5 signs you aren't getting enough protein

By Naveed Saleh, MD, MS
Published January 8, 2021

Key Takeaways

The presence of protein in the body is fleeting. There is no way to physiologically store protein for later use. At a minimum, people need about 10% of their caloric intake derived from protein. This protein should come from varied sources, such as turkey breast, yogurt, and black beans.

Because protein is necessary for healthy tissue function, including the skin, bones, muscles, and organs, the effects of protein deficiency are systemic.

Here are five signs and symptoms indicative of hypoproteinemia.


Malnutrition, kidney, and liver disease can all lead to edema induced by low protein levels in the blood. Proteins help retain salt and water inside blood vessels. Specifically, when the concentration of the blood protein albumin drops, fluid retention occurs. Edema due to protein deficiency usually occurs in the lower extremities, including the feet, ankles, and lower legs.

Decreased muscle strength

Decreased protein intake is correlated with lower muscle strength and hindered physical performance in older adults. 

Results of a Scottish study published in Clinical Nutrition indicated that in a sample of 722 elderly participants—of which 60% were women—daily intake of less than 1 g per kg adjusted body weight negatively affected muscle strength and physical performance in the elderly, regardless of confounders including comorbidities, physical activity, and body habitus. This negative effect was pronounced among women.

Of note, adjusted body mass is an obesity consideration defined as metabolically active lean body tissue. This metric obviates the miscalculation of nutritional requirements in those with obesity.

According to the authors, “Adequate intake of dietary protein has been recognised as a key modifiable factor in muscle ageing and physical decline. The muscle protein synthesis (MPS) response to protein (amino acids) ingestion is blunted in older adults, especially at lower doses leading to a negative balance between skeletal MPS and muscle protein breakdown.” 

Lowered immunity

The chemical composition of proteins includes molecules made of nitrogen, carbon, hydrogen, and oxygen. These compounds are necessary for proper immune function, thus with protein deficiency, immune function decreases.

According to a study published in the Journal of Obesity & Weight Loss Therapy, protein deficiency’s impact on immunity is connected with the effect of immune system regulators for some amino acids. Deficiency in essential amino acids can also cause suppression of the immune system. “The latest studies show that protein metabolism play[s] an important role in formation of natural and acquired immunity against infections,” the authors wrote. 

Bone fractures

Proper nutrition bolsters bone development and protects against mechanical stress, according to a review published in the International Journal of Vitamin and Nutrition Research. The authors cite research supporting the importance of protein in the prevention of fractures.

“Several studies point to a positive effect of high protein intake on bone mineral density or content. This fact is associated with a significant reduction in hip fracture incidence, as recorded in a large prospective study carried out in a homogeneous cohort of postmenopausal women,” the authors wrote.

“Low protein intake (< 0.8 g/kg body weight/day) is often observed in patients with hip fractures and an intervention study indicates that following orthopedic management, protein supplementation attenuates post-fracture bone loss, tends to increase muscle strength, and reduces medical complications and rehabilitation hospital stay,” they added.

On the other hand, the researchers suggested that high-protein diets are probably not detrimental to bone mass and strength. Nevertheless, they cautioned against the combined intake of high-protein (>2.0 g/kg body weight/day) and low-calcium (<600 mg/day). In the aggregate, a combination of adequate vitamin D, dietary protein, and calcium levels are necessary to preserve bone function and prevent osteoporosis.


Dietary consumption of protein mediates adaptations in dietary intake, with energy intake and metabolism under homeostatic control. According to the protein leverage hypothesis, protein intake is narrowly controlled in humans, rats, mice, and other species, with these organisms preferentially consuming to meet protein requirements compared with requirements for fats and carbohydrates. 

According to this hypothesis, an increase in dietary protein density decreases consumption of carbohydrates and fats, thus lowering energy intake, as well as promoting satiety, weight loss, and glycemic control. Conversely, a reduction in protein intake increases total energy intake secondary to overconsumption of carbohydrates and fats to meet protein requirements. These patterns are supported by preclinical and some clinical studies.

According to the authors of a study published in Scientific Reports, “The hyperphagic effects of moderately low protein diets are purported to be through multiple mechanisms. These include imbalances in plasma and brain amino acid concentrations in rats, modulation of energy sensors in the hypothalamus and anterior piriform cortex in rats, and increased activity in the reward areas such as the orbitofrontal cortex and striatum in humans.”

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