Michelin-starred chef Chris Horridge is mixing a carrot purée in front of me. Telling me to note the "amazing explosion of flavours", he hands me a spoonful, after adding coriander. "We're looking at ways to create it with uncooked carrots so we can keep the live enzymes. If we can, we're on to a winner," he says. Next comes a spoonful of seeds – sunflower, hemp, pumpkin, poppy and sesame – smattered with glutamate-rich soy sauce, which tastes surprisingly delicious. "The heat affects the omega-3, so we only roast half of the seeds," he explains.
We're standing in what he calls his "lab/playzone" in the kitchens of The Bath Priory hotel where, as head chef, he creates the nutritionally balanced Michelin-starred dishes he's fast becoming known for. Jars of echinacea and pure wheat-germ oil sit beside a wall chart listing the pHs of various ingredients. There's a microscope to study the plants he picks on his walks to use in his dishes, and a model of the vitamin C's molecular structure ("Vitamin C is interesting because it can donate an electron without becoming a free radical itself").
The smells drifting from the kitchen are mouth-watering, but I am feeling a little bamboozled. I have spent the morning hearing his nutritional dilemmas. How can he best replicate the pH of out-of-season carrots to match the taste of in-season carrots? Which ingredients promote the zinc in beef without detracting from it? What happens to omega- 3 when heated?
It's all part of Horridge's idiosyncratic approach to gourmet health food, which has not only earned him a Michelin star and accolades from Condé Nast Traveller magazine, which recently named Bath Priory one of the world's best hotel restaurants, but won the respect of scientists in the fight against cancer. "We're doing something called three-dimensional cuisine, which is about presentation, flavour and nutrition. The nutrition is the interesting part, because there are plenty of chefs looking at presentation and flavour but not nutrition. We're doing healthy food to a Michelin-starred standard."
Healthy eating is a passion for him. His food is mostly dairy- gluten- and sugar-free (he's proud that a lactose-intolerant or coeliac can eat well in his restaurant), and peppered with ingredients normally found in health food. Whether it's ginseng or echinacea, which may strengthen the immune system, or bee pollen to help combat allergies, each ingredient is prepared to boost nutritional value. But the real health benefits, he says, lie in the way the ingredients work together.
Take his Neston Park fillet, watercress purée and orange zest daube, with beef-vanilla reduction, for example. "We know that 40 per cent of zinc in beef is available, so how can we enhance it? We know we can help the absorption of zinc with vitamin A, so we put it with liver, which is high in retinol, a more readily available source of vitamin A. We also put it with watercress, which is high in iron, and combine it with orange zest, the vitamin C of which helps with absorption of the iron. The next thing to investigate is: does the vitamin C prohibit the absorption of the zinc in the beef, or work against the vitamin A?"
This might sound clinical if it weren't for the fact that the food tastes so amazingly good. Besides, what other chef cares about your hay fever or digestion problems? Each meal starts with a mandarin- and red-pepper sorbet "to aid absorption of the meal", while the seared monkfish canapé features capers, which have quercetin, "a natural antihistamine".
Many dishes are sent to his team of scientists and nutritionists to be further investigated. His orange-zest purée, for example, is currently at Reading University, to see whether the bitterness can be eliminated without destroying the flavonoids, which may help fight diabetes and heart disease ("the bitter bits are good for you"). This research is then used to explore the role of diet in the fight against cancer, a passion of his. "The most exciting bit is using the research to help other people," he says.
It's a mission that is gathering momentum. He has recently went to Parliament, where he met the former head of the Cancer Prevention Unit at the World Health Organisation at a reception. In October, he hosts a meal at Bath Priory to raise funds for the World Cancer Research Fund (WCRF), with which he works closely. Other projects on the boil are a research group to see how patients' recovery rates can be enhanced through diet ("40 per cent of cancers can be prevented through food, but only 2 per cent of research is done in this area"), and a recipe book for WCRF ("of Michelin-starred recipes without the nasties associated with good food"). There's talk of a TV series as well.
Horridge's own experience with cancer came when his mother died of cancer 12 years ago, when he was in the RAF. Around the same time, he had a major operation and ate a special diet providing his recommended daily amount of vitamins and minerals. "Within two weeks, I was back at work and the doctor was surprised at how well I'd healed up." But it wasn't until he came to Bath Priory, after working at Raymond Blanc's Le Manoir aux Quat' Saisons for five years, that his passion for healthy eating began. "Some people say, 'But I like to indulge when I go out', but that's the whole point: you can indulge without it being bad for you. If we can do an éclair and crème brûlée with no cream and 75 per cent less sugar, and it tastes exactly the same, why not have that instead?"
Speaking of which, I see a dessert heading my way. It's his cheddar strawberries, lime brûlée and basil ice cream with vanilla straw and berry juice. The brûlée and ice cream are non-dairy, with minimum sugar, the sponge is gluten-free. Not that you'd know. I crack into the brûlée, and scoop up ice cream decorated with ox-eye daisies. The strawberries' phytochemicals may help to fight stomach cancer, while the juice may have antibacterial qualities. And it's delicious.
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Chris Horridge's tips for healthy cooking
GROW YOUR OWN MICROHERBS
"Research from America says there are about 50 per cent more nutrients in broccoli shoots than in a whole head of broccoli (weight for weight). You can buy sprouters from health shops and sprout your own broccoli shoots, flax and sunflower seeds. Then add to salads for texture."
COOK VEGETABLES IN THEIR OWN JUICES
"We cook most of our vegetables in their own juices, particularly carrots and fennel, to keep in nutrients and enhance flavour. Cooking them in water means the vitamins leach out. Buy more vegetables than you require, juice 25 per cent and cook the rest in a little of the juice."
CARAMELISE MEAT IN COCOA BUTTER
"You can buy cocoa butter, which is non-dairy, on the internet, and use instead of butter."
"This method ends up with a beautifully cooked fish, retaining, we believe, as many nutrients as possible. First set the oven to 50C, and once it's heated (check with a thermometer), cook for around 12 minutes, depending on cooker. If white protein leaks out of the fish, the oven is too hot; if it hasn't started to cook, it's too low. You should be able to press the fish so it parts along the zigzag line. At 50C, most of the omega-3 should still be in the fish."
ADD GLUTAMATE-RICH FOOD
"We use glutamate-rich food such as tomatoes to give a feeling of wanting more. Our tomato essence is perfect with quinoa, which is packed with antioxidants. Roughly chop tomatoes, onions, garlic and basil plus seasoning, then blend for 10 seconds so it's still rough. Place a clean, wet cloth napkin over a bowl, pour in purée and hang in fridge so liquid drips through cloth into bowl. The liquid should be straw-coloured and transparent, but with a great tomato taste. Use it to cook quinoa, as if you're doing a risotto. Finish with seeds and nuts."
"A Lunch with Chris Horridge and Nutritionist Tanya Page" is at The Bath Priory on 19 August ( www.thebathpriory.co.uk)