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Comparing the pharmacokinetics of bioactive components and physiological effects of consuming encapsulated instant coffee versus traditional instant coffee brewed in water.

Coffee has gained interest for its role in the prevention of non-communicable diseases such as heart and liver diseases. Population based studies have reported that consuming 2-4 cups of coffee per day is associated with lower death rates and, notably reductions in the incidence of heart disease. However, these observational trials do not directly prove health improvement from drinking coffee. This current trial will provide vital information to inform a large scale randomised controlled trial assessing the effects of coffee consumption on risk markers for developing cardiometabolic disease (such as type 2 diabetes, heart and liver diseases) to test causality.


Purpose of the study

The main outcome will be to assess whether the active ingredients in coffee (bioactive components) are handled by the body in the same way (e.g. absorbed at the same rate) when consumed in the form of capsules versus a drink. In addition, we will also aim to investigate the impact of coffee on cardiometabolic health outcomes (e.g. blood pressure, blood glucose and health markers) to see whether differences exist between the different forms of coffee or compared to no coffee and determine if select genotypes impact the metabolism of coffee bioactive substances. The study findings will guide the design of future studies in understanding the health outcomes associated with coffee intake.

Who can take part in this study?

We are looking to recruit 16 participants (both male and female). To take part, eligible volunteers must meet the following criteria: 
• Healthy males and pre-menopausal females (must have regular menstrual cycles) 
• Aged between 18 to 45 years 
• Body mass index (BMI) between 18.5-30 kg/m2

Exclusion criteria
Should any of the following apply, unfortunately, you would be unable to participate: 
• Sensitivity to coffee and caffeine 
• Food allergies relating to the test meals provided (such as gluten or lactose intolerance) 
• Current smoking and vaping use. 
• Medical history of chronic diseases (cancer, high blood pressure (hypertension), type 2 diabetes, heart attack and/or any other heart disease related diseases, gastrointestinal disorders, hyperlipidaemia, kidney or liver disease). 
• Diagnosed with anaemia 
• Prescribed any medication relating to the study outcome measures (such as blood pressure lowering, anti-inflammatories or blood thinners). 
• Drinking more than the recommended intake for alcohol (> 14 units/week) 
• Taking any supplements (vitamins, minerals, probiotics). 
• Any other unusual medical history or diet and lifestyle habits or practices that would preclude volunteers from participating in a dietary intervention and metabolic study (e.g. pacemaker) 
• Planning on a weight-reducing regimen (lost >3 kg in the last 6 months) 
• Parallel participation in another intervention study 
• Pregnancy, planning a pregnancy in the next 6 months or breastfeeding 
• NHS blood donation in the last 3 months

What will taking part in the study involve?
If you would like to participate, you will first need to complete a short screening questionnaire via email, after which potentially eligible volunteers will be invited to attend a screening visit (approx. 45 mins) in the Hugh Sinclair Unit of Human Nutrition, found in the Harry Nursten building, ºÚ¹Ï³ÔÁÏÍø, RG6 6DZ.
Screening visit
The visit will take place in the morning, and we would like you to arrive in an unfed state (fasted, not eating or drinking anything except water from 8 pm the night before). First, the study will be explained in detail, and your consent for participating will be taken. After that, we shall ask you to confirm the information in the health and lifestyle questionnaire, including questions about your medical history and food habits. Your height, weight and blood pressure will then be measured before a small blood sample (7 ml, volume equivalent to half a teaspoon) is collected. You will be provided with a light breakfast before you leave. If any of your screening results are outside of the normal ‘healthy’ parameters, these will be reported to you and your GP. If you are found suitable for the study and willing to participate, you will be invited to attend the Hugh Sinclair Unit of Human Nutrition for three study phases, one month apart. Each phase will include a main study visit which will last approximately 8.5 hours each, plus a short visit (approximately 30 mins) the following day. Details of what is involved are summarised below. Before you start the study, we would like to record your usual dietary habits on three weekdays and one weekend day. To do this you will be given access to an app called Libro to record all the foods and drinks you consume over a 24 hour period on the days assigned by the researchers.

Pre-study Day
You will be asked to follow a low-polyphenol diet (defined as low in fruits and vegetables and no coffee or tea) and alcohol for 48 hours before the study day and abstain from strenuous exercise for 24 hours. Clear guidance on acceptable foods and caffeinated drinks that can replace your usual coffee and tea intake will be provided in advance, and a meal for the evening before the study visit will be provided. You will be asked to fast for 12 hours before the study day, not eating or drinking anything except water (ad libitum) during this time.

Main study visits
You will be asked to arrive at the clinical unit at approximately 8 am, where measurements of weight, body composition and blood pressure will be taken. You will then be taken to a temperature-controlled room to lie down and relax before the cannulation. During this time, a finger-prick blood sample will be collected to recheck your haemoglobin level before a cannula (small plastic tube) is inserted into your forearm by a research nurse. This will remain in place to allow blood samples to be taken during the 8-hour study day. Two fasted blood samples (14 ml each, approximately two tablespoons) will be taken. Blood samples (between 4-14 ml) will then be taken from the cannula at regular intervals (total 140 ml per study visit) after consuming either coffee in the form of capsules and water or the drink within 5 min. You will receive breakfast (cereal and milk) for 1 hour post coffee consumption and lunch (sandwich with crisps and biscuits) for 5 hours post coffee. Blood pressure will be measured at regular intervals throughout the study day. The cannula will be removed, a low polyphenol evening meal will be provided after 8 hours (at the end of the study visit), and a snack will be provided to consume during the evening. You will be asked to collect urine throughout the day (0-8 hours) in the clinical unit, and then you will be provided with a cool bag and container to collect urine from 8-24 hours after coffee consumption at home. You will need to return the next morning in a fasted state to provide a blood sample (14 ml) and return the urine sample. Four weeks later, you will be scheduled to repeat the study phase but with an alternative intervention to the one your originally received, and a month after that you will be scheduled to repeat the study phase with the final intervention. Whilst you are participating in the study it is important for you to attend all visits to the best of your ability. If the appointment or study day is not convenient on a particular date, please contact the study investigators as soon as possible so that an alternative date can be offered to you

Study contact
Please contact   for more information about this study.