Introduction

Definition of food intolerance

A food intolerance, or food sensitivity, affects the way your body breaks down certain foods in your digestive system.¹ Unlike a food allergy, a food intolerance is not life-threatening but the symptoms caused by your body struggling to digest the food may be unpleasant.

The common symptoms of a food intolerance occur a couple of hours after ingesting the specific food or ingredient in the food you are intolerant to and include:

• Gas
• Diarrhoea
• Headaches²
• Abdominal pain¹
• Nausea²
• Bloating¹

Less-known symptoms of food intolerances that may occur include exhaustion, constipation, aching joints and rashes.¹

Definition of chronic fatigue syndrome (CFS)

Chronic fatigue syndrome, also known as myalgic encephalomyelitis is a condition which causes extreme tiredness and negatively affects different parts of the body. The tiredness must last for at least 6 months to be classed as CFS.³

CFS is diagnosed based on symptoms and the NHS describes these as:

• Intense fatigue which can cause individuals to struggle in carrying out day-to-day activities
• Disturbances in normal sleep patterns; waking up exhausted, insomnia or sleeping too much
• Inability to focus or problems with memory (known as brain fog)
• Post-exertional malaise where symptoms worsen after efforts requiring mental or physical engagement, may take several weeks to improve and do not improve with rest
• Possible joint or muscle pain, high temperature or headaches 

Relationship between food intolerance and CFS

Patients with CFS show a tendency towards somatic symptom disorder traits which means they may have physical symptoms such as pain or weakness which don’t appear to have a medical explanation.⁴ 

Studies suggest that food intolerances in CFS are not caused by the condition but are a result of this somatisation trait in patients with CFS.⁴

Food Intolerance

Types of food intolerance

There are many different types of food intolerances which describe the specific ingredients in foods which people are sensitive to. Food intolerances vary between individuals and patients with CFS don’t show the same pattern of foods they have to avoid.⁵

People with CFS can show intolerance to lactose, gluten (which is seen as non-celiac gluten sensitivity), or histamine (found in wine and cheese).¹

Fructose malabsorption

People with CFS may be sensitive to some sweeteners such as sugar, corn syrup, aspartame, or saccharin, and may have difficulty in absorbing fructose.⁵

Additives and preservatives intolerance

Food additives like MSG or preservatives can have a negative impact as well as artificial colours and flavours.⁵

Chemical sensitivities

People with CFS may also have an intolerance to alcohol and be sensitive to tobacco.⁵

Caffeine and other stimulants may also cause symptoms.⁵

Individuals with the condition may show sensitivities to things which aren’t food. The ME/CFS & Fibromyalgia self-help website lists examples of these such as:

• Mould
• Dust
• Grass
• Perfumes
• Cigarettes
• Diesel

Diagnosis of food intolerance

Diagnosing a food intolerance may involve eliminating the food and seeing whether symptoms improve. It may also involve keeping a food diary, carrying out blood tests, or conducting a lactose intolerance breath test.¹

Chronic fatigue syndrome

Possible causes of CFS

The exact cause of the condition is still being researched, yet according to the Mayo Clinic, the factors contributing to the development of CFS are thought to be:

• Viral or bacterial infections
• Genetics
• Mental or physical stress
• Problems converting fats and sugars from food into energy

General treatment

As CFS presents differently in each individual, treatment plans are tailored to meet the needs of patients.

• Energy management treatment helps people learn how to make the most out of the energy they have without worsening their symptoms
• Cognitive Behavioural Therapy can help people learn how to live with the condition
• The NHS offers suggestions on lifestyle changes you can undertake to manage the more general symptoms

The link between food intolerance and CFS

Theories and hypotheses

Immune system interactions

A potential explanation of the cause of CFS may be the interaction of a virus or another stressor within the immune system.⁷ It is thought that this virus or other stressor changes the systems of brain chemicals that determine how the body reacts to substances like chemicals or alcohol, thus contributing to CFS.⁷

Immune system dysfunction may be responsible for a greater number of allergies present in people with CFS, but food intolerances are not caused by the same immune system allergic reactions.⁷

Another explanation may be dysfunction in the way in which sensory information about things like pain, touch, temperature, light and noise are communicated to the brain.⁷

Inflammation and oxidative stress

CFS may be caused by oxidative stress which is when there are too many unstable molecules, called free radicals, and not enough good antioxidants which causes cells to become damaged.^8,9 This is important because it means that with further research, antioxidants such as some dietary supplements may be used to treat CFS.⁸

Food intolerance may be involved in oxidation through the induction of cytokines which act against inflammation.⁸

Impact of food intolerance on CFS symptoms

Around 1/3^rd of individuals with CFS and fibromyalgia are affected by food sensitivities or have difficulty absorbing nutrients.¹⁰ This can lead to gastrointestinal symptoms like gas, nausea, diarrhoea and heartburn.¹⁰ Food intolerances can also contribute to the possible symptoms of CFS by causing muscle pain, headaches, changes in pulse, and worsening fatigue.¹⁰

Management and treatment

Managing food intolerance in CFS patients

Dietary modifications

Figuring out which foods you are sensitive to may be difficult especially if multiple foods are causing your symptoms. The advice is to remove all potential triggers from your diet and then reintroduce them one by one and monitor your body’s reaction over several days.¹⁰

However, it is advised that individuals with CFS discuss any potential food intolerances with their doctor as removing many foods from your diet may result in malnutrition and worsen symptoms of the condition.

Once you have identified what types of foods are causing your symptoms, the two main treatments are elimination diets and rotation diets.¹⁰

As people with CFS may experience symptoms similar to those of IBS, a dietitian may decide to try out a low-FODMAP diet.

Elimination diets

Elimination is used for foods which cause severe symptoms which are distressing to individuals such as nausea, diarrhoea or rashes10.

Rotation diets

Rotation diets are used when a food doesn’t cause symptoms when it is only eaten from time to time. This can range between 4 to 7 days.¹⁰

Nutritional support

Supplements

If you are worried about not getting enough nutrients because of your diet, a multivitamin with no more than 100% of your daily recommended intake can be taken.¹¹

A vitamin D tablet is recommended for people with CFS, especially if they are often at home.

The Association of UK Dieticians recommends that your GP should refer you to a dietician specialising in CFS if you are:¹¹

• Noticing unintentional changes in your weight
• Engaging in a restrictive diet
• Experiencing severe or very severe symptoms of CFS 

Younger persons with CFS experiencing the above or stunted growth should be referred to a paediatric dietitian with expertise in CFS.¹¹

Having a balanced diet is important in CFS, however, food intolerances can make this hard to achieve. It is important to listen to your body and avoid eating foods which don’t feel right even if that includes ‘healthy’ foods such as some fruit and vegetables.¹⁰

Avoid restrictive diets such as the ketogenic diet;it is much healthier to follow a balanced adult diet containing all major food groups with the exception of foods which you are intolerant to.¹⁰

Conclusion

A food intolerance can cause symptoms such as diarrhoea, bloating and gas. Chronic fatigue syndrome is a condition which causes extreme tiredness and affects different parts of the body. People with CFS may have a somatisation trait which may manifest as food intolerances. These can include intolerance to lactose, gluten, histamine or fructose. The link between CFS and food intolerance may be due to a virus or another stressor and its impact on the immune system or due to oxidative stress. The management of food intolerances mainly involves the elimination or rotation of diets.