Comparing the Effect of Whey and Soy Protein on the Absorption of Pomegranate Polyphenols in the Human Body

Pomegranate (Punica granatum L.) fruits are widely consumed as pomegranate juice (PJ), and their health benefits have been studied extensively in animals and humans (1-6). The pomegranate fruit is a rich source of polyphenols, most of which are ellagitannins (ETs). Pomegranate extracts,which incorporate these major polyphenols from the pomegranate fruit, have been developed in dry and liquid forms to provide alternative convenient sources for obtaining the bioactive polyphenols found in PJ. We have previously reported on the pharmacokinetics and metabolism of pomegranate polyphenols, after the consumption of PJ in normal healthy human volunteers (7). In humans, ETs are converted to ellagic acid (EA) in the small intestines and absorbed with a maximum plasma concentration observed at approximately 1 hour. EA disappears from plasma 6 hours after administration of PJ. Ellagitannins and ellagic acid remaining in the intestine and are then further converted by gut microflora to urolithin-A, absorbed and derivatives, which are metabolized by phase II enzymes and excreted in human urine for up to 48 hours after consumption of PJ(7).

Polyphenols are dietary constituents of plants associated with health-promoting effects. In the human diet, polyphenols are generally consumed in foods along with macronutrients. Because the health benefits of polyphenols are critically determined by their bioavailability, the effect of interactions between plant phenols and food macronutrients is a very important topic. The protein-polyphenol complexes can significantly change the plasma kinetics profile. (8) Protein-polyphenol binding is mediated by a combination of hydrogen and hydrophobic bonding depending on chemical (polarity) and structural (size/shape) properties of interacting molecules. Covalent interactions between purified glycinin, a soybean storage protein, and selected flavonoids and phenolic acids have also been reported. Recently it is reported that protein-rich defatted soybean flour protects anthocyanins during transit through upper digestive tract for subsequent colonic delivery/metabolism (9).

Inclusion criteria

• Male or female >20 and < 45 years of age at the time the consent form is signed.
• Subject must sign the Institutional Review Board-approved written informed consent prior to the initiation of any study specific procedures or randomization. A subject will be excluded for any condition that might compromise the ability to give truly informed consent for participation in the study.

Exclusion criteria

• Any subject who is eating more than 4 servings per day of fruits and vegetables, taking vitamin supplements or taking any antibiotics or other medication or dietary supplement which interfere with the absorption of polyphenols.
• Any subjects with a history of gastrointestinal surgery (except for appendectomy), diabetes mellitus, or other serious medical condition, such as chronic hepatitis or renal disease, bleeding disorder, congestive heart disease, chronic diarrhea disorders, myocardial infarction, coronary artery bypass graft, angioplasty within 6 months prior to screening, current diagnosis of uncontrolled hypertension (defined as BP >160mmHg, diastolic BP>95mmHg), active or chronic gastrointestinal disorders, bulimia, anorexia, laxative abuse, or endocrine diseases (except thyroid disease corrected with medication to normal laboratory values) as indicated by medical history or routine physical examination.
• Major surgery within 12 weeks prior to subject randomization and/or screening, especially cardiac surgery
• Is currently a smoker who has a therapeutic plan to quit smoking anytime during the study period; or if not a current smoker, has quit smoking within the past 3 months.
• Known HIV positive.
• Clinical evidence of current malignancy with the exception of basal cell or squamous cell carcinoma of the skin and cervical intraepithelial neoplasia.
• Currently receiving systemic chemotherapy and/or radiotherapy.
• Active bleeding.
• Subject has any disorder (excluding illiteracy or visual impairment) that compromises the ability of the subject to give written informed consent and/or to comply with study procedures.
• Subject who is allergic to soy protein.
• In the opinion of the study investigator has a risk of non-compliance with study procedures, or can not read, understand or complete study related materials.