Ability of a Tea Leaf Extracts Preparation to Slow Down Carbohydrate and Fat Absorption
Condition: Diabetes; Overweight
MeSH terms: Overweight
Study type: Interventional
Phase: Phase 1

Summary: 
      Objective - A variety of herbal, over-the-counter preparations of tea leaves are said to
      reduce the rate of absorption of fat ( allegedly via inhibition of pancreatic lipase) and
      carbohydrate (via inhibition of carbohydrate digestion and blocking of glucose transport by
      the intestinal mucosa). There has been some study of the ability of these products to reduce
      the blood glucose increase observed after a carbohydrate meal and to reduce blood cholesterol
      levels in chronic studies. The purpose of the present study is to objectively determine if
      one cup of "tea" made from a combination of three types of tea leaves (mulberry, black and
      green tea) can cause malabsorption of carbohydrate and fat taken in conjunction with the tea.

      Research Design - The study will consist of a double blind, placebo controlled crossover
      study in 20 healthy subjects. On one of two days (one week apart) the subjects will ingest a
      standard meal consisting of 30 g of sucrose (in the tea) and 30 g of starch in the form of
      white rice plus 10 g of fat as butter. To measure triglyceride absorption, each meal will
      also contain 250 mg of 13-C labeled triolein. Triolein is a commonly ingested fat consisting
      of glycerol bound to three oleic acids. 13-C is a stable (non-radioactive) isotope of carbon.
      On one of the test days the subjects (randomly) will concurrently consume the active
      preparation, a tea containing extracts of the three types of tea leave described above plus
      the meal, and on the other test day they will consume the meal with a liquid placebo
      preparation (warm water, sugar and food coloring). Subjects will provide a breath sample
      before and at hourly intervals for 8 hours after ingestion of the meal. Carbohydrate
      malabsorption will be determined by the hydrogen concentration in the breath samples and fat
      malabsorption by the concentration of 13-CO2 in the breath samples.

      Clinical Significance - An increase in breath hydrogen indicates carbohydrate malabsoption
      and a low 13-CO2 indicates lipid malabsorption. Objective evidence that the tea leaf extract
      actually induces carbohydrate and/or fat malabsorption could provide the basis for further
      studies.
    

Detailed description: 
      One of the commonly cited beneficial effects of tea is its ability to induce weight loss.
      Support for this contention include a controlled human trial showing increased weight loss
      when tea was added to a dietary regimen, and a mouse study demonstrating that administration
      of a tea extract with a high fat diet eliminated the weight gain observed in the absence of
      tea. Several different mechanisms have been postulated to account for this weight control.
      Multiple studies have reported modest increases in energy expenditure associated with
      ingestion of oolong or green teas. In addition, tea could inhibit the absorption of
      carbohydrate and/or fat. Studies supporting the possibility of carbohydrate malabsorption
      include a in vitro studies showing that constituents of tea inhibit the activity of
      carbohydrate digesting enzymes (α-amylase and α-glucosidase, and the mucosal uptake of
      glucose via an interaction with sodium dependent glucose transporters. The in vitro
      demonstration that tea extracts inhibit pancreatic lipase activity suggests that tea might
      interfere with triglyceride absorption.

      However, there have been no in vivo studies in humans or animals showing that tea
      preparations actually are capable of causing malabsorption of either carbohydrate or fat. In
      the present study, we utilized measurements of breath H2 and 13CO2 to investigate the ability
      of a mixture of black, green and mulberry tea leaf extracts to induce malabsorption of
      carbohydrate and fat in healthy volunteers.

      Protocol - The study group consisted of 20 healthy volunteers (ages 23 to 52, 10 females and
      10 males). The subjects fasted after their usual dinner on the day preceding the study until
      the following morning (approximately 8 am) when the experiments were performed. After
      collection of baseline breath samples for H2 and 13CO2 analysis, the subjects ingested the
      test meal that consisted of cooked white rice and butter. The rice was boiled for20 minutes,
      and then individual portions (176 g, which contained 50 g of carbohydrate) were weighed and
      frozen with 10g of butter. Immediately prior to ingestion, the meals were warmed in a
      microwave oven, and 0.2 g of 1,1,1-13C-triolein (Cambridge Isotope Laboratories, Andover, MA)
      was thoroughly mixed into the meal. Concurrent with ingestion of the meal, the subjects
      randomly were assigned to drink either 500 ml of the warm active tea preparation containing
      10 g of sucrose or 500 ml of a placebo preparation that also contained 10 g of sucrose.
      Breath samples were then collected at hourly intervals for eight hours. At the end of each
      test period, subjects were asked to rate a variety of symptoms including nausea, bloating,
      abdominal discomfort, and rectal gas (as well as obfuscating symptoms) on a previously
      described linear scale that ranged from zero (none) to 4 (severe). In addition, the number of
      loose bowel movements were noted. One week later the test was repeated with the subjects
      receiving the opposite preparation from that used in the initial study. The study was
      approved by the Human Studies Subcommittee of the Mpls. VA Medical center and informed
      consent was obtained from all subjects.
    

Intervention name(s): tea extracts
Intervention type(s): Drug
Allocation: Randomized
Intervention model: Crossover Assignment
Masking: Double
Primary purpose: Treatment
Keywords: glucose; lipid; diabetes; overweight