Gellan gum (GG) is a food grade polysaccharide produced by fermentation. In-vitro studies and in vivo pilot studies suggest that adding gellan gum to rice during cooking might reduce the extent of the increase in circulating blood glucose seen after its consumption (glycaemic response). This study will explore whether such a modification in response is sustained, particularly over a period of 7 days of consumption.

BACKGROUND: Rice is a carbohydrate-rich staple source of food for around half of the world population. Consumption is estimated to be 480 million tonnes per year. According to The Food and Agriculture Organization of the United Nations (FAO), rice is easily accessible to people in Asia, Pacific region, parts of Latin America and the Caribbean and, increasingly in Africa. Rice plays an important role in achieving an adequate dietary intake in these countries.

However high consumption of white rice has been linked with high obesity rates and increased risk for type 2 diabetes . However, it is still the favoured type of rice among consumers, contributing to the observed increasing trends in diet-related diseases in countries with high rice consumption . Modifying the properties of white rice products (e.g. reducing the glycaemic index and/or increasing satiety) with relatively simple interventions can contribute to producing foods that may promote better health due to modified digestion and post prandial metabolic and appetitive profiles. One way to reduce the glycaemic index of white rice may be the addition of hydrocolloids. These have previously been shown to modify the digestibility of foods . The health advantage derived from such modifications would be beneficial for consumers worldwide. Preliminary in-house in vitro digestion data suggested that the addition of gellan gum to rice cooking may reduce digestibility rates though mechanisms yet to be understood. Gellan gum (GG) "is a high molecular weight, water-soluble anionic, extracellular polysaccharide which is produced by the microorganism Sphingomonas elodea during fermentation". GG is commonly used as a gelling agent in foods. Gels formed by gellan gum have high resistance to acid, heat, and enzyme activity. The United States Food and Drug Administration (FDA) has approved the use of GG as a food additive for the human consumption (US.FDA, 2018). It is also approved by the European Community as a food additive with code (E-418). Gellan Gum is gluten free and broadly applied in gluten free foods to provide improved texture and good taste to pasta, biscuits, candy and dairy products. Therefore, it has been proved safe in the amounts the investigators intend to use, it is also suitable for people diagnosed with Coeliac disease as well as suitable for vegetarians, kosher and Halal diets, which make it acceptable for consumption and dietary intervention across different populations.

AIM: The overall purpose of this study is to explore the impact of cooking rice with gellan on the glycaemic and appetitive responses in healthy participants. Both the acute response to one meal will be considered, and the impact on the acute response having consumed the rice once a day over the preceding 7 days. Tolerance will also be considered.

HYPOTHESIS: This work will test the hypothesis that the addition of gellan gum to jasmine rice during cooking will reduce the post prandial glycaemic response. The investigators will also explore associated food intake, appetitive responses and tolerance during both the acute single meal exposure and over a 7 day period of consuming the same portion of rice each day, therefore testing the stability of the glycaemic and appetitive responses after a 7 day period of consumption. Establishing that any acute effect noted is sustained over a period of consumption will be important prior to recommending the addition of gellan to rice cooking as a therapeutic or public health strategy.

Inclusion Criteria:

• Not currently taking any medications (except the oral contraceptive pill)
• Aged 18-65 years old
• Body mass index (BMI) ≥ 18.5 and ≤ 24.9 kg/m2
• Able to give informed consent
• Apparently healthy: no medical conditions or previous gastrointestinal surgery which might affect study measurements.

Exclusion Criteria:

• Fasting finger prick screening blood sugar level higher than 5.4 mmol/L
• Restrained eating behaviour as determined by Eating habits and SCOFF screening questionnaires
• Participation in another nutritional or biomedical trial 3 months before the pre-study screening or during the study.
• Reported participation in night shift work during the two weeks prior to pre-study investigation or during the study. Night work is defined as working between midnight and 6.00 AM.
• Strenuous exercise for more than 10 hours per week.
• Consumption of ≥21 alcoholic drinks in a typical week
• Reported weight loss or gain ≥ 10 % of bodyweight during the six months period before the pre-study examination.
• Following a medically- or self-prescribed diet during the two weeks prior to the pre-study examination and until the end of the study
• Dislike of the products served as the dietary test treatments
• Any allergy or food intolerance to the test treatments
• Pregnancy or breastfeeding declared by candidate
• Antibiotic or prescribed probiotic treatment in the past 12 weeks
• Poor understanding of the spoken and/or written English language
• Having taken part in a research study in the last 3 months involving invasive procedures or an inconvenience allowance

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