As a result of starvation or a protein-deficient diet, what happens to blood protein concentration?

In cases of starvation or a diet deficient in protein, the concentration of blood proteins, particularly albumin, decreases. This reduction in protein levels leads to a decrease in the oncotic pressure within the blood vessels, which is the pressure exerted by proteins in the blood that helps keep fluid in the vascular compartment. When the oncotic pressure drops, it results in an imbalance that causes water to accumulate in the tissue spaces, leading to edema.

This physiological response occurs because the lack of adequate proteins means there are fewer molecules to draw water into the bloodstream from surrounding tissues. Instead, fluid shifts out of the blood vessels into the surrounding interstitial spaces, causing swelling and contributing to the overall impaired fluid balance in the body. Thus, the decrease in blood protein concentration due to starvation or protein deficiency is directly linked to the accumulation of water in tissues.