This is the 91st instalment in a series on dementia, including the research into its causes and treatment, advice for carers, and stories of hope

What we put on our plates does far more than fuel our bodies – it affects our heart health, inflammation levels, hormone regulation, blood pressure, sleep quality and mood.

Each of these elements is a major risk factor for dementia. Dr Helen Macpherson, an associate professor at Deakin University’s Faculty of Health in Australia, rates diet an 8.5 out of 10 in terms of its importance for long-term brain health.

“Diet has a direct effect on the brain in terms of the nutrients we supply it with,” Macpherson says, noting that a poor diet also acts as an indirect driver of chronic conditions that slowly erode cognitive function.

While most of us can easily identify a healthy meal – one packed with fruits, vegetables, whole grains, nuts and seeds – fewer realise how well a toxic diet can masquerade as a nutritious one. From yogurts packed with hidden sugars to fitness bars loaded with preservatives, dietary appearances can be deceptive.

The four tiers of food

Macpherson, who has published studies on the impact of diet on brain health in midlife, uses the internationally recognised Nova scale to identify these hidden hazards.