This study was approved by the Faculty of Health Sciences and Sport Research Ethics Committee. All participants provided informed, written consent prior to taking part in the study. Participant data were protected in accord with the guidelines of the Data Protection Act [ 21 ]. All testing occurred in the Nutrition or Resting Laboratories at the University of Stirling. The participants of this study were recruited from staff and students at the University of Stirling. In total, 15 individuals provided informed written consent to participate in the study with three dropouts (one case of illness, two dropped out due to not liking mussels), resulting in a total of 12 participants (8 men and 4 women). Participant characteristics are presented in Table 1 . Given the purpose of the study, participants were required to not regularly meet the recommended daily intake of oily fish/omega-3 or be taking any kind of omega-3 supplement. Exclusion criteria prohibited any participants suffering from a shellfish or a similar allergy from participating. Recruitment was achieved through posters positioned around the University and via word of mouth.

Participant dietary intake was recorded using 3 days/week food diaries. Participants were provided with scales to weigh food accurately. Food diary data were input and analysed by nutritional software (Nutritics Academic Edition v4.267; Nutritics, Dublin, Ireland). Scales and a stadiometer were used to measure weight (kg) and height (cm), respectively. Blood samples were taken via finger prick using sterile lances. The blood was then collected on cards pre-treated with butylated hydroxytoluene (BHT; 50 mg/100 mL in ethanol). Cards were stored in clean/dry Tupperware tubs with desiccant before being transferred to the desiccator to dry each sample to completion. Blood samples were collected in duplicate in a rested, fasted state.

2.3. Design

The experimental design used for this study was a repeated measures model, with each participant undergoing two baseline-testing days on two consecutive weeks (W1 and W2) to demonstrate the stability of their blood analysis, followed by six feeding occasions on non-consecutive days over the next two weeks (W3 and W4).

On day 1 in Week 1 (W1), participants had their height and weight measured and provided a blood sample via finger prick. They were asked to fill in a food preference questionnaire so that the meals provided in the testing portion of the study were suited to tastes. Participants also received 3 days/week food diaries and food scales to record food consumption over the course of the 4-week study. Participants were asked to maintain their habitual activity levels throughout the study. On day 1 in Week 2 (W2), participants again had their height and weight assessed and handed over their recorded food diary to allow calculation of the caloric and macronutrient requirements for their test meals. They provided a second finger prick blood sample and were given another 3 days/week food diary. Subjects were asked to attend the laboratory on three non-consecutive days for the following 2 weeks (W3 and W4) to receive their test meals (see Table 2 for the macronutrient breakdown and Table 3 for the recipes).

A finger prick blood sample was then taken on the Monday morning following each feeding week. Blood samples via finger prick were always taken in the morning while participants were in an overnight fasted state. Weight was measured each time participants entered the laboratory for blood sampling to ensure stable weight during the course of the study (W1, W2, W3, and W4). Food diaries were handed in on the first day of W2, W3, and W4. Finally, in W3 and W4, participants received meals containing mussels as the protein component of the meal 3 times per week at lunchtime, individualised to the food diaries completed in W1.

As discussed above, the test meals were tailored to the individual participant dependent upon the results of their food diary analysis. Baseline food diaries were analysed in Nutritics (Nutritics Academic Edition v4.267; Nutritics, Dublin, Ireland), and from this, the meals were designed to contain one-third of each participant’s typical daily calorie intake. The macronutrient split was as follows: 60% carbohydrate (CHO), 20% fat, and 20% protein (PRO). Every participant received a minimum of 80 g of cooked mussels. Meals were provided on Monday, Wednesday, and Friday. They were fed at lunchtime in one of two self-selected feeding slots, either 12:00 p.m. or 1:00 p.m.