Protein Deficiency

What protein does

Protein provides amino acids, the building blocks for muscle, skin, hair, enzymes, hormones, antibodies and blood proteins such as albumin. The body cannot store protein, so a steady intake is needed. When intake falls short, the body breaks down muscle to supply essential amino acids.

Causes

Low intake

• poverty, food insecurity
• older age with poor appetite, dental problems or living alone
• eating disorders such as anorexia nervosa
• alcohol use disorder
• very restrictive diets
• cancer and its treatment, depression

Poor absorption

• celiac disease, Crohn's disease, chronic pancreatitis
• malabsorption syndromes and bariatric surgery

Increased loss or need

• kidney disease with protein in the urine (nephrotic syndrome)
• liver disease (reduced albumin production)
• burns, major surgery, severe infections, trauma
• protein-losing enteropathy
• pregnancy and breastfeeding with inadequate intake

Signs and symptoms

• muscle wasting and weakness, see muscle wasting
• edema: swelling of the legs, feet, belly or face, as low albumin lets fluid leak into tissues
• hair changes: thinning, brittle or lighter-colored hair
• skin and nail changes: dry, flaky or darkened patches; brittle nails
• fatigue and reduced stamina
• slow wound healing and pressure sores
• frequent infections
• fatty liver
• bone loss and fractures
• stunted growth in children

Kwashiorkor vs marasmus

Both are forms of severe acute malnutrition, mainly seen in low-income countries, famine and conflict, but can rarely occur elsewhere with extreme diets or neglect.

Diagnosis

• history: diet, weight change, appetite, illnesses, alcohol, medicines
• examination: weight, BMI, muscle mass, edema, skin and hair
• blood tests: albumin and prealbumin (affected by inflammation, so interpreted with care), complete blood count, electrolytes, kidney and liver function
• urine tests for protein loss
• screening tools such as the Mini Nutritional Assessment for older adults
• tests for underlying causes, such as celiac disease

How much protein you need

Good protein sources include meat, poultry, fish, eggs, dairy, beans, lentils, tofu, tempeh, nuts, seeds and whole grains. Plant-based diets easily meet needs when they include a variety of legumes, soy and grains.

Treatment

• Mild deficiency: increase protein at each meal, add snacks such as yogurt, eggs, nuts or beans, and use protein-enriched foods or oral nutritional supplements.
• Older adults: combine protein intake with strength exercises to rebuild muscle, see sarcopenia.
• Treat the cause: malabsorption, kidney disease, eating disorders, alcohol use, depression.
• Severe malnutrition: gradual refeeding under medical supervision, with monitoring of phosphate, potassium and magnesium to prevent refeeding syndrome. Children with kwashiorkor or marasmus receive therapeutic milk formulas or ready-to-use therapeutic food, and treatment of infections.

Frequently asked questions

What are the signs of protein deficiency?

Common signs include muscle loss and weakness, swelling in the legs or feet, thinning hair, brittle nails, dry or flaky skin, fatigue, slow wound healing and frequent infections. Children may grow poorly. Many of these signs have other causes, so see a doctor.

How much protein do I need per day?

Most healthy adults need about 0.8 grams of protein per kilogram of body weight, or about 0.36 grams per pound. Older adults, pregnant or breastfeeding people and those recovering from illness or surgery often need more.

What is the difference between kwashiorkor and marasmus?

Kwashiorkor is severe malnutrition with swelling from fluid retention, skin rashes and an enlarged liver. Marasmus is severe wasting from a lack of calories and protein, without swelling. Both mainly affect young children in areas with food shortages.

Can vegetarians or vegans get enough protein?

Yes. A varied plant-based diet with beans, lentils, soy foods, nuts, seeds and whole grains provides enough protein for most people. Those with high needs, such as athletes, older adults and pregnant people, may need to plan more carefully.

Can protein deficiency cause swelling?

Yes. Low protein reduces albumin in the blood, which normally holds fluid in blood vessels. When albumin falls, fluid leaks into tissues, causing swelling (edema) in the legs, feet, belly or face, as seen in kwashiorkor and severe liver or kidney disease.