Few human intervention studies have examined the short term (<4 weeks) effects of high
(plant and animal) protein diets (25-30 percent of total energy intake) on intestinal
microbiota composition [Beaumont et al., 2017; David et al., 2014]. One study suggests
that long-term dietary patterns which involve increased consumption of protein (meat and
dairy) can shift the composition of the gut microbiota towards an ecosystem in which taxa
possessing proteolytic fermentation pathways are most abundant [Blachier et al., 2019].
Increased proteolytic activity is associated with increased gene expression of negative
bacteria and increased uremic toxins and microbial metabolites which can potentially
result in damage to the gut microstructure, activation of immune/ inflammatory responses
which over a prolonged period of time may have negative health outcomes [Windey et al,
2012]. These system-level shifts in composition and metabolism hint at the complexity of
metabolic interactions occurring in the host-microbiome symbiosis, but more information
is needed on the processes underlying these changes.
There is current interest in the functional benefits of plant-based proteins, but with a
lower bioavailability it is unclear as yet what the metabolic fate of these proteins is.
Furthermore, relative to dairy proteins, plant-based sources of protein have different
compounds within the structure, such as micronutrients and fibre and it is unclear if
these compounds can modulate the potential negative impact of high diary protein diets on
the microbiome.
The PROMEPHY study will focus on better understanding the metabolic and physiological
impact of high protein diets from different (alternative) protein sources in humans. The
results will provide novel insights into plant-based protein sources and may enable
future application in products available to the consumer.
The primary objective of this study is to compare the changes in serum essential amino
acid bioavailability after two weeks of daily consumption of a plant based protein mix
with the changes in serum essential amino acid bioavailability after two weeks of daily
consumption of a milk protein isolate.
Secondary objectives of this study are:
To compare the changes in serum essential and total amino acid bioavailability after
two weeks of daily consumption of a milk protein isolate, a milk and plant based
protein mix, a plant based protein mix and finally a plant based protein mix with
fibre.
To compare the changes in taxonomic microbiota and proteome composition after one
week and after two weeks of daily consumption of a milk protein isolate, a milk and
plant based protein mix, a plant based protein mix and finally a plant based protein
mix with fibre.
This is a randomised, double-blind, crossover, single centre study. It is anticipated
that 15-20 healthy participants will be recruited (men and women, aged 18-50 years) for
this cross-over design study (see eligibility).
Proposed methods
This study will involve participants attending an initial screening session, followed by
3 laboratory visits to the Human Physiology Laboratory at Anglia Ruskin University,
Cambridge, UK, for each of 4 trials (total of 13 visits). A brief overview of the key
visits are provided here:
Screening session Volunteers will initially be required to attend a study briefing
session and screening assessment to confirm eligibility. This will take place at Anglia
Ruskin University, Cambridge, UK. Participants will be required to provide written,
informed consent and will receive information on study arrangements.Volunteers eligible
for participation will be provided with stool collection material and will receive
instructions on collection and storage of the stool sample. Subjects eligible for
participation will then visit the Human Physiology Laboratory, Anglia Ruskin University,
Cambridge, UK a further 12 times over 4 trials.This is a longitudinal, cross-over design
study, with at least 6 weeks between each trial (hence the study period will last at
least 32 weeks). The outline of each trial is provided below. For each trial there will
be 3 visits i.e. trial 1a, 1b, 1c.
Visits 1a, 2a, 3a and 4a (same general protocol for visits 1c,2c,3c,4c) Following an
overnight fast (10 hours), subjects will come to the Human Physiology Laboratory, Anglia
Ruskin University, UK for a bioavailability assessment. The research team will receive a
stool sample that subjects collected at home maximally three days prior to the study
visit and the Bristol Stool Chart that subjects completed on the same day of the stool
sample collection. Habitual dietary intake will be assessed via a mobile application
(MyFitnessPal). Body weight will be measured. Subjects will consume one serving of one of
the four study products (randomization at Visit 1a, one portion contains 20 grams of
protein) dissolved in water 200 ml water, and consumed within 10 minutes. Blood samples
will be drawn at T= -20 and -5 min (baseline) and at t= 15, 30, 45, 60, 75, 90, 105, 120,
150, 180, 210, and 240 min after study product intake by a qualified phlebotomist.
Samples will be assessed for uremic markers (baseline only) and amino acid profiles. A
gastrointestinal tolerance questionnaire will be completed at several time points (before
study product intake and at 90 and 240 min). Throughout the study visits subjects are not
allowed to eat, but will drink 200 ml water at T=95 and T=185 min. In addition,
participants will be asked to abstain from any physical exercise other than incidental
walking during the study visits. After this study visit a 2-week (± 2 days) dietary
intervention will start, with the first serving at home taken in the evening.
Participants will receive 50 g of protein to consume daily at home (1 x 25 g in morning
and 1 x 25 g in evening), not combined with a meal. Participants will undertake a
follow-up assessment 2 weeks later using the same protocol outlined above.
Visits 1b, 2b, 3b and 4b One week after visit a, participants will visit the Human
Physiology Laboratory, Anglia Ruskin University, Cambridge, UK again for visit b after an
overnight fast (at least 10 hours). The research team will receive a stool sample that
participants collected within 3 days prior to the study visit and the Bristol Stool Chart
that participants completed on the same day of the stool sample collection. Body weight
will be measured. A fasting blood sample will be taken only for assessment of uremic
markers.
Each trial will be separated by at least a 6 weeks washout period.
In this study four study products will be investigated:
Product A: Milk protein isolate
Product B: Milk and plant based Protein mix
Product C: Plant based protein mix
Product D: Plant based protein mix with fiber