Worth noting: “Protein deficiency, just like a lot of things in the field of medicine, is a spectrum,” says Dr. Brill. “You can have a mild protein deficiency and conversely, you can have a severe protein deficiency.” However, it’s important to note that severe, life-threatening forms of protein deficiency are rare, particularly in the United States. “In our society, it would be uncommon to see very severe deficiencies, unless the individual has an underlying intestinal disorder, liver or kidney disease, or a psychiatric eating disorder,” explains Dr. Lacqua.
That’s because most people in the U.S.—even those who don’t eat meat—tend to get enough protein in their diets. According to a 2013 study funded by the National Institutes of Health and published in the Journal of the Academy of Nutrition and Dietetics, the median protein intake of vegetarians and vegans is still above the recommended dietary allowance (RDA).1
And how can you tell if you have low protein levels? Per Dr. Lacqua, clinicians will order a “simple blood test” to check your albumin and globulin levels (two types of proteins found in your blood) to determine if they are, in fact, too low. The state of decreased protein levels in the blood is medically known as hypoproteinemia.2
How much protein do you need?
So, how much protein do you need? The answer isn’t so simple, because it varies from person to person. Protein needs are based on your age, sex assigned at birth and gender identity, health history, and how much exercise you typically get in a day, according to the U.S. National Library of Medicine. But for a general idea, the RDA for a healthy adult with minimal physical activity is 0.8 grams of protein per kilogram of bodyweight every day, per guidance published in the Annals of Nutrition and Metabolism.3 That equates to 0.36 grams of protein per pound of bodyweight. For example: The recommended daily protein intake for a 200-pound person is 72 grams.
That said, people who frequently exercise may require more protein. In a 2016 position statement from the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine, experts advised active adults and athletes to aim for 1.2 to 2 grams per kilogram of bodyweight (or 0.5 to 0.9 grams of protein per pound).4
If you’re looking for more personalized protein recommendations based on your lifestyle, consider chatting with a registered dietitian or your health care provider to ensure you’re meeting your needs. They can help assess your diet to see if your protein intake is falling short.
What is the main cause of protein deficiency?
The main cause of protein deficiency is, of course, not eating enough protein-rich food sources. However, Dr. Gonzalez explains that certain groups of people need to pay closer attention to their protein intakes, like vegans, vegetarians, and the elderly. Severe deficiencies can also occur in individuals with gastrointestinal health problems like celiac disease, ulcerative colitis, or Crohn’s disease, says Dr. Brill, as these disorders can make it difficult to properly absorb proteins in the gut. Again, clinical protein deficiency, even among vegans, is pretty rare, since hitting 0.8 grams of protein per pound of bodyweight isn’t super challenging for most Americans who have access to plentiful food (even if that food is all plant-based).
What are the signs of protein deficiency?
Protein deficiency symptoms vary based on how severe the condition is. However, there are some red flags worth considering for a true deficiency, even though it is rare:
1. Protein cravings
If you’re not eating enough protein, in the short term, your body may tell you by literally craving it, Dana Hunnes, Ph.D., R.D., senior dietician at UCLA Medical Center and adjunct assistant professor at the Fielding School of Public Health, tells SELF. You should give in to these cravings. If you’re really jonesing for a chicken sandwich or a bowl of lentil soup, listen to your body and eat up.
2. Sugar cravings
“Protein (along with fat) digests slower than carbohydrates. If you eat a meal that is mostly carbohydrates with not enough protein, it will digest more quickly and will cause your blood sugar to rise,” Alissa Rumsey, M.S., R.D., a New York City-based dietitian and the author of Unapologetic Eating. This rise is followed by a drop—and when blood sugar is constantly spiking and dropping, we crave more sugar. The key is to eat protein with carbs so that everything digests more slowly, and the blood sugar changes are more gradual over time.
You’ve probably noticed that you tend to be hungrier throughout the day when you have a lack of protein in your meals. That’s because protein decreases your level of the “hunger” hormone ghrelin and stimulates the production of other hormones that make you feel satiated.5 As a result, not getting enough protein can increase your appetite and actually cause you to eat more.6
4. Weakness and fatigue
“For most people, eating too little protein over the course of one day will not make you feel less energy or strength, particularly if you are getting a sufficient number of calories in that day,” Hunnes says. But long term, your body may break down your muscles to try and supply your body with sufficient protein, leading to loss of energy and strength, she explains.