1.Stevia
Stevia (Stevia rebaudiana Bertoni) is a member of the Compositae family and this plant is also commonly known as honey leaf, sugar leaf and sweet leaf ( Dinçel,2018). The sweet compounds found in stevia leaves are diterpene glycoside (steviol glycoside) compounds, where the main sweetener compound is stevioside. Stevia production occurs in three ways; The first one is powder stevia obtained by drying, grinding and packaging direct stevia leaves, the other two are concentrated stevia extract and powder stevia extract. Stevia sweetener; In addition to its properties such as being 250-300 times sweeter than sucrose, having high heat and pH stability, baking and oven stability, being soluble in alcohol, and not having a metallic taste in the mouth, its most important feature is that it is obtained naturally (İnanç, 2009).
According to some researchers, it has been reported to have antihypertension, antihyperglycemic and anti-human rotavirus disease healing properties (İnanç,2009).
Compared to other sweeteners, Stevia has been found to have positive effects on phenylketonuria and diabetes patients. It has been stated that especially Steviol glycosides can be used easily by obesity, hypertension and diabetes patients by replacing sucrose (İnanç, 2009).
STUDIES:
Free radical production plays a role in the pathogenesis of diabetes. Therefore, free radicals are effective in the pathophysiology of diabetes complications in various ways and different mechanisms. A model of human type II diabetes can be created by administering nicotinamide (NA) and streptozotocin (STZ) to rats. The aim of this study was to determine the effects of Stevia rebaudiana Bertoni (SrB) and L-NNA (N-nitro L-arginine) on free radical formation in STZ-NA-induced type II diabetic rats. In this study, rats were treated with SrB and L-NNA 5–8 weeks after inducing diabetes. Levels of glutathione peroxidase (GPx), superoxide dismutase (SOD), catalase (CAT) and malondialdehyde (MDA) were determined in liver homogenates and erythrocyte hemolysates. At the same time, nitric oxide synthase was detected in liver homogenate and serum. z (NOS) levels were measured. To examine histological changes in diabetes, liver tissue samples were stained with hematoxylin-eosin and examined with a light microscope. Although fasting and postprandial blood sugar levels were high in the diabetic groups, blood sugar levels decreased significantly in the treated diabetic groups. Although erythrocyte MDA levels decreased in the stevia-treated diabetic group, L-NNA treatment increased lipid peroxidation in both the control and L-NNA-treated diabetic groups. No differences were determined in terms of tissue CAT, NOS and erythrocyte SOD and CAT activities compared to the control. While normal histological structure was observed in the liver samples of the control group, necrotic cells with pyknotic nuclei and eosinophilic cytoplasm and sinusoidal dilatation were determined in the liver tissues of the diabetic control group. Compared with the diabetic control group, hepatocyte structure was normal in the diabetic L-NNA group. However, it was determined that SrB and L-NNA treatment provided high protection in hepatocytes. Our findings showed that SrB and L-NNA treatment in diabetes reduced blood glucose levels and had some positive effects on oxidative and histological changes, however, L-NNA, a NOS inhibitor, was less effective on type II diabetes compared to SrB (Özbayer ,2011).
Research on how stevia may affect blood sugar in individuals with diabetes is inconsistent. Some early studies show that taking 1000mg daily of stevia leaf extract, which contains 91% stevioside, may reduce blood sugar after meals by 18% in people with type 2 diabetes. However, other research shows that taking 250 mg of stevioside 3 times daily does not reduce blood sugar levels or HbA1c (a measurement of blood sugar levels over time) after three months of treatment(Bilgi,2021). It is not clear how it will affect pressure. Some research shows that taking 750-1000 mg of stevioside, a chemical compound in stevia, daily lowers systolic and diastolic blood pressure. With this However, other studies show that the use of stevioside does not reduce blood pressure (Bilgi, 2021).
In addition, some studies show that polyphenol oxidase and peroxidase, which are found as natural inhibitors in the aqueous extracts of Stevia rebaudiana, reduce the use of chemical additives added to foods. and it has been stated that these additives reduce the harmful effects. In another study, it was proven that the maximum steviol concentration in the blood of hamsters fed with steviol at doses of 250 mg/kg body weight per day is not toxic (Dinçel, 2018).
The FDA stated that stevia cannot be used as a food additive (food preservative) because It has been declared that there is no sufficient evidence on it yet, but it has also been stated that it can be used safely as one of the food ingredients (İnanç, 2009).
2.Agave Syrup
Agave syrup is a naturally sweet substance produced by cooking agave pine trees. Agave syrups are in great demand as sugar substitutes due to their low glycemic index, antioxidant capacity and antibacterial properties (Mellado-Mojican et al.2015). Its fructose content is high (85-90%), sweetening power is 1.4, glycemic index is 11-15, caloric value is 3.1 kcal/g (İşgören,2019).
F / G ratio, It is an indirect measure of sweetening capacity. When comparing the F/G ratio among natural sweeteners, Agave syrups had the highest F/G ratios, while corn and sugar cane syrups had the lowest ratios. Therefore, agave syrups exhibit a higher sweetening capacity compared to other natural sweeteners (Mellado-Mojican et al.2015).
The main carbohydrates in agave sap are complex forms of fructose, one of which is inulin, inulin is a polymer of fructose. In this case, the extract is not too sweet. The agave extract is heated to 140°F for approximately 36 hours. Complex fructosans are hydrolyzed and broken down into fructose units. Thus, the solution becomes rich in fructose. Agave Syrup, "low glycemic" It is advertised as and marketed towards diabetics. Agave contains low amounts of glucose (10%). However, it contains an unusually high concentration of fructose (90%) compared to glucose. For this reason, it has a low glycemic index (Kohler, 1998). Therefore, it should not be forgotten that the risks associated with excessive fructose consumption also apply to agave syrup (İşgören, 2019).
3.Sucrose
Sucrose, the most well-known disaccharide, consists of one glucose and one fructose molecule. It is absorbed by being broken down into glucose and fructose in the small intestines. It is naturally found in large amounts in sugar cane and sugar beets, and in small amounts in honey, fruits, vegetables and nuts. Natural disaccharides first hydrolyze into their monosaccharides in the small intestine, then they are absorbed and metabolized to provide energy (İşgören, 2019). Sucrose is the most used sugar in the food industry and is often a popular ingredient used to achieve sweetness. It is extracted from sugar cane or sugar beets; baking, beverage, confectionery, gel and jam etc. It is used as an industrial sweetener (Konar,2019).
Simple sugar consumption may negatively affect diabetes control, therefore it is recommended that sucrose intake should not exceed 10% of the total daily energy intake (Öztürk,2019).
Sweeteners are important sugar substitutes used to enhance the palatability of foods and beverages while avoiding excessive energy intake. Some studies have shown that sweeteners can be used as a potential body weight management tool, showing a positive role in body weight loss. However, some studies have shown that sweeteners have an active metabolic role in the human body and can disrupt human metabolism by inducing glucose intolerance, causing obesity and metabolic syndrome. Sweeteners are the group whose effects on the intestinal microbiota are most studied. People have approximately 10 times more microorganisms (approximately 100 trillion) in their gastrointestinal systems than the number of somatic cells in their bodies. Approximately The most common ones in the intestinal microbiota, which includes 1000 different species, are; Firmicutes, Bacteroidetes, Proteobacteria, Fusobacteria, Verrucomicrobia, Cyanobacteria and Actinobacteria species (Öztürkcan,2020).
In a study conducted on mice, bacterial changes in the intestinal flora were observed after 3 days of consumption of 20% sorbitol or sucrose. Consumption of sorbitol did not show a significant change on bacteria, and consumption of sucrose also decreased the total number of aerobes and anaerobes in the feces (Öztürkcan, 2020).
4.Thaumatin
The sweetness of the fruits of Thaumatococcus danielli (Marantaceae), an African plant, comes from the protein mixture called 'Thaumatin' I, II and III. The mixture of sweet proteins is called 'Talin'. The molecular weight of all components is 2200u. Tallinn is a commercial sweetener widely used in Japan and England(Tanker,1993)
It is 2000-3000 times sweeter than sucrose. It is stable in heat and acidic solutions. It has high solubility in water. It is a low-calorie sweetener. In addition to its sweetening feature, it is also used for flavor purposes. It has been designated as GRAS by the FDA. It has been approved in the European Union since 1984. Its ADI value is 50 mg/kg/day (İşgören, 2019).
Thaumatin maintains its stability in a wide pH range. Since it is not stable against temperature, it is not suitable for use in products that will be heat treated at high temperatures. Its solubility in water is also quite high and it is possible to prepare even >1000g/L solution. The use of thaumatin as a sweetener in food and beverages is allowed in Israel, Japan and European Union countries, and in the USA it is allowed to be used as a flavor enhancer in beverages, jams and jellies, dairy products, instant coffee and teas and bubble gum (Yılmaz, 2011). p>
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