Elizabeth Peyton-Jones may be 49 but she could easily pass for a 30-something. The naturopath and herbalist, whose clients include large corporations and celebrities such as actress Thandie Newton, 42, believes that everyone can look younger and healthier simply by changing what they eat and how they cook.

“Food is very powerful,” she says, “but people have forgotten that. You wouldn’t feed a racehorse a pork pie, would you? And yet we expect to be at the top of our game without realizing that if you want to have clear, glowing skin, sparkling eyes and a body that works well, then your diet is fundamental.”

Peyton-Jones, a married mother of two stepchildren, has been practicing for 20 years now. She became interested in nutrition after getting a bacterial infection and being brought back to health by a friend armed with fruits and veggies. She is amazed at how the world has changed since then, how ideas that used to be unusual (juicing good, sugar bad) are now mainstream.

Her approach is heartfelt, but it is also refreshingly straightforward and, most importantly, practical. Peyton-Jones worries that thinking around nutrition has become too faddish.

“If I could tell people one thing, it is that there are no ‘superfoods,’ ” she says. “There are 2,000 great vegetables out there and variety is the way to go.”

Our approach to food, she says, has become too complicated. And thanks to celebrity chefs and cooking shows, we set our standards so high that we are afraid of cooking for ourselves.

“The only things you can do wrong with food are to oversalt it, oversugar it, overcream it and overcook it. If you’re not doing that, then there’s very little you can do to ruin your food.”

Eating her way means you eventually reach your optimum weight. “You don’t eat as much, get as hungry or crave food, so you lose weight. It is very difficult to be fat on this diet.”

So does Peyton-Jones attribute her youthful looks and slenderness to her way of eating?

“One hundred percent,” she says. “I just don’t seem to get cravings like other people do, although I eat a lot. People are always surprised by how much I eat.”

Peyton-Jones’ rules will help you get the nutrients you need to stay young and vibrant. You don’t have to follow them slavishly: Just let them inform your thinking around food.

“Cook Yourself Young” by Elizabeth Peyton-Jones is published by Quadrille, to be distributed in the US by Chronicle in February 2016. The Kindle edition is available to buy online now.

By addictive I mean processed foods, those with refined or hidden sugar, salt and “bad” fats. Pretty much everything in a box or packet. These are addictive, as they make your body crave more of them.

Food addictions are tough to crack, and my rule of thumb is to allow a week for each year of addiction. So, if you are 36 and have eaten lots of refined sugar since the age of 16, don’t expect to be free of it until 20 weeks after you stop eating it.

Nuts offer major youth-giving bonuses and can be substituted for every kind of dairy. Instead of cow’s milk, for example, use nut or seed milk. Just take one cup of nuts — almonds, perhaps, or cashews — and whizz in a blender with two cups of water. I don’t recommend shop brands, as they are full of either sugar or preservatives.

Alternate varieties for a range of flavors and benefits. Eating a couple of Brazil nuts a day is thought to decelerate the arrival of gray hair, while pistachios contain an anti-inflammatory that strengthens skin.

I’m amazed by how timid we are about using herbs in the Western world. Herbs have antioxidants and are anti-inflammatory. They do pretty much all the youth-giving you need: they strengthen cells, joints, muscles, veins, blood and organs (fennel and cumin are great for your stomach); make eyes, hair and nails shine; and heal skin.

Chuck handfuls of parsley, coriander, dill and other leafy herbs into casseroles minutes before serving. Use herbs as you do vegetables: Make soups with them, or eat them raw in salads.

Garlic and turmeric are in my top youth-giving foods for their hormone-balancing, anti-inflammatory properties, and mint and nutmeg are up there, too.

The cooking process should retain maximum nutrients and antioxidants in all our food, to sustain us and keep us looking and feeling younger.

Steam frying is my top way to cook rejuvenating, tasty meals, because it brings the richness of frying with less than 1 teaspoon of oil (that tiny amount helps us to absorb the essential fat-soluble vitamins A, D, E and K).

Eat ripe and red as they then contain more lycopene, an antioxidant that protects against cell deterioration and keeps you looking and feeling younger.

How to cook: Raw, paste, canned; all are good.

Eat four times a week for younger-looking skin, hair and nails. It has 25 vital nutrients and antioxidants, including five anti-inflammatories, so it’s a great all-around age minimizer.

How to cook: Eat in guacamole and salads or use for creamy smoothies, soups and puddings.

“I’m a huge fan of this; I eat it with salmon and adore the punch of horseradish mash,” says Peyton-Jones. An antioxidant and anti-inflammatory.

How to cook: Use raw for maximum pungency. Grate and mix with natural yogurt, cider vinegar or grated apple as a sauce for pulses or fish.

Nothing beats cucumber for dewy skin. It’s high in silica, which helps to keep connective tissue healthy (the muscles, ligaments, tendons, cartilage and bone that hold you together).

How to cook: Use raw in juices, salads and cold soups.

Underrated and underused in the West, radishes are fabulous detoxers; if ever you feel like an inner cleanse, eat a radish. They are low-cal, high-fiber and anti-inflammatory.

How to cook: Delicious raw in salads or steamed with other vegetables; they add a sharp antidote to any sweetness.

Naturally high in sugars, parsnip is very high in soluble and insoluble fiber, which reduces blood cholesterol and helps gut function.

How to cook: Juice (raw) with other vegetables (it adds sweet creaminess), roast, use in soup.

Kale is a nutritional powerhouse, probably the most palatable way to get a big shot of calcium in a low-cal way.

How to cook: Juice, steam, steam fry.

High in protective carotenes and anti-inflammatory, these help regulate blood sugar and are youth-giving for skin and muscles.

How to cook: Roast to make into soups, or add to casseroles, curries and risottos.

Go for these over regular mushrooms: They offer a rejuvenating boost. They reduce cholesterol and help fight infection and disease.

How to cook: Add to soups, casseroles, savory dishes and omelettes.

A good little youth-giving helper, full of vitamins C and E, potassium, magnesium and dietary fiber. It’s a very low-sugar fruit, so if you’re craving a sweet snack that won’t shoot your blood-sugar levels sky high, this is it.

How to cook: Eat raw or juice.

These buttery, nutty legumes are a great low-fat, high-protein option. They help to reduce cholesterol and blood sugar and are high in iron and molybdenum, a mineral that helps detox the sulphites in processed foods and wine. With plentiful fiber and folic acid, they’re great for the gut and encourage optimum cell functioning.

How to cook: Use in hummus, falafel, pies, curries, casseroles, soups or salads.

Powerfully nutrient-dense, high not just in vitamins and minerals but in cancer-fighting compounds and amino acids that help detox at a cellular level, this is the Holy Grail of anti-aging. If you drink alcohol, asparagus can alleviate the aftereffects and protect hard-working liver cells.

How to cook: Serve as a starter or side, or chop into salad.

Carrots contain high levels of beta carotene and other antioxidants, with protective powers against cancer, heart disease, high cholesterol and even sight problems.

How to cook: Juice, eat raw or cooked in soups, breads and cakes. Buy organic, or always peel them, as the skin can harbor pesticide residues.

It’s low-calorie yet bursting with vitamins, minerals and antioxidants. The deep green color and peppery taste are a giveaway that it’s alkalizing, detoxing and generally good for head-to-toe youthing.

How to cook: Eat raw in salads; juice; or even make into a tea.

Currants are super-rich in GLA (gamma-linolenic acid), which is very good for skin.

How to cook: Eat raw with coconut cream or add to ice cream. Try frozen when fresh is not available.

This is highly alkalizing, and a good source of minerals and fats that fight bacteria and fungi.

How to cook: Buy cans of whole milk, not the low-fat version (from which the “good” fats have been removed) and use wherever you would use cow’s milk — on cereal, in curries, soup and so on.

Like all oily fish (salmon, sardines, herring), it’s high in omega-3 fatty acids that help reduce cholesterol, protect against heart disease and cancer, and ease joint pain and arthritis (the anti-inflammatory effect). Good for lowering depression and boosting memory.

How to cook: Grill or bake with tart flavors: try gooseberry or fennel.

A nutrient-dense cruciferous vegetable that boosts antioxidant uptake, helps with detox and protects against cell deterioration, so it’s a good all-around youth-giving choice.

How to cook: Eat raw, fermented in sauerkraut or lightly steamed.

This Peruvian grain is a great protein source for the gluten- and wheat-free. I recommend it for its youth-giving properties, as it’s a seed, not a grain, and contains all the essential amino acids, plus a healthy dose of vitamins, minerals and fiber.

How to cook: Cook on its own or chuck raw into soups and casseroles. Try quinoa flour when baking.

Crunchy, tangy and bittersweet, they act as an anti-inflammatory and artery declogger, and also protect against heart disease and viral infections.

How to cook: Use in salads, in sauces with meat, or as a relish.