Source: American College of Physicians / Annals of Internal Medicine |
Date: June 3, 2026

Chinese Study: Sweetened Coffee Linked to Lower Risk of Early Death

Key Findings:

Study from Southern Medical University in Guangzhou tracked over 171,000 people for 7 years.
Unsweetened coffee reduced death risk by 16 to 21 percent.
Coffee sweetened with one teaspoon of sugar per cup reduced risk by 29 to 31 percent.
Results for artificial sweeteners were inconclusive.
The study is observational, not experimental. It does not prove direct cause and effect.
Warning: Ready-made coffee drinks from chains contain much higher amounts of sugar.

Researchers from Southern Medical University in Guangzhou, China, published a new study in the journal Annals of Internal Medicine. The study examined the effect of sweetened coffee on the risk of early death. It included more than 171,000 participants from the UK Biobank project. The average follow-up period was about seven years.

As a result, the study found that drinking moderate amounts of coffee, whether sweetened or unsweetened, is associated with a lower risk of death. This research is one of the first large-scale studies to directly compare the effect of adding sugar to coffee on long-term health outcomes.

Key Results: Up to 31 Percent Lower Death Risk

The researchers divided participants into groups based on their coffee consumption. These groups included non-drinkers, unsweetened coffee drinkers, sugar-sweetened coffee drinkers, and artificially sweetened coffee drinkers. After seven years of follow-up, the results were clear.

First, people who drank any amount of unsweetened coffee were 16 to 21 percent less likely to die compared to non-drinkers. Second, those who drank 1.5 to 3.5 cups per day of sugar-sweetened coffee were 29 to 31 percent less likely to die. The researchers noted that these participants added only about one teaspoon of sugar (approximately 4 grams) per cup on average.

In contrast, the results for those who used artificial sweeteners were inconclusive. The reduced risk applied to deaths from cancer and cardiovascular disease as well.

Summary of Results

Coffee Type	Daily Amount	Reduction in Death Risk
Unsweetened coffee	Any amount	16% to 21%
Sugar-sweetened coffee (1 tsp per cup)	1.5 to 3.5 cups	29% to 31%
Coffee with artificial sweeteners	Varies	Inconclusive

Why Is Coffee Beneficial? Possible Mechanisms

Coffee contains biologically active compounds that offer potential health benefits. The most important are antioxidants and polyphenols, especially chlorogenic acids. These compounds fight oxidative stress and inflammation. They also improve blood vessel function and glucose metabolism. In addition, caffeine enhances cognitive function and may reduce the risk of neurodegenerative diseases.

As a result, moderate coffee consumption has been linked to a lower risk of type 2 diabetes, stroke, heart disease, certain cancers, liver disease, and depression. However, the question remains: why did coffee with a small amount of sugar show even better results? Researchers believe that a small amount of sugar (one teaspoon) is not enough to cancel out the large benefits of coffee. But this needs further confirmation.

Important Caveats: Not a License to Add Excess Sugar

The researchers emphasize that these results do not mean adding sugar to coffee is beneficial in itself. The study observed an association, not a direct causal relationship. It is possible that people who regularly drink sweetened coffee also have a generally healthier lifestyle. Furthermore, the amount of sugar used in the study was very small (one teaspoon per cup).

In contrast, ready-made coffee drinks from major chains contain much larger amounts of sugar. A single drink can contain 20 to 50 grams of sugar. This far exceeds health recommendations. The World Health Organization recommends that free sugars should be less than 10 percent of daily calories. For an average adult, that is about 50 grams (12 teaspoons) per day. The ideal amount is less than 5 percent (25 grams or 6 teaspoons).

Therefore, researchers advise drinking coffee black or with a very small amount of sugar (no more than one teaspoon per cup). Avoid heavily sweetened drinks, heavy cream, and flavored syrups. Home brewing is preferable for better control of ingredients. Individuals with insomnia, anxiety, or stomach issues should consult their doctor.

Frequently Asked Questions About the Sweetened Coffee Study

Q: Does this study prove that adding sugar to coffee is healthy?

A: No. The study found a statistical association, not a causal relationship. The amount of sugar used was very small (one teaspoon per cup). A generally healthy lifestyle may also play a role.

Q: What is the optimal amount of coffee per day according to the study?

A: The optimal range is 1.5 to 3.5 cups per day. This amount was linked to the largest reduction in death risk.

Q: Do the results apply to instant coffee?

A: Yes, the study included various types of coffee. However, benefits are usually greater with filtered or freshly ground coffee.

Q: What is the daily sugar limit according to global guidelines?

A: The WHO recommends less than 10 percent of daily calories (about 50 grams or 12 teaspoons). The ideal is less than 5 percent (25 grams or 6 teaspoons).

Q: What about coffee with artificial sweeteners?

A: The results were inconclusive. There is not enough evidence of benefits or harms from this study.

Q: Can I drink sweetened coffee from commercial coffee shops?

A: Most coffee shop drinks contain very high amounts of sugar (20 to 50 grams). This may cancel out potential benefits and increase health risks. It is better to order black coffee or add a small amount of sugar yourself.

Prepared by: Scientific News Unit – Qahwa World – based on a study published in Annals of Internal Medicine on May 31, 2022, and the accompanying press release from the American College of Physicians.

Disclaimer: This information is for educational purposes and does not replace medical advice.

Publication date: June 3, 2026

What if your favorite sugary coffee drink could do more than just keep you awake? A groundbreaking study by researchers at Hiroshima University, published in npj Science of Food, suggests that sweetened caffeine might fundamentally alter your biological rhythms, shifting your internal clock in ways never observed before.

The study examined the behavior of male mice consuming caffeine paired with sweeteners like sucrose. The results were striking: mice shifted from their natural nocturnal habits to being active during the day, with some showing extended activity cycles lasting 26–30 hours—far beyond the standard 24-hour circadian rhythm. Surprisingly, this effect occurred regardless of whether the central circadian clock, located in the brain’s suprachiasmatic nucleus (SCN), was functional.

The key finding? Sweetened caffeine didn’t just disrupt the central clock—it also desynchronized peripheral clocks in the kidneys, liver, and other organs. Using advanced imaging techniques, researchers observed reduced amplitude and misaligned phases in these clocks, signaling a broader biological disruption.

Why Does This Matter?

Unlike plain caffeine, sweetened caffeine interacts with the brain’s reward system, potentially boosting dopamine production. Dopamine, often called the “feel-good” neurotransmitter, plays a critical role in motivation and pleasure but may interfere with the body’s natural sleep-wake cycle. This could explain why sugary caffeinated beverages, so beloved for their flavor, might also be uniquely disruptive to biological rhythms.

The findings could have profound implications for human health. Sweetened caffeine products—like energy drinks and sugar-laden coffees—are staples in many diets. If similar effects occur in humans, this raises concerns about how these beverages may contribute to sleep disorders, metabolic dysfunction, and even long-term health risks.

The Bigger Picture

Caffeine has long been studied for its effects on alertness and performance. However, this study sheds new light on the interplay between caffeine, sweeteners, and circadian biology. While plain caffeine has been shown to extend activity cycles in previous research, the addition of sugar creates a unique impact, indicating that dietary habits might shape our internal clocks in unexpected ways.

As the researchers point out, much remains unknown about the mechanisms driving these effects. Are they specific to mice, or could humans experience similar disruptions? Could the dopamine boost from sweetened caffeine contribute to addiction-like behaviors, further compounding its impact on health? These are questions the research team hopes to explore in future studies.

What Does This Mean for Your Morning Cup?

While caffeine is often celebrated as a productivity booster, this study suggests that pairing it with sugar might come at a cost. Sweetened caffeinated beverages could desynchronize your internal rhythms, potentially affecting sleep quality, mood, and overall health.

This research is a wake-up call for those who rely on sugary energy drinks or lattes to power through their day. It highlights the need to reconsider how our favorite drinks influence not just our energy levels but our bodies’ fundamental biological processes.

As science delves deeper into the relationship between diet and circadian biology, one thing is clear: the seemingly harmless combination of caffeine and sugar might be far more complex—and impactful—than we ever imagined.

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