What Happens if You Eat Only Protein?

Proteins are very valued nutrients due to their role in muscle building, but as well as any other nutrient, an excess of protein could lead to health drawbacks (1). 

In this article, we will answer the query “What Happens if You Eat Only Protein?” We will explore relevant topics such as the effect of a high protein diet in different organs like your gut, kidney, and liver; then, we will briefly present the role of other nutrients in your health and how to do a proper high-protein diet.

What Happens if You Eat Only Protein?

Protein is an essential nutrient needed for a correct nutrition, growth, and metabolism (1). But if you eat only protein you will increase the risks of malnutrition due to the deprivation of micronutrients found in other foods, like whole-grains, fruits, and vegetables (2). 

Beyond the nutritional deficiencies, an only protein diet could increase the risks of cardiovascular diseases, kidney disease, and impairments in liver function. Remember that everything in excess is not good for your health, this includes valuable nutrients like proteins (3-5).

What are the Impact on Nutritional Balance and Deficiencies?

Eating only protein might involve eating only lean meats and egg whites; even though there are some vitamins and minerals in lean meats and egg whites, for example, B vitamins, iron, selenium, and zinc, your body will be deprived of several essential micronutrients (6).

For example, vitamin C found in fruits and vegetables is indispensable to strengthen your immune system, especially against respiratory diseases (6).

Calcium and vitamin D of milk and dairy products are important micronutrients to prevent osteoporosis, and other bone related diseases. On the other hand, vitamin D is also needed for a good immunological response against infectious diseases (6).

You will be likely to have a deficiency of vitamins A and E because they are liposoluble vitamins, therefore, found in fats like vegetable oils. The precursors of vitamins A and E, carotenoids and tocopherol, are found in fruits and vegetables (6).

Vitamins A and E are needed for good eye health and skin health; in fact, these vitamins are related to lower risks of skin cancer (6).

What are the Effects on Gut Health?

Eating only protein could lead you to a fiber deficiency; fiber is a non-digestible carbohydrate with key functions in your intestine functions and health (7).

A simple drawback of consuming low or null fiber is constipation, due to low mobility of your intestine. However, everything you eat is going to be fermented by your microbiota, in other words, the bacteria that live in your gut (7,8). 

If you eat just protein, your microbiota will create an excess of toxic metabolites like amines, sulfhydric acid, and ammonia. Amines, sulfhydric acid, and ammonia in high concentration could be toxic, and increase the risks of cardiovascular diseases or detriment your neurological health (8).

Are there Potential Stress on Kidneys and Liver?

There is controversy about the role of protein in kidney damage on healthy people, however, in people who already have a kidney disease, it is mandatory to reduce the protein intake. Similarly, there is no conclusive evidence to ensure that high protein load could impair liver functions (3-5).

Nevertheless, here are some key points to address according to long terms of a high protein diet (3-5):

• A high protein intake could increase the kidney filtration, causing a gradual wearing down the glomeruli of your kidney.

• Certain amino acid metabolism like Glutamate and Glycine could alter the liver’s pH, causing damage to liver’s cells.

• The amino acid’s metabolism create ammonia, if it is not eliminated, ammonia can increase the risk of cardiovascular diseases, and cause damage to organs like liver and kidney

Take into account that a high protein diet is the one which provides more than 1 g/kg of protein, or above 15 % of your total calorie intake (2); hence, consuming only protein could exacerbate the effects discussed here.

What is the Role of Carbohydrates in the Body?

Carbohydrates are the main and more available energy source for your body. Carbohydrates are stored as glycogen in your liver and muscles, so it is the first energy used when you do all your activities and exercise (2).

Moreover, non-digestible carbohydrates like fiber are important to maintain a good digestion and intestinal health (2,7).

What is the Role of Fats in the Body?

Fats are needed to create energy stores; in contrast to glycogen, fat storage is intended for long-term usage, for example, during long fasting periods (9).

Additionally, fat reservoirs also contain liposoluble vitamins like vitamin D, A, and E, so your body can prevent a vitamin deficiency if you are deprived of those vitamins (9).

Another role of fats in the body is that fats can be precursors of cellular components and hormones (9).

How Can You Do a High-Protein but Healthy Diet?

You can do a high protein but healthy diet by incorporating all macronutrients and food groups in your diet (2). For example, you should eat carbohydrates, fats, and proteins from the following sources:

• Lean meats

• Eggs

• Milk and dairy products

• Cereals and Whole-Grains

• Legumes

• Fruits

• Vegetables

To ensure a high-protein intake, you can estimate your protein requirements in a range of 1 to 1.2 g/kg of weight, for example if you weigh 70 kg, you can eat between 70 and 84 g of protein (2). Here is a list of how much protein is provided by different foods.

However, it is extremely recommended that you seek professional advice from a nutrition specialist. A nutritionist will adjust all your macronutrient requirements.

Conclusion

In this article, we answered the query “What Happens if You Eat Only Protein?” We explored relevant topics such as the effect of a high protein diet in different organs like your gut, kidney, and liver; then, we briefly presented the role of other nutrients in your health and how to do a proper high-protein diet.

References

1. Olson B, Marks DL, Grossberg AJ. Diverging metabolic programmes and behaviours during states of starvation, protein malnutrition, and cachexia. J Cachexia Sarcopenia Muscle, 2020;11(6):1429–46.

2. Cena H, Calder PC. Defining a healthy diet: Evidence for the role of contemporary dietary patterns in health and disease. Nutrients, 2020;12(2):334.

3. Cuenca-Sánchez M, Navas-Carrillo D, Orenes-Piñero E. Controversies surrounding high-protein diet intake: satiating effect and kidney and bone health. Adv Nutr, 2015;6(3):260–6.

4. Díaz-Rúa R, Keijer J, Palou A, van Schothorst EM, Oliver P. Long-term intake of a high-protein diet increases liver triacylglycerol deposition pathways and hepatic signs of injury in rats. J Nutr Biochem, 2017;46:39–48.

5. De Chiara F, Ureta Checcllo C, Ramón Azcón J. High protein diet and metabolic plasticity in non-alcoholic fatty liver disease: Myths and truths. Nutrients, 2019;11(12):2985.

6. Godswill AG, Somtochukwu IV, Ikechukwu AO, Kate EC. Health benefits of micronutrients (vitamins and minerals) and their associated deficiency diseases: A systematic review. International Journal of Food Sciences, 2020;3(1):1–32.

7. Snauwaert E, Paglialonga F, Vande Walle J, Wan M, Desloovere A, Polderman N, et al. The benefits of dietary fiber: the gastrointestinal tract and beyond. Pediatr Nephrol, 2022.

8. Cai J, Chen Z, Wu W, Lin Q, Liang Y. High animal protein diet and gut microbiota in human health. Crit Rev Food Sci Nutr, 2022;62(22):6225–37.

9. Lees RS. Impact of dietary fat on human health. In: Omega-3 Fatty Acids in Health and Disease. 1st Edition. Boca Raton, FL: CRC Press; 2020. p. 2–38.