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Obesity: which role have the consumption of tea and coffee?

Tea, coffee and public health

Tea and coffee are the most popular drinks, the most traded and appreciated products that come from developing countries. Their global consumption is steadily increasing due to their sensory and health properties. They can help prevent and fight obesity, a current health pandemic. The leading cause of death worldwide are diseases related to metabolic dysfunction. The most significant in this respect is being overweight, which affects about 2 billion people worldwide, of which 650 million are frankly obese. By causing inflammation, overweight and obesity can promote diabetes, cardiovascular and reproductive diseases as well as tumors. In addition to these health risks, they cause mobility problems as well as social and sexual relationship problems.

They lower self-esteem and overall quality of life. They also lead to considerable economic losses. Healthcare related to obese patients costs at least 25% more and causes losses of an average of 2% of a country’s gross domestic product. The prevention and treatment of diseases using natural products and functional foods of plant origin have always been the basis of folk and oriental medicine. Today they are experiencing a renaissance and their popularity is also growing in official medicine and in self-therapy. Coffee and tea could be promising candidates for the prevention and treatment of various diseases including obesity. Although they are very popular, the critical point is to use them correctly.

Health benefits of tea

Green tea polyphenols are effective against chronic inflammatory conditions of the liver, gastrointestinal tract and against neurodegenerative diseases. The effect of polyphenols can be explained in part by their action on the gastrointestinal microbiota. A link has been established between green tea consumption and memory in older men. It is remarkable that the memory of the old women was not affected. Catechins in tea may have an anticancer effect. They inhibit cell multiplication, trigger their apoptosis (death) and autophagy, and reduce the viability of cancer cells. They can even enhance the therapeutic effects of medicine against cancer diseases and simultaneously mitigate their negative side effects.

Most animal and human studies report that tea (extracted from the leaves of the tea tree) reduces the manifestations of metabolic syndrome, diabetes and cardiovascular disease (including the reduction of the risk of heart attack). Other studies have shown the positive effect of tea on the decrease of blood insulin, but not on the concentration of glucose, triglycerides, fatty acids and adipose tissue hormones, however, they reported that the decreased blood glucose levels can be caused by the action of green tea polyphenols on the production of glucose in the liver.

Health benefits of coffee

Clinical studies have shown that coffee’s ability to reduce blood sugar does not depend on caffeine but on its other components. This effect probably results from the chlorogenic acid; it has antioxidant and anti-inflammatory effects, can influence glucose and lipid metabolism. Thanks to its antioxidant, anti-inflammatory and metabolic effects, coffee has a preventive and therapeutic influence against diabetes, cardiovascular diseases, tumors, inflammation, fatty liver disease and Parkinson’s disease. Its consumption can be recommended not only to healthy people but also to people with high cholesterol and blood sugar, with hypertension, metabolic syndrome or diabetes.

The antidiabetic effects have been determined not only for chlorogenic acid but also for other components such as caffeine, caffeic acid and ferulic acid. Large-scale studies have shown a correlation between the habit of consuming coffee and the reduction of mortality related to cardiovascular disease, a reduction in the risk of heart attack and diabetes. Contrary to popular belief, drinking coffee is not linked to an increased incidence of cardiac arrhythmias. Thanks to the ability of coffee’s antioxidants to neutralize free radicals and reduce disease and mortality, like tea, coffee has earned the title of “longevity drink”.

Proven effects of tea on obesity

All the studies performed have validated the ability of tea and its components to reduce fat reserves and body weight in humans. This effect was achieved thanks to polyphenols. According to existing data, epi-gallocatechin and tea leaf caffeine have independent but synergistic effect mechanisms on weight loss. According to some sources, black tea polyphenols are more efficient than green tea polyphenols, but other authors report evidence of a stronger effect of green tea. It is assumed that the tea molecules reduce fat stores through several pathways:

  • affect neuroendocrine metabolic regulators of appetite and reduce food consumption;
  • reduce the emulsion and absorption of lipids and proteins in the gastrointestinal system and consequently reduce the caloric intake;
  • act on the gastrointestinal microbiota (lacto- and bifidobacteria), responsible for digestion. For example, they produce short fatty acids, which increase the rate of lipid metabolism;
  • inhibit the differentiation and proliferation of pre-adipocytes;
  • reduce the production of lipids in the liver and promote lipolysis;
  • stimulate the conversion of white adipose tissue into brown, increase its oxidation, combustion and energy expenditure through the production of heat.

However, it must be taken into consideration that the effect of green tea and its molecules only occurs when large doses are consumed. Vazquez Cisneros et al. (2017) recommended a daily dose of 100-460 mg of epi-gallocatechin gallate plus 80-300 mg of caffeine per day over the course of 12+ weeks. Yang et al. (2016, 2018) recommended 3-4 cups of strong tea (600-900 mg of catechins) per day for at least 8 weeks.

Proven effects of coffee on obesity

Results from in vitro and animal studies suggest that coffee can reduce fat accumulation in the body through several mechanisms:

  • inhibits the multiplication of adipocytes;
  • affects transcription factors and other proteins involved in the production of lipids in these cells;
  • through an action on the gastrointestinal microbiota, which also influences obesity.

Thanks to these effects, coffee can reduce fat reserves in obese animals and humans and reduce body weight in humans. A study by Sarriá et al. (2018) determined a positive effect of green and roasted coffee on metabolic indices but not on patients’ body weight. Scientific results validate the application of coffee extract for weight loss and the treatment of certain metabolic disorders (diabetes, obesity, etc.). Coffee has a number of other positive physiological effects on health and longevity. The negative side effects of coffee are not serious and only appear when the consumption is excessive. This knowledge makes it possible to recommend coffee extract as an ingredient in a drink intended for weight loss.

But how much do you need to drink to see the effects?

All types of tea have a positive effect on health and weight loss. However, it must be remembered that the effects of tea will only manifest themselves at high doses (3-4 cups of strong tea per day, which represents 1-2 g of tea containing 100-600 mg of polyphenols) and long-term use . The minimum duration of treatment is 8 weeks. For those who are not used to drinking large quantities of tea, there is an alternative: condensed tea or its pure components. As for coffee, however, a cup of strong coffee contains 60 mg of pure chlorogenic acid. This dose has essentially no effect on the absorption of chlorogenic acid in the body.

The metabolic effect is obtained with a daily intake of at least 510 mg of chlorogenic acid and 120 mg of caffeine. This evidence speaks in favor of roasted coffee extract with approximately 400 mg of caffeine and/or 510 mg of chlorogenic acid, which corresponds to 3-5 cups of strong coffee per day to be used for weight reduction. This amount can be considered a metabolically safe and efficient dose. For those who cannot handle so many coffees a day, coffee can be replaced by an adequate amount of chlorogenic acid and caffeine. This can be achieved with supplements that can be purchased online or in specialized shops.

  • edited by Dr. Gianfrancesco Cormaci, PhD, specialist in Clinical Biochemistry.

Scientific references

Tang GY, Meng X, Gan RY et al. Int J Mol Sci 2019; 20:6196.

Tabrizi R et al. Crit Rev Food Sci Nutr 2019; 59:2688-2696.

Yang CS, Wang H et al. J Food Drug Anal 2018; 26:1-13.

Tajik N, Tajik M et al. Eur J Nutrition 2017; 56: 2215-2244.

Pan MH, Gao Y, Tu Y. Food Functions 2016; 7:4481-4491.

Li Y, Wang C et al. Diabetes Metab Res Rev 2016; 32:2-10.

Huang J, Wang Y et al. Eur J Clin Nutr. 2014; 68: 1075-87.

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