Food intolerance and fatigue. Is there a link?

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It’s perfectly normal to experience fatigue from time to time. From poor sleeping patterns to stress, overworking to changes in routine, there are many lifestyle factors which can lead us to feel tired and lethargic.

But if this exhaustion continues, and there doesn’t seem to be a clear reason, it might be worth taking a closer look at your diet to understand whether something you’re eating could be contributing to your feelings of fatigue.

What is fatigue?

Fatigue is a term used to describe a sensation of tiredness or low energy. Not to be confused with feeling sleepy which in itself can be a symptom, fatigue is more extensive, can be long-lasting and includes lack of motivation. It can also be experienced alongside conditions such as brain fog, where you struggle to focus and concentrate.

What causes fatigue?

Fatigue can be a symptom of many different illnesses, some more obvious than others. It’s always worth talking with your GP to rule out any serious underlying conditions which could be causing you to feel constantly tired. Some of the common causes of fatigue include:


Anaemia occurs when you do not have enough red blood cells needed to transport iron and haemoglobin through the bloodstream to your organs. Being anaemic can mean that you feel more tired or cold than usual. You might also notice that your skin seems too pale. This is because your organs aren’t receiving the oxygen they need.

Underactive thyroid

An underactive thyroid gland means you have too little of the thyroid hormone thyroxine in your body, making you feel tired. You’re also likely to put on weight and have aching muscles. It’s most common in women and happens more often as you get older.

Coeliac disease

A lifelong condition, coeliac disease is caused by the immune system reacting to gluten, a protein found in grains such as wheat, barley and rye and products like pasta, bread, cakes and cereals.

Around one in 100 people in the UK are affected, but research suggests many of them don’t know they have the condition. Other symptoms of coeliac disease, apart from tiredness, are diarrhoea, bloating and weight loss.

Chronic fatigue syndrome

Chronic fatigue syndrome (also known as myalgic encephalomyelitis, or ME) is a severe and disabling fatigue that persists for at least four months. Sufferers may also experience symptoms such as muscle or joint pain.


As well as causing feelings of sadness and anxiety, depression can also make you feel drained of energy.

Depression can stop you falling asleep or cause you to wake up early in the morning, contributing to poor sleeping patterns and a persistent feeling of tiredness. It can also cause you to oversleep, making it harder to establish good routines.

Food intolerance

Many of us have experienced that tired feeling after a big meal. After eating a large quantity of food, the body works hard to digest the meal, causing you to feel sleepy.

But if you have a food intolerance, this sensation can happen more often, even when you’re eating what appears to be light or nutritious meals, depending on what it is you’re reacting to. As the body reacts to the food it perceives as a threat, it works overtime to fight it, using up energy and causing you to feel more tired that you otherwise would.

The feelings of fatigue can also be a symptom of the stress your body is experiencing from other more typical food sensitivity symptoms, such as irritable bowel syndrome (IBS), cramps, and migraines. Tiredness can also arise from the body not being able to absorb certain nutrients from the food you’re eating, leading to lower energy levels.

Taking control of your diet

Fatigue can be triggered by many factors. If you’re suffering with the symptoms outlined in this article, it’s important to talk with your GP to rule out anything serious.

If you suspect that something you’re eating could be causing issues that are contributing to your feelings of fatigue, it might be time to consider the foods you’re consuming.  

Getting to the bottom of a food intolerance can be frustrating. Elimination diets, where you remove one ingredient at a time for a few weeks to see how you feel, can take a long time to reveal your triggers. As many of us react to between two and six ingredients, it can be a while before you’re able to see the bigger picture.

Additionally, the foods that you react to can often be surprising. It’s common to blame a few ‘usual suspects’ when it comes to food intolerance but anything, from beef to broccoli, could be the cause.

At Smartblood, we offer a comprehensive test to help you take control of your diet quickly and discover your own particular trigger foods. 

Our home-to-laboratory service, using ELISA plate testing, gives you fast, accurate results that pinpoint exactly which foods you are reacting to. Tests are completed in our accredited laboratory by trained experts with clear, easy to understand results sent to you by email within three days.

The test is also supported by a 30-minute telephone consultation with our BANT registered Nutritional Therapist to help you understand the results of your test and make safe, sustainable changes to your diet.

Could you have a food intolerance?

If you think that food intolerance may be responsible for your symptoms then we believe that our easy-to-complete tests could help you. Find all your food intolerances at once with a full Smartblood test.

Around 10% of our customers exhibit no IgG reactions to the 134 foods whatsoever – we provide non-reactive customers with a 100% REFUND so they can continue their investigations through other testing.

Find out today with Smartblood.

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