The ultimate guide to what to eat to beat heart disease, strokes, cancer and Alzheimer's.

When I was a child, doctors sent my grandmother home in a wheelchair to die. Diagnosed with end-stage heart disease, she already had so much scar tissue from bypass operations that the surgeons had essentially run out of plumbing. There was nothing more to do, they said; her life was over at 65.

For many children, it’s seeing a beloved relative ill and in pain that leads them to want to become doctors. But, for me, it was watching my grandma get better. Soon after she came home, she saw a report on TV about Nathan Pritikin, an early lifestyle-medicine pioneer who’d been gaining a reputation for reversing terminal heart disease.

He’d just opened a new clinic — and, in desperation, my grandmother booked in for a supervised plant-based diet and exercise programme. They wheeled my grandmother in — and she walked out on her own.

I’ll never forget that. Within three weeks, she was actually walking ten miles a day. When I was a child that was all that mattered: I got to play with Grandma again. But over the years, I grew up to understand the significance of what had happened.

At that time, the medical profession didn’t even think it was possible to reverse heart disease.

Drugs were given to try to slow the progression, and surgery was performed to circumvent clogged arteries, but the disease was expected to get worse and worse until you died.

Now, however, we know that as soon as we stop eating an artery-clogging diet, our bodies can start healing themselves.

My grandma was given her medical death sentence at 65. Thanks to a healthy diet and lifestyle, she enjoyed another 31 years on this earth.

The woman once told that she had only weeks to live didn’t die until she was 96 years old.

Her near-miraculous recovery not only inspired one of her six grandchildren to pursue a career in medicine, but granted her enough healthy years to see him graduate from medical school. And I’ve since made it my life’s mission to study the evidence-based links between disease and nutrition.

I now have a team of researchers and volunteers who last year alone helped me dig through 24,000 papers published on the subject.

The result of all this research has been quite astounding. It’s now clear, for example, that the vast majority of premature deaths in the UK and U.S. could be prevented.

Many people assume the diseases that kill us are pre-programmed into our genes. High blood pressure by 55, heart attacks at 60, maybe cancer at 70, and so on . . . But for most of the leading causes of death, our genes usually account for only 10–20 per cent of risk.

The other 80-90 per cent of risk? It’s our diet and lifestyle. The typical Western diet is the number-one cause of premature death and the number-one cause of disability. In other words, a long and healthy life is largely a matter of choice.