Study under review: Food Inhibits the Oral Bioavailability of the Major Green Tea Antioxidant Epigallocatechin Gallate in Humans
Epigallocatechin gallate (EGCG) or epigallocatechin-3-gallate (structure shown in Figure 1) is a catechin best known for being in various teas. Specifically, it’s one of the most abundant flavonoids present in the leaves from Camellia sinensis. The US Department of Agriculture reports that EGCG is found at concentrations of 42.45 mg/100 g of leaves in white tea and at 70.20 mg/100 g in green tea.
EGCG, green tea and green tea extracts have been claimed to have antidiabetic, anticarcinogenic, weight loss and anti-inflammatory properties. However, when studied closer, the evidence becomes flimsy for some of these claims for a couple of reasons. One reason is that the biochemical components in green tea are different from those in extracts, which is again different from pure EGCG. In particular, green tea also contains three other catechins whose effects may be overlapping, as well as caffeine and theanine that each in their own right carries some biological activity. Thus, assigning biological activity to EGCG from studies using green tea or extracts is difficult. Furthermore, while EGCG and green tea extracts have shown promising results in several types of in vitro experiments, they have sometimes translated poorly into human in vivo studies. As of now, the FDA does not condone health claims associated with EGCG or green tea.
Some of the discrepancies reported can possibly be attributed to varying bioavailability with different types of administration, especially as oral bioavailability appears to be quite poor in rodents, which does not appear to be the case for humans. Thus, while EGCG has been associated with many types of effects, the evidence is far from solid.
The purpose of the present study was to examine how well EGCG is absorbed in healthy humans when ingested alone, with a breakfast, or in a strawberry sorbet, and thus essentially to find out whether EGCG has better bioavailability when consumed with water and on empty stomach or when ingested with food.
Green tea and one of its active components, EGCG, have a lot of health claims associated with them, some more well-supported than others. However, one confounding factor in studying EGCG’s effects is its absorption from the gut and whether it depends on food consumption or not. The purpose of this study was to examine this question in healthy humans.
Other Articles in Issue #11 (September 2015)
A shot to the gut
Alcohol intake and gut impacts have been researched before, but we still aren’t sure what exactly goes on after people drink. This study looked at what happens with gut bacterial products when people have multiple drinks at one sitting ... aka “binge drinking”.
Can omega-3s prevent cognitive decline?
One of the most important issues with aging is decreased cognitive ability and eventually dementia. Since the brain has such high omega-3 content, many people supplement for prevention of these issues. This large, multi-year study put that practice to the test.
The study that didn’t end the low-fat/low-carb diet “wars”
A recent metabolic ward study set the low-carb world on fire, and produced many inaccurate media headlines disparaging low-carb diets. We cover the study and its implications, detail by detail.
- Interview: Dylan Dahlquist, MSc(c)
When is breakfast the most important meal of the day?
With an increasing amount of research pointing to benefits of intermittent fasting, breakfast has been shunned by more and more people. But for those with type 2 diabetes, blood sugar is a central issue, and breakfast may play a major role in regulating it.
What to Expect When We’re Expecting: Fetal Programming and the Development of Taste Preferences
By Margaret Leitch, Ph.D.
Gluten-intolerant? There’s a pill for that
Some people are lactose intolerant, but still drink milk thanks to the availability of lactase enzymes. That setup isn’t yet possible for those who don’t handle gluten well. This study examines the efficacy of a promising enzymatic adjunct to a gluten-free diet.
Vitamin D(efense) against Crohn’s disease?
Immune benefits are often listed among the multitude of possible vitamin D effects. Most of the time, this is simplified to “defense against colds and flu”. But many conditions have an immune component — this particular study examines potential mechanisms by which vitamin D may help Crohn’s disease.
Green tea: a potential pain in the neck
Though it may not be as effective for fat loss as early studies suggested, green tea is still seen as extremely healthy. But animal evidence has pointed to possible thyroid side effects from excessive green tea consumption. How convincing is this evidence?