use may cause acne or affect the microbiome.
- Kidney or liver damage: Long-term and excessive use of whey protein may result in kidney or liver damage, particularly when combined with physical inactivity.
- Allergies: Whey protein may be unsuitable for people with milk allergies.
- Lactose intolerance: Some types of whey protein contain lactose, making them unsuitable for people with lactose intolerance.
Dosage
The amount of whey protein people can take to gain muscle depends on their body weight and activity level. A 2019 study suggests that, at rest, a single serving of around 0.24 grams per kilogram (g/kg) of body weight is enough to maximize muscle protein synthesis. For intensive workouts, a single dose of 0.4 g/kg or more may be better.
This is in addition to the daily requirement of protein, which for people building muscle or doing intense physical training is around 1.6 g/kg of body weight daily. Individuals can get this protein from meat, fish, dairy, legumes, soy, or other plant sources as part of their diet.
Protein Supplements and Specific Conditions
Protein supplements are now used in the dietary management of patients with various medical conditions, leading researchers to study their effects on health.
Protein Supplements and Kidney Disease
Dietary protein intake plays a significant role in determining the workload of the kidneys, affecting glomerular filtration. For those suffering from CKD, reducing protein intake can help reduce hyperfiltration and slow the progression of chronic nephropathies.
Supplementation with a high-protein plant-based diet has been observed to decrease mortality in patients suffering from CKD. Plant-based proteins also affect cholesterol metabolism and are associated with a decreased production of uremic toxins.
According to the nutritional guidelines in CKD (K-DOQI 2020), adults with CKD 3-5 (who are not on dialysis) and are metabolically stable are recommended to follow a low-protein diet that provides 0.55 to 0.60 g of dietary protein per kilogram of body weight per day. Alternatively, a very low-protein diet can be followed, providing 0.28 to 0.43 g of dietary protein per kilogram of body weight per day with additional keto acid/amino acid.
Protein Supplements and Cancer
Several studies have shown the potential benefits of protein supplementation in treating cancer-related cachexia, which causes progressive muscle and adipose tissue atrophy. Whey protein, in particular, contains high levels of leucine and other essential amino acids, crucial for muscle protein synthesis and preservation of lean body mass.
Protein Supplements and Immunity
Whey protein is a promising treatment for patients with immunity-related diseases because it can help regulate the immune system by significantly increasing lymphocyte proliferation and human neutrophil responses. Whey protein can modulate the immune system and has antibacterial, antiviral, and antifungal properties.
Protein Supplements and Blood Pressure
Subjects consuming whey protein-based supplements regularly show significantly lower systolic blood pressure, while subjects who consume soy-based protein supplements have been reported to show a significant decrease in their systolic and diastolic blood pressures.
Protein Supplements and Diabetes
Lower postprandial glucose levels have been observed in diabetic subjects, which can be attributed to the lower glycemic index of these supplements. This can lead to an indirect decrease in diabetes-related complications.