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SOY NUTRITIONAL CONTENT

Like other legumes, soybeans are rich in nutrients. However, the macronutrient profile of soybeans differs in some important ways from most other legumes. Soybeans are higher in both protein and fat than other beans and are relatively low in carbohydrates.

MACRONUTRIENTS IN SOYBEANS

Protein: Soybeans derive about 35 to 38 percent of their calories from protein compared to approximately 20 to 30 percent in other legumes. Soy protein is also of the highest quality. Under guidelines adopted by the Food and Drug Administration and the World Health Organization for evaluating protein quality for children and adults, soy protein isolate receives a rating of 1, which is the highest possible score. This means that the quality of soy protein is equal to that of meat and milk proteins.


Fat: Approximately 40 percent of the calories in soy derive from fat; most legumes (with the exception of peanuts) contain between 2 and 14 percent fat. The fat portion of the soybean is used extensively both in the food industry and directly by consumers. Soybean oil is a common cooking oil; cooking oils sold as "vegetable oil" are usually soybean oil.


Most of the fat in soybeans is unsaturated. Polyunsaturated (primarily linoleic acid), monounsaturated (oleic acid) and saturated (primarily palmitic acid) fats make up 63 percent, 23 percent, and 14 percent respectively of the fat in soybeans. [USDA] The polyunsaturated fat content of soybeans is of interest because it includes linolenic acid (seven percent of the total fat content), an omega-3 fatty acid. Soybeans are one of the few plant sources of omega-3 fatty acids. Omega-3 fatty acids may be essential nutrients for infants and they may also help to reduce risk of both heart disease and cancer.


Some soyfoods have the fat removed. Defatted soy flour is available and the amount of fat in textured soy protein is negligible. Reduced-fat tofu and reduced or non-fat soymilk are also available to consumers who need to decrease fat in their diets.



Source: USDA

Fiber: All whole, unprocessed plant foods contain dietary fiber. One serving of soybeans provides approximately eight grams of dietary fiber. However, some soyfoods are processed in ways that decrease their fiber content significantly. Tofu and soymilk contain very little fiber, while soyfoods that utilize the
whole bean — such as tempeh, soy four and textured soy protein — are high in fiber. About 30 percent of the fiber in soyfoods is soluble fiber.


MICRONUTRIENTS IN SOYFOODS

Calcium: Many soyfoods are good sources of calcium. One half cup of cooked soybeans provides 88 mg of calcium. Processing affects the calcium content of soyfoods considerably. Many brands of tofu are made using calcium sulfate as a coagulant (sometimes referred to as "calcium-set" tofu) and can contain between 120 and 750 mg of calcium per 1/2 cup serving. Soymilk contains about 93 mg of calcium per one cup serving. However, a growing number of calcium-fortified soymilks are available; these often contain between 200 and 300 mg of calcium per serving. Although soyfoods are high in both oxalates and phytate, two compounds that inhibit calcium absorption, the calcium from soyfoods is very well absorbed and has a fractional absorption rate equal to that of milk.


Iron: A 1/2 cup serving of cooked soybeans provides four mg of iron. However, both phytate and soy protein reduce iron absorption so that the iron in soyfoods is generally poorly absorbed. Vitamin C can increase the amount of iron absorbed from soyfoods considerably, although absorption rates are still low. Iron may be better absorbed from fermented soyfoods like tempeh and miso.


Other nutrients: Soyfoods are high in zinc; 1/2 cup of cooked soybeans contains one mg of zinc. However, zinc is poorly absorbed from soyfoods. Soyfoods are also rich in copper and magnesium. Like many whole plant foods, soyfoods are also rich in B-vitamins, particularly niacin, pyridoxine and folacin.


NUTRIENT CONTENT OF SOYFOODS
Food Calories Protein
grams
Carbohydrate
grams
Fat
grams
Saturated Fat
grams
Soybeans
 1/2 cup, cooked
149 14.3 8.5 7.7 1.1
Tempeh 1/2 cup 165 15.7 14.1 6.4 1.1
Textured
 Soy Protein
 1/2 cup, cooked
59 11 7 0.2 fat-free
Soynuts 1/4 cup 202 15 14.5 10.0 1.6
Tofu 1/2 cup 94 10 2.3 5.9 0.9
Soy flour,
  defatted 1/4 cup
81.7 12.8 8.4 0.3 .02
Soymilk,
 plain 1 cup
79 6.6 4.3 4.6 0.5


Food Niacin
mg
B6
mg
Folic Acid
ug
Calcium
mg
Iron
mg
Magnesium
mg
Copper
mg
Zinc
mg
Soybeans
 1/2 cup, cooked
1.35 .20 47 88 4.42 74 .35 .99
Tempeh 1/2 cup 3.8 .25 43 77 1.9 58 .55 1.5
Textured Soy
 Protein
 1/2 cup, cooked
.75 .12 --- 85 2 86 .32 1.37
Soynuts 1/4 cup 0.6 .09 91 59 1.65 63 .35 1.35
Tofu 1/2 cup 0.2 .06 19 130* --- 127 .24 1.00
Soyflour,
 defatted 1/4 cup
0.65 .14 76 60 2.3 72 1 .61
Soymilk,
 plain 1 cup
1.4 .10 4 93 1.38 45 .288 .54
Miso 2 Tbsp. 0.3 --- 10.1 23 .95 14.5 .15 1
Adult Recommended
 Daily Allowance
15 1.6-2.0 180-200 800 10-15 280-350 1.5-3.0 12-15

Source: USDA
 
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