Does metformin lower your risk of cancer or dementia?
People with diabetes who take metformin may develop cancer and dementia less often, but the evidence is mixed and does not apply to people without diabetes. For dementia, newer blood sugar medications perform better than metformin in studies.
People with type 2 diabetes who take metformin develop cancer less often than people with diabetes who do not take it. For digestive cancers the chance is about 21% lower, and for urological cancers and blood cancers about 12 to 13% lower. For cancer overall, estimates vary: some studies see a risk reduction of 35%, others less. But that figure should be read with caution: there is wide variation between studies, and there are signs that favourable results are published more often than neutral ones. Whether this also applies to people without diabetes has not been studied.
For dementia the picture is more mixed. One larger analysis found that people with diabetes who took metformin had a lower chance of developing dementia, with a risk ratio of 0.76. But more recent and larger analyses found no meaningful difference. Compared with other diabetes medications, metformin also does not come out well: newer blood sugar medications show a clearly better effect in studies, with a risk ratio of 0.56 compared with metformin at around 0.89, a level at which any effect is barely present.
For Alzheimer's disease specifically, the evidence is even contradictory. A number of analyses found no protective effect, and in people of Asian background some studies pointed to an increased risk. Studies on memory and other cognitive functions also still contradict each other too much to establish any clear direction.
There is also a relevant safety consideration: metformin can cause a vitamin B12 deficiency, which is itself linked to cognitive decline. That makes the risk-benefit picture less straightforward for people who already have a higher risk of dementia. If you take metformin, discuss with your doctor whether your vitamin B12 level is being monitored.
The evidence rests almost entirely on research involving people with type 2 diabetes who were followed for years without anyone being randomly assigned to a group. Because of this, cause and effect cannot be established. For cancer, there are signs of selective publication of favourable results, which may inflate the findings. For dementia, several recent and large analyses contradict one another; an overarching review of many studies combined rated the evidence as inconsistent and of low quality. There are no usable data on people without diabetes.
Does exercise lower my risk of cancer?
Regular physical activity is associated with a clearly lower risk of several cancers in large population studies. Alongside that, aim to reduce the number of hours you spend sitting during the day, and use sun protection if you do a lot of outdoor sport.
Does working with pesticides increase your risk of cancer?
Working with pesticides is associated in multiple studies with an increased risk of several types of cancer, including bladder, bowel, and blood cancers. Avoiding unprotected contact is sensible, especially if you are pregnant or planning to become pregnant.
Does drinking less alcohol meaningfully reduce your cancer risk?
Drinking less alcohol meaningfully reduces your risk of several cancer types, although it takes years before the full effect becomes visible. Stopping sooner yields greater health gains.
Which lifestyle factors reduce your cancer risk the most?
Not smoking, a healthy weight, regular exercise and little or no alcohol have the strongest and best-supported protective effect. Combining all these factors lowers cancer risk the most, even when a hereditary predisposition is present.
Does metformin help you stay healthy for longer?
Metformin can largely prevent diabetes in people with prediabetes or metabolic syndrome, and that brings real health benefits. Whether it also slows ageing in healthy people has not yet been demonstrated.
Does metformin help with weight loss?
Metformin helps with weight loss, but the effect is modest: expect a few kilograms, not a dramatic transformation. Lifestyle changes work better in the short term, but weight loss with metformin remains stable over the long term. Discuss it with your doctor if you want to know whether it suits your situation.