Green tea - Weight loss master or handbrake?
Green tea has recently earned itself a host of highly sung accolades in the health and fitness industry. This ancient plant known traditionally as ‘Camellia Sinensis’ by its botanical name is an evergreen plant and in many cultures is simply called the “Tea Shrub”. Traditionally used as a beverage among emperors of ancient China some near 4000 years ago, it was used as a well-being beverage that gave more flavor than water, slight stimulation, digestive aid and was believed traditionally to ward off dis-ease states such as:
- Aches and pains.
- Poor mood.
- Invigoration of the Heart Chakra (this is likely due to the caffeine increasing heart rate)
- Improvement of mental clarity.
Moving forward over the few thousands of years…
We arrive at the modern-day time frame where green tea is still used all around the globe. However, its latest attraction is more so to do with its effects on weight loss! Is this just a sales tactic to push more of this so evergreen tea shrub, or is there some merit behind this? Let’s turn to the scientists for their ever grey ‘unphased by marketing hype’ approach for the results…
First, we must look at the component of green tea used in the marketing of these weight loss products that you simply add a sachet of to water and now you instantly have 50 cups of tea in your fingertips. How the heck does that math even work? The answer… Extracts. What we are looking at is high dose green tea extract labeled as EGCG or Epigallocatechin gallate if you want to wrap your tongue around that one. For the purpose of repetition and to save you frustration, for the rest of the article we will simply refer to it as EGCG.
In 2016 a study was conducted on the effects of high-dose green tea extract EGCG on a randomized double-blind placebo clinical trial to study the effects of EGCG in regards to the weight-loss claims that surrounded the extract. Here is the outline of the study:
Daily intake: 856.8mg
Prospect: Weight reduction and changes in lipid profiles and obesity-related hormonal profiles in women with central obesity.
Methods: 115 women were screened to partake in the study, 102 of them showed a BMI index of 27kg/m(2) and a waist circumference of 80cm and greater. These 102 women we considered eligible candidates for the study. From there, the women were at random, selected to participate in either the placebo or high-dose group.
Measures were taken:
- Anthropometric measurements (assessing physical size, shape, and composition of the individual’s body)
- Lipid Profiles.
- Obesity-related hormonal profile changes including Ghrelin, Leptin, adiponectin, and insulin.
Results are drawn from this clinical trial:
- Significant weight loss from an average of 11.3 – 11.5kg across the 12 weeks.
- Decreased total cholesterol.
- Decreased LDL Plasma levels.
- Significant reduction in Ghrelin levels.
- Elevated Adiponectin (Protein hormone involved in the regulation of glucose levels and fatty acid breakdown)
Conclusions are drawn – there were no significant side effects drawn from the study and it is believed that the changes were drawn from the EGCG effects of Ghrelin secretion inhibition, and an increase in adiponectin levels as a result. (1) Through this we can then draw a final theoretical conclusion that suppression of appetite through inhibition of ghrelin will lead to a reduction of hunger signaling significantly, therefore, being more prone to caloric intake and through this a reduction of weight is likely to occur.
Long term Ghrelin Inhibition/reduction of secretion
First let’s understand the critical role of Ghrelin in the body because all we are told is that Ghrelin is our hunger and growth hormone peptide, so naturally the thought process behind suppressing it seems admirable and genius. A simple fix, except for when it isn’t… Ghrelin is more than just a hunger hormone and we know from previous methods of inhibiting hormones that there has to be a trade-off elsewhere somewhere along the line. Here are the other mechanisms of actions for Ghrelin, being that it is a peptide (providing specific function) there are many ghrelin receptors in the body:
- The hypothalamic-pituitary-adrenal axis and the hypothalamic level and regulation of energy balance.
- Growth hormone attributes.
- Distributed at the level of cardiomyocytes and endothelial cells (cardiovascular system health).
- Vascular function.
- Increasing Nitric Oxide availability.
- Anti-oxidant and anti-inflammatory effects.
- Improvement of insulin sensitivity.
- Improves/ decreases blood pressure through modulation of the sympathetic nervous system.
It is believed that Ghrelin is a promising candidate for future cardiovascular drug research. (2)
Green Tea - Thyroid Effects and mineral binding:
Recently we talked about goitrogens and the effects on the thyroid, the enlargement of the gland creating a goiter and binding up of available iodine for the conversion of TSH to T4 and T3. Catechins are flavonoids and are found naturally in the EGCG component of green tea also are known as goitrogens. High doses of EGCG equivalent from ranges administered at 20-100mg per kg of bodyweight were administered of high dose green tea extract groups and showed to have an anti-thyroid agent effect typical features that include:
- Decrease of thyroid peroxidase and 5'-deiodinase
- Elevated thyroidal Na, K+ATPase activity.
- Reduction of T3 and T4 levels but an increase of Serum levels of TSH meaning that conversion is being halted and the Thyroid axis is trying to get any TSH it can convert down to active T3 and T4 with no avail.
“Taken together, these results suggest that catechin present in green tea extract might behave as an antithyroid agent and possibly the consumption of green tea at high dose could alter thyroid function adversely.” - https://www.ncbi.nlm.nih.gov/pubmed/20561943
Catechins bind to the following:
The recommended daily average ranges from 5-1000mg of EGCG from supplements. On average, a standard 250 ml cup of green tea contains 50-100mg of EGCG, so if you are having 50 cups equivalent, you may want to check the label regarding the extract but by this math, you’re looking at around 2500-5000mg a day…
One scientific panel concluded that: “catechins from green tea infusion, prepared in a traditional way, and reconstituted drinks with an equivalent composition to traditional green tea infusions, are in general considered to be safe according to the presumption of safety approach provided the intake corresponds to reported intakes in European Member States.” - https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2018.5239.
- Proteins, EGCG has been shown to impact and bind with egg white protein, interfering with digestion.
- High copper content competes with the Inhibition of iron absorption in intestinal cells and is instead excreted out in feces instead of being uptaken into the bloodstream.
- Binding of Iodine inhibiting it being utilized by the thyroid.
Is Matcha much better?
Unfortunately, no, a standard cup of Matcha Contains around 137 times more EGCG than that of standard green tea.
So, what’s the verdict?
A general consensus on most things that are extremely concentrated… or just things in general we consume; everything in moderation. We harp on about it but it's true more is not always better. While your standard cup of green tea is not at all likely to send you over the safety limit of daily intake, anything that promises around 50 x that should probably deservingly take a closer inspection of its suitability for you as an individual.
To avoid the binding effects of green tea to your nutritional mineral and protein requirements, it’s a great idea to have your green tea either side if a meal instead of with your food.
1.The therapeutic effect of high-dose green tea extract on weight reduction: A randomized, double-blind, placebo-controlled clinical trial. Chen IJ1, Liu CY1, Chiu JP1, Hsu CH2. Clin Nutr. 2016 Jun;35(3):592-9. DOI: 10.1016/j.clnu.2015.05.003. Epub 2015 May 29.
2. Human Ghrelin: A Gastric Hormone with Cardiovascular Properties. Virdis A1, Lerman LO, Regoli F, Ghiadoni L, Lerman A, Taddei S. Curr Pharm Des. 2016;22(1):52-8.
3. Daily Intake data - https://efsa.onlinelibrary.wiley.com/doi/10.2903/j.efsa.2018.5239
4. Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats. Chandra AK1, De N. Food Chem Toxicol. 2010 Aug-Sep;48(8-9):2304-11. doi: 10.1016/j.fct.2010.05.064. Epub 2010 Jun 1.
5. Carrasco, N., 1993. Iodide transport in the thyroid gland. Biochim. Biophys. Acta
6. Divi, R.L., Doerge, D.R., 1996. Inhibition of thyroid peroxidase by dietary flavonoids.
Chem. Res. Toxicol. 9, 16–23.
7. J Nutr Biochem. 2007 Mar; 18(3): 179–183. doi: 10.1016/j.jnutbio.2006.12.005 Green Tea as Inhibitor of the Intestinal Absorption of Lipids: Potential Mechanism for its Lipid-Lowering Effect1 Sung I. Koo* and Sang K. Noh2
8. Mineral impact: https://www.sciencedaily.com/releases/2010/08/100823152309.htm
9. Differential regulation of Na,K-ATPase alpha 1, alpha 2, and beta subunit mRNA and protein levels by thyroid hormone. B Horowitz, C B Hensley, M Quintero, K K Azuma, D Putnam and A A McDonough
10. Goitrogenic/antithyroidal potential of green tea extract in relation to catechin in rats. Chandra AK1, De N. Food Chem Toxicol. 2010 Aug-Sep;48(8-9):2304-11. doi: 10.1016/j.fct.2010.05.064. Epub 2010 Jun 1.
12. Biol Pharm Bull. 2018;41(4):524-529. doi: 10.1248/bpb.b17-00805. Inhibitory Effect of (-)-Epigallocatechin-3-O-gallate on Octanoylated Ghrelin Levels in Vitro and in Vivo Nakajima K1, Oiso S1, Kariyazono H1.