In my teens I was a junk-food junkie. It was chips, whatever. But now I'm a grandpa and pushing 50, I'm really health-conscious. You know what changed me? When I started in Joseph and the Amazing Technicolour Dreamcoat on Broadway in 1992, I had to be in shape - I was wearing a loincloth. I did it for six years, so I was constantly in the gym, and aware of what I was eating. It set me on a good path.

I'm reading a book called The China Study. It's the largest ever study on the proliferation of cancer and how nutrition plays a part. Wholegrains and green, leafy vegetables are what we should be eating, and it shows how bad animal protein is for you. This is the exact diet that we are asked to follow in the Mormon religion. No tea, alcohol or tobacco - we stay away from caffeine - and it says to eat whole grains and raw foods 'in the season thereof'. And meat sparingly.

Even though Mom brought out the Osmond Brothers' Mother's Cookbook, she wasn't the healthiest cook - lots of meat and fats. But I was always on the road, so whatever was on the hotel menu, that was it. Mainly the club sandwich. I'm the expert there, and I've just had one for lunch.

When I'm away from home, my wife Debbie keeps getting on at me about not eating. Here's my problem. When I'm involved in a project I totally forget to eat, and often don't have time. So I always carry a Melaleuca protein bar, which I get by mail order. I love them. I drink gallons of white grape juice, and I have fruit for breakfast. I love all fruit except for soft apples. No thank you! And I eat a tremendous amount of raspberries and blueberries. I can't cook, but I make my own smoothies. I love live-culture yoghurt, strawberry or vanilla, and I top that with Trail Mix, all kinds of nuts - unsalted of course - with raisins. I sprinkle flaxseed over the mixture. And I make a mean peanut butter and banana sandwich.

I have a very weak stomach if it's something I don't like. I take a fish oil supplement along with the other vitamins, seven in all, but I just don't like fish. Can't eat sushi, not even a California roll. Can't do it, I'll just barf. I tried it the other night. Debbie said, 'Come on, grow up!' Took me to the restaurant, tried one. Had to leave. It's the fishy taste.

And I love all vegetables, but don't even offer me eggplant or okra. Disgusting! But I have a fetish for peas, raw peas. You know, pea pods you snap open and eat the raw peas? I can't get enough of those. When I was doing Joseph in Chicago, I found a pea farmer and I asked him if I could rent his farm for a day. He said, 'Come on over, you don't need to rent it. Just bring some pictures for my wife and kids.' So I walked away with 12 bags, and I ate every single one of them.

But my big treat would be Häagen-Dazs Chocolate Chocolate Chip ice cream. Hello! Hurt me! If I see it I have to have it, and I can eat a tub at one sitting. My last meal? A club sandwich, of course. Followed by a tub of Häagen-Dazs.

White grape juice

Grape juices contain about 50 per cent more sugar than, say, a cola drink, causing the body to dump a whole load of fat-inducing insulin into the system.

Fresh peas

Rich in lutein (important for vision), folic acid and vitamin E, peas are also a source of protein, so his 'craving'may be Donny's body trying to bump up his protein intake.

Raspberries and blueberries

Raspberries are a good source of ellagic acid and blueberries are rich in pterostilbene, which may have cancer-protective qualities.

Häagen-dazs chocolate chocolate chip ice cream

This highly processed, sugar-stacked food will do nothing to help Donny's quest for optimum health.

Yoghurt

I prefer yoghurt to milk, as the fermenting process 'pre-digests' its protein and sugar and makes it more digestible. Plus, the live cultures in yoghurt may have benefits for health.

Trailmix

Nuts, seeds and dried fruit are highly nutritious, natural foods, that I think make an ideal snack for the health-conscious who find themselves eating on the go.

Club sandwich

Most breads release their sugar quickly into the bloodstream, which can cause surges of insulin, weight gain and increase the risk of heart disease and type 2 diabetes.

Protein bar

I believe that truly healthy eating means basing the diet on natural and unprocessed foods, so I am highly dubious about the supposed merits of this product.

· Love Songs Of The 70s (Decca/Mercury), by Donny Osmond, is out now