glycemic indices and glycemic scores of composite meals from sweet potato and plantain peels

Description

ABSTRACT

Glycemic index is an important parameter designed to quantify the relative blood glucose response of foods in comparison with reference glucose. Determination of glycemic index and loads of carbohydrate- rich foods play as tools of nutritional guidelines for glycemic control and to reduce the risk of diabetic complications. Thus, the aim of this study was to determine glycemic index and glycemic loads of sweet potato and plantain peels which are commonly consumed food items of Nigeria.

The 23 healthy subjects were participated in the study from owerri, Imo State of Nigeria; the mean age was 27 ± 2 years. The sweet potato food items and plantain fruits were removed from bunches, washed, peeled manually, sliced (5mm width) using a slicer, steam blanched at 100 oC for 15 min and dried in a conventional oven (model pp 22 US, Genlab, England) at 60 oC to constant weight. The dried slices were milled, sieved to pass through 0.25mm mesh sieve, packaged in a low density polyethylene bag. Participants were informed to consume 50 g of carbohydrate portions of tested and reference foods. Blood sample were collected at 0 (fasting), 30, 60 and 120 minutes after ingestion of tested and reference foods. Glycemic index value of foods was calculated from the ratio of incremental area under the glucose curves of the foods. Glycemic loads for each food was determined from its glycemic index value and carbohydrate content. Data were statistically analysed by ANOVA and differences between means identified by the student t-test.

The plantain peels and sweet potato had a medium glycemic indices (GI: 60), in spite of they generated a high glycemic loads of 26 and 24 respectively. The plantain peels and sweet potato had significantly lower (p<0.0001) blood glucose response was noticed as compared to white bread. There was no difference of GI and GL of tested foods within the participants and statistically not significant (p>0.05).

This study showed that the plantain peels and sweet potato foods had a medium glycemic index and high glycemic loads. The tested foods had significantly lower blood glucose response as compared to reference food of white bread. The resulted GI and GL data of tested foods could be help as guide of food choices to control glycemic level and to reduce the risk of diabetic complications.

 

TABLE OF CONTENTS

COVER PAGE

TITLE PAGE

APPROVAL PAGE

DEDICATION

ACKNOWLEDGEMENT

ABSTRACT

CHAPTER ONE

• INTRODUCTION
• BACKGROUND OF THE STUDY
• PROBLEM STATEMENT
• AIM AND OBJECTIVES OF THE STUDY
• RESEARCH HYPOTHESIS
• SIGNIFICANCE OF THE STUDY
• SCOPE OF THE STUDY
• LIMITATIONS OF THE STUDY
• RESEARCH QUESTION

CHAPTER TWO

LITERATURE REVIEW

• SWEET POTATO
• NUTRITIONAL VALUE OF SWEET POTATO
• HEALTH BENEFIT OF SWEET POTATOES
• PLANTAIN PEEL
• NUTRIENT COMPOSITION OF PLANTAIN PEELS
• PLANTAINS PEELS ANTI-NUTRIENTS AND PROCESSING METHODS
• GLYCEMIC LOAD CONCEPT
• PORTION SIZE AND GLYCEMIC CONTROL
• DETERMINATION OF GLYCEMIC INDEX
• GLYCEMIC LOAD AND HEALTH
• GLYCEMIC LOAD AND DIABETES
• GLYCEMIC LOAD AND CORONARY HEART DISEASES
• GLYCEMIC LOAD AND OBESITY
• FACTORS AFFECTING PREFERENCE AND FOOD CHOICE

CHAPTER THREE

• MATERIAL AND METHODS
• STUDY DESIGN AND PERIOD
• SELECTION OF STUDY SUBJECTS
• PREPARATION OF THE RESEARCH FOODS
• DATA COLLECTION PROCEDURE
• LABORATORY SAMPLE COLLECTION FOR GLYCEMIC INDEX AND GLYCEMIC LOADS
• DETERMINATION OF GLYCEMIC INDEX AND GLYCEMIC LOADS OF FOODS
• DATA QUALITY CONTROL
• STATISTICAL ANALYSIS
• ETHICAL CONSIDERATION

CHAPTER FOUR

4.0      RESULT AND DISCUSSION

CHAPTER FIVE

• CONCLUSION

REFERENCES

ABBREVIATIONS AND THEIR MEANINGS

ADA      : American diabetic association

ANOVA  : Analysis of variance

AUC      : Area under curve

AOAC   : Association of official analytical chemistry

BMI      : Body mass index

BP         : Blood pressure

CHO     : Carbohydrates

SBP       : Systolic blood pressure

DBP      : Diastolic blood pressure

DM       : Diabetes mellitus

IDF        : International diabetes federation

T1DM  : Type 1 diabetes mellitus

T2DM  : Type 2 diabetes mellitus

GI          : Glycemic index

GL         : Glycemic load

Hc         : Hip circumference.

Kg/m²  : Kilogram per meter square

IAUCf   : Increment area under curse of diets above fasting baseline

IAUC r  : Incremental area under curve of reference above fasting baseline

Min       : Minutes

Mg/dl   : Milligram per deciliter

MmHg :  Millimeter mercury

SD         : Standard deviation

SPSS     :  Statistical               package for      social sciences

Wc        : Waist circumference

WHR     : Waist to hip ratio

WHO    : World health organization

 

                                                            CHAPTER ONE

1.0                                                    INTRODUCTION

1.1                                      BACKGROUND OF THE STUDY

The glycemic index (GI) is an important parameter, which designed to quantify the relative blood glucose response of foods (Wordu et al, 2013). It was first measured in 1981 by David Jenkins for the purpose of the ranking carbohydrate rich foods based on how they elevate blood glucose level after their intake (Foster-Powell et al, 2012). The glycemic index value is calculated by measuring the incremental area under the blood glucose curve following ingestion of a 50 gram of carbohydrate test food and compared with the area under the blood glucose curve following an equal intake of carbohydrate rich reference food (Foster-Powell et al, 2012). The numerical value of GI is determined  by measuring of the incremental area under the blood glucose response curve (iAUC) for the test food is divided by the incremental area under the blood glucose response curve for the reference food and the result is multiplied by 100 (Wolever et al, 2012).  The GI of each food was then calculated as the mean value across all subjects consuming that food (Camille et al., 2014). The test foods are then assigned a category based on their 0-100 ranking and the glycemic index values are categorized into low when less than 55 , medium if the values found between 55-70 and high when its value is greater than 70 (Wolever et al, 2012).  . Glycemic load (GL) refines; the concept of glycemic index to quantify the impact that a carbohydrate containing foods. The glycemic load value of a typical serving of each food was calculated by using the formula of: GL = GI × grams of carbohydrate in the typical serving size/100 (Wolever et al, 2012).  .

Glucose is utilized by the tissues and organs of body for purpose of fuels and the precursor for conversion to other intermediate molecules (Rajinder et al., 2012). After a high carbohydrate diets, the  blood glucose rises from a fasting level of 80-100 mg/dl (5  mM) to 120-140mg/dl (8 mM) within a period of 30 minutes to one hour and regulated in a narrow range (Rajinder et al., 2012). Within subsequent increase in blood glucose will also trigger the release of the insulin hormone from pancreatic beta cells (Rajinder et al., 2012).

The excess consumption of high glycemic index foods can lead to hyperinsulinemia, insulin resistance, weight gain and obesity (Perceval etal., 2011). The development of diabetes mellitus, obesity, cancer and cardiovascular disease has been reported to be linked to high glycemic index foods. The studies shown that, there was a positive correlation between consumption of foods with high glycemic index and increased risk of chronic disease such as diabetes (Perceval et al., 2011). The  nutrition plays a key role in the management and treatment of diabetes mellitus, thus foods with a low glycemic index can be beneficial in reducing the incidences of chronic diseases by avoid uncontrolled postprandial glucose load  (Perceval et al., 2011). WHO recommended that the GI of foods be used in conjunction with information about food composition to guide food choices and at least 55% of energy be derived from carbohydrate and should be rich in dietary fiber and low glycemic index ranking (Jenkins et al, 2012). The consumption of  foods with low glycemic index has several health benefits, these include reduced insulin demand, improved blood glucose control, weight losing and reduced blood lipid levels benefits by reducing the rate of carbohydrate absorption. In fact that some foods on the world market have been show their glycemic index rating on the nutrition information panel (Jenkins et al, 2012).

The socio-economic progress of Nigeria depends on the performance of agriculture sector. The root crops in country are covered by more than 1.62% of the small area under  all crops in the country. The potato, sweet potatoes and taro cover 25.2%, 38.11% and 19.72% of the total root crop area respectively and these crops contributed about 23.35%, 38.44% and 17.74% of the total root crop production respectively in the Nigeria. Plantain is an important staple food for  many countries including an Nigeria (Jenkins et al, 2012). Plantain is rich in carbohydrates, calcium, vitamins B and C and essential minerals and inferior in protein and fat content, so that the soybeans are often used to balance the diet in plantain consuming area. However, the nutrient composition has been varied based on varieties, age of the harvested crop, soil conditions and climate (Jenkins et al, 2012).

Sweet potato (Ipomoea batatas), is the most important food crops in the world due to its high yield  and ranked as the seventh most  commonly consumed carbohydrate rich foods in the world (Jenkins et al, 2012). Sweet potato is nutritionally high in carbohydrates contents and low in fat and protein constituents. It is also a good source of antioxidants, fiber, zinc, potassium, sodium, manganese, calcium, magnesium, iron, vitamin C and beta-carotene (Made et al., 2012). The  hypoglycemic activity response of sweet potatoes is associated with their resistant starch and digestibility (Made et al., 2012).

In view of these facts, it is important to determine the glycemic index and glycemic loads  of cassava and sweet potato foods to provide information on the GI and GL to guide food choices and avoid uncontrolled postprandial glucose load that could helps to guide food choices for management and prevention of DM complications. Although, there is no studies have been conducted on the information of the glycemic index and glycemic load of plantain and sweet potato peels foods of Nigreria. Therefore, the aim of this current study is to determine the GI and GL values of commonly consumed plantain and sweet potato peels of owerri, Imo State of Nigiria.

1.2      PROBLEM STATEMENT

Diabetes mellitus is a chronic metabolic disorder that characterized by the persistent of hyperglycemia due to defective insulin secretion or defective insulin action (Alemu, 2015). The prevalence of diabetes mellitus has been increasing from time to time in the world (Made et al., 2012) of affecting more than 366 million peoples and  its number is expected to rise to 552 million by 2030, due to the consequence of urbanization, obesity, sedentary lifestyles and other factors (Alemu, 2015). Nigeria is among the most populated country in Africa and currently challenged by the growing magnitude of chronic non communicable diseases like diabetes and its prevalence in Nigeria is around 1.9%, this is because of ageing of the population and lifestyle associated with rapid urbanization (Alemu, 2015). DM is mainly categorized as  type  1 diabetes mellitus, type 2 diabetes mellitus, and gestational (Alemu, 2015). Type 1 diabetes mellitus (T1DM) is typically a result of an autoimmune mediated process in which pancreatic β-cells  are destroyed resulting absent insulin  production (American Diabetes Association, 2012). Type 2 diabetes mellitus (T2DM) is characterized by the presence of chronic hyperglycemia, which results from resistance to insulin actions on peripheral tissues (American Diabetes Association, 2012). Most of the complications of diabetes mellitus are is associated with chronic hyperglycemia and increased generation of oxygen derived free radicals, which may lead to damage and failure of the kidneys, eyes, nerves, heart and blood vessels (Alemu, 2015). This study was carried out to determine the glycemic index (GI) and glycemic load (GL) values of commonly consumed plantain and sweet potato peels which will be very useful in controlling hyperinsulinemia, insulin resistance, weight gain and obesity.

1.3      AIM AND OBJECTIVES OF THE STUDY

The main aim of this study is to determine the glycemic index (GI) and glycemic load (GL) values of commonly consumed plantain and sweet potato peels of Owerri, Imo State of Nigiria.

The objectives of the study are:

1. To determine the glycemic response to ingested
2. To determine the glycaemic load of sweet potato and plantain peels.

• perform proximate analysis sweet potato and plantain peels

1. to understand the nutritional value of sweet potato and plantain peels.

1.4      RESEARCH HYPOTHESIS

H0 = There is no significant difference in the glycemic load of sweet potato and plantain peels.

H1= There is a significant difference in the glycemic load of sweet potato and plantain peels.

1.5      SIGNIFICANCE OF THE STUDY

Essentially, the glycemic load, which is the product of the glycemic index and the carbohydrate content of a given food, may be more useful than only the glycemic index. This is because the glycemic load takes into account the portion size of the food as well as the carbohydrate content. Glycemic load is a significant factor in dietary programmes aiming at the metabolic syndrome, insulin resistance, and weight loss.

When mixed meals containing carbohydrate foods of different glycaemic index are consumed, it is known that the difference in postprandial blood glucose response is maintained (Mathewos et al., 2015). However, the extent of this differential blood glucose response may be dependent on the size of the meal consumed. It is hoped that this study will come up with the optimal size of sweet potato and plantain peels which when consumed will have no effect on the blood glucose level. Knowledge of the glycemic load of sweet potato and plantain peels could serve as a guide to diabetics to choose the sweet potato and plantain variety with the best glycemic load.

It may also inform nutritionists, dieticians and diet therapists on the optimal sweet potato and plantain peels variety to recommend to prediabetics and diabetics when they counsel their clients. Since sweet potato and plantain peels is widely eaten across Nigeria, providing information on the nutritional value on sweet potato and plantain peels would be worthwhile and helpful to consumers. It is anticipated that the findings from the study will provide literature on sweet potato and plantain peels and its nutritional value.

This study will solve the problem of high intake of food containing large amount of carbohydrates. Example such as sweet potato and plantain peels. The study also makes important contribution to future research by contributing to the existing literature particularly on nutrition.

1.6        SCOPE OF THE STUDY

The research focused on sweet potato and plantain peels and their impact on the blood glucose. This study investigated all the possible sweet potato and plantain peels that are consumed in the country and to analyze the extent to which each of variety affects the blood glucose level.

1.7      LIMITATIONS OF THE STUDY

The study determined the glycemic indices and glycemic load of varieties of sweet potato and plantain peels. Sweet potato and plantain peels mixtures were analyzed. Findings cannot be easily generalized for other carbohydrate foods. The study focused on the effect sweet potato and plantain peels has on blood glucose level after it has been digested and so healthy individuals were used for the study. Diabetics already have elevated blood glucose levels and using them for the study may not be appropriate.

1.9      RESEARCH QUESTION

1. Do sweet potato and plantain peels high glycemic index scores?
2. What is the glycemic index of sweet potato and plantain peels?

Does sweet potato peels have high glycemic index than plantain peels?