Study: Green Tea & Coffee Daily Lowers Diabetes Mortality Risk

We know green tea is great for us, but now a new study has found that it can be a lifesaver, especially for diabetics. The study reveals that drinking four or more cups of green tea along with two cups of coffee (or more) can lower the risk of death among diabetics by 63 percent. While that’s a lot of caffeine, the study also found that it wasn’t the caffeine that was the active ingredient that made the results so striking. Rather, the antioxidants in the tea, combined with coffee throughout the day, are what made the difference.

The researchers also found that drinking just green tea alone, or just coffee alone has beneficial effects, but the combination of drinking both daily reduces the risk of death even further.

Study finds drinking green tea and coffee help diabetics

The study, published in the British Medical Journal (BMJ), tracked 4,923 Japanese people with type 2 diabetes over five years using a self-reported questionnaire. The researchers found that drinking a high number of cups of green tea daily was associated with a lower risk of death – and the odds decreased as the number of cups of tea increased: One cup daily was associated with a 15 percent lower risk, while four or more cups or more daily were linked with a 40 percent lower risk.

Among coffee drinkers, one daily cup was associated with 12 percent lower odds of dying and increasing this to two or more cups lowered the risk further by 41 percent. However, the risk of death was even lower for people who drank both green tea and coffee, with the lowest risk of 63 percent occurring among those who drank four or more green teas a day and two or more coffees a day.

It’s important to note, however, that any observational study does not establish "cause," meaning the fact that they drank more tea and coffee may not be the reason they lived longer, but one small piece of a larger lifestyle puzzle. Moreover, the type of green tea available in Japan may not be the same as elsewhere, and self-reported consumption is subjective and inaccurate.

Despite these general caveats, other research has suggested that compounds called flavonoids in green tea and coffee are beneficial against disease risks such as heart disease and diabetes.

Why are green tea and coffee beneficial for health and diabetes?

Research suggests that phenols and caffeine in coffee may be responsible for the reduced risk of developing type 2 diabetes, while another study found that decaffeinated coffee was equally effective and suggested that components other than caffeine are responsible for the beneficial effect.

The researchers noted that a phenolic compound called chlorogenic acid reduces oxidative stress and glucose absorption in the intestines, and this may be key in how coffee prevents diabetes.

Regarding green tea, compounds called catechins may improve glycemic response, but the beneficial effects in diabetes are inconclusive. Green tea is especially high in a polyphenol called epigallocatechin gallate, or EGCG, a powerful antioxidant that has been shown to have anti-cancer capabilities that may even be able to help halt tumor growth. Green tea contains more EGCG than other types of tea.

Green tea and weight loss studies

The weight-loss effects of tea may be beneficial for diabetes. Some research suggests that both black tea and green tea may help with weight loss, and this may be due to complex interactions with the gut microbiota, short-chain fatty acids, and lipid metabolism.

Manufacturers cash in on these claims, marketing ‘slimming tea’ in various forms. However, inconsistent study results and inconclusive evidence mean we still don’t know how, or indeed if, they work for everyone.

Furthermore, a scientific report by the European Food Safety Authority advised that green tea supplements may be toxic to the liver.

How much green tea and coffee should you drink?

This brings us to the next question of how much to drink. The current study suggested at least four cups of green tea and at least two cups of coffee to lower the risk of death in an older adult with diabetes.

However, other studies have suggested ideal amounts for different health conditions. For example, for high blood pressure, a 2017 study showed that participants who drank less than one cup or more than two cups had the least risk - this advice would translate to either stop drinking coffee or drink a whole lot more!

Additionally, a recent 2021 study indicated a 53 percent higher risk of dementia for people consuming six cups of coffee a day compared to one to two cups.

Much of the research has suggested a ‘U’ or ‘J’ shaped association between coffee consumption and health, with most benefits being seen in ‘the middle grounds’. With this in mind, experts such as Johns Hopkins Medicine recommend between 1-5 cups of coffee to help prevent chronic diseases.

However, too much caffeine from coffee or tea can lead to side effects such as anxiety, increased heart rate, and trouble falling asleep, so people should drink the amount that suits them.

How to choose a healthy beverage if you have high blood sugar

When choosing hot drinks if you have diabetes, the main point to bear in mind is to avoid additions that make the drink unhealthy. For example, sugar, syrups, and high-fat dairy can all add calories and spike blood sugar.

Matcha is considered to be a superior green tea because it has more antioxidants than regular green tea. People with diabetes can also choose other types of tea that have minimal impact on their blood sugar, and many of these have additional antioxidant or herbal benefits. For example:

Redbush or ‘rooibos' tea, caffeine-free and high in antioxidants
White tea, rich in antioxidants that fight inflammation
Green teas including matcha, sencha, and bancha
Black teas such as Ceylon, English breakfast, or Earl Grey
Oolong tea, which has specific compounds that promote fat burning
Herbal teas such as chamomile, peppermint, or ginger

About the above list, always check that herbal teas are suitable if you are taking medication or have a health condition,

The healthiest way to drink coffee and green tea

Ordering your morning Starbucks can be a minefield if you have diabetes since so many of the drinks contain added sugars and extra full-fat dairy that can drive up insulin and create havoc in the bloodstream. Instead, avoid the syrup-laden caramel macchiatos and frappuccinos, or even the healthy-looking juice and enticing sounding smoothies can spike your blood sugar.

There’s no magic cure for diabetes, so following a healthy whole-foods plant-based diet low in simple carbs combined with daily activity, and medication can help manage the condition. So easy wins such as choosing the most beneficial beverage (like green tea or black coffee) are especially appealing if they work to lower the risk of health complications and can become part of a daily habit.

Unfortunately, people with diabetes have a higher risk of health complications and premature mortality, and during the COVID-19 pandemic, deaths from diabetes have risen 14 percent – the most significant rise for decades. Moreover, people with diabetes are twice as likely to have heart disease or a stroke than people without diabetes, according to the American Diabetes Association.

While research has highlighted the beneficial effects of compounds in green tea and coffee for cardiovascular disease and inflammation, few studies have evaluated how consumption affects mortality in diabetes.

Bottom Line: Drinking tea and coffee may have benefits for those with diabetes.

Higher consumption is linked to a reduced risk of death among older adults and may help people with diabetes to manage their weight or avoid the condition in the first place. Moderate consumption of around 1-5 cups a day seems to be beneficial, although research is still inconclusive.