Protein is an essential nutrient that your body needs for many important functions, including:

• Building and repairing tissues

• Producing enzymes and hormones

• Regulating blood sugar levels

• Maintaining a healthy immune system

• Protecting your bones and muscles

When you don’t eat enough protein, your body can’t function properly and you may experience a variety of health problems, including:

• Mood dis-regulation:  Indispensable amino acids in protein are precursors to serotonin and dopamine, which can affect one's energy level and may hamper responsiveness to anxiety and stress.  

• Edema:  Swelling in the abdomen and extremities (legs, feet, and hands) and is one of the more common signs of protein deficiency.  A possible explanation is that albumin (a proteins that circulate in your blood) helps to keep fluid from building up in your tissues. 

• Hair loss and skin aging:  Protein is essential for the growth, repair, and maintenance of all tissues in the body, including hair and skin.  When you don't get enough protein, your body can't produce enough new hair or skin cells, and the cells that you do have can start to break down.  This can lead to a number of problems, including hair loss and premature skin aging: resulting from a loss of elasticity, which contributes to skin wrinkling and sagging.   

• Food cravings: Protein helps regulate your appetite and hunger hormones, such as ghrelin and leptin. If you don't get enough protein, you may feel hungrier and crave more food, especially carbohydrates and sweets.  This can lead to overeating and weight gain.

• Muscle loss: Protein helps you maintain muscle mass and strength. Without enough protein, you may lose muscle and feel weaker and more tired.

• Muscle weakness or muscle wasting: Protein is the building block of your muscles, skin, enzymes and hormones.  If you don't get enough protein, your body may break down your muscles to get the amino acids it needs, leading to muscle loss and weakness.

• Sarcopenia is a type of muscle loss that occurs with aging and/or immobility.  Insufficient protein intake is a key factor in sarcopenia. Sarcopenia  can lead to disability and frailty resulting in falls.  And, falls may lead to death. 

• Low blood pressure and low heart rate: Protein is essential for maintaining blood volume and pressure, as well as heart function.  If you don't get enough protein, you may experience low blood pressure, low heart rate, dizziness and fainting.

• Nutrient malabsorption: Protein helps your body absorb and use other nutrients, such as iron, calcium and vitamin B12.  If you don't get enough protein, you may develop deficiencies in these nutrients, which can cause anemia, osteoporosis and nerve damage.

• Liver problems: Protein is needed for the synthesis of many liver enzymes that help detoxify your body and metabolize drugs and alcohol.  If you don't get enough protein, you may develop fatty liver disease, which can impair liver function and cause inflammation and scarring.

• Anemia: Protein is a component of hemoglobin, which is the protein that carries oxygen in your red blood cells.  If you don't get enough protein, you may have low hemoglobin levels and reduced oxygen delivery to your tissues, which can cause anemia.  Anemia can make you feel weak, tired, pale and short of breath.

• Immunity: Protein is involved in the production of antibodies, which are proteins that fight off infections and diseases, including recurrences of cold sores.  If you don't get enough protein, you may have a weakened immune system and be more prone to getting sick or having complications from illnesses.

• Muscle and joint pain: Protein is necessary for the formation of collagen, which is a protein that provides structure and support to your bones, cartilage, tendons, ligaments and fascia. If you don't get enough protein, you may have reduced collagen synthesis and increased collagen breakdown, which can cause joint pain, stiffness and inflammation.

• Sleep issues: Tryptophan is an essential amino acid, which is a key building block for serotonin, melatonin, endorphins, and other metabolites, which help to improve sleep, see Tryptophan: A Dream Amino Acid.

How much protein do you need?

The amount of protein you need depends on your age, sex, activity level and overall health.  The Dietary Reference Intakes (DRIs), established by the Health and Medicine Division of the National Academies of Sciences, Engineering and Medicine, state minimum requirements for the intake of protein, vitamins, minerals and other important nutrients for sustaining life. Further, the DRI requirements are stated for healthy individuals. 

However, 2-Dooz has also studied this topic and has arrived at adjusted DRIs, see the article IAA ADRI.  The ADRIs are made under the assumption that most individuals chronically experience one or more stressors that require protein consumption (in particular IAAs) beyond the levels recommended in the DRIs. 

How to get enough protein?

There are many ways to get enough protein in your diet. Some good sources of protein include:

• Meat, poultry, fish

• Eggs

• Dairy products

• Beans, lentils, nuts and seeds

• Whole grains

If you are concerned that you are not getting enough protein, talk to your doctor or a registered dietitian.

References

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[2] Atli Arnarson , 8 Signs and Symptoms of Protein Deficiency, healthline, 31 October 2017, https://www.healthline.com/nutrition/protein-deficiency-symptoms.

[3] Christine Mikstas, Signs You're Not Getting Enough Protein, Nourish by WebMD, 2 December 2022, https://www.webmd.com/diet/ss/slideshow-not-enough-protein-signs.

[4] Jan Annigan, Consequences of Low Protein Daily Intake, SFGATE, 27 December 2018, https://healthyeating.sfgate.com/consequences-low-protein-daily-intake-6330.html.

[5] Debra McKenzie, How Can a Lack of Protein Affect a Person?, Healthfully, 28 November 2018, https://healthfully.com/how-can-a-lack-of-protein-affect-a-person-7656044.html.

[6] Richmond, C., Signs You're Not Getting Enough Protein, WebMD, 2 December 2022, https://www.webmd.com/diet/ss/slideshow-not-enough-protein-signs. 

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[9] Thoma A, Lightfoot AP. NF-kB and Inflammatory Cytokine Signalling: Role in Skeletal Muscle Atrophy. Adv Exp Med Biol. 2018;1088:267-279. doi: 10.1007/978-981-13-1435-3_12. PMID: 30390256.

[10] Iddir M, Brito A, Dingeo G, et al. Strengthening the immune system and reducing inflammation and oxidative stress through diet and nutrition: Considerations during the COVID-19 crisis. Nutrients. 2020;12(6):1562. doi:10.3390/nu12061562.

[11] Groenendijk I, den Boeft L, van Loon LJC,b de Groota LCPGM. High versus low dietary protein intake and bone health in older adults: A systematic review and meta-analysis. Comput Struct Biotechnol J. 2019;17:1101–1112. doi:10.1016/j.csbj.2019.07.005

[12] Morell P, Fiszman S. Revisiting the role of protein-induced satiation and satiety. Food Hydrocolloids. 2017;68:199-210. doi:10.1016/j.foodhyd.2016.08.003

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[14] Santos-Lozada AR. Trends in Deaths From Falls Among Adults Aged 65 Years or Older in the US, 1999-2020. JAMA. 2023;329(18):1605–1607. doi:10.1001/jama.2023.3054