Older adults have very specific food and nutrient requirements and often struggle to meet these needs due to poor appetite, reduced functionality and dexterity. Protein (both quality and quantity) is an important macronutrient in maintaining muscle in older adults which can help prevent falls, delay disease onset and help individuals maintain independence. Fortifying regular/ everyday foods with additional protein is one strategy to help older adults meet these increased protein needs. However, it is well established that protein is the most satiating of the nutrients we eat, yet less is known about how this is impacted by age and protein type. This study aims to test 2 protein fortified porridge recipes in older adults (and a control recipe) with outcomes focused on protein bioavailability, appetite and satiety responses.

Older adults have very specific food needs, not just in terms of the nutritional composition, but also because of reduced ability to prepare foods due to reduced functionality and dexterity. Foods may also become less appealing and less palatable with decreases in smell, taste and sight. Older adults often have a smaller appetite due to numerous factors including sensory decline, frailty, reduced activity and delayed gastric emptying. As such, fortified recipes of normal everyday foods can provide palatable familiar foods, that can be easy to prepare, whilst providing sufficient nutrients in a smaller portion size.

Within meals, the quality and quantity of dietary protein plays a significant role in maintaining muscle mass in older adults which can prevent falls and help older adults maintain their independence. Animal-based proteins (such as diary proteins) are complete protein sources that can lead to an improved muscle mass synthesis response compared to plant-based protein. However, it is also well established that protein is the most satiating of the nutrients we eat; yet less is known about how this is effected by age and by protein type. Hence, the addition of protein to a meal may result in an undesirable compensatory decrease in food intake in older adults, which may worsen undernutrition rather than preventing it. This issue is all the more worthwhile to investigate as ageing is known to alter hunger and satiety regulation mechanisms. Gastric emptying and gastrointestinal transit has been shown to delay in older adults. Slower gastric emptying can result in the stomach remaining distended a longer period of time and satiety being maintained. In addition, several studies have demonstrated the presence of higher levels of the hormones that control appetite in older compared to young individuals.

This study will be testing protein fortified porridge, a recipe that has been developed with older adults. It will assess how much of the protein in the meals is absorbed into the body and the impact it has on food intake, appetite, emptying from the stomach and hormones related to appetite. It will compare three recipes: a standard porridge recipe (control), a recipe fortified with milk protein (animal based protein), and a recipe fortified with soya (plant based protein).

Inclusion Criteria:

• Aged 70 years or over (no upper age limit), equal number of males and females
• BMI range: 18.5-30kg/m2
• Regularly consume 3 meals a day (with breakfast by 11am, lunch and dinner)
• Able to test the dishes provided
• Able to feed themselves
• Able to provide informed consent
• Understand English

Exclusion Criteria:

• Existing neurological or gastrointestinal condition
• Current chewing or swallowing difficulties (such as dysphagia)
• Existing cognitive or psychiatric disorder
• Taking medications that can significantly affect taste changes, appetite or gastric emptying
• On a special or therapeutic diet
• Have any food allergies or intolerances that will be worsened with meals provided in the study
• Have a history or drug or alcohol misuse
• Smoke more than 10 cigarettes a day
• Those who score ≤22 on the T-CogS exam

For participants providing blood samples:

• Anaemia (men: haemoglobin<130 g/L and women <115 g/L)
• Hypertension (systolic blood pressure > 140 mmHg, diastolic blood pressure > 90 mmHg)

No personal identification data will be shared. The study is not under an obligation to share data, however it is possible that some of the individual (unliked / non identifiable) data will be useful in a meta analysis and, hence sharing individual participant data (IPD) will be considered.

Single blinded study. All participants will consume 2 fortified meals and 1 placebo/ control meal. All participants will be blinded to the intervention provided