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Food sensitivity, also known as food intolerance, can be defined as a reproducible, adverse reaction to a food, or food ingredient, at a dose tolerated by most people. It is technically described as non-allergenic food hypersensitivity as it does not involve the immune system, unlike in cases of food allergy where an immune response is involved. Typically the features of food sensitivity are less severe and take a longer time to manifest, compared with food allergy where symptoms can be potentially life-threatening and occur soon after ingestion.
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Food sensitivity is often misdiagnosed due to the lack of well-controlled clinical trials proving its existence. However, it is very difficult to investigate food sensitivity in the same way as you would a particular medical intervention because of the number of variable factors involved, such as the type, amount and frequency of foods consumed in a typical diet as well as other environmental factors that could provoke similar symptoms.
Food sensitivities that involve particular food additives are more easy to study and have indeed shown that certain individuals can be sensitive to synthetic colourings, such as azo dyes, as well as the preservatives, sodium benzoate, benzoic acid, sulphur dioxide and sulphites.
Other studies have excluded gluten (a protein found in wheat, barley and rye) and casein (a protein found in milk and dairy products ) in children with autistic spectrum disorder (ASD) and attention deficit hyperactivity disorder (ADHD) and have noted improvements in behaviour and communication. It is important to note that these trials did not take any baseline dietary measurements and so the ‘exclusion’ diet, whilst excluding certain food groups are highly likely to increase intakes of fruits, vegetables, fish, seafood, nuts, brown rice and soya-based foods ( eg. tofu and soya milk ), all of which are rich sources of key nutrients known to be vital for good physical and mental health The positive outcomes highlighted from these studies may have more to do with which.
foods were included, rather than excluded, or even a combination of both.
Food sensitivity can occur for a variety of reasons, outlined in detail below:.
- Enzyme -Deficiency: The classic example would be the loss of the lactase enzyme needed to breakdown lactose found in milk and dairy foods. The undigested lactose is fermented by gut bacteria that produce large amounts of organic acids and gases, resulting in abdominal pain, distension and diarrhoea
- Pharmacological: Some foods contain pharmacologically active substances that can cause adverse effects in some people. Good examples include caffeine, found in in coffee and cola drinks, and monosodium glutamate, often used in manufactured foods and some Chinese meals
- Histamine-Release: Foods, such as shellfish and strawberries, contain histamine-releasing agents which can cause adverse reactions in sensitive individuals
- Irritant: Excessive consumption of foods such as onions, nuts and prunes can act as an irritant to the gastrointestinal tract (gut) and result in unpleasant symptoms
- Toxic: A small number of foods contain naturally occurring toxic compounds, such as lectins found in under-cooked kidney beans, which can be lethal
Depending on the actual cause, food sensitivity can cause adverse effects throughout the body. If the gut is involved, symptoms can include vomiting, diarrhoea, constipation, irritable bowel syndrome, infantile colic, abdominal pain and bloating. However, these symptoms may also be a consequence of poor nutrition and dysbiosis, which is when the beneficial bacteria that live in the gut are out of balance with more harmful varieties. This can often occur following a period of gastroenteritis or after taking broad-spectrum antibiotics. Including probiotic-enriched food and drinks in your diet and eating foods that contain prebiotics, which help feed the probiotic bacteria, can help redress the balance in favour of beneficial bacteria and consequently improve gut function. Prebiotic-rich foods include oats, bananas, onion, garlic, leeks, artichokes and asparagus.
If the gut is not working properly then potentially any food could exacerbate the situation and cause symptoms to worsen. In these situations it is difficult to differentiate between food sensitivity and compromised gut function.
The diet suitable for people with food sensitivity will depend on which food, or food ingredient, is causing the problem. If a particular food, or food ingredient, is suspected then the tried and tested method for diagnosis is a period of dietary exclusion followed by re-introduction of the food without the sufferer knowing to see if it has any effect and then a second exclusion. If the presence and absence of the food correlates with the presence and absence of symptoms then a positive diagnosis can be made.This should only be the case if the testing is blinded. If a reaction is severe re-introduction should be carried out with medical supervision.
In cases where multiple foods are suspected, a few foods diet, which consists of foods highly unlikely to cause a reaction ( eg. rice, lamb, pears ), is followed until symptoms disappear. This is then followed by a systematic blinded re-introduction of single foods, one at a time, allowing the identification of any problem foods to be easily identified whilst avoiding unnecessary restrictions.
Individuals with suspected or proven food sensitivity, who are excluding major food groups, should seek the advice of a qualified Dietitian to avoid compromising nutrient intakes and consequently their physical and mental health.
Many people who have been motivated to change their diet in an attempt to relieve the effects of food sensitivity will remain interested in maintaining good nutritional health and continue to eat well. A well-balanced food sensitivity diet can still be rich in fibre, vitamins and minerals, all of which are vital for good brain and body functioning as well as reducing the risk of developing certain cancers and cardiovascular disease.
Very young children and babies should not have any dietary restrictions imposed upon them unless they are clinically indicated and are supervised by a Doctor and Dietitian. The restricted nutrient intake that might result can significantly compromise children’s growth and development.
The same risk applies to older children and adolescents because of their high requirements needed to sustain good physical growth and mental development.
Women planning a pregnancy, are already pregnant or are breast feeding should also avoid any dietary restrictions, unless recommended by a Doctor or Dietitian, as they can compromise nutrient intakes and ultimately the health of both mother and baby.
Individuals suffering from any chronic medical condition or recovering from surgery should not follow a restricted diet without medical supervision as this can exacerbate symptoms and slow down recovery and wound healing.
The most nutritionally balanced diet is one that includes a wide range of different foods and so the main risk attached to the food sensitivity diet depends on the particular restrictions involved. In some cases, avoidance of the offending foods is nutritionally insignificant and can be easily excluded eg. caffeine drinks and strawberries.
The greatest nutritional risk is associated with the exclusion of entire food groups, such as dairy foods and gluten-containing cereals. Gluten-free diets can be low in fibre, which is needed for good bowel function and helps to protect against cardiovascular disease, and cows milk-free diets can be low in calcium and iodine, which are important for bone strength and brain function.
Advice from a Dietitian should ideally be sought to ensure nutritional adequacy and allow discussion of.
suitable substitute foods and dietary supplements, where appropriate.
A final point worth mentioning is that substitute foods are not always available, are usually more expensive and following these diets can make eating out and social occasions more difficult.
The subject of food sensitivity remains contentious, with many healthcare professionals debating its prevalence. The lack of well designed clinical trials and the huge increase in self-diagnosis has certainly made it difficult to establish the true incidence and aetiology of food sensitivity. Another problem is that conditions can go undiagnosed if individuals self-diagnose food intolerances or rely on dubious tests.
Research findings support the view that some sensitive individuals can react badly to certain food additives but intolerance to major food groups has been difficult to evaluate. Those trials that have demonstrated improvements on a gluten-free and casein-free diets have not taken into account the other changes that have occurred in the diet and are often assessed by parents and carers, making their findings subjective.
Fundamentally in cases of food sensitivity the diet needs to be fully assessed to see what is missing, in terms of foods that provide key nutrients, as well as what is being included that could be triggering an intolerance.
Bateman et al. ‘The effects of a double-blind, placebo-controlled, artificial food colourings and benzoate preservative challenge on hyperactivity in a general population sample of pre-school children.’ Archives of Disease in Childhood 89: p506-511
‘Briefing Paper: Food Allergy and Intolerance.’ British Nutrition Foundation September 2000.
Johansson et al. ‘Revised nomenclature for allergy for global use: report of the nomenclature review committee of the world allergy organisation.’ Journal of Allergy and Clinical Immunology 2004; 113 p832-836.
Knivsberg et al. ‘A randomised, controlled study of dietary intervention in autistic syndromes.’ Nutritional Neuroscience 2002 5 (4) p251-261
Millward et al. ‘Gluten and casein-free diets for autistic spectrum disorder.’ Cochrane Database 2004 (2): CD003498
Pelsser & Buitelaar. ‘Favourable effect of a standard elimination diet on the behaviour of young children with attention deficit hyperactivity disorder (ADHD): a pilot study.’ Ned Tijdschr Geneeskd 2002 146 (52) p2543-2547 e-publication (abstract)
Picado. ‘Classification of severe asthma exacerbations: a proposal Classification of severe asthma exacerbations: a proposal.’ European Respiratory Journal 1996 (9) p1775-1778
The British Dietetic Association. 5th Floor Charles House 148/9 Great Charles Street Queensway Birmingham B3 3HT.www.bda.uk.com. The British Nutrition Foundation 52-54 High Holborn,.
London WC1V 6RQ. www.nutrition.org.uk. .
The Food Standards Agency.www.food.gov.uk
Emma Mills, RD.
French diet see Northern European diet.