For many years, metformin has been considered the first-choice medicine for treating type 2 diabetes. Millions of people take it every day to help control blood sugar and reduce the risk of diabetes complications.
Now, researchers believe this well-known medicine may have another unexpected advantage: it could be linked to a lower risk of prostate cancer in men.
Researchers from the University of Otago reviewed a decade of scientific evidence to better understand the long-term health effects of metformin. Their analysis included studies involving approximately 2.25 million people with type 2 diabetes, making it one of the largest reviews of its kind.
Type 2 diabetes is a chronic disease in which the body cannot effectively use insulin. High blood sugar over many years increases the risk of heart disease, stroke, kidney failure, blindness, and nerve damage. Metformin lowers blood sugar mainly by reducing the amount of sugar released by the liver and improving the body’s response to insulin.
Previous research has already suggested that people taking metformin often have lower rates of heart disease and may live longer than expected. Some studies have also reported possible benefits for brain health. The new review confirmed these patterns, finding lower risks of cardiovascular disease, dementia, and overall death among metformin users.
The most surprising finding involved prostate cancer. Researchers found that men with type 2 diabetes who used metformin appeared less likely to develop this common cancer. Although scientists have previously explored whether metformin might reduce the risk of several cancers, the evidence relating specifically to prostate cancer has been limited.
Prostate cancer is the second most commonly diagnosed cancer in men worldwide. Many cases are successfully treated when detected early, but advanced disease can be difficult to manage. Because age is one of the biggest risk factors, preventing prostate cancer has become increasingly important as populations grow older.
Senior researcher Associate Professor Yoram Barak said the findings were exciting because they suggest metformin may have wider health effects than previously recognized.
However, he emphasized that people without diabetes should not begin taking metformin simply to reduce cancer risk. Much stronger evidence is needed before such recommendations can be made.
The researchers also highlighted the importance of studying healthy aging. Modern medicine is helping people live longer, but many older adults spend their later years living with chronic illnesses. Understanding whether existing medicines can slow age-related diseases could improve quality of life while reducing healthcare costs.
There are important limitations to this research. Because it is based on previously published studies, it can only identify associations rather than prove cause and effect.
Differences in diet, exercise, smoking, healthcare access, or other medications may partly explain the lower cancer rates. Randomized clinical trials would be needed to determine whether metformin directly protects against prostate cancer.
Even with these limitations, the review strengthens the growing view that metformin may offer health benefits beyond diabetes control. Future research will determine whether its effects on aging and cancer prevention are real and whether they apply to people without diabetes.
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The findings were published in the journal Rejuvenation Research.
Source: University of Otago.
