ABSTRACT
Effect of controlled fermentation with Candida tropicalis on glycaemic index of cassava, maize and sorghum flours and blood glucose response, protein utilization, mineral and vitamin bioavailability of their blends in diabetes induced adult rats was studied. Candida tropicalis was isolated and used in semi-solid state controlled fermentation of the starchy foods at 0, 24, 48 and 72h. Physicochemical composition of the fermented starchy flours and two under-exploited unfermented legume seed flours of Bielschmeidia gabonensis (BG) and Cola gigantean (CG) used as soup thickeners were determined. Standard techniques and statistical methods were adopted to generate data, separate and compare means of preliminary results. Three diets based on 24h fermented cassava (CA24h), maize (MA24h), sorghum (SO24h) and unfermented Cola gigeantea (CG) were used for the rat study. These test diets provided 1.6g nitrogen daily and 20g total dietary fibre/1000kcal in a ratio of 1:2, soluble: insoluble dietary fibre to mimic traditional diets. Rat chow (RC) served as the control. Sixteen adult rats (160-196g) were allotted to both control and 3 test diets in groups of 4 on the basis of body weight. The rats were individually housed in metabolism cages, induced diabetes with streptozotocin and fed ad libitum in a14-day balance study. Food intake, body weight, fasting blood glucose (FBG), plasma proteins, blood urea nitrogen (BUN), carcass nitrogen (CN), liver composition, protein, vitamin and mineral bioavailability were determined. All analyses were done using standard techniques to generate data. Completely randomized design was adopted for the bioassay. Students’ t-test, Duncan’s new multiple range test and Fisher’s least significant difference test were employed to separate and compare means statistically (p<0.05). CG had significantly (p<0.05) lower GI (68.30% versus 85.82), Ca and Fe and significantly (p<0.05) higher oxalate than BG (13.86g versus trace). The CA24h, MA24h, SO24h flours had the best chemical value for viscosity (4.21cps, 2.49cps and 3.01cps, respectively), TDF (6.24%, 6.36% and
5.69%, each); TS (67.17%, 56.35% and 56.96%, each) and GI (44.01%, 47.43% and 46.68%, respectively). These GI values were significantly
(p<0.05) lower relative to their controls (93.06%, 94.76% and 84.66%, respectively). Calcium (Ca), zinc (Zn), magnesium (Mg) and riboflavin in fermented flours increased significantly (p<0.05) while Iron (Fe) significantly (p<0.05) decreased relative to the controls (0.64-0.73mg versus
0.0-0.40mg). Test diets had significantly (p<0.05) high oxalate relative to the safe level (3.75g versus 6.0g, 8.0g and 11.5g for CA24h CG, MA24hCG and SO24hCG, respectively). Test diets significantly (p<0.05) reduced blood glucose (BG) in all groups of rats (420-465mg/100ml to
82.0-83. 50mg/100ml). N balance was positive for all groups of rats. Rats fed MA24hCG diet had significantly (p<0.05) higher food intake and biochemical profile over those of both control and other test diets. Thiamin, riboflavin and niacin retentions were negative for all rats (-0.003 to
-0.012mg; -0.40 to -0.88mg and -39.22 to -53.25mg, respectively). Calcium retention was positive for both test and control diets (101.89mg –
188.80mg). Mg retention was positive for CA24hCG (4.12mg) and MA24hCG (5.48mg) test diets alone. Fe retention was negative for all the groups (-30.35 to -68.07mg). Zn content of the diet was negligible, as well as in the metabolic waste. Candida tropicalis fermentation reduced GI of the traditional high GI starchy staples from 84-94% to 45-47%. C. gigeantea had lower GI than B. gabonensis. The novel diets based on blends of these low GI starchy flours and Cola gigeantea (a leguminous soup thickener) (in 1:2 ratio of soluble to insoluble dietary fibre) produced high dietary fibre diets which attenuated the high blood glucose in diabetic adult rats but compromised their protein utilization as well as mineral and vitamin balance. Further investigations on diabetic rats fed varying ratios of these low GI fermented traditional starchy staples and Cola gigeantea are needed to clearly establish safer levels of the blends with regard to food intake, weight loss and glycaemic control.
CHAPTER ONE
1.1 Background to the study
INTRODUCTION
Food is fundamental to human survival and constitutes a form of cultural expression. A people’s culture has a lot of influence on the kind of foods they eat and how they eat them. Hence, the term traditional foods, has been adopted to describe all foods from a particular culture, available from local sources and culturally acceptable as appropriate and desirable foods (Kulhnlein & Receveur, 1996). These traditional foods are often used in nutritional sciences as basis for ensuring and optimizing the utilization of indigenous foods and their health benefits by individuals, households and communities. Traditional foods are obtained from two main sources; namely plant and animal sources.
Plant foods have remained the ultimate source of nutrients for larger population of the world. Plant materials are used for socio-cultural, diabolic, nutritional and therapeutic purposes. The global concern for the diversification of the uses of plant foods to improve normal and therapeutic nutrition has shifted scientists’ interest to enhancing the potential sources of beneficial constituents in plant foods. One approach is through food biotechnology. Food-enhancing biotechnology has challenged scientists to integrate it within their own research and innovative systems, in accordance with their local needs and priorities. In this regard, Tagwireyi (2003) posits that the potential of biotechnology exists in sub-Saharan Africa if it can be adapted to the prevailing diet-related problems in the region.
A variety of plant foods (maize, rice, sorghum, millet, yam, cassava, cocoayam and legumes) are mainly produced as subsistence food crops in Africa. They are more commonly and widely consumed in Nigeria and other developing countries than in the developed world. They are also relatively cheap and contribute appreciably to the nutrient intake (energy, protein, fat, vitamins and minerals) of the less developed world. In Nigeria, starchy staples (cereals, roots/tubers) and legumes constitute the major part of the traditional diets, up to
70% and 25%, respectively. However, while cereals are the major staples in the north with higher intake of animal protein sources (mutton, beef and milk), starchy roots and tubers are the main staples in the south with relatively more consumption of legumes (Maziya-Dixion et al., 2004).
A comprehensive review of available information on the nutritional and chemical composition of indigenous plant foods consumed in Nigeria has been published (Osagie & Eka, 1998). The results from the various researchers on plant foods focused mainly on their nutrient and anti-nutrient contents. Nevertheless, there is still much to be learnt about some of the non-nutrient components of the traditional plant foods. The full exploitation of a plant material for normal and therapeutic purposes may not be realized until the potentials of the plants are properly elucidated.
Despite the presence of anti-nutrients in raw foods, foods of plant origin also contain many bioactive compounds, which are not regarded as nutrients, but have possible benefits to human health. These include phytochemicals and dietary fibre, which are found naturally and abundantly in all plant foods. Phytochemicals are generally defined as naturally occurring components of plants that have physiological effects in humans beyond the traditional nutrients they contain (Liu, 2004; Nyam News, 2005). They act as natural defense systems for their host plants and also provide colour, aroma and flavor (McCarty, 2004). Phytochemicals’ direct antioxidant activity as well as modulation of enzyme expression or
hormone activity, contribute to their disease-preventing effects and protection from vascular diseases and many cancers in particular (McCarty, 2004).
Dietary fibre, on the contrary, consists of a heterogeneous mixture of non-starchy polysaccharides (NSP) (Kritchevisky, 1988) found naturally and abundantly in all plant foods. It is defined as ‘polysaccharides and lignin that are not digested in the human small intestine’ (Champ, Langkilde, Brouns, Kettlitz & Collet, 2003). In cereals, starchy roots and tubers, it occurs as water-insoluble NSP (cellulose and lignins). The more water-soluble NSP tend to have viscosifying properties and occurs in leguminous seed crops mostly as storage polysaccharides (gums and hemicellulose); and in leaves, vegetables and fruits as pectin. The benefits of dietary fibres in relation to chronic diseases have been reported by some workers (Fung, Glen, John-Cliff & Feritt, 2002; Jenkins et al., 2003; Champ et al., 2003; WHO,
2003). Specifically, there have been reviews on the role of soluble dietary fibre-rich foods in the dietary management of diabetes and cardiovascular diseases (Odenigbo, 2001; McCarty,
2004). Despite these findings, there are stray reports on the beneficial effects of dietary fibre- rich traditional diets based on the more commonly and highly cherished starchy staples.
More recently, resistant starch has received attention as one of the components of carbohydrate foods that is closely linked to glycaemic control. This is because the dietary fibre analytical methods were unable to recover oligosaccharides and carbohydrate polymers of less than 50 or 60 degrees of polymerisation (DP) (Champ et al., 2003). Resistant starch has been defined as starch that escapes digestion in the small intestine and becomes available for fermentation by the microflora in the large intestine (Englyst and Cummings, 1990). It has been shown to have a close link with gelatinization, a process that leads to the production of retrograded starch. Evidently, gelatinization favours starch hydrolysis and production of high glycaemic index foods. Conversely, retrogradation retards digestion and attenuates blood glucose response to foods. Due to its health implications, it has been recommended that food labels should reflect the resistant starch contents of foods. Currently, it appears that such information on local foods is not existent in Nigeria.
The various sources of dietary fibre and resistant starch contain different levels of active ingredients (Imeson, 1994) with varying glycaemic effects (Onyechi et al., 1998; Champ et al., 2003). This variation is associated with the term glyacaemic index (GI). Leeds, Brand-Miller, Foster and Colagiuri (1998) described it as the ranking of foods based on their immediate effects on blood glucose levels compared with equal amount of reference food (a substance which produces the greatest rise in blood sugar levels). The starchy foods have high GI (>70%) and are consumed as main ingredients in mixed meals traditionally
compared to the low values (<50%) for legumes, fruits and vegetables. The latter are consumed in lesser quantities in Nigeria. The low-GI foods have different effects when utilised in isolation and in mixed diets. Considering high intake of carbohydrate in Nigeria, what would people with diabetes in Nigerian reckon with? The quantity or type of carbohydrate consumed? Both have been shown to play important and respective roles in determining the physiological effects of dietary fibre in diabetes control (Ellis, 1999).This calls for evidence-based studies that might highlight possible ways of developing low GI starchy staple-based traditional diets/products and a sound dietary guideline for type 2 diabetics in Nigeria.
It has been argued that high dietary fibre intake influences mineral and vitamin bioavailability. This presents a risk of deficiencies of these nutrients, especially with regard to those associated with diabetes control like zinc, iron, calcium and magnesium as well as thiamin, riboflavin and niacin. Many foods rich in fibre have also been reported to be rich sources of nutrients such that mineral uptake and thus mineral balance would not be adversely influenced by ingestion of these foods (Frolich, 1996). It appears then that there exists an agreement among proponents of dietary fibre research that the risk of mineral and vitamin deficiencies is minimal when dietary fibre intake is reasonable and the mineral and vitamins intake adequate. The need to elucidate information on amount of minerals and vitamins provided by a high-fibre traditional diet as well as the amount absorbed and used by the body becomes imperative.
The International Institute of Tropical Agriculture (IITA, 1988) has defined a staple food crop as that which accounts for more than 200 calories per day in the diet of individual.Tubers/roots contain 1-1.4% protein, 24.5-35% carbohydrate (Platt, 1985) and 8.5- 17.4% dietary fibre (Tanya, Mbofung & Keshinro, 1997). The proteins of roots and tubers are deficient in sulphur-containing amino acids (methionine and cystine) (Bradbury& Halloway, 1988).Cereals contain 6.96-13.69% protein, 68-89.89% carbohydrate (Osagie & Eka, 1998) and 5.1-6.4% dietary fibre (Tanya et al., 1997). The nutritional quality of most cereals is poor because they contain less of the essential amino acids, particularly lysine, needed for growth and maintenance (FAO/WHO, 1973). Both roots/tubers and cereals are generally less viscous. The more viscous legumes (including oil seeds) contain 20-40% protein, 41-61% carbohydrate but 18-20% for oils seeds (Platt, 1985; Osagie & Eka, 1998), and 6-25% dietary fibre (Ene-Obong & Carnovale, 1992; Nwokolo & Smartt, 1996). Any food processing technique that would improve the nutritional quality, physico-chemical
properties and glycaemic indices of these important edible traditional staples would affect better glycaemic control.
Fermentation was identified as simple economic household and industrial biotechnological technique. However, household fermentation is more widely used in Nigeria and has wide application traditionally in many parts of the world (Alnwick, Moses & Schmidt, 1987). Although very few fermented foods are produced and consumed in Nigeria, they make appreciable contribution to the nutrient intake of Nigerians (Onofiok, Nnanyelugo & Ukwondi, 1996). A lot of work has been conducted on the effect of fermentation on plant foods to improve their nutritional quality (Obizoba & Egbuna, 1992; Nzomiwu, 1994); bioavailability (Nnam, 2008) safety (Mortarjemi & Nout, 1996) and acceptability (Tomkins et al., 1987). Available information on the effect of fermentation on carbohydrates only reported increases in total soluble and reducing sugars (Oyewole & Odunfa, 1989; Mlingi,
1987) and reduced starch, oligosaccharides and total crude fibre levels (Riet, Weight, Cilliers & Datel, 1987). Such works aimed at reducing the dietary bulk properties and viscosity of foods to improve starch and protein digestibility and nutrient density of the diets for feeding infants and young children to treat and /or control malnutrition.
Natural fermentation is recognized as an important processing method of cassava and corn (maize) into food for household consumption (Odunfa, 1985). Ihedioha and Chineme (1999) had reported that depletion of protein of “gari”, which was associated with increased fermentation period (72-96h), led to increased diabetogenicity in rats. On the contrary, controlled fermentation has been used for protein enrichment of cassava and maize flours (Azoulay et al., 1980) used fermentation methods for protein enrichment of cassava and maize flours with Candida tropicalis. Their results showed increases from 3.1-18.8%, 1.1-
7.7%, 0.7-2.7%, 0.5-2% for total protein, lysine, methionine and cystine contents, respectively. From the above literature and considering the factors that affect GI of a food/diet already mentioned earlier, it is pertinent to employ a fermentation process that would both improve the protein level and modify the carbohydrate contents of the starchy foods/diets. This process should maintain an acceptable level of digestible carbohydrate of the starchy staples as well as favour an increase in their GI lowering properties.
The burden of chronic diseases is rapidly increasing worldwide. These diseases are defined by World health Organization (WHO) (2009) as diseases of long duration and generally slow in progression. They include, cardiovascular diseases (including hypertension and stroke), respiratory diseases, diabetes, obesity, some cancers and liver cirrhosis (WHO, 1990). There is mounting evidence that these diseases are the major cause of preventable
deaths in adults in both the richest and the poorest countries (WHO, 2006). In 2001, these diseases contributed approximately 60% of 56.5 million total reported deaths in the world and approximately 46% of the global burden of disease (WHO, 2003). It has been projected that by 2020, diet-related non-communicable chronic diseases (NCDs) will account for three- quarters of all deaths worldwide and that 70% of deaths due to diabetes will occur in developing countries. A worrying trend in Nigeria is that priority is given to alleviation and eradication of hunger, malnutrition and infection while little concern has been shown to combat diet-related NCDs in the country.
Diabetes is no longer regarded as the disease of affluent countries. In 1998, WHO declared it a major public health problem, which cuts across all races of the world. It ranks fourth among the diseases of public health importance worldwide (WHO, 2006). It is a disorder characterized by an elevation of fasting blood glucose, caused by relative or absolute insulin deficiency (WHO, 2006). It is mainly associated with disturbances of carbohydrate metabolism. It also involves disturbances of fat and protein metabolism. It subjects the sufferer to a variety of difficulties and presents a high level of complications, which if not properly managed, can lead to death. There are two major types of diabetes: type 1 and type
2 diabetes mellitus. They are also known as insulin dependent (IDDM) and non-insulin
dependent diabetes (NIDDM). Type 2 diabetes, is the most common type, accounting for 90-
95% of all diabetes cases (Levitt, 2008). About 10% of the national income of most countries in Sub-Saahara Africa is spent on diabetes treatment (Mbanya & Ramaiya, 2006). The enormous and escalating economic and social cost of type 2 diabetes, make a compelling case for attempts to reduce the risk of developing the condition as well as for energetic management of this established disease.
Diet is recognized as an important component in diabetes management. The beneficial effects of dietary fibre content of plant foods in moderation of glucose and lipid metabolism, mostly due to their viscous and fermentability properties have been reviewed above. Actualization of these health benefits has remained a mirage in Nigeria due to disproportionate intake of high GI starchy staples even in combination with dietary fibre-rich food sources like legumes. Inadequate habitual intake of fruits and vegetables at household level poses additional problem to achieving good glycaemic control. Growth of interest in the modification of starch contents of plant foods with high GI, to clinically safe levels, has been put forward as one of the strategies to encourage inclusion of more plant foods in the diets. It is necessary to explore food processing techniques that could help to achieve such objectives. It becomes imperative to study the nutritional and therapeutic potentials of the processed
traditional starchy staples and selected under-exploited indigenous leguminous plant foods as well as their metabolic effects when consumed as mixed diets.
1.2 Statement of the problem problem
Nutritional problem of public health importance is one that affects over 1% of the population. Type 2 diabetes mellitus qualifies as one and its prevalence rate appears to be on the increase. According to ACC/SCN report (1997), diabetes mellitus ranked fifth among the leading NCDs worldwide, affecting about 2% and 2.2% of the world’s population. A decade later, diabetes escalated from fifth to fourth position among the NCDs (cardiovascular diseases, cancers, chronic respiratory diseases and diabetes) with prevalence rates of 30%,
13%, 7% and 2%, respectively WHO (2006; 2008). A similar number remain undiagnosed (Parillo & Riccardi, 2004). WHO (2001) projected a 122% rise in the number of adults with diabetes by 2025. It thus appears that more people are continuously affected due to population growth without a corresponding increase in prevalence rate.
The overall prevalence of type 2 diabetesin Africa is 4.5% (Mbanya & Ramaiya,
2006). In rural Africa, it is less than 1%. However, it escalates up to 30% in the urban areas as a consequence of unhealthy lifestyles. These include abandonment of natural foods which are rich in complex carbohydrates, proteins and dietary fibres for high consumption of high fat and highly processed and genetically modified and refined/sugary foods, sedentary occupations, inadequate physical activity, stress, tobacco use and increased drug and alcohol consumption. Jervell (1995) stated that diabetes is not only a chronic disease but also a risk factor for coronary heart disease, hypertension, stroke, myocardial infarction and even sudden death, accounting for 9% of all deaths (WHO, 1999).Diabetes is the only metabolic disease that has direct influence on the three major energy–giving nutrients (CHO, fat and protein). Uncontrolled type 2 diabetes precipitates risk of developing complications with increased morbidity and mortality rates. Its attendant high cost of medical treatments, is reduced if good glycaemic control is maintained.
In Nigeria, a national survey recorded an average prevalence rate of 2.7% with similar pattern in both sexes and slightly varying prevalence rates in different geographical locations (FMH, 1992). The International Diabetes Federation (IDF) (2003)recorded
3.9%.One-third of Nigerians live in urban areas with growth rate of 6% per year (ACC/SCN,
1993) and annual increase of 0.3% in prevalence rate of type II diabetes. Again, a good number of people still live with it undiagnosed. Based on this, the prediction that undiagnosed diabetes would have approached 25% by 2010 is worrisome, especially in
southern Nigeria where densely populated urban centres predominate. With the prevailing trend of replacing the consumption of more complex form of traditional diets with high intake of refined carbohydrates (Western) diets, the situation in Nigeria calls for great concern and urgent action because carbohydrate (CHO) food group forms over 70% of the local diets.
One major predicament in achieving good glycaemic control in Nigerian diabetics is
lack of evidence-based dietary guidelines developed from locally available and commonly consumed foods/dishes that would integrate individuals’ food habits with their lifestyles. Over the years, diet has been implicated both as one of the aetiological factors to the development of diabetes (Hoet, 1997) as well as a key component in diabetes management (Pan, Li & Hu, 1997). Despite this level of scientific knowledge, progress in production and evaluation of most appropriate diets for diabetics has been slow and complicated. This is because the plant foods which form the base for the diets are under-exploited.
Food habits are very difficult to change.High intakes of carbohydrate-rich food sources in Nigeria, particularly cereals, roots/tubers, have qualified them as staple foods. Restriction of carbohydrate–rich sources is a serious threat to Nigeria’s survival. Diabetics are particularly adversely affected due to misinformation and inability to seek dietetic intervention. Such dietary misinformation has led to the development of psychosocial problems in diabetics because they feel denied and full of anxiety in anticipation of lifestyle changes (Nicholas, 1996). Nigeria is also endowed with numerous leguminous plants. Therapeutic potential of some of these legumes have been documented (Onyechi et al., 1998; Odenigbo, 2001). Many of the leguminous seeds used for thickening soups, sauces and stews in Nigeria have been documented (Udenta, Ellis & Thomas, 2004); and are often eaten as accompaniments with the “foo-foo” prepared from starchy staples.
Conventionally, type 2 diabetes is controlled with diet alone or diet and hypoglycaemic drugs (in combination with insulin in few cases). Most often, diabetics are advised to consume only those foods with low GI values like legumes, vegetables and unripe plantain. The restriction has two adverse effects: either the diabetics become too rigid with their food selection which might cause starvation and frequent hypoglycaemic attacks (Macdonald, 1998) or consume more carbohydrate per meal from the low GI diets, which precipitates poor diabetic control (hyperglycaemia) (Sameron, Manson, Stampler, Colditz & Willet, 1997). This has resulted in reduced intake or total avoidance of starchy staples and overall poor diabetes management in Nigeria with its attendant high cost of medical treatment. Considering the high intake of starchy foods in Nigeria, it is imperative to explore
possible ways of ensuring adequate and safe levels of intake of indigenous rich sources of carbohydrate to achieve good glycaemic control for people with diabetes. Nutritionists and Dietitians, in addition to their role of ascertaining the nutritional quality, bioavailability, safety and acceptability of the biotechnologically produced plant foods are also challenged to explore their therapeutic potentials through simple biotechnological techniques. Unfortunately, the commonly employed simple and more economical household fermentation techniqueapplied during the traditional methods of processing and preparation of the starchy staplesreduces viscosity and highly degrades the starch content of the foods, producing high GI foods that increase post-pandrial blood glucose. Exploring a fermentation technique that uses a particular organism under controlled conditions to improve the nutritional quality and GI of the starch-based traditional diets deserves much more attention. This calls for an alternative fermentation process like controlled fermentation, though this technique may be difficult for household level application.
The drift from rural to urban areas continues to be on the increase with a corresponding rise in the prevalence of type 2 diabetes resulting from high consumption of refined carbohydrate or carbohydrate overload from dietary intake. There is need to match the challenging trend in dietary habits biotechnologically using locally available plant foods that are beneficial to health when packaged for consumption in bothrural and urban areas.
Dietary fibre and resistant starch have both been recognized as the major interrelating factors that determine the bioavailability of carbohydrates expressed as GI (Englyst & Englyst, 2005). These authors have suggested that food processing techniques that retain or introduce characteristics that slow carbohydrate digestion should be explored. Mitchell, Greenfield and Doelle (1986) developed a model for protein enrichment of starchy foods for developing countries using semi-solid state controlled fermentation, which involves gelatinization and production of retrograded starch (mainly amylose) from processed cereals. Use of microorganism like C. tropicalis (Azoulay et al., 1980) and Rhizopus oligospurus (Mitchell et al., 1986) in controlled fermentation have improved the protein content of cassava and corn flours. There is dearth of information on the effect of this fermentation technique on the nutrient and non-nutrient composition of fermented staple food crops in relation to glycaemic index (in vitro).
Harden, Judd and Hockaday (1993) advocated direct evaluation of GI of many meal combinations based on indigenous, more widely and frequently consumed foods. From the point of view of improving the glycaemic control and lipid metabolism, two principal
approaches have been used to study the effects of increasing carbohydrate and fibre in diabetes management:
i) by supplementation of the low fibre foods with fibre-rich sources (for instance, guar gum, flours from tallow tree and counter wood tree seeds and locust bean); and
ii) by selective use of dietary fibre–rich foods.
The supplementation of foods with water-soluble NSP has been more successful clinically (Onyechi et al., 1998) without much consideration to the fibre supplied by other ingredients in the recipe used. According to Lupien (1998), purified forms of fibres ingested as supplement are more likely to compromise mineral status because they do not contribute to mineral uptake and would provide some free groupswith an affinity for binding minerals. The controversies among the proponents of dietary fibre research regarding the effects of dietary fibre-rich foods on mineral bioavailability (Faireahter-Tait & Hurrell, 1996, Gibson, 2007) further stresses the need to explore fully the effects and nutritional benefits of traditional diets by selective use of dietary fibre–rich indigenous foods.
Therefore, the second approach of selective and holistic use of dietary fibre content of a mixed meal than the soluble-NSP supplements needs to be explored. However, one major limitation of this option is lack of information on dietary formulation using a food-based approach (FAO/WHO, 1996), which portrays long term effects of diets as consumed. There is dearth of information on the total dietary fibre content and the ratio of soluble to insoluble dietary fibre fractions of low GI meals as consumed traditionally in Nigeria as well as their clinical effectiveness.
The thrust of this research is to explore food processing techniques that would reduce the GI of the more commonly consumed starchy staples used as “foofoo” and use selective approach with food-based dietary guidelines to formulate dietary fibre-rich blends fromthe processed starchy staples and selected under-exploited leguminous soup thickeners; andinvestigate their nutrient profile as well aseffect of such traditional foods on glycaemic response in diabetic adult rats.
1.3 General objective
The study investigated the effect of controlled fermentation of some traditional foods on the glycaemic response of diabetic adult rats
Specific objectives were to:
1. isolate and use Candida tropicalis in controlled fermentation of the cassava, maize and sorghum flours;
2. determine proximate composition, dietary fibre, starch, viscosity, in vitro GI and micronutrients of the fermented starchy and unfermented legume flours from Cola gigeantea and Bielschmeidia gabonensis);
3. determine anti-nutrients and food toxicants in the legume flours;
4. select fermented starchy staples as well as the legume with desirable physicochemical profile for diet formulations;
5. determine the chemical content of the these diets and
6. evaluate the effects of these diets on blood glucose, protein utilization, mineral and vitamin bioavailability in diabetes–induced adult rats.
1.4 Significance of the study
There are discrepancies between the dietary recommendations for people with diabetes and the actual practice by diabetics due to differing food habits and inadequate dietetic information. This has posed some challenges on researches. The findings from this research, if adequately published, may provide baseline data that willgive rise to evidence- based practice for the control of diabetes in this part of the world or rekindled the interests of food and nutrition-related scientists for further research on the traditional food crops studied.
The evidence from the results could be used by local food industries. These industries could in turn produce the controlled-fermented dietary fibre-rich,low GI starchy flours at affordable prices for culinary use in both rural and urban household.
The in vitro method of estimating the glycaemic indices of foods appears to be a more cost-effective method than in vivo, especially if human subjects are involved. The data obtained on GI values of locally available foods through this method, could be used subsequently to generate data for compilation of GI values of our local foods. The additional data generated from the chemical analyses of traditional foods studied could also be used to complement the information in the Food Composition Tables currently being used. These information will be useful to Dietitians, Nutritionists and other food related scientists.
Most often, people with diabetes over-restrict their intake of starchy staples. It is believed that the results of this study may provide scientific evidence for dietary management of type
2 diabetes mellitus. It would assist to improve the quality of information disseminated to the diabetic population, their families and entire community by dietetic and other health-care professionals, especially those involved in diabetes care. Over time, this may contribute to the continuous search for effective ways of possibly reducing morbidity and mortality rates as well as complications associated with uncontrolled type 2 diabetes mellitus.
This material content is developed to serve as a GUIDE for students to conduct academic research
EFFECT OF CONTROLLED FERMENTATION OF SOME TRADITIONAL FOODS ON THE GLYCAEMIC RESPONSE OF DIABETIC ADULT RATS>
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