What foods are lowest in protein?

Some of the lowest-protein foods are: Pure fats, such as oils and butter Pure carbohydrates, such as sugar, fruit juice, and candy Fruits and vegetables are generally low-protein foods, although some fruits and vegetables can contribute meaningful amounts to your daily protein intake.

Diet and Nutrition

Protein Deficiency: Signs of Low Protein and How to Treat

Written by Joanna Foley, RD | Reviewed by Karen Hovav, MD, FAAP

Updated on September 14, 2026

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Key takeaways:

Protein deficiency can be caused by a lack of protein in your diet or medical conditions like gastrointestinal disorders and liver disease.
Signs of low protein can include brittle nails, loss of muscle mass, weakness, and slow wound healing.
Protein deficiency treatments depend on the cause and may include increasing protein intake or treating an underlying medical condition.

Most people in the U.S. get enough protein in their diet. But how much protein you need depends on your age, activity level, and overall health. If you consistently don't get enough protein, it could affect your muscles, immune system, hair, and nails.

Here, we'll explain the common signs of a protein deficiency — plus, who may be at risk and when to talk with a healthcare professional.

What are the most common signs of low protein?

You won’t get symptoms from occasionally not meeting your protein needs. But if you don't meet your protein needs for a long time, you may develop signs of a protein deficiency.

Keep in mind that these signs aren’t specific to low protein. They can be caused by other conditions as well, so having one or more of them doesn't necessarily mean you're low in protein.

Loss of muscle mass

Your body needs protein to build and maintain muscle. When you don't get enough from your diet, your body breaks down muscle tissue to meet its protein needs. This can lead to gradual muscle loss over time.

Muscle weakness

Losing muscle mass can make you feel weaker. Or it can make everyday activities more difficult, such as opening a jar, carrying groceries, or getting up from a chair. Muscle weakness can also occur when your body doesn't have enough protein to support normal muscle repair and function.

Brittle hair and nails

Hair and nails are largely made of a protein called keratin. When protein intake is very low, the body prioritizes protein for more essential functions, which can affect hair and nail growth. This may cause brittle nails or hair thinning, loss, or changes in texture.

Slow wound healing

Protein is important for building new tissue and repairing damaged tissue. If you don't get enough, cuts, wounds, or other injuries may take longer to heal. This is one reason adequate protein intake is particularly important after surgery, an injury, or a serious illness.

Getting sick more often

Protein plays an important role in your immune system. Your body uses protein to make antibodies and other immune-related proteins that help fight infections. Severe or prolonged protein deficiency can weaken immune function, which may make it harder for your body to respond to infections.

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Swelling

Swelling, or edema, can occur with severe protein deficiency. One protein made by the liver — albumin — helps keep fluid inside your blood vessels. When albumin levels become very low, fluid can leak into surrounding tissues. This can cause swelling, particularly in the legs, feet, or abdomen.

Changes in mood and concentration

Your body uses amino acids from protein to make neurotransmitters, including serotonin and dopamine, which help regulate mood and other brain functions. Some research suggests that lower protein intake may be linked to depression and changes in cognitive function.

Poor growth in children

Children need protein to build new muscle, bone, and other tissues as they grow. Severe or prolonged protein deficiency can interfere with normal growth and development.

How much protein do you need?

The amount of protein you need depends on your:

Age
Body size
Activity level
Overall health

The Recommended Dietary Allowance (RDA) for protein is 0.8 g per kilogram of body weight per day, or about 0.36 g per pound. For someone weighing 180 lbs, this would equal about 65 g of protein per day.

The RDA is designed to meet the protein needs of most healthy adults. It's a minimum target intended to help prevent protein deficiency. But some people may benefit from getting more protein than the RDA, particularly during periods of increased physical demands or muscle loss. These include:

Older adults: Older adults may need about 1.2 g to 2 g of protein per kilogram of body weight per day. This is partly because aging is associated with a gradual loss of muscle mass and a reduced ability of muscles to respond to dietary protein.
Adults who exercise: Physically active adults may benefit from 1.4 g to 2 g of protein per kilogram per day. If you’re doing resistance training and limiting your calorie intake, you might benefit from even higher amounts of protein, 2.3 g to 3.1 g per kilogram per day.
People trying to lose weight: A high-protein diet of about 1 g to 1.6 g of protein per kilogram per day may support weight loss and help with weight maintenance.
Critically ill adults: People who are critically ill — meaning they have a life-threatening issue — may need up to 1.5 g to 2 g of protein per kilogram of body weight.

What causes a protein deficiency?

While protein deficiency is unusual in the U.S., there are many possible causes for why someone may have insufficient protein. These can include:

Not getting enough protein in your diet: This may be due to an eating disorder, lack of food access, or dietary restrictions.
Certain gastrointestinal disorders: Some conditions prevent your body from absorbing protein properly. Examples include Crohn’s disease and celiac disease.
Bariatric surgery: After bariatric surgery, people may have trouble getting enough protein because they eat less at each meal. Research suggests that protein is the most common macronutrient that patients don’t get enough of after surgery.
Liver diseases: Having liver disease like cirrhosis can lead to malnutrition due to poor appetite and impaired nutrient absorption.
Kidney disease: People with chronic kidney disease often have different protein needs, depending on the stage of their condition and whether they’re receiving dialysis.
Serious injury, illness, or infection: These conditions can increase your body’s protein needs, especially during recovery.

How is protein deficiency diagnosed?

There’s no single test to diagnose a protein deficiency. A healthcare professional may use blood tests and review your diet to look at your protein intake and overall health.

Blood tests: Blood tests can measure albumin and total protein levels. Albumin is the most common protein in your blood. The total protein test measures albumin plus other blood proteins. Low levels may be a sign of a protein problem, but these tests alone can’t diagnose protein deficiency. A healthcare professional may recommend other tests to find the cause.
Diet review: A healthcare professional, such as a dietitian, can review what you typically eat and estimate how much protein you get each day. They can compare this with how much protein you need based on your age, activity level, and overall health.

Keep in mind that protein deficiency from not eating enough protein is rare in the U.S. Most people can get enough protein from both plant and animal sources.

When to see a doctor for protein deficiency

Contact a healthcare professional if you:

Have signs of protein deficiency, such as swelling or muscle weakness
Are having trouble getting enough protein from your diet, either because of a very limited diet or difficulty eating enough food.
Have lost weight or muscle without trying
Have a health condition that may affect how your body absorbs or uses protein, such as liver or kidney conditions

A healthcare professional can help determine whether you’re getting enough protein and whether your symptoms may have another cause.

How is protein deficiency treated?

Treatment for protein deficiency depends on the cause. For someone who hasn’t been eating enough protein, it’s best to increase the amount of protein in your diet. Examples of high-protein foods include:

Meats
Fish
Eggs
Nuts
Beans

You may need to introduce protein slowly to give your body time to adapt.

If you have a protein deficiency due to a medical condition, treating the underlying cause is an important part of treatment. In cases of severe protein deficiency, a healthcare professional or dietitian may recommend a nutrition plan to safely increase protein and calorie intake.

How long does it take to recover from a protein deficiency?

Recovery from protein deficiency can take a few weeks to several months, depending on how severe it is and what caused it. When low protein levels are caused by not getting enough protein, blood protein levels may improve within 2 to 4 weeks after getting enough protein and calories.

But rebuilding lost muscle can take several months. Recovery may take longer if an underlying illness is contributing to the deficiency. People with severe malnutrition may need to increase food intake slowly under medical supervision to prevent serious complications.

Frequently asked questions

Some of the lowest-protein foods are:

Pure fats, such as oils and butter
Pure carbohydrates, such as sugar, fruit juice, and candy

Fruits and vegetables are generally low-protein foods, although some fruits and vegetables can contribute meaningful amounts to your daily protein intake.

Protein deficiency can be serious when it’s severe or lasts for a long time. Mild or short-term protein deficiency is usually treatable and can improve with adequate protein and nutrition. Severe or prolonged deficiency can lead to muscle loss, delayed healing, and growth problems in children, as well as other serious health problems.

The bottom line

Despite the emphasis on protein seemingly all around us, most healthy people in the U.S get more than enough protein in their diets. But protein deficiency is possible if you’re not able to get enough in your diet or you have a medical condition that affects how much protein you need or are able to absorb.

For most people, focusing on a varied diet with enough protein is more useful than counting every gram. Talk with a healthcare professional if you’re losing weight or muscle without trying, having trouble eating enough, or have a health condition that affects your nutrition.

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Written by:

Joanna Foley, RD

Joanna Foley, RD, is a registered dietitian (RD) and the owner of joannafoleynutrition.com, a private nutrition consulting business. She has previously worked as a clinical dietitian and outpatient renal dietitian.

Edited by:

Sophie Vergnaud, MD

Sophie Vergnaud, MD, is the Senior Medical Director for GoodRx Health. A pulmonologist and hospitalist, she practiced and taught clinical medicine at hospitals in London for a decade before entering a career in health education and technology.

Reviewed by:

Karen Hovav, MD, FAAP

Karen Hovav, MD, FAAP, has more than 15 years of experience as an attending pediatrician. She has worked in a large academic center in an urban city, a small community hospital, a private practice, and an urgent care clinic.

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References

Aller de la Fuente R. (2022). Nutrition and chronic liver disease. Clinical Drug Investigation.

Baum, J. I., et al. (2016). Protein consumption and the elderly: What is the optimal level of intake? Nutrients.

GoodRx Health has strict sourcing policies and relies on primary sources such as medical organizations, governmental agencies, academic institutions, and peer-reviewed scientific journals. Learn more about how we ensure our content is accurate, thorough, and unbiased by reading our editorial guidelines.

Protein Deficiency: Signs of Low Protein and How to Treat

Key takeaways: