Impact of Reducing Dietary Intake of Red and Processed Meat Intake on Fasting Lipemia in Healthy Participants (ELM)

In UK adults, meat provides approximately 40% of the average daily protein intake and makes a significant contribution to intake of thiamin, niacin, vitamin B12, iron, zinc, potassium, and phosphorus. However, excessive consumption, particularly of red and processed meat, is associated with increased risk of developing a range of chronic diseases, including cardiovascular disease (CVD), obesity, type 2 diabetes and some cancers. Meat production significantly contributes to the production of greenhouse gasses (GHG) and hence global warming. Given the predicted global increase in the human population, coupled with the rise in demand for meat within emerging economies, it has been suggested that concerted efforts should be made to alter dietary patterns and reduce meat intake. Moreover, a number of reports have suggested that replacing meat with non-meat protein-rich products has health benefits. Such products tend to be inherently lower in total and saturated fat and, higher in fibre and as such, could also be cardioprotective.

The aim of this trial will be to investigate whether, with appropriate non/reduced-meat alternatives and motivational support, free living subjects can significantly reduce their meat intake and whether such dietary changes positively impact on a range of cardiovascular risk factors.

Trial design; A non-randomised, single group study design, with an initial control period will be used.

Participants; Forty healthy men and women will be recruited from the general population of Nottinghamshire, UK. All participants will attend the David Greenfield Human Physiology Unit (Queen's Medical Centre, Nottingham, UK) for an initial medical screening visit to confirm health status. In addition, blood pressure (BP) will be measured at the left upper arm (after lying semi-supine for 5min) using automated oscillometry, and body mass index (BMI) will be calculated from measured height and weight. If participants are suitable to take part with regards to their health questionnaire and BMI measures, a venous blood sample will then be taken to assess full blood count, urea, and electrolytes. Those taking lipid-lowering medication, or who report using nutritional strategies to lower their cholesterol, will be excluded. Participants will be accepted onto the trial if they report habitual consumption of 4-5 portions of red and/or processed meat per week (with 3-4 of these being consumed as main meals), they do not have food allergies related to soya or mycoprotein, and do not demonstrate any clinically significant abnormalities on screening.

Study Protocol; After recruitment, participants will be asked to record all food intake (including snacks and drinks) in a diet diary, for 4 days (3x week or work days, and 1x weekend or rest day) prior to assessment visit 1, for baseline assessment of macronutrient and energy intake. Individuals will be asked to complete further 4-day diet diaries in the week before assessment visits 2,3 and 4 (weeks 4, 10, and 16), to assess any changes in macronutrient or energy intake and meat consumption which may have occurred as a consequence of the intervention. Household measures will be used to estimate portion size, and diaries will be analysed using a food composition database. To calculate habitual diet composition, a mean daily intake will obtained from all 4 days of each recording period, and these data will be combined to produce group means.

Assessment visits will take place in the morning after the individual has fasted from midnight the night before. Initially, measurement of body mass will be made to the nearest 0.1kg using a Seca 882 Digital Scale, and waist and hip circumference will be assessed (with the participant standing) mid-way between the lowest rib and the iliac crest, and at the greater trochanters, respectively. Participants will then be asked to rest, semi-supine, on a couch for >5min before having their resting BP measured, and estimation of body composition made using bioelectrical impedance. A 5ml fasting blood sample will be taken for determination of serum insulin, total cholesterol, high density lipoprotein cholesterol (HDL), low density lipoprotein cholesterol (LDL), triacyl glycerides (TAG) and whole blood glucose. In a subset of the cohort (n=26, 13 Male:13 Female), flow mediated dilatation (FMD) will also be measured on the laboratory visits when fasted, after resting semi-supine for 1 and 2 hours.

Intervention; After visit 1 (week 0) assessment, participants will be asked not to make any changes to their lifestyle and to continue their habitual diet until visit 2 (week 4) when a second assessment will be made ('control' period). The 12 week 'intervention' period will begin on the day after the second study visit. Participants will be given information regarding how meat intake can safely be reduced in their diet, including a recipe book containing ideas for meals using meat analogues and other protein sources. A range of frozen meat-free (soya or mycoprotein 'mince', mycoprotein sausages, meatballs and 'steak strips') and reduced meat products (pork sausages, beef meatballs, beef mince and beef burgers made with 50% meat and 50% soya or mycoprotein) are available for the participants to use to aid this reduction in red meat intake. In addition, a range of dried beans (red kidney, haricot, black turtle), pulses (chick peas, green and red lentils) and grains (quinoa) will also be offered. Weekly telephone contact with the study participants will be maintained over the intervention period to improve compliance, to identify any problems and to arrange further food deliveries.