Helen is a registered dietician and spokesperson for the British Dietetic Association. She has more than 20 years' experience working in the NHS, PR and the food and pharmaceutical industries.

‘There’s growing evidence suggesting the same risk factors for heart disease and stroke – such as being overweight, having hardened arteries or high blood pressure – may also increase the risk of developing Alzheimer’s and vascular dementia (the second most common form of dementia),’ says dietitian Helen Bond. ‘This may be to do with the supply of blood to the brain.’

In a recent study, scientists scanned elderly people’s brains and found those with hardened arteries and high blood pressure were more likely to show the changes in the brain associated with Alzheimer’s.

Fats that cause inflammation

The scientists concluded that the known risk factors for heart disease, such as smoking and a diet high in trans and saturated fats, may also contribute to Alzheimer’s. A 2006 study found that even a moderate intake of saturated fat in mid-life doubled the risk of dementia.

Trans fats (man-made hard fats used in foods such as biscuits), in particular, made cell membranes harder and less permeable. This makes it more difficult for the cells to dispose of waste, such as proteins called amyloids. As a result, these amyloids build up, in and around cells, causing them to malfunction. They then trigger inflammation in the brain, blocking signals and resulting in Alzheimer’s symptoms.

Beware processed food

The body’s response to infection is shown as inflammation – swelling, pain and redness as the immune system deals with the problem. But research has also pinpointed a state called metaflammation – a less severe type of inflammation, affecting organs, including the heart and brain tissue. It’s thought to be the body’s reaction to substances that aren’t immediately dangerous but are unfamiliar, such as processed food and lots of saturated fat, alongside other factors such as inactivity, stress and pollution.

Fats that benefit your brain

Not all fats are bad, however. There’s promising evidence that omega-3 fats (found in salmon, fresh tuna and sardines, for example) play a beneficial role in preventing cognitive decline. Unsaturated fats, eaten in moderation (found in avocado and olive oil, fish and other vegetable oils, for example), can also help cut your risk.