The goal of this intervention trial is to investigate the potential of an artisan cheese aged in hay to induce changes in the gut microbiota in a manner which mediates a reduction in total cholesterol in participants with elevated total cholesterol. The main questions it aims to answer are:

Does daily consumption of a hay aged cheese over 12 weeks reduce total cholesterol by at least 0.5mmol/l when compared the control cheese (cheddar)? Are changes in total cholesterol level reflected in changes in gut microbiota composition and activity as measured by deoxyribonucleic acid (DNA) sequencing of stool composition and short chain fatty acid levels in urine?

Participants will be asked to consume 30g portions of cheese every day for 12 weeks. This study is conducted in parallel, with participants either allocated onto the control arm (cheddar) or intervention arm (hay-aged cheese). Blood, stool, and urine samples will be taken throughout the trial, body mass index (BMI) and blood pressure will also be measured.

Cheese production involves the use of starter culture bacteria, many of which are species with recognised probiotic potential. Additionally, the food matrix of protein and fat is thought to protect these cultures during human digestion, allowing them to reach the large intestine alive. Previous studies have indicated that cultures present in cheese can persist in the gut microbiome and exert a positive effect. Further studies have indicated that regular cheese consumption, despite having a high proportion of saturated fats, has been associated with lower cholesterol levels. This is thought to be mediated by the food matrix which reduces the release of fat during digestion, and recent work by the investigators has suggested that changes in the gut microbiota activity induced by cheese consumption may also have a role. This laboratory work has shown that cheese can boost the production of propionate (a microbially derived metabolite) in a gut model system, particularly a variety of cheese that is aged in hay (Witheridge-in-hay). Propionate in the gut is known to have a role in cholesterol regulation. The hypothesis is that cheese is a source of probiotics, and the hay on the rind of Witheridge-in-hay acts in a prebiotic manner; therefore this cheese is synbiotic and has the potential to confer multiple health benefits including reduced total cholesterol concentration mediated by a change in gut microbiota composition. In the proposed study, participants (ages 18-65, with elevated cholesterol between 5.5-7.5mmol/l) will consume a thirty-gram portion of cheese a day, either Witheridge-in-hay or cheddar as a control, for twelve weeks. Effects will be determined by collecting stool samples, urine, and blood from participants to measure bacterial composition, fermentation end products, and cholesterol levels respectively, as well as body mass index (BMI) measurements and blood pressure for further assessment of cardiovascular and weight gain effects. Samples will be collected at baseline, mid-intervention, and post-intervention.

Inclusion Criteria:

• Participants aged 18 to 65 years old
• Regular consumer of cheese
• In generally good health but with total cholesterol level between 5.5-7.5 mmol/l and body mass index (BMI) between 18-32 kg/m2 at screening visit
• Willing and able to comply with study instructions

Exclusion Criteria:

• Use of antibiotics in the last 6 months prior to the study.
• Use of prebiotics, probiotics, laxatives, anti-spasmodic, anti-diarrhoeals, herb supplements in the last 4 weeks prior to or during the study period.
• Any chronic gut disorders/disease such as irritable bowel syndrome, inflammatory bowel disease, etc or other conditions that might affect the gut environment e.g. coeliac disease.
• High blood pressure, anaemia, high blood lipids (total cholesterol >7.5mmol/l), or inflammatory conditions
• Taking medication for anaemia, high blood pressure, high blood lipids , inflammatory conditions or depression
• Anyone diagnosed with vitamin deficiencies, diabetes, heart disease (previous stroke or heart attack) or have a pacemaker, kidney, bowel or liver diseases, cancer or hormone abnormalities.
• Pregnant, lactating, breast feeding or planning a pregnancy within the next 6 months
• Peri- or postmenopausal women
• Lost more than 3kg of body weight in the last 6 months
• Food allergies and intolerances
• Participants currently involved or will be involved in another clinical or food study in the previous 3 months

Participants will not be told which cheese they have been allocated, but the appearance of the cheese (hay-aged vs cheddar) will likely make it obvious to the participants.