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Intolerance Testing

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If you give 'intolerance testing' a search on Google, you could be convinced otherwise - my search came up with 44,600,000 results - impressive hey! The companies advertising these intolerance tests, often have pretty websites with very convincing stats and terminology. However, behind the frontage and their expensive prices (as an example; £199 to analyse 'reactivity' to 200 foods & drinks and 30 minutes with a Nutritional Therapist - who, just to highlight does not need to have any certified qualification to give out nutrition advice), the companies themselves are also admitting that their testing cannot 'diagnose, treat or cure any specific food intolerances' and 'are not a substitute for professional medical advice' - you just need to look at the small print.


So why do people do it? I fully understand why - having worked with lots of people who are frankly in a desperate situation (exacerbated by long NHS waiting lists or not getting answers from their GP), with their bowels & gastrointestinal (GI) symptoms, they turn to whatever they can and will pay whatever price, because these tests give them a bit of hope. And often, by following the intolerance testing advice and removing dozens of foods from their diet, voila - their symptoms are resolved and the intolerance tests has done it's job! However, the problem with this is that these intolerance tests are almost a 'lucky dip' - causing people to remove foods from their diet unnecessarily - very rarely there will be this many foods that would exacerbate someone's bowel habits & GI symptoms. This can then result in having an extremely restricted diet but also in some, it may cause nutritional deficiencies - behaviours that we don't want to be encouraging. 


Here are some of the types of 'intolerance' testing out there: 


  • Kinesiology - the idea is that foods can cause an imbalance in the body and this can be detected through testing your muscle response. By holding the food being tested in a glass vial, the kinesiologist will look at your muscle response to that particular food, however evidence suggests that there is no scientific backing to this metho and would not be recommended to diagnose an intolerance. 

  • Hair analysis - a common one that I hear about in my practice. A small lock of your hair is sent off to a lab - your hair lock is then analysed by looking at the 'energy fields' and are compared to a database. This testing is used for recreational drug testing & lead poisoning, however NICE (National Institute of Clinical Excellence), advises that this process should not be used to advise on intolerances. 

  • IgG blood test - not to be confused with  an IgE test, which does have evidence behind it to test for allergies. IgE testing should only be used in a medical setting, alongside your detailed clinical history and a qualified health care practitioner. IgG testing however does not have any evidence to support it's use. The test suggests that if there is an increase of IgG antibodies to a certain food, this would indicate an intolerance - however IgG antibodies to foods are found in everyone, including those who don't suffer with any symptoms and therefore is not appropriate for diagnosing intolerances. 

  • Pulse test - your pulse is monitored prior to eating the 'suspicious' food and also monitor for 15 minutes afterwards. If your pulse increases by ten beats per minute after eating the food, then supposedly this suggests you have an intolerance to it ... but once again, there is no evidence to this. 

Before talking about how to actually diagnose an intolerance, I wanted to highlight the importance of when you should go and speak to your GP. Symptoms of intolerances such as bloating, loose stools, flatulence and / or abdominal pain, are also common with various GI conditions such as coeliac disease, inflammatory bowel disease & pancreatic insufficiency. If you are concerned about your symptoms, please always speak to your GP first - they are able to carry out various tests to diagnose / exclude GI conditions. It is very important to speak to your GP if you experience blood or mucus in your stools, unintentional weight loss or fatigue, alongside the GI symptoms. 


In terms of evidenced based tests to diagnose intolerances - we are pretty limited. Some hospitals, although few & far between, have access to a hydrogen breath test machine, which can test for lactose intolerance. The machine measures the amount of hydrogen (in parts per million - PPM) as a baseline, then again after you have a drunk a lactose containing drink. If the number increases by 20 PPM above your baseline figure, then it is assumed you have a lactose intolerance. However, in my years of working as a dietitian, I have very rarely come across patients having had this, particularly in the NHS. 

Therefore the most common way to diagnose a food intolerance is by following a period of exclusion (often 2-4 weeks) whilst monitoring symptoms, followed by reintroduction to confirm it does bring on symptoms and thus confirm the intolerance. Some people however may have no idea what it is that is causes their symptoms, so picking out what to exclude can be really tricky!

This is where myself and my other gastro dietetic colleagues come in. We have A LOT of experience with this ... including what are common trigger foods, but also using individual diet histories and food & symptom diaries to identify possible triggers. And unlike the 'intolerance tests' bought off the internet, we will also consider whether the restrictions are appropriate for you as an individual and any nutritional deficiencies you may come up against .... so a plea from me (hopefully I have convinced you anyway) - please PLEASE don't waste your money on 'bogus' intolerance testing. If you have concerns, initially consider talking to your GP. Following this request a referral to a dietitian - either through the NHS, take a look at the Freelance Dietitians website or check out to find out how I can support you.

Author: Katie Westwood BSc RD, Specialist Gastro Dietitian 

Published July 2021, Updated November 2023 

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