Tea and coffee
After water, coffee and tea are the two most commonly consumed beverages on the planet. They are brimming with antioxidants, flavonoids, and other biologically active substances that may be good for health.
- Research suggests that drinking at least three cups of either black or green tea per day reduces the risk of stroke (3) and cancer. (4,5)
- Some teas taste sweet to the palate without added sugar: Try fruit-flavored herbal teas, or teas with cinnamon or vanilla.
The key to tea: Antioxidants
Polyphenols are likely the key component to what makes tea a healthy drink. These chemical compounds act as antioxidants, which fight against free radicals in the body. Free radicals can alter DNA by stealing its electrons, and this mutated DNA can increase LDL cholesterol or alter cell membrane traffic – both harmful to our health. Though green tea is often considered higher in polyphenols than black or oolong (red) teas, studies show that – with the exception of decaffeinated tea – all teas have about the same levels of these chemicals, albeit in different proportions.
While the antioxidant action of tea is promising, some research suggests that the protein and possibly the fat in milk may reduce the antioxidant capacity of tea. (6) Flavonoids, the antioxidant component in tea, are known to bind to proteins and “de-activate,” so this theory makes scientific sense. (7)
One study that analyzed the effects of adding skimmed, semi-skimmed, and whole milk to tea concluded that skimmed milk significantly reduced the antioxidant capacity of tea. The fattier milks also reduced the antioxidant capacity of tea, but to a lesser degree. (6) Overall, it’s important to keep in mind that tea – even tea with milk – is a healthy drink. To reap the full antioxidant benefits of tea, however, it may be best to skip the milk.
Three big benefits of tea:
1. Reduced risk of cardiovascular disease
Polyphenols, the antioxidants abundant in tea, have been shown to reduce the risk of death due to cardiovascular disease (8), including stroke. (9,10) In one study of 77,000 Japanese men and women, green tea and oolong tea consumption was linked with lower risk of death from cardiovascular disease. (11) Other large-scale studies show that black tea also contributes to heart health (3), with research suggesting that drinking at least three cups of either black or green tea per day appears to reduce the risk of stroke by 21 percent. The study also stated that drinking tea may be one of the most significant changes a person can make to reduce his or her risk of stroke. (3)
2. Protection from cancer
Research shows benefits for a variety of types of cancer, including ovarian and digestive system cancers. (4,5) Green tea might also have a positive effect in reducing risk of breast, prostate, and endometrial cancers, though more evidence is needed. (12)
Learn more about cancer and antioxidants.
3. Reduced risk of high blood pressure
In a study of green and oolong tea consumption, regular consumption for one year reduced the risk of developing hypertension. (13) Long-term regular consumption of black tea has also been shown to lower blood pressure. (14)
Think before you drink: Potential pitfalls
Be wary of weight-loss claims. Some advertisements claim that tea can speed weight loss, but research on the effects of green tea and fat reduction have shown little promise of weight loss benefits. (15) Moreover, it’s best to skip any so-called “diet” teas that may contain potentially harmful substances such as laxatives.
Beware the bottle. Avoid purchasing expensive bottled teas or teas in coffee shops that contain added sweeteners. To enjoy the maximum benefits of drinking tea, consider brewing your own at home. You can serve it hot, or make a pitcher of home-brewed iced tea during warmer months.
Though further research is needed to confirm the benefits, recent studies show that tea holds promise in preventing cardiovascular disease, cancer, and hypertension – and that there are no serious risks associated with drinking it. So pick a color and pour a cup to maximize the health benefits.
- 54% of American adults drink coffee every day, with an average of about 3 cups per day.
- It’s considered safe to drink up to six cups of coffee per day. In fact, research suggests that drinking coffee may reduce some disease risks.
- Some people may want to consider avoiding coffee or switching to decaf, especially women who are pregnant, or people who have a hard time controlling their blood pressure or blood sugar.
- It’s best to brew coffee with a paper filter to remove a substance that causes an increase in LDL cholesterol.
Four noted benefits of coffee:
1. Possible reduction in heart disease and stroke risk
Studies suggest that drinking coffee regularly decreases risk of heart disease or stroke.
- The Nurses health Study of 83,076 women showed that regular coffee consumption was associated with a modest reduction in stroke risk. (17)
- Another study of 37,514 participants concluded that moderate coffee drinking was associated with a reduced risk of heart disease. (18)
2. Lower risk of developing type 2 diabetes
Research shows that caffeine raises blood sugar in the short term, but the antioxidants in coffee <<link to antioxidant article>> may improve insulin sensitivity and lower the risk of type 2 diabetes over many years (3-5).
- A study of over 125,000 participants tracked coffee consumption and new cases of type 2 diabetes for 18 years. This study showed that women who drink more than six cups of coffee per day reduced their risk for developing type 2 diabetes by almost 30 percent. (19)
- Decaffeinated coffee was also beneficial in reducing type 2 diabetes risk, but the benefit was less pronounced. (20)
- A study of 74,749 women analyzed the intake of caffeinated and caffeine-free beverages with respect to the development of type 2 diabetes. The study showed that caffeinated coffee reduced type 2 diabetes risk by 4% and decaffeinated reduced the risk by 7%. This suggests that a component of coffee independent of caffeine, perhaps antioxidants found in both regular coffee and decaf, is responsible for the decrease in type 2 diabetes risk. (19)
3. Protects against gallstones
- A study of 46,008 men tracked their development of gallstone and their coffee consumption for 10 years. After adjusting for other factors known to cause gallstones, the study concluded that men who consistently drank coffee were significantly less likely to develop gallstones compared to men who did not. (21)
- A similar large study found the same result in women. (22)
4. Lower risk of developing Parkinson’s Disease
- A study tracked coffee consumption and Parkinson’s Disease development of 6,710 men and women over 22 years. In that time, after adjusting for known risks of Parkinson’s Disease, coffee drinkers had a significantly lower risk of developing the disease than non-drinkers. (23)
Hidden calories in coffee drinks
A plain “black” cup of coffee is a very low calorie drink – 8 oz only contains 2 calories! However, adding sugar, cream, and milk can quickly bump up the calorie counts. A tablespoon of cream contains 52 calories, and a tablespoon of whole milk contains 9 calories. While 9 calories isn’t a lot, milk is often poured into coffee without measuring, so you may be getting several servings of milk or cream in your coffee. A tablespoon of sugar contains 48 calories, so if you take your coffee with cream and sugar, you’re adding over 100 extra calories to your daily cup. It’s important to be aware of and account for these calories as part of your daily eats, or consider going with skim milk in your coffee (only 5 calories per tablespoon).
The real caloric danger occurs in specialty mochas, lattes, or blended icy coffee drinks. These drinks are often super-sized and can contain anywhere from 200-500 calories, as well as an extremely large amount of sugar. With these drinks, it’s best to enjoy them as a treat or dessert, and stick with plain, minimally sweetened coffee on a regular basis.
Read more about coffee and health in our Ask the Expert: Coffee and Health interview with Dr. Rob van Dam.
3. Arab L, Liu W, Elashoff D. Green and black tea consumption and risk of stroke: a meta-analysis. Stroke. 2009;40:1786-92.
4. Lee AH, Su D, Pasalich M, Binns CW. Tea consumption reduces ovarian cancer risk. Cancer Epidemiol. 2013;37:54-9.
5. Nechuta S, Shu XO, Li HL, et al. Prospective cohort study of tea consumption and risk of digestive system cancers: results from the Shanghai Women’s Health Study. Am J Clin Nutr. 2012;96:1056-63.
6. Ryan L, Petit S. Addition of whole, semiskimmed, and skimmed bovine milk reduces the total antioxidant capacity of black tea. Nutr Res. 2010;30:14-20.
7. Arts MJ, Haenen GR, Wilms LC, et al. Interactions between flavonoids and proteins: effect on the total antioxidant capacity. J Agric Food Chem. 2002;50:1184-7.
8. Kuriyama S, Shimazu T, Ohmori K, et al. Green tea consumption and mortality due to cardiovascular disease, cancer, and all causes in Japan: the Ohsaki study. JAMA. 2006;296:1255-65.
9. Hollman PC, Geelen A, Kromhout D. Dietary flavonol intake may lower stroke risk in men and women. J Nutr. 2010;140:600-4.
10. Larsson SC, Virtamo J, Wolk A. Black tea consumption and risk of stroke in women and men. Ann Epidemiol. 2013;23:157-60.
11. Mineharu Y, Koizumi A, Wada Y, et al. Coffee, green tea, black tea and oolong tea consumption and risk of mortality from cardiovascular disease in Japanese men and women. J Epidemiol Community Health. 2011;65:230-40.
12. Johnson R, Bryant S, Huntley AL. Green tea and green tea catechin extracts: an overview of the clinical evidence. Maturitas. 2012;73:280-7.
13. Yang YC, Lu FH, Wu JS, Wu CH, Chang CJ. The protective effect of habitual tea consumption on hypertension. Arch Intern Med. 2004;164:1534-40.
14. Hodgson JM, Puddey IB, Woodman RJ, et al. Effects of black tea on blood pressure: a randomized controlled trial. Arch Intern Med. 2012;172:186-8.
15. Jurgens TM, Whelan AM, Killian L, Doucette S, Kirk S, Foy E. Green tea for weight loss and weight maintenance in overweight or obese adults. Cochrane Database Syst Rev. 2012;12:CD008650.
16. Coffee THO. National Coffee Association USA.
17. Lopez-Garcia E, Rodriguez-Artalejo F, Rexrode KM, Logroscino G, Hu FB, van Dam RM. Coffee consumption and risk of stroke in women. Circulation. 2009;119:1116-23.
18. de Koning Gans JM, Uiterwaal CS, van der Schouw YT, et al. Tea and coffee consumption and cardiovascular morbidity and mortality. Arterioscler Thromb Vasc Biol. 2010;30:1665-71.
19. Bhupathiraju SN, Pan A, Malik VS, et al. Caffeinated and caffeine-free beverages and risk of type 2 diabetes. Am J Clin Nutr. 2013;97:155-66.
20. Salazar-Martinez E, Willett WC, Ascherio A, et al. Coffee consumption and risk for type 2 diabetes mellitus. Ann Intern Med. 2004;140:1-8.
21. Leitzmann MF, Willett WC, Rimm EB, et al. A prospective study of coffee consumption and the risk of symptomatic gallstone disease in men. JAMA. 1999;281:2106-12.
22. Leitzmann MF, Stampfer MJ, Willett WC, Spiegelman D, Colditz GA, Giovannucci EL. Coffee intake is associated with lower risk of symptomatic gallstone disease in women. Gastroenterology. 2002;123:1823-30.
23. Saaksjarvi K, Knekt P, Rissanen H, Laaksonen MA, Reunanen A, Mannisto S. Prospective study of coffee consumption and risk of Parkinson’s disease. Eur J Clin Nutr.
24. Ascherio A, Zhang SM, Hernan MA, et al. Prospective study of caffeine consumption and risk of Parkinson’s disease in men and women. Ann Neurol. 2001;50:56-63.
The aim of the Harvard T.H. Chan of Public Health Nutrition Source is to provide timely information on diet and nutrition for clinicians, allied health professionals, and the public. The contents of this Web site are not intended to offer personal medical advice. You should seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition. Never disregard professional medical advice or delay in seeking it because of something you have read on this Web site. The information does not mention brand names, nor does it endorse any particular products.