It's hard to imagine former Miss World Rosanna Davison with a face full of spots, but she says that it happened to her a few years after winning the title in 2003.

"I was feeling tired and run down," she remembers, over a couple of glasses of sparkling water in The Westbury, "and my mother thought it was because I was vegetarian and that my diet was lacking in some way. I went to see a nutritionist, who advised me to introduce three portions of dairy into my diet. Within a week I had full-blown acne, which was definitely not a good thing for a young woman's confidence. I decided to abandon the advice, and within a couple of weeks my skin had cleared up."

A couple of years later, Rosanna realised that she also had a problem with gluten.

"Like my mother and my brother, if I have a problem then it shows on my skin before it shows anywhere else. It's our weak spot. I figured out that gluten was causing chronic breakouts, particularly when I was travelling for work or eating out in restaurants a lot. I'd be picking at the breadbasket, or eating sandwiches, and my skin would be inflamed and sore. For someone else, a gluten intolerance could manifest itself in their joints or muscles, but for me everything shows in my skin first.

"Anyway, I stopped eating wheat and within a week or two it had all calmed down. Ever since, I have avoided wheat and gluten, and the odd time I would have a bit of bread my stomach would get crampy and bloated."

Rosanna was interested in pursuing a career in sports science and nutrition when she left school, but was persuaded instead to read for a general arts degree in sociology and history of art at UCD.

In 2010, motivated in part by her personal journey towards figuring out an eating regimen that would keep her feeling and looking well during a busy modelling career, she embarked on a course in naturopathic medicine, from which she graduated two years ago.

And now she has written a book, Eat Yourself Beautiful, in which she espouses her philosophy of plant-based functional nutrition, and shares her advice for using food to achieve the potential for health and natural beauty inherent in every individual.

"A huge proportion of preventable diseases are attributable to a deficiency in certain nutrients," she says, "and I've certainly found that to be true myself. I'm all about making sure that every bite of food you have is doing your body good and is not harming you in any way. Wheat, dairy and refined sugar are trigger foods for a lot of people, and so none of the recipes in the book include these ingredients."

Rosanna has adhered to a vegan diet, which is free from gluten, dairy and refined sugar, since she adopted it as a practical college project for a week. She immediately noticed striking benefits in terms of weight loss, glowing skin and shiny hair and decided to keep going.

Recently she persuaded her husband of just over a year, Wes Quirke, to go gluten-free too.

"Earlier this year Wes was getting rheumatoid arthritis in his knuckles and knees, as well as back pain. I said to him 'Stop with the pizzas and beer at the weekend, you can get gluten-free everything these days!' - and within a couple of weeks these pains had left him. So now he is really receptive to anything that I say to him."

Although Wes, a keen fitness fan, still eats animal protein in the form of salmon and eggs for breakfast, and chicken for lunch ("he looks after the animal protein side of things, and I do the veggies," says Rosanna about the allocation of kitchen duties in the Davison Quirke household, "I like there to be an even division of labour!") his experience of ditching the gluten has made him one of his wife's most enthusiastic supporters.

Wes' reaction was not a surprise to Rosanna, because she has seen the same thing time and time again with the private clients she sees as a nutrition therapist.

"It does take people a bit of time to come around to the idea of changing. It's all very well for me to be explaining research theories, but in order for them really to understand, they have to experience the benefit for themselves."

Of course, there's a school of thought that says that it is not the gluten that causes many people to experience digestive upset when they eat commercially-produced bread, but rather the chemical improvers, additives and preservatives used to make the product that cause problems. Although Rosanna agrees that proper sourdough bread is easier on the digestive system, she is a believer in non-coeliac gluten sensitivity, and cites research that shows gluten to be the bad guy responsible for a huge range of medical conditions from autism spectrum disorders to schizophrenia to arthritis.

Rosanna is keen to point out that although she adheres to a vegan diet, her book is not intended to convert her readers to the vegan way of life. Rather, its aim is to encourage everybody to introduce more vegetables into their diet via what she calls 'functional nutrition'.

"Food has a function in supporting the immune system, or skin, or hair or keeping weight off. In the book, the food tastes good and looks good too, so it makes it a bit different to a normal cookbook.

"It's about taking baby steps. Perhaps start by introducing a meatless Monday, and eating a vegetarian meal one night of the week at first. I'm no chef, but the recipes came about via my own experimentation, when clients would ask me, for instance, how to get more broccoli into their diet - for recipes that were more interesting than just plain steamed vegetables. I try all the recipes out on Wes, so they've all passed the 'man-test'.

"People can dip in and out of the book, they can even just go to the sweet treats and desserts section if they fancy a recipe for something sweet that's really tasty but just not as naughty as a traditional dessert full of refined sugar."

For those who want to take things further, Eat Yourself Beautiful contains a seven-day eating plan designed, says Rosanna, to flood the body with the nutrients that it needs to function at its best, and help anyone determined to embark on a healthier way of eating or to address niggling health issues through diet.

"It's suitable as an elimination diet," says Rosanna. "Those blood tests are expensive, so I suggest clients pick a two-week period during which they are not traveling or going out for dinner, and just knuckle down and cut out whatever it is that they suspect may be causing their problems. By the end of two weeks they are usually glowing and feeling much better."

These days, Rosanna does not have time to take on any new clients, as she is busy with promoting the book and modelling assignments, mainly in Germany, where she has a manager. She will be appearing at Oktoberfest, which she says is great fun, and is happy to pose with one of the giant tankards of beer, although she won't be drinking any of it.

For the future, she is keen to develop her brand through her website and Instagram (she has over 90,000 followers), and is thinking about a series of one-day workshops with expert speakers to help people get started on an Eat Yourself Beautiful lifestyle. It's hard to think of anyone better qualified to spread the word.

For now, though, she's enjoying married life at home in Cabinteely with Wes, and their two Pomeranian dogs, Leo and Ted, with Ted sleeping on the end of the couple's bed each night and Leo banished downstairs for snoring.

"We've been in the house for about three years now and at the beginning I was obsessed with home décor but the house started to feel a bit cluttered so I had to stop. Then when we got married, people gave us some lovely paintings and picture frames, and it's definitely 'done' now.

"One of the nicest paintings we got was from my aunt, Susan Morley, who was married to Paolo Tullio.

"It's so sad," she says of the passing, in June, of Weekend's esteemed restaurant critic. "I was going through addresses for the book launch and Paolo's address came up, he was like a second dad to us growing up. We spent every second weekend with the Tullios and went on holiday with them every year. We miss him."

There are a number of reasons for bloating, from food intolerances to poor digestive health and even inadequate water intake, fibre and exercise. If you are switching over to a more plant-based diet rich in fruit and veggies, then it's perfectly normal to feel bloated for the first seven to 10 days while your system adapts to the extra fibre. It's nothing to worry about! If the discomfort and bloating continue, you may want to investigate other possible causes. Here are my top 10 tips to beat the bloat in just a fortnight or less.

Rosanna's Top 10 ways to beat the bloat

1 Food intolerances

First, isolate and eliminate 'trigger' foods. Gluten in wheat can be particularly difficult for humans to digest and can cause an inflammatory reaction in the intestinal lining, which may lead to a 'leaky' gut and a spectrum of health problems, such as autoimmune diseases. If you suspect that you have an intolerance, try eliminating the food completely for 11 days. On the 12th day, eat as much as you want of that food and then monitor your symptoms over the following two to three days. If the bloating and other discomforts reappear, then it may be best to avoid that food item entirely. The elimination diet is quite a straightforward way of figuring out what food causes problems and many of my clients find it useful. Refined sugar is also a common cause of bloating, as it can encourage unfriendly bacteria and yeast overgrowth in the gut.

2 Chew your food

Ensure that you're not gulping down your food and swallowing too much air or not chewing it properly. Chew your food well, until it's almost soupy in texture when you swallow it.

3 Probiotics

Take them in capsule form or enjoy them in foods and drinks like sauerkraut, raw apple cider vinegar and coconut water kefir for their huge benefits. A healthy body should have 80-85pc friendly bacteria. One of the many reasons I recommend reducing or eliminating animal protein foods is because rotting heavy proteins in our guts create the ideal breeding ground for unhealthy bacteria, creating intestinal toxaemia, accelerated ageing and a whole host of other problems. Meanwhile, good bacteria improve digestion, B vitamin synthesis in the gut and overall energy. They also enhance nutrient absorption to improve skin and they help to get rid of bloating.

4 Take digestive enzymes

These can really help with digestion. Simply swallow a capsule with some water before a cooked meal and an extra one during the meal if it's particularly heavy or high in fat or animal protein.

5 Eat more fibre

Consuming plenty of dietary fibre every day is essential for a healthy digestive system and to prevent constipation, a major cause of bloating. Whole fruits, vegetables, gluten-free whole grains, nuts, seeds and legumes are the best sources of fibre.

6 Water and exercise

Water is essential to flush out the system and improve peristalsis in the intestine. Aim to drink 2 litres of water per day, and more if you're exercising or during spells of hot weather. Adding a slice of lemon to your water can help enhance the flavour. Regular exercise also helps to reduce bloating, boost the action of the gut and improve lymphatic drainage.

7 Eat fruit on an empty stomach

Avoid eating fruit after a meal because it digests faster than heavier protein and fat-rich foods, causing it to ferment and produce gases that cause bloating.

8 Prebiotic foods

Certain foods contain prebiotics, which are non-digestible elements that feed and

stimulate the action of those all-important probiotics in the gut. These foods include raw bananas, chicory, leek, garlic, onion and Jerusalem artichoke. Try to include one or more of these foods in your diet every day.

9 Herbal teas

Herbal teas are a wonderful replacement for caffeinated drinks and can really help to soothe or stimulate the digestive system. Try peppermint, ginger or fennel and aim to have two to three cups a day.

10 Boost your enzymes

Low hydrochloric acid in your stomach can occur for a number of reasons, and this may lead to bloating and digestive discomfort. Before your main meal, eat a digestion-boosting garden salad or a couple of pieces of raw pineapple or papaya. They contain bromelain and papain respectively, which have proteolytic qualities that can boost the breakdown of protein foods in the stomach. The salad is a 'bitter', which can also boost hydrochloric acid production.

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