Tofu, also known as soybean curd, is a soft, cheese-like food made by curdling fresh hot soymilk with a coagulant. Traditionally, the curdling agent used to make tofu is nigari, a compound found in natural ocean water, or calcium sulfate, a naturally occurring mineral. Curds also can be produced by acidic foods like lemon juice or vinegar. The curds then are generally pressed into a solid block.

Tofu is rich in high-quality protein. It is also a good source of B-vitamins and iron. When the curdling agent used to make tofu is calcium salt, the tofu is an excellent source of calcium. While 50 percent of the calories in tofu come from fat, a 4-ounce serving of tofu contains just 6 grams of fat. It is low in saturated fat and contains no cholesterol. Generally, the softer the tofu, the lower the fat content. Tofu is also very low in sodium, making it a perfect food for people on sodium-restricted diets.