Can metformin really cause dementia?

If the news reports describing a new study from Australia are to believed, type-2 diabetics who use metformin may face increased risk of dementia.

What the reports don’t tell you is why the study found the drug to be associated with cognitive problems. And that’s where the real story is.

As you know, if you’ve been reading Insiders’ Cures and the Daily Dispatch for a while, I believe metformin is a very safe, effective drug for lowering blood sugar.

Its benefits are so great it’s worth finding solutions to its “side effects.” Especially when those solutions are easy—and are things everyone should be doing anyway.

Understanding the numbers

The researchers gathered data from several sources throughout Australia and found that diabetics were 50 percent more likely to suffer some cognitive impairment compared to non-diabetics.

Among those with diabetes, the ones taking metformin scored significantly worse on cognitive measures. In fact, they had more than double the rate of dementia than other diabetics. If you just look at their statistics, it seems like a pretty clear- cut case against metformin.

But as we know, there’s often more to the story than what makes the headlines. In fact, if you look at the actual numbers instead of the percentages, the differences are not as dramatic as they seem. On a standard measure of cognitive function, metformin users averaged 22.8, whereas others scored an average of 24.7. That’s less than two points difference. Which is not nearly as alarming as the statistical analysis makes it sound.

Still, it’s important to understand the reasons for the difference, so you can protect both your blood sugar and your brain. As it turns out, there’s a simple explanation for the findings. And the good news is, it’s something that can be addressed and turned around easily.

A little basic knowledge of nutrition will put it all in perspective. And a willingness to employ basic nutrients as truly “complementary” medicine will mitigate any of metformin’s negative effects.

The brain vitamin

First a little background. Since the 1970s, clinicians and scientists have been aware that metformin use is associated with lower levels of vitamin B12. The culprit here may be an interaction between metformin and a receptor in a part of the small intestine. This interaction may inhibit the body’s ability to absorb and use vitamin B12. Absorbing adequate vitamin B from the diet requires healthy stomach and intestinal functions. Many factors can interfere with or inhibit the absorption process—including metformin.

And if you continue digging into the numbers of the Australian analysis, you’ll see that the evidence supports this theory. Among patients with diabetes, cognitive function measures were lower among those who had low levels of vitamin B12 in their blood. B12 deficiency is a well- known cause of cognitive decline.

Too bad more doctors don’t know about this problem and advise their patients. It’s easy to fix once you know a little nutrition. And it’s important to address it early, because the effects can become permanent if not addressed within a year of when the symptoms start.1

So the real issue this study points out is not that metformin harms cognition. The real news is that anyone taking metformin should also  be taking B vitamins.

We have known for decades that B vitamins are critical for healthy brain and nervous tissue. In Europe, B vitamins are even called “neurovitamins” because of their essential role in brain function.

Because metformin decreases B12 absorption, people taking it may not be able to get enough of the vitamin from a well-balanced diet alone. That’s especially true for people who follow a vegetarian diet, have had gastrointestinal surgery, or take drugs that suppress stomach acid (which are used in epidemic proportions today).

Amazingly enough, despite metformin’s long market history, there are currently no clinical guidelines in place for monitoring or supplementing B vitamins.

And of course, the government’s paltry Recommended Daily Allowances (RDAs) are nowhere near sufficient to deal with these issues. Maintaining “adequate” vitamin B12 levels is not good enough to reverse the potential effects of metformin, nor to reduce the risk of cognitive decline in later life.

Every person taking metformin should also be taking high-quality B vitamins. In fact, good levels of B vitamins, including vitamin B12, should be part of any natural approach to healthy brain function— especially with aging. See sidebars for recommended doses and forms for achieving optimal levels.


Which  B12 is best?

When choosing a B12 supplement, you may be confused about the terminology. You’ll need to choose between two forms: cyanocobalamin or methylcobalamin.

Once it is in the body, cyanocobalamin is converted into the physiologic forms methylcobalamin and adenosylcobalamin (bound with a nucleic acid). However, outside the body methylcobalamin can be chemically unstable. If a micronutrient is unstable, it can break down before you take it, and you don’t know what (if any) potency is left—or what potentially dangerous byproducts may be present.

I recommend cyanocobalamin because it is much more stable before it gets into the body. Stability is important during manufacturing and shipping, so that a product stays fresh, safe and potent for you on your shelf.

Note that a trace amount of the chemical group cyanide is used during the processing of cyanocobalamin. The small trace poses no danger and can actually have a nutritive effect in trace amounts in light of the biological concept of hormesis (which is too big a topic for this article; for more on that, consult my medical textbook, Fundamentals of Complementary & Alternative Medicine, 4th edition; Elsevier Health Sciences, 2011). There are actually trace amounts of arsenic and cyanide naturally occurring in fruits (especially the seeds and pits) and nuts. In nature, this probably helps keep many small predators, such as microbes and insects, from spoiling the fruit and the seed while having no effect regarding human consumption.


Brain-boosting vitamin B doses

Thiamine……………………………………………………2.5 to 5.0 mg
Vitamin B-6 (pyridoxine) …………………………….5 to 10 mg
Folate (L-methylfolate) ……………………………….800 to 1600 mcg (0.8 to 1.6 mg)*
Vitamin B 12 (cyanocobalamin) ……………………20 to 40 mcg

*For folate, I recommend Metfolin®, which is high quality, bioavailable, and pharmaceutical grade



1. Abyad A. Prevalence of vitamin B12 deficiency among demented patients and cognitive recovery with cobalamin replacement. J Nutr Health Aging. 2002;6:254-260.