Health advice: low-carb diets - Telegraph This week's question I have been on a low-carb, high-protein diet for a year now and have lost 15lb. I love my new body but is it safe to stay on this diet in the long-term? The nutritional therapist: Melanie Brown Carbohydrates are your brain's primary fuel, and research has shown that low-carb diets can impair cognitive function and memory in particular. Long term it's important to eat some "good" carbs. You also need fibre to keep bowels moving, so eat plenty of vegetables, as well as fruit and grains, such as oats or rye. Low-carb diets are high in protein, and too much meat can be a cancer risk, so eat plenty of plant protein, such as lentils, beans and nuts. The GP: Rupal Shah There isn't much long-term safety data on low-carb diets. However, it has been shown that avoiding carbohydrates tends to raise cholesterol levels (especially compared with other popular diets, such as the Mediterranean). One Swedish study also suggested that people on low-carb diets have higher rates of heart disease and stroke. With any kind of restrictive diet, it's important to eat enough fruits and vegetables to avoid vitamin deficiencies. The nutritionist: Nigel Denby Protein helps keep you feeling full, which is why high-protein diets are so popular. However, you need only a small amount each day - about 1g of protein for every kilogram you weigh. Too much can put a strain on your kidneys. I'd suggest you reintroduce into your diet slow-release carbs, such as grainy breads, sweet potato and basmati rice, as they keep you full and contain fibre for a healthy digestion. Carbs are your body's preferred energy source. Send your health questions, for publication only, to stellahealth@telegraph.co.uk To contact any of our specialists: Melanie Brown is at melaniebrownnutrition.com, Rupal Shah is at Bridge Lane Group Practice (0844 477 3306), Nigel Denby (132harleystreet.com).