The potato is widely known as a starchy vegetable, often considered a simple source of carbohydrates. This reputation often overshadows its other nutritional components, leading many to overlook its protein content. The protein within the potato holds a surprising secret regarding its quality. Unlike many common plant sources, potato protein naturally contains all nine essential amino acids that the human body cannot produce. This completeness makes the potato an unexpectedly high-quality contributor to dietary protein.
Nutritional Profile of Potato Protein
A medium-sized potato (approximately 5.3 ounces) typically provides 3 to 4 grams of protein when consumed with its skin. While this volume is not substantial compared to meat or legumes, the protein contributes about 10 to 11 percent of the potato’s total caloric content. The majority of the potato’s calories come from its high starch content.
The quality of this protein makes the potato stand out among plant-based foods. Protein is constructed from amino acids, and the nine essential ones must be obtained through diet. Potato protein is classified as a “complete protein” because it includes all these necessary building blocks. Its amino acid profile is notable for its high concentration of lysine, an amino acid often lacking in cereal grains like wheat and corn. This makes potato protein an excellent complement to a grain-centered diet.
Biological Value and Completeness
The usability of a protein source is measured by how well the body can digest and utilize its amino acids, not just by raw quantity. One measure of quality is Biological Value (BV), which estimates the proportion of absorbed protein incorporated into the body’s proteins. The BV for potato protein is high, often scoring between 90 and 100, a range that rivals whole egg protein.
A more modern metric is the Digestible Indispensable Amino Acid Score (DIAAS), which accounts for the digestibility of each essential amino acid separately. Some potato varieties have a DIAAS value ranging from 99 to 114. This score places it above many common plant proteins, including soy protein, which typically scores around 90.
This high quality is due to a balanced amino acid profile that avoids the problem of a “limiting amino acid.” A limiting amino acid is the essential amino acid present in the smallest proportion relative to the body’s needs, restricting the full utilization of other amino acids. Its generally balanced profile ensures the protein is highly usable by the human body.
Maximizing Protein Retention and Bioavailability
Preparation methods significantly influence how much of the potato’s protein is absorbed and used. Eating raw potatoes is not recommended due to poor digestibility and the presence of anti-nutritional factors. Cooking is necessary because heat denatures the proteins, making them more accessible to digestive enzymes.
Cooking dramatically increases the protein’s digestibility, raising it from about 40 percent in a raw potato to over 80 percent in a cooked one. Boiling often results in the highest protein quality scores for the whole potato. Studies show that boiled potato had the highest Protein Digestibility Corrected Amino Acid Score (PDCAAS) compared to other home cooking methods.
Baking and microwaving are also effective methods for retaining protein quality. Frying, especially for long periods, can negatively impact the amino acid score due to high heat exposure. The majority of the protein resides in the flesh, not just the skin, so consuming the whole potato after proper cooking ensures maximum protein and nutrient intake.