Miracle Tea? This Is What You Need To Know

This is part of the write up.. but good enough for your understanding!

 

 

What are the active compounds in green tea? 

 

 

Green tea is known to contain numerous compounds with biological activity including amino acids, xanthines, pigments, antioxidants, carotenoids, vitamins, minerals, as well as flavonols such as quercitin, kaempferol and myricetin.

The bioactive compounds in green tea that may have the greatest significance are polyphenols called catechins. These include Epicatechin (EC) epicatechin-3-gallate (ECG), epigallocatechin (EGC) and epigallocatechin-3-gallate (EGCG).

The green tea catechin of most importance for weight loss is called epigallocatechin gallate, which is a mouthful, so it’s commonly abbreviated as EGCG. The catechin content in tea depends on a variety of factors including the type of tea, where the tea is grown, how the tea is grown, when the tea is harvested and how it is processed. Normally 10-20% of the catechins in green tea are EGCG. (Graham 1992).

It’s important to note that some of the research on health and weight loss benefits of green tea is conflicting and this may be largely due to the fact that the catechin content in various batches of tea can vary so much.

Caffeine Content of Tea 

The most well known compound found in tea is caffeine. Both regular and green tea contain caffeine, unless decaffeinated, although tea does not contain as much caffeine as coffee. Black tea contains substantially more caffeine than green or oolong tea. According to a research review by Carmen Cabrerra, PhD., the caffeine amounts in tea are as follows:

Decaffeinated tea .6 – 3 mg/150 ml

Oolong tea 18-33 mg/150 ml

Green tea 15-25 mg/150 ml

Normal Coffee 80-115 mg/150 ml

The removal of caffeine in decaffeinated teas can not only affect the taste, but also the quality or quantity of flavonoid compounds found in the tea (despite some label claims to the contrary). Whether or not decaffeination reduces the amount of catechin and other active compounds in green tea depends on the process used.

There are two processes for decaffeination. One involves an ethyl acetate solvent to remove the caffeine. The other process uses carbon dioxide (water and effervescence). Green tea decaffeinated with the solvent retains only about 30% percent of its EGCG and other important catechins. Green tea that was decaffeinated with carbon dioxide retains up to 95% of the catechins (McKay 2002). 

If you choose a decaffeinated green tea and you’re drinking it in order to obtain health and anti-obesity benefits, look for the carbon dioxide method as it is more likely to have retained the catechin content. Most reputable brands will list the method used on their label, as it makes sense to advertise the carbon dioxide method of decaffeination if used, because savvy consumers may be looking for it. If it’s not mentioned, then you can assume it wasn’t used.

Decaffeinated teas usually have less than 3 mg of caffeine per 150 ml of tea, however, I found one brand advertised as "decaffeinated" which contained 10 mg of caffeine per serving. This would more correctly be labeled as a "reduced caffeine" tea, not a decaffeinated tea, so if you are avoiding or limiting caffeine for any reason, be certain to read labels carefully.

What Are The Effects And Benefits

Of Green Tea On Health? 

 

Chen Zang, a pharmacist from the Tang dynasty (618-907 AD) said, "Every medicine is the only medicine for a specific disease, but tea is the medicine for all diseases." Modern science today is showing that the Chinese may have been right. A review of the pub med research data base shows 2287 citations referencing cell (in vitro), animal and human green tea studies.

There are currently hundreds of human studies showing potential health benefits of green tea. A recent review of the literature (Cabrerra, 2006) does a good job of summarizing the green tea research to date and listed the following potential health benefits:

1. Neutralizes free radicals (antioxidant)
2. Prevents certain forms of cancer
3. Prevents atherosclerosis (plaque formation)
4. Reduces risk of blood clotting
5. Decreases blood pressure
6. Decreases incidence of death from stroke
7. Decreases incidence of death from coronary heart disease
8. Reduces total cholesterol
9. Reduces LDL cholesterol
10. Elevates HDL (good) cholesterol
11. Improves glucose tolerance and insulin sensitivity
12. Protects against osteoporosis and increases bone mineral density
13. Protects against solar ultraviolet radiation
14. Reduces dental cavities and improves oral health
15. Inhibits hepatic fat accumulation
16. Improves immunity
17. Reduces inflammation
18. Kills unfriendly bacteria and viruses

Although some of the research on green tea and health is conflicting or inconclusive, there is strong evidence from human studies that many of these proposed green tea benefits are real and clinically significant.

For example, research indicates that the EGCG in green tea is a particularly powerful antioxidant (Langley-Evans 2000, Rietveld 2003). Several studies suggest that green tea has higher antioxidant activity than vegetables such as garlic, kale, spinach and brussel sprouts (Cao 1996). Green tea also appears to have stronger antioxidant properties than black tea (Langley 2000).

Despite the large amount of research, not everyone agrees that all of the health benefits have been conclusively proven yet. Blood pressure is a good example. A review paper in the Journal of the American College of Nutrition reported that early studies in animals and humans showed reduced blood pressure from consumption of green tea polyphenols, but concluded that recent studies do not support a hyposensitive effect of green tea (McKay 2002).

Nevertheless, the total body of research to date is very compelling and merits more research as well as the recommendation to add tea as part of a health promoting lifestyle.

Green Tea For Weight Loss? 

In addition to the huge list of potential health benefits of green tea, there has been great interest expressed in green tea as a potential weight loss aid. This report was written to focus primarily on the anti obesity and metabolism-stimulating effects of green tea, as the health benefits of green tea is too broad and deep a subject to cover in this publication.

Green tea and green tea extract (supplements/capsules) have proven effects on increasing short term energy expenditure and fat oxidation (increasing use of fat as fuel), and may have an effect on body weight loss, body fat loss and preventing weight regain. However, the long term effects of green tea on body composition are much less definitive (and very often exaggerated).

Weight Loss And Metabolism-Stimulating Benefits

Of Green Tea - Mechanism of Action 

 

How does green tea work? The physiology and biochemistry gets complicated very quickly, but here is a brief explanation:

It has been known for many years that tea catechins inhibit catechol O-methyl-transferease (also known as COMT), which is the enzyme that degrades noradrenaline (Borchardt 1975). Noradrenaline is a catecholamine which binds to the adrenergic receptors on the fat cells and stimulates thermogenesis. By inhibiting the COMT enzyme that degrades noradrenaline, green tea extends the thermogenic action of noradrenaline. (Shixian 2005)

Caffeine acts by inhibiting phosphodiesterase, an enzyme that degrades intracellular cyclic AMP and by antagonizing the negative modulatory affect of adensosine on increased noradrenaline release (Kovacs 2006)

When consumed together, both caffeine and catechins result in an increased and or prolonged effect of noradrenaline on lipid and energy metabolism.

Some researchers (Nagao 2005) have suggested that the increase in thermogenesis and reduction in body fat in humans can’t be completely explained by the inhibitory effect on COMPT and that other mechanisms must be involved.

The latest research (Moon 2007) lists numerous other mechanisms through which EGCG might reduce body weight and body fat and it’s also likely that other compounds with pharmacological activity may contribute to an anti obesity effect in other ways.

These mechanisms are far too complex to discuss in this report, but one that has piqued the interest of obesity researchers is the possible inhibition of fat cell (adipocyte) proliferation, based on in vitro studies.

As we know that obesity is not just a problem of fat cell size, but also fat cell number, it will be interesting to see what future human research reveals regarding these findings on green tea and fat cells.

Weight Loss And Metabolism-Stimulating Benefits

Of Green Tea – What The Research Says 

Compared to the numerous studies that investigate green tea’s health effects, there are relatively few human studies that examine the effects of green tea on energy expenditure and fat oxidation. In the past two years, however, the amount of research on green tea and weight loss has increased substantially.

The studies published so far suggest that green tea may have some legitimate benefits to men and women seeking body fat loss, primarily by way of short term increased metabolism (higher energy expenditure also known as "thermogenesis") and increased fat oxidation (the use of fat as the fuel source over other substrates).

When discussing thermogenesis, it’s important to re-emphasize that green tea contains caffeine, and caffeine itself is thermogenic. Research has shown an increase in short term resting metabolic rate of 3-4% over 150 minutes with the ingestion of 100 mg of caffeine (Dulloo 1989). 

Although the researchers concluded that this increase in energy expenditure was "significant," most people agree that drinking coffee or even popping caffeine pills by themselves does not demonstrably reduce body fat or body weight and long term intervention studies in humans have shown no effect of caffeine consumption on body weight (Pasman 1997).

When combined with other compounds such as ephedrine, that’s a different story, as caffeine has proven to potentiate the effects of ephedrine (Toubro 1993). However, some people are sensitive to caffeine and concerns about the stimulatory and cardio vascular effects of ephedrine have caused many people to look for other options.

The stimulatory effects of caffeine are well known and the increase in energy and alertness produced from a cup of java is considered a benefit by many people. Green tea contains only about 20% of the caffeine that coffee does, but it’s possible that this caffeine has some synergistic effect with the EGCG in green tea.

Recent studies suggest that green tea, while not as effective as caffeine and (the now banned) ephedrine, may be better than caffeine alone for increasing fat oxidation and energy expenditure. The effects of certain compounds in green tea appear to stimulate energy expenditure beyond and independent of the caffeine content.