Cashews are a popular ingredient in plant-based diets, often used as a source of protein, healthy fats, and texture. Protein is a macronutrient composed of amino acids, which serve as the fundamental building blocks for tissues, enzymes, and hormones. For those monitoring their nutritional intake, the question of whether cashews provide a complete protein profile is common. The direct answer is that cashews, like most nuts, are not classified as a complete protein source.
What Makes a Protein Complete?
A food is designated as a complete protein only if it contains all nine of the essential amino acids (EAAs) in adequate proportions. The human body requires 20 different amino acids for optimal function, but it can only synthesize 11 of them internally. The remaining nine must be obtained directly through diet:
- Histidine
- Isoleucine
- Leucine
- Lysine
- Methionine
- Phenylalanine
- Threonine
- Tryptophan
- Valine
If a food contains all nine EAAs, but one is present in a quantity too low to support the body’s needs, that food is considered an incomplete protein. This is governed by the “limiting amino acid,” which is the EAA present in the smallest amount relative to the body’s requirement. The limiting amino acid determines the overall usability of the protein. Consuming a variety of protein sources is necessary to ensure the body receives sufficient amounts of all nine essential amino acids.
Cashews’ Amino Acid Profile
Cashews are a nutrient-dense food, providing protein, healthy monounsaturated fats, and minerals like copper and magnesium. While they contain all nine essential amino acids, the concentration of one or more is too low to meet the definition of a complete protein. The primary limiting amino acids in cashews are typically the sulfur-containing amino acids, specifically methionine and cysteine.
If cashews were the sole source of protein in a diet, the body would not efficiently utilize the other amino acids for protein synthesis. The low level of methionine and cysteine prevents the full utilization of the other eight essential amino acids. Cashews remain a high-quality source of protein, offering approximately five grams per one-ounce serving. Their status as an incomplete protein highlights the need for dietary variety.
Pairing Cashews for a Complete Protein
The nutritional gap created by the limiting amino acid in cashews can be bridged through complementary proteins. This involves combining two or more incomplete protein sources whose amino acid deficiencies cover one another. Since the body maintains a pool of amino acids throughout the day, these complementary foods do not need to be consumed in the same meal to be effective.
Cashews, being low in methionine and cysteine, pair well with foods rich in these sulfur-containing amino acids. Grains, such as rice, oats, or whole wheat, are typically higher in methionine and cysteine, making them an excellent complement. Cashews are also sometimes low in lysine, which is abundant in legumes like beans, lentils, and peas. Combining cashews with roasted chickpeas or adding them to a lentil-based curry are simple ways to create a complete protein profile over the course of a day.