Abstract
Background
There have been no studies directly investigating the relationship between protein, fibre and AD, specifically brain and plasma Aβ. This cross sectional study examined whether intake fibre and protein, are associated with plasma and brain Aβ levels using Australian elderly cohort drawn from the larger Australian Imaging, Biomarkers and Lifestyle study of ageing [AIBL] cohort.
Methods
The AIBL study is a longitudinal study of 1112 volunteers including healthy controls (HC). Of the baseline 541 HCs completed the Cancer Council of Victoria Food Frequency Questionnaire (CCVFFQ). DNA was isolated from the leucocytes, using Qiagen Midiprep kits, and APOE genotype was determined using polymerase chain reaction amplification and restriction enzyme digest techniques. 162 participants underwent a [11C] Pittsburgh compound-B positron emission tomography (PiB PET) scan.
Results
The average age, body mass index and energy intake of participants was 69.84, 26.57 kg/m2 and 1693.06 kCal per day respectively. Mean daily protein and fibre intake was 84.44 and 22.96, respectively. The average Aβ1-40, Aβ1-42 and PiB PET SUVR was 151.43 and , 33.81 pg ml-1 and 1.41 respectively. When PiB PET SUVR was used as a categorical variable, there was 12.594 higher odds of being PiB PET positive if protein intake was in the lowest intake tertile compared to the highest intake tertile (p < 0.05). Additionally, there was 8.425 higher odds of being PiB PET positive if protein intake was in the middle intake tertile compared to the highest intake tertile (p< 0.01).
Conclusions
Study indicates if participants had a higher protein intake, they had a lower odds of having a level of Aβ in the brain to categorize them as PiB PET positive. There were no associations between fibre intake, protein intake, and the fibre: protein ratio with Aβ level in the plasma or PiB PET SUVR as a continuous score. The study highlights the potential negative impact of low protein intake on brain Aβ load. However, longitudinal studies are needed to assess the impact of low protein consumption on risk of AD and related diseases. These results would be of considerable interest to researchers, public health officials and the lay public.