Protein Side Effects: What You Need to Know

Side Effects of Protein

While ensuring adequate protein intake is important for preventing protein deficiency, it is equally vital to be aware of the potential side effects of excessive protein consumption.

1. Digestive Discomfort

One of the most frequently reported protein side effects is digestive discomfort. The digestive system can sometimes react unfavourably if you consume protein through whole foods or supplements like protein powders.

Bloating and Gas: Protein supplements, especially those derived from whey, casein, or soy, can cause bloating and gas in individuals who are lactose intolerant or sensitive to these ingredients. When the body cannot fully break down these proteins, it leads to fermentation in the gut, causing bloating and flatulence[3].

Constipation: Excessive protein intake, particularly from protein-rich diets, can sometimes lead to constipation. High-protein diets are often low in fibre, which is crucial for healthy digestion. Without enough fibre to support bowel movements, protein can sluggish the digestive system, causing constipation[4].

2. Kidney Health

A common concern associated with high-protein diets is their potential strain on the kidneys. While this is generally only a concern for individuals with pre-existing kidney conditions, it’s essential to understand how protein affects kidney function.

Kidneys are crucial in filtering waste products from the blood, including those produced by protein metabolism. When you consume high amounts of protein, your kidneys need to work harder to eliminate the waste, which can lead to a decline in kidney function over time[5].

3. Bone Health

One of protein’s more debated side effects is its potential impact on bone health. High-protein diets may lead to calcium loss, weakening bones over time[20].

The acid-base theory suggests that consuming large amounts of animal protein, which contains sulphur, creates an acidic environment in the body. The body may draw calcium from the bones to neutralise this acidity, potentially leading to bone loss over time[7].

4. Protein Overload and Liver Function

Like the kidneys, the liver plays a crucial role in processing the nutrients you consume, including protein. While moderate protein intake supports healthy liver function, excessive amounts can put undue strain on this vital organ[21].

The liver breaks down proteins into amino acids, which are then used by the body. However, when excessive protein is consumed, the liver may struggle to process it efficiently, leading to a build-up of by-products like ammonia, which can be harmful in large quantities[9].

Over time, consuming too much protein can place stress on the liver and potentially contribute to liver strain. Individuals with pre-existing liver conditions, such as hepatitis or cirrhosis, should consult their doctor before significantly increasing their protein intake to avoid further complications[10].

5. Weight Gain

While many people take protein supplements to support weight loss or muscle gain, they may unintentionally contribute to weight gain if not used properly.

Protein supplements, especially those designed for muscle gain, are often calorie-dense. Consuming more protein than your body needs can lead to excess calories, which may result in weight gain[11].

Some protein supplements contain added sugars, flavourings, or other ingredients that can increase your calorie intake without realising it. It’s important to check the labels and choose cleaner, low-sugar options to avoid unwanted weight gain[12].

6. Allergic Reactions

Not all proteins are suitable for everyone, and some people may experience allergic reactions to certain types of protein supplements.

Dairy-based protein powders, such as whey and casein, can trigger allergic reactions in individuals who are allergic to dairy. Symptoms may include hives, swelling, or difficulty breathing. Plant-based protein powders, like pea or hemp protein, may serve as better alternatives for those with dairy allergies[13].

Soy protein is another common allergen. If you suspect you are allergic to a particular protein supplement, it is important to consult a doctor and switch to a hypoallergenic option[14].

7. Hormonal Imbalance

Soy-based protein supplements have gained popularity, especially among vegetarians and vegans. However, there is ongoing discussion about their potential impact on hormone levels.

Soy contains compounds known as phytoestrogens, which can mimic oestrogen in the body. Some research suggests that consuming large quantities of soy protein could lead to hormonal imbalances, particularly in men, as phytoestrogens may influence testosterone levels[15].

8. Hydration Issues

High protein intake can impact hydration levels, as protein metabolism requires more water than carbohydrates or fats. A high-protein diet may lead to dehydration if adequate water intake is not maintained[22].

When consuming large amounts of protein, your kidneys need more water to eliminate the byproducts of protein metabolism, such as urea and ammonia. Insufficient hydration can result in dehydration, which may cause fatigue, headaches, and reduced physical performance. Drinking plenty of water when following a high-protein diet is essential to avoid these issues[17].