Is Too Much Protein Bad For You?

Diet trends come and go all the time, but if there is one that has stuck around for years (sometimes wrapped up in slightly different packaging or with a new label), it’s the high-protein diet. 

While getting enough protein is essential for your body to thrive and your health to be at its best, consuming more protein than you need is a whole different kettle of fish. Let’s find out why.

Why is protein important?

Protein sits alongside carbohydrates and fats as one of the three macronutrients our bodies need for energy and optimal functioning. Protein is often referred to as the “building blocks” of the body, as once eaten, it’s broken down into different amino acids which are used for a range of vital processes such as muscle growth, cell repair, hormone production and immune function.

Aside from being essential for an array of important jobs, protein-rich foods also require more energy to digest than carbs and fats and are very satiating, meaning they can help with weight management by keeping you feeling full for longer.

How much protein should you eat a day?

According to Harvard Health, the weight-based recommended daily allowance is 0.8 grams of protein per kilogram of bodyweight, which for a 140 pound adult (or 64 kg), amounts to 51 grams of protein per day. Of course, protein recommendations are more nuanced than this as highly active people, growing teenagers, the elderly and those with certain health conditions may require more, but it’s a helpful starting point for the general population.

How to get enough protein

The other important thing to know is that for most people, getting enough protein isn’t a difficult job that requires a huge amount of effort or calculation. If you’re eating enough calories, consuming a balanced diet and including a source of protein in each meal throughout the day, getting enough protein shouldn’t be anything to worry about. 

When we talk about protein sources, we’re usually referring to foods naturally high in protein such as meat and dairy, but it’s important to know that all foods (even foods we typically think of as carbs!) contain protein - they just differ in quantity and quality. 

Although you have a much wider range of protein-rich foods you can include throughout your day and week if you eat meat, fish, eggs and dairy, there are plenty of plant-based protein sources available such as tofu, beans, quinoa, lentils, nuts and seeds (all of which are incredibly rich sources of nutrients for meat-eaters too!). As the American Heart Association highlights, not eating meat doesn’t mean you can’t get enough protein. 

Your body can also only absorb so much protein in a single sitting, so cramming it all into one meal isn’t the way to go. Spread your protein intake throughout the day, aiming for 15-30 grams of protein per meal. If your meal includes a good source of protein, this shouldn’t be an issue!

Should you have allergies or intolerances, or be following a strict diet for any reason, it’s best to consult a professional dietician to make sure you’re getting enough protein, calories and nutrients.

Can you eat too much protein?

Even for a highly active person or someone suffering from age-related muscle loss, the Mayo Clinic recommends 1-1.5 grams of protein per kilogram of bodyweight, and Harvard Health and the Mayo Clinic say it’s best to eat no more than 2 grams of protein per kilogram of bodyweight each day. 

Your body only needs so much protein per day, and Dietitians Australia explains that your body can’t store any excess for later or automatically use it for muscle growth. Consuming more than 40 grams in one meal doesn’t offer your body more benefits than the recommended 15-30 grams, and any extra is used in the same way as extra energy from carbohydrates or fat burned for energy or stored in the body as fat.

A high-protein diet can definitely cause other side effects, but here is where things get interesting. It’s not as simple as pointing a finger at protein alone - it’s more about how eating a lot of protein can cause knock-on effects for the rest of your diet.

Where a high-protein diet can go wrong:

• When you eat more than you need, the body stores it as fat, even if your diet is high in protein. If you’re trying to gain weight, this might be great news, otherwise, it’s something to be aware of if you’re following a high-protein diet as a weight-loss or weight-management strategy.

• Most protein sources derived from animals are low in fibre, such as meat, fish, eggs and dairy. If the focus of each meal is protein, you could end up eating a low-fibre diet, causing digestive issues such as bloating, pain, discomfort and constipation. 

• Prioritising protein above everything else can mean neglecting other important food groups such as carbohydrates, whole grains, fruits and vegetables - especially since protein is the most satiating macronutrient. These foods offer an abundance of nutrients and are so important for energy, digestion and overall health!

• Many people use protein powders as a supplement, which can come with a long list of additives, sweeteners and artificial flavourings. Products at the supermarket labelled “high-protein” don’t necessarily equate to high-nutrition either! Always do your research before buying any supplements or foods with “high-protein” labels and try to keep the additives to a minimum.

• Several pieces of research (here, here and here) have shown a high-protein diet can increase your risk of conditions such as heart disease, high cholesterol, kidney disease and some cancers if you’re consuming a lot of red meat or processed meats which are high in saturated fat.

• A high-protein diet can be taxing on your kidneys too, so isn’t recommended for those with a history of or existing kidney issues.

• Finally, a high-protein diet based on lean meats, fish, dairy or protein supplements can quickly rack up a far more expensive grocery bill than what you budgeted for!

Eat for your health

Eating a nutritious, balanced diet with plenty of protein can be quite simple. The Cleveland Clinic recommends trying to get all (or most) of your protein from whole foods rather than supplements and including a lean source of protein in each meal. Fill the rest of your plate with other nutritious goodies like fruit and veg, whole grains, nuts and seeds. 

Even if you’re not following a vegetarian or vegan diet, experimenting with different sources of protein can expand your nutrient intake and boost your health - especially if you tend to go for red or processed meats.

One 2024 study of 48,762 female participants aimed to evaluate the role of protein in long-term health outcomes and healthy aging - meaning women who were free of 11 major chronic diseases, had good mental health, and no cognitive or physical impairments. They found that sufficient protein intake was significantly associated with higher odds of healthy aging, and that plant-based sources of protein were also associated with higher odds of good mental health and the absence of physical impairment. All the more reason to bump up the number of plants on your plate!

Getting enough protein is essential for good health and performance. Getting far more than your recommended daily intake? Chances are, you’re not helping yourself as much as you think. Give protein the shining role it deserves on your plate while still spotlighting all the other amazing food groups, too.