Influence of Proteins on the Bioavailability of Carotenoids
Condition: Absorption; Chemicals; Healthy Diet; Metabolism
Study type: Interventional

Summary: 
      A postprandial intervention study is conducted on healthy male subjects to evaluate whether
      the addition of proteins (why protein isolate, soy protein) can help to increase the
      bioavailability of carotenoids from a tomato/carrot beverage.
    

Detailed description: 
      Participants who agree to sign the Informed Consent Form and are considered eligible for
      participation will be scheduled for a first and brief screening visit enrolment visit) to
      collect a spot urine and blood sample (20 ml) that are meant to check the subjects anemic
      status and analyze the sugar levels as well as plasma lipids such as triglycerides, in order
      to screen for any abnormal health condition (e.g. onset of diabetes) that they might not be
      aware of at the date of the information session and that might not make them eligible for
      this study.

      If at this stage they are still considered eligible for the study, participants will commence
      the 4 week trial phase which includes 3 washout periods, 1 short screening visit and 3 full
      day (i.e. 10.5 hours) clinical visits. The screening visit, called preliminary visit, will
      take place at the beginning of the trial phase. A blood sample will be collected to determine
      the baseline levels of triglycerides and plasma carotenoids at the beginning of the trial,
      prior to the first washout phase.

      The first washout week starts on day 1 after the preliminary visit and will have a duration
      of 14 days during which the participants will be asked to stay on a low carotenoid diet (i.e.
      to avoid the intake of colored fruits and vegetables), to reduce the basal levels of blood
      circulating carotenoids.

      During the 1-day appointments at the Clinical and Epidemiological Investigation Centre
      (CIEC), one of the three test meals will be given to the participants in 6 different orders,
      making 6 treatment patterns. Assuming that all 24 participants are successfully recruited, we
      will have 4 randomly allocated participants per pattern.

      On clinical visit days, participants will be asked to report at the CIEC's facilities,
      starting from 7:30 am, and a baseline blood sample (20 ml) will be drawn at 0h time point. A
      trained nurse will insert a cannula in the forearm of the participant that will be left in
      place during the whole staying for the commodity of the participant.

      Immediately after the baseline blood draw, a test meal composed of a mixture of carrot and
      tomato juice (350 mL in total), to which 5 mL of peanut oil will be added, 40 g of toasted
      bread (white wheat, with 10 g margarine plus 20 g cream-cheese) and a glass of water (approx.
      300 mL) which may or may not contain 30 g of proteins (either a plant based protein or a
      dairy-based proteins) will be served. The entire test meal must be eaten within 30 min, under
      supervision.

      Post-prandial blood samples (20 ml each) will be collected at timed intervals (before, 2h,
      3h, 4h, 5h. 6h, 8h and 10h after test meal intake). Participants will receive a standardized
      lunch 4 hours after test meal intake (c.a. 12:00 pm), consisting of a toasted sandwich (white
      wheat bread, ca 60 g), with ca. 60 g turkey with some margarine to spread on the bread (ca 10
      g), a Greek yogurt (140 g) and a small apple. A courtesy meal 10 hours after test meal intake
      for dinner and at the end of the visit. No other foods or beverages except water (ad libitum)
      will be allowed during the day (including during breakfast and lunch if desired).

      This first clinical appointment will be followed by a 1 week washout period, during which
      he/she will continue on a low carotenoid diet (3rd week of washout diet). At the end of the
      3rd week of washout, the second appointment at the LIH clinical center will take place. The
      procedure for this day is the same as mentioned above. The second appointment is followed by
      the 4th and last washout week and at the end the participant will have the 3rd and last
      appointment at the Luxembourg Institute of Health (LIH) clinical center, which will be
      identical to the other visits. For all washout periods the participants will be asked to fill
      a provided food journal, on a daily basis, where they will write down what they have eaten
      during the day. This will be used to check compliance with the washout period and better
      interpret personal data.

      Stool collection: For a limited number of subjects (n=6), the samples will be collected
      following intake of all 3 test meals. For this purpose, Containers for collection and plastic
      clip-bags and bags will be handed to participants. Boxes with cooling elements for stool
      collection will likewise be given. Also, six fecal color markers will be provided to the
      participants. For each clinical visit, two fecal marker are needed. Collections will start
      from the excretion of the first fecal color marker (brilliant blue) which will be taken at
      the beginning of the fasting period, i.e. the day before each clinical day. The collection
      will continue to the excretion of the second fecal marker which should be taken on the
      morning of the day following each clinical visit (before breakfast). Samples will be returned
      after the clinical test day as soon as the last fecal marker has been excreted (normally
      resulting in 2-3 day complete fecal samples), and could be collected once in between by staff
      from the LIH if needed.
    

Intervention name(s): Intervention with soy protein isolate; Intervention with whey protein; Intervention without protein addition
Intervention type(s): Other; Other; Other
Intervention description(s): Test meals will be served to the subjects, containing soy protein isolate:
350 mL carrot/tomato juice (50:50, v/v), with 30 g added soy protein, plus 5 ml peanut oil
as morning test meal, served together with 40 g toasted bread and 20 g of cream-cheese plus 10 g margarine.; Test meals will be served to the subjects, containing soy protein isolate:
350 mL carrot/tomato juice (50:50, v/v), with 30 g added whey protein isolate, plus 5 ml peanut oil
as morning test meal, served together with 40 g toasted bread and 20 g of cream-cheese plus 10 g margarine.; Test meals will be served to the subjects, containing soy protein isolate:
350 mL carrot/tomato juice (50:50, v/v), plus 5 ml peanut oil
as morning test meal, served together with 40 g toasted bread and 20 g of cream-cheese plus 10 g margarine.
Allocation: Randomized
Intervention model: Crossover Assignment
Intervention model description: Twenty four male individuals from or living in the region of Luxembourg will be recruited for this study. The number of participants is based on a randomized block design, constituting of 6 blocks of 4 subjects, each will be served different sequences of test meals (A, B, C/A, C, B/B, C, A/B, A, C/C, A, B/C, B, A) in order to cancel out any potential effect of sequence of meals.
Thus, each subject will act has his/her own control. Test meal intake will be separated by 1 week.
Masking: Single (Participant)
Primary purpose: Basic Science
Keywords: Carotenoids; Postprandial absorption; Area-under-curve; Bioavailability; Proteins; Tomato juice; Carrot juice; Randomized cross-over