Studies focusing on the ingestion of diets containing soy protein as compared with control diets (that did not contain soy protein) demonstrated that soy protein is effective in lowering serum total cholesterol, LDL-Cholesterol, and triglycerides ~10% in individuals with hyperlipidemia.  Greater decreases in serum lipids were demonstrated with greater amounts of soy protein, however significant decreases were seen with 25 grams of soy protein per day.  No Random Control Trials (studies with a control and experimental group that show cause and effect) of soy protein have been done to evaluate the risk of coronary heart disease (CHD).

This information is from the 2001 Hyperlipidemia project. 
 

• Grade I means there is Good/Strong evidence supporting the statement;
• Grade II is Fair;
• Grade III is Limited/Weak;
• Grade IV is Expert Opinion Only;
• Grade V is Not Assignable.
• High (A) means we are very confident that the true effect lies close to that of the estimate of the effect;
• Moderate (B) means we are moderately confident in the effect estimate;
• Low (C) means our confidence in the effect estimate is limited;
• Very Low (D) means we have very little confidence in the effect estimate.
• Ungraded means a grade is not assignable.