Soy protein

Studies in people

• Benefit

  Muscle building and recovery²

  Soy protein builds lean muscle about as well as whey, and may help antioxidant levels in athletes.

• Benefit

  Cholesterol levels in adults⁴

  Soy protein may lower total and LDL cholesterol and triglycerides, and slightly raise HDL cholesterol, in adults.

• Benefit

  Kidney health in diabetes⁵

  In people with diabetes, swapping soy protein for animal protein may lower kidney filtering pressure and protein in urine.

• Benefit

  Bone-building hormone⁶

  In people, soy protein raised a bone-building hormone more than casein did, but did not change cholesterol.

• No harm found

  Muscle soreness after exercise⁷

  In soccer players, soy protein did not reduce muscle soreness or damage after hard training.

• Benefit

  Heart and gut health⁸

  Soy protein and soy fiber are common in foods, and soy fiber may help with laxation and cholesterol.

• Benefit

  Cholesterol and blood pressure⁹

  Soy protein, eaten as part of a low-saturated-fat diet, may lower cholesterol and blood pressure.

• Benefit

  Cholesterol and heart health¹⁰

  Eating soy protein as part of a low-fat diet lowered cholesterol in studies, but soy pills are not recommended.

• Benefit

  Weight and body fat¹¹

  A high-soy-protein, low-fat diet helped overweight people lose weight and fat while keeping muscle.

• No harm found

  Hormone effects in children¹²

  Long-term feeding with soy protein formula did not seem to cause oestrogen-like hormone effects in young children.

• Concern

  Iron absorption from food¹³

  Soy protein kept iron from being absorbed, and removing its phytic acid helped only partly.

• Benefit

  Blood vessel health¹⁴

  In kidney transplant patients, eating soy protein for five weeks improved blood vessel function, but the benefit faded after they stopped.

• Benefit

  Blood sugar after meals¹⁵

  In healthy young people, eating 40 g of soy protein before a glucose drink lowered the blood sugar rise.

• Benefit

  Muscle mass in older adults¹⁷

  In older people not yet frail, daily soy protein soymilk was linked to slight muscle mass gains, but more research is needed.

Animal and lab studies only

• Benefit

  Diabetes and blood sugar²¹

  In lab studies, soy protein and its peptides helped control blood sugar and inflammation linked to diabetes.

Study type not stated

• Benefit

  How soy lowers cholesterol²⁰

  Soy protein may lower cholesterol, but scientists do not yet know which part of soy does it.

How it’s made and used

• Muscle strength and size³

  In people doing weight training, soy protein supplements gave similar strength and muscle gains as whey protein.

• Growth hormone release¹⁶

  Soy protein alone raised growth hormone in women, but eating it in a meal did not.

• Meat-free food texture¹⁸

  Soy protein is used to make meat-free foods, but scientists are still working out how its gel texture forms.

• Plant-based cheese quality¹⁹

  Soy protein with soybean-derived casein may make plant-based cheese taste and work more like dairy cheese.

• Fat in sausages²²

  In lab-made sausages, soy protein gel used at 75% instead of fat held more water and scored well in taste tests.

• Lab test variation²³

  Soy protein's quality score can vary depending on which lab tests it.

The signal at the top counts the findings in people and in animal and lab studies. A concern in studies of people outranks animal and lab studies, and “No concerns” needs at least one finding in people. When most findings in people point one way, the page leans that way (“Mostly”), and every finding is still shown. Findings whose study type is not stated are shown but not counted. This page is a reference, not medical advice. It describes what regulators and published research say. Talk to a doctor or dietitian about your own diet.