Effects of Purple Sweet Potato on Bone Metabolism

EFFECTS OF PURPLE SWEET POTATO ON BONE METABOLISM

Sponsoring Institution

National Institute of Food and Agriculture

Project Status

TERMINATED

Funding Source

EVANS-ALLEN

Reporting Frequency

Annual

Accession No.

0220272

Grant No.

(N/A)

Project No.

KYX-50-09-24H

Proposal No.

(N/A)

Multistate No.

(N/A)

Program Code

(N/A)

Project Start Date

Oct 1, 2009

Project End Date

Sep 30, 2012

Grant Year

(N/A)

Project Director
wang, C.

Recipient Organization
KENTUCKY STATE UNIVERSITY
(N/A)
FRANKFORT,KY 40601

Performing Department
Human Nutrition & Health

Non Technical Summary
Osteoporosis is a debilitating and costly disease that affects millions of people. About 10 million individuals in the United States have the disease and another 34 million have low bone mass with increased risk for osteoporosis. The annual cost for treating osteoporosis related fractures in the U. S. is currently estimated to be $19 billion and is expected to rise to approximately more than $25 billion by 2025. Eight million of those affected by osteoporosis are women. Therefore, identification of treatment or prevention strategies for osteoporosis in postmenopausal women has significant socioeconomic implications. Currently available therapies have side effects that drive significant number of people to seek other alternatives. In addition, treatment becomes ineffective once bone fractures occur. Thus, research into novel nutritional strategies for preventing osteoporosis is urgently needed. Previous efforts to prevent osteoporosis have focused on calcium and vitamin D intake due to their recognized importance in bone metabolism. Epidemiological studies of human subjects have suggested that fruit and vegetable consumption may contribute to bone growth in children and the maintenance of bone density in adults. Recent studies showed that foods rich in anthocyanins, such as prunes and blueberries, prevent bone loss due to estrogen deficiency. Anthocyanins content of purple sweet potatoes is comparable to that of purple fruits such as blueberries. Purple sweet potato powder has strong antioxidant activities. Anthocyanins extracted from purple sweet potatoes protect liver function and suppress atherosclerotic lesions in mice. However, it is not clear whether purple sweet potato would help to prevent bone loss as observed for blueberries. Further research is also needed to clarify how the effects of purple sweet potato on bone may be influenced by dietary calcium intake. We will conduct two experiments with ovariectomized rats as the experiemntal model to determine the potential benefits of purple sweet potatoes on bone health. If the beneficial effects of purple sweet potatoes are confirmed, this project will add new options for postmenopausal women to prevent osteoporosis. The identification of new health benefits of purple sweet potato may also encourage local farmers to produce purple sweet potatoes locally.

Animal Health Component

(N/A)

Research Effort Categories

Basic

100%

Applied

(N/A)

Developmental

(N/A)

Classification

Knowledge Area (KA)	Subject of Investigation (SOI)	Field of Science (FOS)	Percent
702	3840	1010	100%

Knowledge Area
702 - Requirements and Function of Nutrients and Other Food Components;

Subject Of Investigation
3840 - Laboratory animals;

Field Of Science
1010 - Nutrition and metabolism;

Keywords

Goals / Objectives
The primary goal of this project will be to develop new nutritional strategies for preventing osteoporosis. The specific objectives of this project will be to: 1.) determine the effects of purple sweet potato powders on bone loss due to estrogen deficiency; 2.) determine the effects of purple sweet potato powder on bone loss due to estrogen deficiency in rats with low or high calcium intake; and 3.) promote consumption of vegetables and fruits for bone health and general wellness. The project will focus on nutrition and osteoporosis, a health problem of both local and national interest, using ovariectomized rats as the experimental model. The research will identify new health benefits of purple sweet potato, which may encourage local farmers to produce purple sweet potato.

Project Methods
Two experiments with female rats will be designed to achieve the objectives of this project. In Experiment 1, sixty adult female rats (> 6 month old) will be assigned into dietary treatment groups (10 rats per group): a. Control (Sham-operated and fed the control diet (AIN93M)), b. OVX Control (Ovariectomized and fed the control diet), c. Low purple sweet potato powder (PSPP) (AIN93M plus 5% PSPP), d. Medium PSPP (AIN93M plus 10% PSPP), e. High PSPP (AIN93M plus 15% PSPP). After 7 days of acclimatization on the control diet, all the rats will be subjected to sham-operation (Group a) or ovariectomy (groups b, c, d, e) and allowed one week for recovery before the experiment starts. A baseline group will be sacrificed at the beginning of the time of ovariectomy surgery to provide the baseline data. Other animals will be fed their assigned diets for 8 weeks before they are sacrificed. Group a will be fed ad lib and the intake of other groups will be adjusted to match the intake of Group a. Purple sweet potato powder will be prepared from purple sweet potato by freeze drying the pureed purple sweet potato at North Carolina University. The powder will replace equal amount of corn starch in the AIN 93M diet and mixed thoroughly with the rest of the ingredients. The amount of macronutrients will be adjusted to make all the diets isonitrogenous and isocaloric. At the end of the 8-week experimental period, blood samples and bone samples will be collected. The physical, chemical and histological properties of the bones will be evaluated. Data will be analyzed by least squares ANOVA using the GLM procedure of SAS. Treatments will be in the model for all dependent variables. Multiple comparisons will be made with the Tukey test among treatment means. In Experiment 2, sixty adult female rats (> 6 month old) will be assigned into dietary treatment groups (10 rats/group): a. Control (Sham-operated and fed the control diet (AIN93M, 0.5% Ca)), b. OVX control (Ovariectomized and fed the control diet AIN93M, 0.5% Ca), c. OVX with low calcium (ovariectomized and fed AIN93M with 0.25% calcium); d. OVX PSPP (AIN93M, 0.5% Ca plus 10% PSPP), e. OVX PSPP with low calcium (AIN93M, 0.25% Ca plus 10% PSPP). One group of rats will be killed at the beginning of the experiment. Other animals will be fed for their assigned diets for 8 weeks before they are killed. Group a will be fed ad lib and the intake of other groups will be adjusted to match the intake of Group a. Procedures for sampling and sample analysis, data analysis will be the same as described for experiment 1.

Progress 10/01/09 to 09/30/12

Outputs
OUTPUTS: Osteoporosis is a major public health threat for an estimated 44 million Americans, or 55 percent of the people 50 years of age and older. Osteoporosis occurs most frequently in postmenopausal women following the decrease in estrogen levels. Hormone-replacement therapy (HRT) is effective in preventing bone loss. However, Food and Drug Administration discourages people to use HRT for osteoporosis prevention because of its side effects. Thus, research into novel nutritional strategies for preventing osteoporosis is urgently needed. Previous efforts to prevent osteoporosis have focused on calcium and vitamin D intake due to their recognized importance in bone metabolism. Epidemiological studies of human subjects have suggested that fruit and vegetable consumption may contribute to bone growth in children and the maintenance of bone density in adults. Recent studies showed that foods rich in anthocyanins, such as prunes and blueberries prevent bone loss due to estrogen deficiency. Anthocyanin content in purple sweet potatoes is comparable or even higher than in blueberries. The objectives of this project were: 1.) To determine the effects of purple sweet potato powders on bone loss due to estrogen deficiency; 2.) To determine the effects of purple sweet potato powder on bone loss due to estrogen deficiency in rats with low or high calcium intake; 3.) To promote consumption of vegetables and fruits for bone health and general wellness. This project provided opportunities to train 9 undergraduate and high school students in food and nutrition research as a part of a special problems class and the Research and Extension Apprentice Program in the summer. At the annual Kentucky State University Field day, we gave presentations on the potential benefits of vegetables, especially purple sweet potatoes, and demonstrated practical ways of preparing purple sweet potatoes and the potato greens to 100 attendants at the monthly gathering of farmers and consumers at the "Third Thursday Thing" held at the Kentucky State University research farms in 2009, 2010 and 2011. Information on the health benefits of purple sweet potatoes and osteoporosis prevention were provided to visitors to the Kentucky State Fairs, and four local health fairs in Frankfort, KY. Surveys were also conducted on the interest of consumers in consuming purple sweet potatoes and related products. This project fostered collaboration between Kentucky State University and North Carolina State University on the preparation of purple sweet potato powder and its analysis. It also strengthened the cooperation between the human nutrition program and the organic vegetables research program at Kentucky State University in exploring the potential of growing purple sweet potatoes under Kentucky conditions. The research information from the project has also been disseminated through scientific presentations and related publications at the annual meeting of Kentucky Academy of Science, the Experimental Biology and the ARD symposium. A procedure for preparing freeze dried purple sweet potato powder was developed. PARTICIPANTS: Changzheng Wang, Principal Investigator, was responsible for the planning and execution of the experiments, publication of the results and reporting to the funding agency. Dr. Lingyu Huang, Co-investigator, assisted the principal Investigator in all aspects of the project. He was responsible for the maintenance and operation of the nutrition lab, supervision of student workers and research assistants, analysis of biological samples, and operation of dual-X-ray energy densitometer. Mr. Cecil Butler, Research Assistant, was primarily responsible for the care of lab animals and preparation of bone samples for histology studies. Dr. V. D. Truong, Department of Food Science, North Carolina State University, helped to obtain the purple sweet potato used in this project and advised on the preparation and analysis of purple sweet potato powder. Dr. Michael Bomford, at Kentucky State University, collaborated on growing purple sweet potato and promote the food use of both the vegetations and tubes of sweet potatoes. Ms. Anya Web, at the Kentucky Department of Public Health assisted us in conducting educational activities at the annual Kentucky State Fair in Louisville, KY. Mr. Travis Flora from the Commonwealth Credit Union assisted us with the educational programs at Health Fairs organized by the Commonwealth Credit Union in Frankfort, KY. Dr. Marion Simon, an extension specialist provided the opportunity for us to provide educational programs at the Kentucky State University Field Day and the "Third Thursday Thing". TARGET AUDIENCES: The target audience of this project include children and adults interested in bone health, and farmers interested in growing purple sweet potatoes. We have provided relevant information through handouts and personal interactions to visitors to the Kentucky State Fair in Louisville, local health fairs in Frankfort, KY. We made presentations and held discussions with participants at the Kentucky State University Field Day and the Third Thursday Thing at the Research Farm of Kentucky State University. The project also provided opportunities to train nine undergraduate and high school students and provided support for four undergraduate students to make presentations at the Kentucky Academy of Science and the ARD symposium in Atlanta. PROJECT MODIFICATIONS: The project was extended for one year because the delay in obtaining the sweet potato and technical difficulties in the preparation of the purple sweet potato powder.

Impacts
Two experiments with rats as the experimental model were conducted. Experiment 1 demonstrated that inclusion of purple sweet powder at up to 10% of the total diet tended to improve bone status of ovariectomized rats but inclusion of the powder at more than 10% tended to cause diarrhea with no additional beneficial effects on the bone. Preliminary data from experiment 2 indicate that inclusion of purple sweet potato powder at 10% of the total diet plus adequate calcium intake had a protective effect on bone mineral content and strength of ovariectomized rats. These results suggest that consumption of purple sweet potatoes may be helpful in the prevention of osteoporosis in postmenopausal women if there results could be substantiated with research involving human subjects. Laboratory analysis demonstrated that sweet potato greens are high in antioxidant activities and a group of 50 people showed high preference for the taste of stir-fried sweet potato greens indicating that sweet potato greens could be an alternative vegetable source for consumers. The organic vegetable research group has included the purple sweet potato in their evaluation of sweet potato varieties at the research farm. Two local farmers have indicated that they would be interested in growing purple sweet potatoes.

Publications

Erica Coleman,Changzheng Wang, Lingyu Huang and Cecil Butler. 2011. Self Perception of Body Weight Status And Willingness to Adopt Healthy Eating And Activity Behaviors Among Kentucky Adults. Presented to 2011 Annual meeting of Kentucky Academy of Science.
Lingyu Huang, Cecil Butler and Changzheng Wang. 2011. A procedure to prepare freeze dried purple sweet potato powder. Presented to 2011 Annual meeting of Kentucky Academy of Science.
Cecil Butler, Lingyu Huang, and Changzheng Wang. 2011. Acculturation and Body Weight Status of Chinese Immigrants in Kentucky. Presented to 2011 Annual meeting of Kentucky Academy of Science.
Changzheng Wang, Lingyu Huang and Cecil Butler. 2011. Childhood experiences with vegetable consumption and current body weight status of Kentucky adults. Presented to Experimental Biology 2011. April 12-13, 2011, Washington DC.
Changzheng Wang, Cecil Butler and Lingyu Huang. 2010. Major nutrition and health concerns among people living in rural Kentucky. Presented to Kentucky Academy of Science. Nov. 12-13, 2010.
Ramona Douglas, Changzheng Wang, Lingyu Huang and Cecil Butler. 2010. Early experiences with vegetable consumption and current body weight status of Kentucky adults. Presented to Kentucky Academy of Science. Nov. 12-13, 2010.
Lingyu Huang, Changzheng Wang, Cecil Butler, Jeremiah D. Lowe and Kirk W. Pomper. 2010. Antioxidant activity of primocane fruiting blackberries grown in Kentucky. Presented to Kentucky Academy of Science. Nov. 12-13, 2010.
Changzheng Wang, Lingyu Huang, Michael Bomford and Antony Silvernail. 2009. Sweet potato leaves as a source of antioxidant phenols. HortScience. 44(4):1096.
Cecil Butler, Lingyu Huang and Changzheng Wang. 2009. Modifying weighing procedures to save time and reduce disturbance to laboratory rats. Submitted to the Annual Meeting of Kentucky Academy of Science, Highland Heights, KY, Nov. 13-14, 2009.
Lingyu Huang, Cecil Butler, Changzheng Wang. 2009. Attitudes about sweet potato as a food source for people. Presented to the Annual Meeting of Kentucky Academy of Science, Highland Heights, KY, Nov. 13-14, 2009.
Lingyu Huang, Cecil Butler and Changzheng Wang. 2009. Effects of tomato and broccoli powder on uterine weight of ovariectomized rats. Presented to the Annual Meeting of Kentucky Academy of Science, Highland Heights, KY, Nov. 13-14, 2009.
Jonathan Strayer, Changzheng Wang, Lingyu Huang and Cecil Butler. 2009 Impact of Knowledge and Attitudes Related to Vegetable Consumption on Body Weight Status of Kentucky Adults. Proceedings of 15th ARD Symposium, Atlanta, March 29 - April 1, 2009. Page 81.
Changzheng Wang, Lingyu Huang, Cecil Butler, Martha Marlette and Susan Templeton. 2009. Frequency of Eating in Buffet Style Restaurants and Body Weight Status of Adults. Proceedings of 15th ARD Symposium, Atlanta, March 29 - April 1, 2009. Page 125.
Changzheng Wang, Lingyu Huang and Cecil Butler. 2012. Body weight perception and willingness to adopt healthy eating and activity behaviors among Kentucky adults. Presented to Experimental Biology 2012, April 21-25, San Diego.