Brain insulin resistance: the hidden risk that can erode your mental faculties

The signs can appear decades before dementia appears, so take control now

I used to live in a rural village in Hertfordshire, north of London. Every year our pub would serve a free Christmas dinner to the local care home residents, and I would be their waitress for the day.

It was a great meal, consisting of a starter (usually soup) followed by the full turkey and trimmings ensemble, with a selection of desserts to finish off.

Every year was the same. Most of the guests would leave aside a large chunk of the main meal so they had room for dessert. Not just one, either – many would plate up with every available option. That was all they wanted.

It’s a common phenomenon. It seems that as people age, their cravings for the sweet stuff intensifies.

If that’s you, I advise that you knock this one on the head now. Even if you don’t develop type 2 diabetes you could end up with something called insulin resistance which can quickly turn into brain insulin resistance, a serious threat to your cognitive faculties.

What is insulin resistance?

Insulin is a hormone produced by the pancreas to regulate glucose in the blood. This glucose comes from dietary carbohydrates.

Insulin resistance arises when your muscles and other tissues no longer respond to insulin, so glucose remains high. The pancreas, sensing this, pumps out more insulin to deal with it, but to no avail.

Insulin is essential, but chronically elevated levels promote age-related diseases. High insulin - hyperinsulinemia - and insulin resistance are major risk factors for cardiovascular disease, hypertension, Parkinson’s disease and Alzheimer’s disease.

There may also be increased fat accumulation, inflammation, oxidative stress, and sarcopenia. Sarcopenia is muscle loss, commonly seen in the elderly. Insulin resistance in muscle cells results in deteroriation of skeletal muscle cell structure and energy production, alongside increased inflammation.

Insulin resistance is a prediabetic stage that could end as type 2 diabetes. In the US, about one in three people are already prediabetic.

Brain insulin resistance

Brain insulin resistance can be present in the ageing brain, even without diabetes. It has been defined as an ‘inadequate response by cells located in the brain, including the cerebral vasculature, to secreted insulin.’

It was always assumed in the past that insulin had nothing to do with the brain, but in the last few decades it has been established that there are insulin receptors throughout the brain, where it is important for function and metabolism.

Insulin crosses the blood brain barrier and once in the brain is involved in regulating mood, glucose levels, cognition and appetite. But if the brain cells have stopped responding to insulin, there may be mood disorders, increased levels of anxiety and reduced ability to cope with stress. Dysfunctional cognition is another possible outcome.

Insulin is in line with the Goldilocks principle: it is required in just the right amounts. Too little or too much can be harmful.