Effect of soy isoflavones and ascorbic acid supplementation on antioxidant activity in postmenopausal women

ISRCTN	ISRCTN98074661
DOI	https://doi.org/10.1186/ISRCTN98074661
Protocol serial number	N/A
Sponsor	Arizona State University - Sustainable Technologies, Agribusiness and Resource Center (USA)
Funder	Arizona State University - Sustainable Technologies, Agribusiness and Resource Center (USA)

Submission date: 04/01/2005
Registration date: 24/02/2005
Last edited: 19/09/2017

Recruitment status: No longer recruiting
Overall study status: Completed
Condition category: Signs and Symptoms

Prospectively registered

Protocol

Statistical analysis plan

Results

Individual participant data

Plain English summary of protocol

Not provided at time of registration

Contact information

Dr Andrea Hutchins
Scientific

Department of Nutrition
Arizona State University
7001 East Williams Field Road
Mesa
85212
United States of America

Phone	+1 480 727 1097
Email	andrea.hutchins@asu.edu

Study information

Primary study design	Interventional
Study design	Randomised, double blind, crossover designed study
Secondary study design	Randomised controlled trial
Scientific title	Effect of soy isoflavones and ascorbic acid supplementation on antioxidant activity in postmenopausal women: a randomised controlled trial
Study objectives	This study investigated the extent to which vitamin C and isoflavones, as single or combined supplements to a habitual diet, provided antioxidant effects by reducing lipid oxidation in blood. Healthy, non-smoking, postmenopausal women were screened for regular soy consumption (one serving per day), vitamin C supplementation (60 mg/day), and postmenopausal status. Utilising a randomised, double blind, crossover design, ten subjects were assigned to one of four dietary treatments. Subjects were instructed to continue their habitual physical activity and dietary habits during the 14-week experiment. The subjects completed consecutive two-day diet and activity logs immediately prior to each fasted blood draw. Diet and activity logs were analysed. Fasting blood was collected in vacuutainers, centrifuged, and plasma aliquots were frozen at -70°C for later analysis. Plasma vitamin C concentration was determined using a 2,4-dinitrophenylhydrazine method by Omaye. Lipid peroxides were measured using the flurometric method. Total cholesterol was determined by a photometric assay; high-density lipoprotein (HDL) cholesterol by a homogenous enzyme immunoassay; and, triglycerides and low-density lipoprotein (LDL) cholesterol by a colorimetric assay (performed by Sonora Quest Laboratories, Phoenix, AZ).
Ethics approval(s)	The Human Subjects Committee of the Institutional Review Board of Arizona State University approved this study; all participants gave written informed consent before participating.
Health condition(s) or problem(s) studied	Antioxidant markers and risk factors for heart disease
Intervention	Ten subjects were assigned to one of four dietary treatments: 1. Supplement of 5 mg isoflavones per kg/body weight (IF) 2. 500 mg vitamin C supplement (VC) 3. Supplement of 5 mg isoflavones per kg/body weight and 500 mg vitamin C supplement (IF-VC) 4. Placebo (C) The two week treatment periods were separated by a two week washout period.
Intervention type	Supplement
Primary outcome measure(s)	Lipid peroxides
Key secondary outcome measure(s)	1. Vitamin C 2. Total cholesterol, including LDL, HDL and Triglycerides (TG) 3. Blood pressure
Completion date	30/06/2002

Eligibility

Participant type(s)	Patient
Age group	Adult
Sex	Female
Target sample size at registration	10
Key inclusion criteria	Healthy, nonsmoking, postmenopausal women were screened for regular soy consumption (less than or equal to one serving per day), vitamin C supplementation (less than or equal to 60 mg/day), and postmenopausal status (one year).
Key exclusion criteria	1. Vegetarianism 2. Current or past diagnosis of cancer 3. Cardiovascular disease or diabetes 4. Chronic illness or inflammation 5. Gastrointestinal disorders 6. Recent (previous six months) use of antibiotics, and use of hypoglycaemic or hypolipidaemic medication 7. Body mass index (BMI) less than or equal to 35 kg/m^2 8. Consumed less than or equal to two alcoholic drinks per day
Date of first enrolment	01/01/2002
Date of final enrolment	30/06/2002

Locations

Countries of recruitment

United States of America

Study participating centre

Department of Nutrition

Mesa
85212
United States of America

Results and Publications

Individual participant data (IPD) Intention to share	No
IPD sharing plan summary	Not provided at time of registration
IPD sharing plan

Study outputs

Output type	Details	Date created	Date added	Peer reviewed?	Patient-facing?
Results article	results	01/07/2005		Yes	No
Other publications	case report	23/06/2005		Yes	No

Editorial Notes

19/09/2017: Publication reference added.