Is Whey Protein Safe or Dangerous? (8 Side Effects)

Is Whey Protein Safe or Dangerous? (8 Side Effects)

Millions of people take whey protein supplements to support active lifestyles, get more out of their workouts, and build more muscle and strength. But is whey protein safe or is it dangerous?

8 Potential Side Effects of Whey Protein

  1. Affects Blood Sugar
  2. Causes Digestive Issues
  3. Leads to Kidney Problems
  4. Causes Liver Problems
  5. Causes Osteoporosis
  6. Protein Spiking
  7. Potential Allergies
  8. Leads to Weight Gain

Like many other supplements on the market, people sometimes hear rumors that protein supplements—and whey protein in particular—can have adverse effects or negatively impact health in the long-run. So, just how safe are protein supplements, and is whey protein bad for you?

Is Whey Protein Safe?

It’s true that whey protein can be bad for you. However, it’s only bad in certain situations. These situations include: 

Over-consumption: This is the main reason why people end up suffering side effects from whey protein. Excessive consumption of any type of protein is bad for your body, and this is the case for any nutrient; you don’t want to eat too much of anything.

If you consume an overabundant amount of protein, not only will your body store this protein as fat but you will also increase your risk of becoming dehydrated. 

Negative reactions to certain medications: Whey protein in particular reduces the effectiveness of Levodopa. This drug is used by people who have Parkinson’s disease.

Whey protein also reduces the effectiveness of Alendronate, which is used by patients who have osteoporosis, as well as Quinolone and Tetracycline, which are antibiotics, and decreases the body’s ability to absorb these medications. 

People who have diabetes may also experience changes to their blood sugar when they consume protein supplements. 

To make sure that whey protein supplements are consumed safely, experts generally recommend that you begin with a moderate dosage for a short period of time, and take note of how whey protein impacts your body before continuing or increasing your dosage.

People who have medical problems or are on medications should take special care and need to check in with their doctors before they consume supplements. 

It is also recommended that only people who are physically active take whey protein supplements. If you are not active, the chance of experiencing an adverse reaction is higher.

Athletes, fitness enthusiasts, and those who workout regularly also require a higher protein intake and tend to benefit most from supplements than other people. 

Safe Dosages and Protein Intake

The recommend dosage for whey protein is one to two scoops (about 25-50 grams) each day. The best time to take whey protein is after you’re done working out, and it’s ideal to follow the serving instructions provided by the package or company website of the supplement product you’re using.

Generally speaking, whey protein has a great safety profile and most people can consume this supplement without any problem, as long as you stick to the recommended dosage and follow the provided instructions. 

The two main side effects that are rumored to be caused by whey protein are kidney damage and contribution to or worsening of osteoporosis. As a matter of fact, research conducted at the University of Connecticut shows that protein actually protects against osteoporosis, and it has no impact on kidneys that are healthy.

Whey protein only has an adverse impact on those who already have liver or kidney issues, and these people should consult with a medical professional before taking any supplements. 

If you consume too much protein, this can lead to digestive issues including cramping, pain, diarrhea, excessive flatulence, and nausea. Some people are also allergic to whey. If you’re allergic or find you have unfortunate digestive reactions to whey protein concentrate, the most common and regular alternative is hydrolysate or isolate proteins.

Whey Protein Quality Issues

As you browse various whey protein supplements, there are a lot of terms and descriptions that may be confusing. Modern marketing can also be very tempting and misleading.

For example, you should carefully consider the serving size advertised on your protein supplement packaging. In the United States, companies aren’t required to disclose exactly how much protein you get for every 100 grams of protein.

Instead, companies often list how much protein there is “per serving.” Two different products can offer 24 grams of protein per serving—but one contains 80% protein because its serving size is 30 grams, while the other has just 69% protein because its serving size is 35 grams. 

If you’ve been consuming the same product for a while, you should check these serving sizes again. It’s common for protein powders to begin as quality products that are eventually replaced by an inferior version over time.

Companies take advantage of the fact that people are often loyal to a product and stop paying attention to the products ingredients. These companies often lack transparency about their changes and don’t provide warnings or changes to their packaging.

For example, your favorite supplement might contain 80% protein, but a few months later, the amount of protein goes down to 70%. This is due to companies changing either the quality of the protein or the ratio of their proprietary blend. 

Advertising that the product is a “proprietary protein blend” can be a trap for consumers as well. Companies attempt to distinguish between proprietary blends or “low-quality whey protein concentrate.”

To decide what’s best for you, however, ignore this and look at the food label. An isolate whey protein product should contain about 90% protein, and concentrates about 80%. Any discrepancy from this should turn you away—no matter how good the proprietary blend appears to be on the surface.

Whey Protein Spiking

Many manufacturers resort to protein spiking. This trick takes advantage of the way protein content is measured by the FDA (as this test measures nitrogen content within protein powder).

While this works in theory because protein should be the only ingredient that supplies this nitrogen, there are cheap nitrogen fillers available that some companies fill their powders with instead.

These fillers include creatine and individual amino acids. Although creatine doesn’t contain any actual protein, it will still register with twice as much protein during the FDA test.

Some companies also use key words such as “organic” or “grass-fed” to market their products and drive up the price. It’s good to know that an organic certification has no impact whatsoever on the composition of whey protein.

There is also not much difference between whey protein that’s sourced from the milk of cows that are conventionally raised, and whey protein that’s sourced from cows that are grass-fed or pasteurized. In the end, there may be no difference between more expensive, organic and grass-fed products and normal, cheaper whey protein products.. 

Whey Protein Contamination

Even well-intentioned and highly established companies can have their protein supplements affected by contaminants, which include plastic derivatives and heavy metals that make their way into products through manufacturing practices and ingredient sourcing.

Unfortunately, contaminants are fairly common because companies aren’t required to test for these. Testing is often expensive and there isn’t a high return on investment for companies when they do test. This, in itself, stops a lot of companies from testing their own supplements. 


If your whey protein product contains preservatives, this is a red flag. Protein powder is preserved through a drying process and since whey protein is dehydrated, this naturally prevents microbial growth. Any additional preservatives should be unnecessary. 


Anti-caking agents are well documented regarding their impact on the body and what happens after ingestion. At small doses, anti-caking agents do not pose a health concern. While they may sound unnatural, they are safe in small quantities.


These thickeners include starches and gum. Starches that are included in whey protein are often in low enough quantity that they don’t make much of a nutritional impact beyond adding another couple of grams of carbs in each serving.

Gums also don’t pose a health concern as the dose in protein powders is too small to have a noticeable effect. In general, thickeners are safe, except for carrageenan—which research claims may cause cancer and has a negative effect on gut health. Avoid products that contain carrageenan; otherwise, you’re safe when it comes to thickeners. 

Artificial Sweeteners

These are synthetic sugar substitutes that are free of calories and taste sweeter than regular sugar. There are six artificial sweeteners that are approved by the FDA: sucralose, saccharin, neotame, aspartame, advantame, and acesulfame potassium. In reasonable doses, these sweeteners are not harmful and won’t promote glucose intolerance or weight gain.


These are sugar alcohols, and are another class of sweeteners. The six polyols that are most commonly used as sweeteners are xylitol, sorbitol, mannitol, malitol, lacitol, and erythritol.

These polyols are 30-100% sweeter than regular sugar, lower in kilocalories, and have less of an impact on blood sugar. Thousands of products use these and you’ll commonly find these polyols in whey protein, however, if consumed in excess, polyols can cause diarrhea and bloating.

Artificial Colorants

Colorants are often used to change the color of a food product. Natural colorants are nothing to worry about. However, artificial coloring has been shown to have some links to allergies, behavioral alterations, genotoxicity, and cancer.

While the research so far has been inconclusive, many people are taking heed and avoiding products that contain artificial coloring, just to be safe. Conducting research to see whether a company’s whey protein products have been tested by third parties can be worthwhile.

Third party companies often test dietary supplements to ensure composition, potency, purity, and quality are all safe and there are no unwanted ingredients such as contaminants or artificial colorants.

Generally, it’s a good idea to do a little research before you purchase a product. For example, you should start by investing in whey protein supplements that are tested by third parties such as:  

  • ConsumerLab (products will display the CL seal)
  • NSF International (the NSF mark) 
  • The United States Pharmacopeia (USP Verified mark)
  • The International Society for Pharmaceutical Engineering, which checks for compliance to Good Manufacturing Practices (GMP)

You can also check to see whether the manufacturer has been given warning letters from the FDA. 

No Supplement Regulation

As protein powders fall under the category of dietary supplements, there is no FDA regulation (meaning that manufacturers are responsible for evaluating safety and labeling products on their own).

As such, the label may say one thing while the product is entirely different. Ultimately, there’s no way of knowing if the product is actually what the manufacturer claims it to be.

The ingredient list of many protein supplements is an entirely different story. While some supplements have a relatively short ingredient list, others do not.

Added Sugars and Toxins

Many protein powders contain large amounts of added sugars, additives, preservatives, artificial flavoring, and the like. Calories, on the other hand, also span quite a range. Some can be minimal with around 100-120 calories per scoop, while others can be more than 1,000 calories. 

Why does this matter? Excess sugar and excess calories equal weight gain and blood sugar destabilization, which have an exhaustive list of health risks associated with each.

According to the American Heart Association, women should limit their sugar intake to no more than 100 calories (25 grams) per day and men to no more than 150 calories (38 grams) per day.

A nonprofit group called the Clean Label Project released a report on toxins in protein powders stating that many powders contain heavy metals (lead, cadmium, arsenic, and mercury), BPA, pesticides, and other contaminants that have been linked to cancer development and other chronic health conditions.

For example, one sample tested contained 25 times the limit of BPA—an endocrine disruptor that’s been shown to cause fertility problems, male impotence, heart disease, and other conditions. 

While not all protein powders contain toxins and contaminants, it’s important to understand what’s going into your supplements. For more information, check out the Clean Label Project’s website and see if your protein powder is on the list. 

Digestive Issues

Digestive issues are becoming one of the most common health issues around, so it’s no surprise that most whey proteins side effects are related to digestion.

Upon consumption, many people experience nasty side effects that include bloating, gas, stomach cramps, and diarrhea. These symptoms usually result from lactose intolerance—a condition where the body does not produce the enzyme needed to digest the sugar lactose.

Did you know that lactose intolerance affects up to 75% of the population? So if you experience these problems after consuming dairy, you’re not alone.

If your body doesn’t digest lactose well, whey isolate may be something to consider as opposed to whey concentrate. Isolates undergo much more processing than concentrates do, leaving a more pure product with less fat, carbs, and lactose.

For the most part, people who are sensitive to lactose will feel better when consuming isolates. Alternatively, if whey-based protein powders are not being digested properly, non-dairy based powders are another great option.

Protein supplements that include egg white protein, beef protein, or vegan blends like hemp, pea, and rice offer high nutrient value without all the unpleasant side effects associated with lactose intolerance.

Intestinal Disturbances

If you’ve recently upped your protein intake without changing anything else in your diet, you may find that you become a little backed up. For some, constipation can also result from lactose intolerance by slowing down the movement of the gut and GI tract.

This isn’t a direct result of consuming more protein, but rather a decrease in fibre intake. People who follow a high protein diet often skimp on other areas in favour of consuming more protein, like fruits and vegetables—some of the best sources of fibre. 

Fibre is crucial in the diet. Not only does it help to feed good bacteria in the gut and intestinal tract, but it helps to form stool and promote regular bowel movements.

If you suspect whey protein is causing constipation, increase your intake of fibre rich fruit and vegetables, or add in a soluble fibre supplement. Alternatively, a probiotic supplement will help to balance out GI tract bacteria and also promote healthy bowel function.


One of the important considerations when choosing a protein powder is to avoid products that trigger an allergic reaction. Dairy allergies, as we mentioned above with lactose, are becoming much more common, so consuming dairy-based protein powders may not be ideal or feasible for some people.

The vast majority of individuals who struggle with dairy will outgrow the intolerance by the age of three, however, there are some individuals who remain sensitive to dairy products throughout their life.

Symptoms of a dairy allergy may include rashes, hives, swelling of the face, swelling of the throat and/or tongue, and a runny or stuffy nose. In rare cases, dairy may trigger an anaphylactic reaction, but these occurrences are rare. 

It’s important to note the difference between a dairy allergy and lactose intolerance. Allergies are triggered when the body produces an immune response to a specific protein, whereby intolerances are caused by an enzyme deficiency; there is no involvement in the immune system in an intolerance. 

Whey Protein and Kidney Damage 

One of the biggest myths out there is that increasing protein intake taxes the kidneys and contributes to the development of kidney disease. While increasing protein intake does burden the kidneys slightly with respect to increasing filtration rates, it’s doesn’t cause damage to your kidneys.

As protein intake increases, increasing amounts of urea and nitrogen excretion causes glomerular filtration rates (GFR) to increase (GFR is a measure of how well the kidneys are filtering blood and removing waste).

Despite an extensive amount of debate on whether high protein diets contribute to kidney disease, there is no evidence to suggest high protein diets are harmful in healthy individuals.

In a meta-analysis of 74 studies on protein and the kidneys, research concluded that there is no need for healthy individuals to restrict protein intake. However, there is research showing that individuals with kidney disease should avoid consuming excessive amounts of protein. 

Studies show that increased protein intake can further tax an already under-functioning kidney and cause further damage. 

Liver Damage?

Like the kidneys, the liver is a processor and is responsible for processing the majority of macronutrients that enter the body. Despite studies on the effects of high protein diets and liver health, there is minimal evidence to suggest high protein intake causes liver damage in healthy individuals.

In order to function properly and repair itself, the liver needs protein. For example, protein is needed to help convert fats to lipoproteins—molecules that help to remove fats from the liver. 

study, published in the journal Clinical Nutrition, of whey protein supplementation on lipid levels showed that taking 60 grams of whey protein daily for a period of 4 weeks helped to reduce liver fat by 21%, as well as reduce blood triglyceride levels by 15% and cholesterol by 7%.

Supplementation did not elicit any adverse effects on glucose tolerance or creatinine clearance. However, it’s important to note that individuals suffering from cirrhosis of the liver or any other liver condition may be at risk of negative effects that can cause further damage.

As the liver is the main detoxification organ for substances like ammonia, a byproduct of protein metabolism, cirrhosis of the liver reduces the body’s ability to metabolize and excrete protein byproducts. Therefore, increased intake can cause high levels of ammonia to build up in the blood and increases the risk of brain damage.

Whey and Osteoporosis 

The relationship between protein intake and bone metabolism has been under discussion for quite some time due to the theory that high dietary protein intake can result in the leaching of calcium from bones, which may lead to osteopenia, predisposing some individuals to osteoporosis.

This notion arose from earlier studies that found that high protein intake produced increasingly acidic urine, which causes the body to release more calcium from the bones in an effort to buffer acidity.  However, more recent studies show this to be untrue. Rather, the body counters acidic urine by absorbing more calcium from the gut. 

meta-analysis of 36 studies looking at protein intake and bone health found that eating more protein doesn’t correspond to decreased bone health, but rather the opposite.

Other studies conducted on the elderly actually suggest that populations who are prone to osteoporosis should consume more protein to help maintain strong bones. 

Protein Supplements Vs. Real Food

As with any diet, nutrient deficiencies are a good possibility unless you’re closely monitoring your food intake. However, they’re especially likely if you’re substituting protein powders in place of real, whole foods. 

Often times, people will throw together a protein shake in place of eating an actual animal or plant based protein, which is all well and good, but the problem arises when you compare the nutritional information of both.

While protein powders may be a good option if you’re in a pinch or adding in a post-workout meal before actually eating, they don’t contain near the same number or array of nutrients as eating a piece of protein itself.

For example, beef is rich in vitamin B12, which can only be obtained through direct supplementation or food. Protein powders don’t generally contain added B12, so you’re losing out on this vitamin by choosing protein powder over a piece of beef.

With that said, we’re not saying you should forget protein powders altogether, we just want you to understand that protein powders are a supplement to your diet, not a replacement for actual food. Viewed this way, you avoid the possibility of experiencing serious nutrient deficiencies in the long-run.

Safety of Whey Protein

The bottom line is that whey protein is a safe supplement to consume. However, for some people, whey protein can cause digestive stress and discomfort and should be avoided.

Most importantly, the type of protein supplement you consume should be part of a healthy diet—not a meal replacement. If you’re looking to include protein powder in your diet, you should opt for a high-quality protein with the fewest possible ingredients. Try to avoid any unnecessary additives and toxic compounds wherever possible.

Although whey protein is safe to consume, it’s a good idea to use caution as you begin to invest in a new supplement. When consuming whey protein, it’s essential to stick to the recommended dose and start slow before you work your way up to a higher dose.

Over-consumption is the leading cause of whey protein side effects. As long as you avoid dangerous ingredients, such as contaminants, artificial sweeteners, and artificial flavorings, you are at low-risk of experiencing any side effects.