The autonomic nervous system has a role in regulating gastrointestinal function and blood pressure (BP) homeostasis, with alterations in autonomic function (AF) being implicated in the pathogenesis of type 2 diabetes1 and as an indicator of cardiovascular disease2. Consequently, AF assessment is widely used to characterise participant cohorts, or detect effects of interventions aiming to improve these chronic diseases. As part of a wider study, AF was measured in 33 healthy adults (18-60y; 20F:13M) in the morning after an overnight fast (~8am; PRE) and in the post-absorptive state 4h after a 75g oral glucose challenge (~1pm; POST). To optimise the design of future studies, the present sub-study assessed whether systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) when semi-recumbent, and after 1 and 2 minutes of standing, were similar PRE and POST (assessed using an automated oscillometric device). Data are expressed as the median [25th-75th percentile range] or effect size.
Females (22 [19-27] y) were younger than males (27 [23-47] y; P<0.05), but BMI was not different (24 [21-30] vs. 24 [23-27] kg/m2respectively). PRE, semi-recumbent SBP (114 [106-130] vs. 123 [116-129] mmHg; P=0.078), DBP (66 [64-77] vs. 76 [69-79] mmHg; P=0.062) and MAP (84 [81-93] vs. 91 [88-97] mmHg; P=0.053) tended to be lower in females, with HR being higher (71 [67-79] vs. 57 [52-66] BPM; P<0.001). Across the 2-minute stand, SBP and MAP did not change from semi-recumbent values, although DBP (P<0.005) and HR (P<0.001) increased; DBP at 1 and 2 minutes being +3.0 and +1.7 mmHg respectively, with HR being +12 and +11 BPM at these timepoints. These responses to standing did not differ between sexes. Compared to PRE, semi-recumbent SBP and HR in females were not different POST, but DBP (-3.8 mmHg; P<0.05) and MAP (-2.8 mmHg; P<0.05) were lower. In males, semi-recumbent HR was similar POST, but SBP (-6.7 mmHg; P<0.05), DBP (-7.5 mmHg; P<0.001) and MAP (-6.5 mmHg; P<0.005) were lower, with reduction in DBP tending to be (P=0.074), and MAP being greater than in females (P<0.05). However, responses to standing POST were similar when compared to PRE and were not different between sexes.
Although cardiovascular response to postural change did not differ between PRE and POST, absolute values for BP variables were impacted, with effect on males potentially being greater. Sex differences in BP and HR have been reported previously3. However, circadian fluctuation in these do not appear to differ between sexes3. Therefore, other factors, such as relaxation status and glucose ingestion, may be implicated in changes observed at POST. Findings suggest that AF in research protocols should be measured at the same time point across repeat visits, ideally in the morning after an overnight fast.

The autonomic nervous system has a role in regulating gastrointestinal function and blood pressure (BP) homeostasis, with alterations in autonomic function (AF) being implicated in the pathogenesis of type 2 diabetes1 and as an indicator of cardiovascular disease2. Consequently, AF assessment is widely used to characterise participant cohorts, or detect effects of interventions aiming to improve these chronic diseases. As part of a wider study, AF was measured in 33 healthy adults (18-60y; 20F:13M) in the morning after an overnight fast (~8am; **PRE**) and in the post-absorptive state 4h after a 75g oral glucose challenge (~1pm; **POST**). To optimise the design of future studies, the present sub-study assessed whether systolic (SBP) and diastolic blood pressure (DBP), mean arterial pressure (MAP) and heart rate (HR) when semi-recumbent, and after 1 and 2 minutes of standing, were similar PRE and POST (assessed using an automated oscillometric device). Data are expressed as the median [25th-75th percentile range] or effect size.
Females (22 [19-27] y) were younger than males (27 [23-47] y; P<0.05), but BMI was not different (24 [21-30] vs. 24 [23-27] kg/m2respectively). PRE, semi-recumbent SBP (114 [106-130] vs. 123 [116-129] mmHg; P=0.078), DBP (66 [64-77] vs. 76 [69-79] mmHg; P=0.062) and MAP (84 [81-93] vs. 91 [88-97] mmHg; P=0.053) tended to be lower in females, with HR being higher (71 [67-79] vs. 57 [52-66] BPM; P<0.001). Across the 2-minute stand, SBP and MAP did not change from semi-recumbent values, although DBP (P<0.005) and HR (P<0.001) increased; DBP at 1 and 2 minutes being +3.0 and +1.7 mmHg respectively, with HR being +12 and +11 BPM at these timepoints. These responses to standing did not differ between sexes. Compared to PRE, semi-recumbent SBP and HR in females were not different POST, but DBP (-3.8 mmHg; P<0.05) and MAP (-2.8 mmHg; P<0.05) were lower. In males, semi-recumbent HR was similar POST, but SBP (-6.7 mmHg; P<0.05), DBP (-7.5 mmHg; P<0.001) and MAP (-6.5 mmHg; P<0.005) were lower, with reduction in DBP tending to be (P=0.074), and MAP being greater than in females (P<0.05). However, responses to standing POST were similar when compared to PRE and were not different between sexes.
Although cardiovascular response to postural change did not differ between PRE and POST, absolute values for BP variables were impacted, with effect on males potentially being greater. Sex differences in BP and HR have been reported previously3. However, circadian fluctuation in these do not appear to differ between sexes3. Therefore, other factors, such as relaxation status and glucose ingestion, may be implicated in changes observed at POST. Findings suggest that AF in research protocols should be measured at the same time point across repeat visits, ideally in the morning after an overnight fast.

The impact of measurement timepoint on autonomic function testing in male and female individuals

Modern nutrition science is young: It is less than one century since the first vitamin was isolated in 1926. Nutrition science stands upon research conducted by academia, the private sector, and nongovernmental organisations, often in collaboration across these sectors. Its evidence base is of fundamental importance to the solving of current challenges and complexities, optimising outcomes, and the prevention of harm.

In order to remain relevant, nutrition science must address the global challenges, including ensuring nutrition security for all, in line with the UN Sustainable Development Goals and in the context of the post-COVID era. It is timely to take stock and consider how nutrition science must move forward.

The conference is designed integrate three symposium sessions which will commence with reflection on historical exemplars of nutrition achievements, then moving the discussion to current challenges which face the discipline and will culminate in scoping the outlook for nutrition science going forward.