Skip to main content

29 Apr, 2019


Our nutritionist Rob Hobson will be answering your most pressing nutrition-related questions each month. This month Rob covers the accuracy of food intolerance tests, how to help acne through diet as well as his take on the Keto diet.


Our nutritionist Rob Hobson will be answering your most pressing nutrition-related questions each month. This month Rob covers the accuracy of food intolerance tests, how to help acne through diet as well as his take on the Keto diet.

How accurate are food intolerance tests?

Despite the popularity of ‘free-from’ diet regimes and products that have flooded the shelves of food stores, allergies and intolerances only affect a very small percentage of the population. The first thing to explain is that an intolerance is not the same as an allergy and many people often confuse the two definitions.

Food allergies are characterised by an unusual reaction to a food which occurs when the body’s immune system mistakes certain proteins as a threat. The reaction can be mild and cause itching inside the mouth, throat and ears as well as rashes, swelling or nausea. In more severe cases some cases a food allergy can be fatal causing anaphylaxis. The reaction is immediate and referred to as an IgE mediated food allergy meaning it involves IgE antibodies of the immune system. In adults the most common allergic foods are peanuts, tree nuts (walnuts, almonds, Brazil), fish and shellfish.

Food intolerances are not the same as allergies. The symptoms of a food intolerance include diarrhoea, bloating and stomach cramps which usually occur several hours after eating. Unlike allergies, they also require a larger amount of food to be eaten to trigger a response.

The common lingo around food intolerances includes:

  • Food hypersensitivity – covers all bad reactions to food
  • Non-allergic food hypersensitivity – food intolerance where the immune system is not involved

Common food intolerances include lactose (dairy foods) and gluten. Clinically there is currently no reliable method of testing for non-coeliac gluten sensitivity. For those that suspect lactose intolerance a diagnosis can be confirmed with a hydrogen breath test. This clinical test for lactose intolerance involves blowing into a balloon-type bag after fasting since the evening before. The test identifies how much hydrogen is present. You will then be given a drink of lactose solution and your breath tested frequently over several hours. If your breath is high in hydrogen, then it’s likely you’re intolerant as bacteria in the gut produce more hydrogen.

Food exclusion and reintroduction is commonly used to identify intolerances and probably the one I would recommend. Suspected foods are excluded for a period of time whilst symptoms are recorded. If these symptoms improve then the food is reintroduced and if they return the that particular food is flagged as causing an issue. This is time consuming and best carried out alongside a dietitian or registered nutritionist with experience in this area. They can then advise you on how to plan your diet properly when excluding certain food groups to avoid nutrient insufficiencies.

There are many other tests marketed such as the York test, pulse test and kinesiology and whilst some people may get positive results, the science and proof of efficacy is lacking. The general opinion amongst experts is that the test results are no better than chance but if you want to try and you get a positive outcome then that’s great.

Is keto a good way to lose weight?

I’m not a massive fan of diets in general but understand that some people prefer this approach to weight loss and there’s nothing wrong with that. The keto diet has helped lots of people to lose weight but in my opinion is not for the faint hearted!

The keto diet works by dramatically limiting the amount of carbohydrate you eat in your diet to 25g-50g per day so that the body switches from using glucose to ketones as its main energy source. Ketones are made in the liver from fatty acids which is why this diet appears to result in a greater loss of body fat than a more traditional low-fat diet. The diet is mostly made up of fat and moderate amounts of protein, which is why many people turn to foods such as meat, full fat dairy and butter to keep their intake high. This can make following the keto diet tricky if you’re vegan but still doable with a bit of planning and guidance.

The downside of the keto diet is the shift from glucose to ketones, which can cause rather nasty side effects such as headaches, fatigue, weakness, smelly breath, nausea, irritability, irregular menstrual cycles, sleep issues and loss of libido. These generally last for up to a week. You will also get pretty dehydrated as your glycogen stores are depleted - glycogen stores glucose in the body and holds 3-4 times its weight in water. The loss of fluid from the body may also deplete you of electrolytes and may lead to muscle cramps.

I wouldn’t do this diet for more than three months as research into the long-term effects of the keto diet is lacking. This diet has been shown to possibly be beneficial for people with diabetes given the low carbohydrate content, but I would be careful if you have this condition and recommend you seek medical advice beforehand.

What you need to consider is how you are going to eat after the diet to keep the weight off which is where I have an issue with diets in general. Many people who like to follow diet regimes often fail to keep the weight off in the long term.

As fruits and vegetables are limited to certain types, make the most of what you can eat and fill upon on them to ensure you glean lots of beneficial micronutrients and fibre. The lack of fibre may also impact on gut bacteria so I would probably advise taking a probiotic whilst you’re doing the keto diet.

My 12-year-old daughter has had acne since age 5. Any tips? She’s already dairy free.

It sounds unusual to have acne from such as young age and definitely not very nice for your daughter. Hormones are usually to blame for acne, which is why it normally occurs in teenagers. The hormones that increase in teenagers are called androgens and these cause the sebaceous glands to enlarge and make more sebum. When too much sebum is produced, hair follicles become blocked and sebum binds with keratin which then traps bacteria and voila, spots.

Cutting out dairy may help but it’s not a given. If you’re cutting dairy out of your daughters’ diet, then it’s important that she is still getting enough calcium so make sure any milk or yoghurt replacement is fortified with calcium. Also includes other calcium-rich foods such as nuts, seeds, green veggies, dried fruit and pulses, which can be added to smoothies or incorporated into lots of different homemade meals. It’s not fully clear why dairy might aggravate or cause acne, but one thought is that it’s due to the artificial hormones given to female cows, which may upset your own hormone balance. Eating a balanced diet of natural unprocessed foods means gleaning plenty of the nutrients that help to keep skin healthy and in good condition. In turn this may help acne prone skin or at least make it less aggressive.

Skin friendly nutrients include:

  • Vitamin A: orange and green fruits and vegetables, fresh tuna, mackerel and eggs
  • Vitamin C: red peppers, berries, broccoli, peas, kale, cauliflower, tomatoes and guava
  • Vitamin E: nuts, nut butters, seeds, extra virgin olive oil, avocado, wheatgerm and oily fish
  • B vitamins (especially B2, B3 and B6): eggs, brown rice, poultry, oily fish, nuts, oats and potatoes
  • Zinc: crab, chicken thigh, tofu, nuts, seeds, lentils, oats and mushrooms
  • Selenium: Brazil nuts, seeds, fresh tuna, poultry, mushrooms, wholegrains.

Omega 3 (found in oily fish) is also important for skin as it helps to maintain cell membranes and encourage effective moisturisation (acne prone skin can often be combination and not just oily). These essential fats also act as an anti-inflammatory in the body (as does beta carotene, which is a precursor to vitamin A and is stored in the fat found just below the surface of the skin), which may benefit acne prone skin.

Another cause of acne in older teenage girls and adult women is polycystic ovary syndrome (PCOS). This can cause excess testosterone, which stimulates the overproduction of sebum. Following a low GI diet is key for PCOS to keep testosterone levels in check, which may help with other symptoms such as acne.

Rob Hobson is a registered nutritionist (BSc, MSc, AFN), published author and food writer. Rob has 15 years of experience working with some of the UK’s leading food companies, government agencies, NHS and private clients as well as regularly writing in the media for publications including the Daily Mail online.