Protein is often associated with muscle building and gym routines, but its importance goes far beyond that. This essential macronutrient plays a vital role in nearly every part of the body. From maintaining healthy skin, hair, and nails to supporting immune function, producing hormones, and repairing tissues, protein is key to your overall health.

Whether you're following a plant-based diet, recovering from illness, or just navigating a busy lifestyle, it's surprisingly easy to fall short on protein if you’re not strategic in your meal planning. 

In this article, we’ll explore the most common causes of protein deficiency, signs to watch for, who’s most at risk, and practical ways to get enough protein in your diet, so you can stay energized, resilient, and strong.

Protein Deficiency vs. Undereating Protein

While they sound similar, protein deficiency and simply under-eating protein are not quite the same. 

Protein deficiency is a more severe clinical condition that occurs when protein intake is chronically low, often leading to noticeable symptoms such as muscle wasting, edema (e.g., swelling throughout the body), and weakened immunity. 

On the other hand, the signs you may be under-eating protein are more subtle. It means you’re not getting optimal amounts for your body’s needs. You might still meet minimum requirements, but not enough to fully support muscle maintenance, hormone balance, or recovery. 

Most Common Causes of Protein Deficiency

Low Overall Intake

Not eating enough protein is the most common cause of deficiency. It often happens gradually and can go unnoticed, especially if you're not tracking your meals or prioritizing balanced nutrition. The general recommendation to prevent a deficiency is about 0.36 grams per pound (about 0.8 grams per kg) of body weight per day, but many experts suggest aiming higher based on age, activity level, and overall health. For those who want to build muscle or are taller/heavier, this can add up to 100-150 grams of protein a day.

Restrictive Diets

People following calorie-restricted diets, skipping meals, or eating mostly ultra-processed foods may not be getting sufficient protein. Similarly, those who follow a vegan or vegetarian diet without carefully planning their meals can struggle to meet their protein needs, especially if they rely heavily on carbohydrate-rich plant foods that are low in protein.

Timing

Consuming most of your protein in one meal (most often dinner) can leave your body lacking throughout the rest of the day. Your muscles, hormones, and cells need a steady supply of amino acids to function properly, which is why spreading your protein intake across meals is so important.

Other Causes of Protein Deficiency

While not eating enough protein is the most common cause of deficiency, it's not the only one. In some cases, underlying health conditions can interfere with how your body absorbs, processes, or uses protein, even if your intake seems adequate.

• Chronic illnesses like diabetes can disrupt metabolism and increase the body’s protein needs. 

• Conditions that affect the liver or kidneys, the organs responsible for filtering and processing nutrients, can also lead to protein imbalances. 

• Digestive disorders such as Crohn’s disease, celiac disease, or chronic pancreatitis may reduce the absorption of amino acids, leading to a deficiency over time.

If you're managing a chronic illness or experiencing unexplained symptoms, it’s a good idea to speak with a healthcare provider who can evaluate your protein status through blood tests and an overall health assessment.

Signs & Symptoms of Protein Deficiency

Protein deficiency doesn’t always show up dramatically at first. In many cases, the signsof undereating protein are subtle and build up over time.

• Muscle loss or inability to build muscle: You might notice reduced strength, slower progress in workouts, or even shrinking muscles, particularly in older adults or those recovering from illness.

• Brittle hair and nails: When your body is short on keratin, a type of protein, you might have brittle nails, increased hair shedding, or hair that feels dry and thin.

• Fluid retention (Edema): A deficiency in albumin, a key blood protein, can cause fluid to leak into surrounding tissues, resulting in swelling. This is most commonly seen in the lower legs, ankles, and feet. Significant edema resulting from low protein intake is typically a sign of a serious illness or severe malnutrition, not mild low protein intake.

• Slow healing and weakened immunity: Wounds that take longer to heal, frequent infections, or getting sick more often may be linked to protein deficiency.

• Fatigue and low energy: Without enough protein, you may feel tired, sluggish, or mentally foggy, even if you're getting enough sleep.

• Low iron levels: Protein helps transport iron throughout the body. If your protein intake is consistently low, it may contribute to iron-deficiency anemia, leading to symptoms such as dizziness, cold hands and feet, or shortness of breath. However, in most adults, iron-deficiency anemia is usually due to low iron intake or absorption, rather than mild, low-protein intake.

Everyday signs like brittle nails or low muscle mass are common and usually improve with small changes like eating more protein, improving digestion, and adding strength training. 

More serious symptoms, such as leg swelling or frequent illness, are rare and usually not caused by a mild, low-protein intake. However, these symptoms don’t always mean you have a serious illness. If they show up or don’t go away, check in with a doctor while you improve your diet.

Who’s Most at Risk of Protein Deficiency?

Some people are more likely to develop a protein deficiency due to higher needs or challenges with dietary intake. These include:

• Older adults: Appetite tends to decrease with age, and chewing or swallowing difficulties can make it harder to eat enough protein-rich foods.

• People on restrictive diets: Limiting food groups or reducing your calorie intake without a strategy can unintentionally reduce protein intake.

• Vegans and vegetarians: Without careful planning, it can be difficult to get all essential amino acids from plant-based sources alone.

• Those on extreme weight-loss plans: Cutting calories too drastically may mean not getting enough protein to support basic functions.

• People recovering from illness or surgery: The body needs extra protein to heal and rebuild tissue, and intake may not meet the increased demand.

• Athletes and highly active individuals: Regular intense training increases protein requirements, which are often underestimated.

• People with chronic illness or digestive disorders: Conditions like Crohn’s disease or kidney problems can interfere with how the body absorbs or processes protein.

Being in one of these groups doesn’t mean you’re definitely protein-deficient, but it does mean you should watch for signs and consider your intake more closely.

How to Fix a Protein Deficiency

Addressing a protein deficiency involves both treating any underlying causes and making intentional changes to your diet and routine. Here are a few things you can do:

Work With a Healthcare Provider 

If a medical condition (like a digestive disorder or chronic illness) is affecting how your body processes protein, consult a doctor or dietitian. Treating the root issue is key to long-term improvement.

Increase Your Dietary Protein

To increase your protein intake, include a protein source in every meal and snack. Animal-based options like eggs, chicken, and dairy are easy go-tos. Plant-based eaters can choose foods like lentils, tofu, or quinoa. 

If you follow a vegan or vegetarian diet,combining different plant proteins, like rice and beans, helps ensure you get all essential amino acids. There are also plenty of high-protein, low-calorie foods that can help you up your protein intake while keeping your calories in check.

Distribute Protein Evenly Throughout the Day

Avoid consuming most of your protein at dinner. Try to get around 20–30 grams of protein per meal to support muscle maintenance and repair. Depending on your body weight or your goals, you might want to aim higher: with the right recipes, you can even fit 50g of protein in one meal.

Use Supplements if Needed

If whole foods aren’t enough, protein powder or bars can help, especially during recovery or periods of high demand. Always consult a healthcare professional before starting any supplement.

With the right approach, even small adjustments can make a big difference in restoring healthy protein levels and supporting your overall well-being.

When to See a Healthcare Professional

While minor dips in protein intake can often be corrected with simple diet changes, persistent or more serious symptoms should not be ignored:

• Ongoing fatigue or muscle weakness that doesn’t improve with rest or food

• Unexplained weight loss or visible muscle wasting

• Swelling in the legs or feet (edema)

• Frequent infections or slow wound healing

• Hair loss, brittle nails, or skin changes without an obvious cause

• Digestive symptoms (like chronic bloating, diarrhea, or poor nutrient absorption)

• History of chronic illness (e.g., diabetes, kidney or liver disease)

It’s always better to check early than to wait until symptoms worsen or become more frequent. Protein plays a role in nearly every part of your health, and catching a deficiency before it worsens can help prevent long-term effects like muscle loss, weakened immunity, or nutrient imbalances.

Take Charge of Your Protein Intake

Protein is more than a fitness trend; it’s essential for your body to function well every day. Even a mild deficiency can affect your energy, strength, and recovery over time. Whether it's due to diet, illness, or lifestyle, spotting the signs early and making a few smart changes can have a big impact. And if you're unsure, checking in with a healthcare professional is always a good idea.

FAQs About Protein Deficiency

1. What Are the Symptoms of a Protein Deficiency?

Some of the most common signs include muscle loss or general weakness, brittle hair and nails, and a constant feeling of fatigue or low energy. You might also notice that you’re getting sick more often or that wounds take longer to heal. In some cases, fluid can build up in the legs or feet, a condition known as edema. Hair thinning or noticeable hair loss is another potential red flag. If several of these symptoms are showing up at the same time, it could be your body’s way of signaling that it’s not getting enough protein.

2. How Do You Fix a Protein Deficiency?

Start by increasing your intake of protein-rich foods, such as eggs, fish, tofu, lentils, or dairy products. Try to spread your protein out across your meals instead of getting it all at once, and make sure it’s part of your everyday routine. If you’ve got any health issues that might affect digestion or how your body uses nutrients, that’s worth looking into as well. 

3. What Are Two Main Causes of Protein Deficiency?

The two main causes of protein deficiency are not getting enough protein through daily meals and having underlying health conditions that interfere with how your body processes protein. Both causes can lead to similar symptoms and often require treatment together.

4. How Can Vegetarians and Vegans Meet Their Protein Needs?

Vegetarians and vegans can meet their protein needs by eating a variety of plant-based foods, such as lentils, tofu, tempeh, chickpeas, quinoa, and soy milk. Mixing different types of plant proteins throughout the day ensures they get all the essential amino acids their bodies need.

5. How Can I Eat More Protein Without Increasing My Calorie Intake Too Much?

Focus on lean, nutrient-dense protein sources like egg whites, low-fat Greek yogurt, tofu, legumes, and skinless chicken. You can also add protein powder to smoothies or snacks for an easy boost without too many extra calories.