Comparison of effects on blood glucose and lipid levels upon consumption of different types of coffee

INTERVENTION: 6 different kinds of test drinks are provided in duplicate: espresso‐, instant, boiled and decaffeinated coffee, as well as water and sugar‐sweetened milk. The details of the test drinks are listed below: Espresso‐coffee: 35ml of the beverage is made from 7g of grounded coffee powder using an espresso machine (Delonghi 680). Served with 50g low‐fat cow's milk and 7,5g white sugar. Caffeine content in one serve of espresso drink is 115mg. Instant coffee: made by adding 2g of instant coffee powder into 140ml of near‐boiling water. Served with 50g low‐fat cow's milk and 7,5g white sugar. Caffeine content in one serve of instant coffee drink is 110mg. Boiled coffee: made by adding 9g of grounded coffee powder into 175ml boiled water. Simmer for 10 minutes and cool in room temperature for 3 minutes. 150ml of the coffee beverage is served with 50g low‐fat cow's milk and 7,5g white sugar. Caffeine content in one serve of boiled coffee drink is 170mg. Decaffeinated coffee: made by adding 2g of decaffeinated coffee powder into 140ml of near‐boiling water. Served with 50g low‐fat cow's milk and 7,5g white sugar. Caffeine content in one serve of decaffeinated coffee drink is 3mg. Control: 140ml of near‐boiling water. Sweetened‐milk: 50g of low‐fat cow's milk and 7,5g of white sugar is added into 140ml of near‐boiling water. The participant arrive in the morning with an empty stomach. He/she will give the first blood sample, then drink the test drink within 10 minutes. After 60 minutes, another blood sample will be taken. Then he/she will have to consume a standard breakfast made up of rice cereal, rice milk and glucose powder in 10 minutes. Investigators will make sure that the participant finishes the test drink and the standard breakfast. There will be two sessions for each test drinks, thus giving 12 sessions in total for each participant. A washout period of three days is given between each session. CONDITION: Postprandial blood glucose and lipid levels. PRIMARY OUTCOME: Plasma glucose level in 3 hours during the session Plasma insulin levels for 3 hours during the sessions SECONDARY OUTCOME: Changes of the total and active GLP‐1 levels in 3 hours during the session (composite). Plasma total cholesterol level for 3 hours during the session Plasma triglyceride levels for 3 hours during the session INCLUSION CRITERIA: 1. Aged between 18‐40 years old 2. Body mass index (BMI) WITHIN the range of 18.0‐23.0 3. Consume at least 2 cups of coffee on a weekly basis in the past 3 months 4. Have never smoked before 5. Not a vegetarian 6. Able to tolerate cow’s milk 7. Able to tolerate caffeine or coffee 8. Not on regular medication, except oral contraceptives 9. Women who are not pregnant or does not plan to be pregnant during the study 10. Without high blood lipid or cholesterol 11. Without diagnosed type 1 or type 2 diabetes 12. Without current or history of cardiovascular diseases 13. Without current or history of liver diseases 14. Without current or history of gastrointestinal diseases 15. Without haemophobia