Green tea, obesity and osteoarthritis (OA)


Summary

Drinking green tea helps with weight loss and reduces the risk of OA.


Obesity and osteoarthritis

Obesity is the result of an imbalance between calorie intake and expenditure. It is a risk factor for OA: Every 5kg of weight gain increases the chance of developing knee OA by 36%.


Weight loss can help relieve symptoms of OA, especially pain. In people who have obesity and OA, losing at least 10% body weight is recommended.


Green tea

Tea is one of the most popular beverages around the world.


It comes from the leaves of the Camellia Sinensis plant and is consumed as green, black or Oolong tea.

Among these different tea varieties, green tea appears to have the most significant influence on health and well-being.

Green tea and obesity

Green tea has been shown to reduce food intake, fat absorption and storage as well as increase energy expenditure and fecal lipid excretion.


EGCG and caffeine are the main compounds responsible for green tea’s weight-loss effect.


Both EGCG and caffeine increase the level of norepinephrine, which enhances energy expenditure as well as the breakdown and burning of fat.


The amount of EGCG and caffeine can vary, depending on the plant species, climate, region and season in which the plants are grown.


Brewing time and water temperature also affects EGCG and caffeine content in green tea.


Generally, a cup of green tea prepared with a standard commercial tea bag brewed in 120ml of hot water for 5 minutes contains approximately 41mg of caffeine and 77mg of EGCG.

Having a total of 2-7 cups of green tea daily (equivalent to 100-600mg EGCG and 4-198mg caffeine) for 8-12 weeks has been shown to significantly reduce body weight, BMI, waist circumference, abdominal and total body fat in overweight people. The associated rate of weight loss, i.e. 114-340g per week, is considered safe and advisable for people with obesity.


Green tea can help you lose weight but whether its weight-loss effect is clinically relevant remains controversial.


Conflicting findings are the result of differences in study design such as ethnicity of study population (Asian vs Caucasian), dose and formula of green tea (extracts vs beverage), diet and activity levels.


Combining green tea with regular moderate-intense exercise can help you lose more weight than exercise alone.


Should I have green tea?

People with major heart conditions and bleeding disorders should not have green tea. Patients suffering from renal failure who may retain aluminium in their body should also not too much drink green tea. This is because tea plants can contain high levels of aluminium. For these patients, consuming green tea may lead to build-up of this metal, which is neurologically toxic.


Caffeine in green tea may interfere with the metabolism of some medications in your body. Consuming caffeine while taking medications that have a stimulating effect on your heart such as medications for asthma may also cause heart palpitation. Consult your doctor about possible interactions between green tea and your medications. Click here for more information about medications that may interact with green tea.


How much green tea can I have a day?

For healthy people, drinking green tea moderately, i.e. 3-10 cups/day, is safe. Overconsumption of green tea can cause headache, dizziness, nervousness, sleep problems, irritability, irregular heartbeats and ear ringing.


If you have osteoporosis, you should not have more than 2-3 cups per day because drinking green tea increases calcium excretion through urine.


Pregnant and breast-feeding women should not drink more than 1-2 cups a day.


How should I have my green tea?

If you want to lose weight, drink green tea before your work-out because this will increase the burning of fat while you exercise.


Drinking green tea during a meal can inhibit your body’s absorption of EGCG and iron. Having green tea before food may help suppress your appetite but is not recommended. The best time to drink green tea is 30-60 minutes after your meal or between meals, which helps digestion and boosts metabolism.


Brewing your tea for a longer duration at moderate instead of high temperature will increase its caffeine and EGCG content, thereby optimising its weight-loss effect.


What about plastic tea bags?

A recent study also shows that if you use plastic tea bags to make your cuppa, you may be ingesting billions of microplastics and nanoplastics that are released from the plastic packaging into your tea.

Avoid plastic packaging and opt for paper teabags or loose tea leaves.


Not all manufacturers will specify their packaging materials. If your teabags are marketed as “silky” or if you can see the tea inside, it is likely they are made from plastic.


Key messages

Drinking 2-7 cups of green tea a day can help you lose weight and prevent OA.


Combining green tea with exercise has added weight-loss effect.


The best time to drink green tea for weight loss is before exercise, 30-60 minutes after food and between meals.


Avoid tea bags made from plastic.


References

  • 6 Best times to drink green tea. Simple Loose Leaf Tea Company. (2019). Retrieved 11 March 2020, from https://simplelooseleaf.com/blog/green-tea/6-best-times-to-drink-green-tea/

  • Al-salafi, R., Irshad, M., & Abdulghani, H. (2014). Does green tea help to fight against obesity? An overview of the epidemiological reports. Austin J Clin Med, 1(3), 1011.

  • Bliddal, H., Leeds, A., & Christensen, R. (2014). Osteoarthritis, obesity and weight loss: Evidence, hypotheses and horizons - A scoping review. Obesity Reviews, 15(7), 578-586. doi: 10.1111/obr.12173

  • Chacko, S., Thambi, P., Kuttan, R., & Nishigaki, I. (2010). Beneficial effects of green tea: A literature review. Chinese Medicine, 5(1), 13. doi: 10.1186/1749-8546-5-13

  • Gahreman, D., Wang, R., Boutcher, Y., & Boutcher, S. (2015). Green tea, intermittent sprinting exercise, and fat oxidation. Nutrients, 7(7), 5646-5663. doi: 10.3390/nu7075245

  • Green tea: Health benefits, uses, side effects, dosage & interactions. (2019). Retrieved 11 March 2020, from https://www.rxlist.com/green_tea/supplements.htm

  • Harpaz, E., Tamir, S., Weinstein, A., & Weinstein, Y. (2017). The effect of caffeine on energy balance. Journal Of Basic And Clinical Physiology And Pharmacology, 28(1), 1-10. doi: 10.1515/jbcpp-2016-0090

  • Hernandez, L., Xu, E., Larsson, H., Tahara, R., Maisuria, V., & Tufenkji, N. (2019). Plastic teabags release billions of microparticles and nanoparticles into tea. Environmental Science & Technology, 53(21), 12300-12310. doi: 10.1021/acs.est.9b02540

  • Huang, J., Wang, Y., Xie, Z., Zhou, Y., Zhang, Y., & Wan, X. (2014). The anti-obesity effects of green tea in human intervention and basic molecular studies. European Journal Of Clinical Nutrition, 68(10), 1075-1087. doi: 10.1038/ejcn.2014.143

  • Hutcheon, D., & Ziegler, J. (2014). Green tea. Topics In Clinical Nutrition, 29(3), 268-277. doi: 10.1097/tin.0000000000000004

  • Jamieson, A. (2019). Billions of microplastics in your tea - Here is what to know. Retrieved 11 March 2020, from https://www.healthline.com/health-news/microplastics-released-into-cup-of-tea#Should-tea-drinkers-be-worried

  • Jowko, E. (2015). Green tea catechins and sport performance. In M. Lamprecht (Eds.), Antioxidants in Sport Nutrition. Boca Raton, Florida: CRC Press/Taylor & Francis

  • Jurgens, T., Whelan, A., Killian, L., Doucette, S., Kirk, S., & Foy, E. (2012). Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database Of Systematic Reviews. doi: 10.1002/14651858.cd008650.pub2

  • Maki, K., Reeves, M., Farmer, M., Yasunaga, K., Matsuo, N., & Katsuragi, Y. et al. (2008). Green tea catechin consumption enhances exercise-induced abdominal fat loss in overweight and obese adults. The Journal Of Nutrition, 139(2), 264-270. doi: 10.3945/jn.108.098293

  • Matsumura, K., Takayama, H., Bae, J., Kurihara, M., Tsutsumi, S., & Hyon, S. (2009). Preservation of platelets by adding epigallocatechin-3-o-gallate to platelet concentrates. Cell Transplantation, 18(5-6), 521-528. doi: 10.1177/096368970901805-606

  • Naumovski, N., Blades, B., & Roach, P. (2015). Food inhibits the oral bioavailability of the major green tea antioxidant epigallocatechin gallate in humans. Antioxidants, 4(2), 373-393. doi: 10.3390/antiox4020373

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