By Dr Naomi Newman-Beinart (PhD), Chartered Psychologist and Nutritionist.
Food intolerances are far more common than many people realise, yet they’ve historically been misunderstood, under-recognised and often dismissed. Unlike food allergies, which can cause immediate and sometimes life-threatening reactions, food intolerances tend to cause delayed, ongoing symptoms that can quietly disrupt daily life for years.
What exactly is a food intolerance?
A food intolerance occurs when the body has difficulty digesting or processing certain foods or food components. Rather than triggering an immediate immune response like an allergy, intolerances usually lead to slower, more subtle reactions. Symptoms can appear hours, or even days, after eating the problem food, making them especially hard to identify.
Common symptoms include:
- Bloating, wind or abdominal discomfort
- Diarrhoea or constipation
- Fatigue or low energy
- Headaches or migraines
- Brain fog or difficulty concentrating
- Skin issues such as rashes or eczema
- Joint or muscle aches
Because these symptoms are often non-specific, many people don’t initially connect them to food at all. Instead, they may assume stress, ageing or a “sensitive stomach” is to blame.
Why food intolerances were overlooked for so long
For many years, food intolerances sat in a grey area of healthcare. They weren’t classified as allergies, they didn’t show up on standard tests, and the symptoms weren’t always easy to measure objectively. As a result, people were often told that “nothing was wrong” even when their quality of life was clearly affected.
Today, the NHS recognises that food intolerance can be genuinely debilitating, particularly when symptoms are chronic and poorly managed.
Where do food intolerances come from?
Food intolerances rarely have a single cause. Instead, they tend to develop due to a combination of factors, including:
- Genetics – Some people are more predisposed to digestive difficulties than others
- Gut health changes – Infections, antibiotics, illness or long-term stress can alter how the gut functions
- Hormonal changes – Including perimenopause, menopause or thyroid conditions
- Environmental factors – Diet, lifestyle, toxins and long-term exposure patterns
- Cumulative exposure – Eating the same foods frequently over many years
Importantly, intolerances can develop later in life, even to foods you’ve eaten without issue for decades.
How can you work out if food is the problem?
Traditionally, people are advised to keep a food and symptom diary and remove suspected trigger foods one at a time. While this can work, it’s often harder than it sounds.
From a health psychology perspective, this approach relies heavily on:
- Accurate recall of everything eaten
- Consistent symptom tracking
- The ability to spot delayed reactions
- Patience and motivation over several weeks
Many people react 24–72 hours after eating a trigger food, which makes it extremely difficult to confidently link cause and effect. This often leads to confusion, frustration and guesswork, and sometimes unnecessary restriction of foods that aren’t actually causing the problem.
There’s also a real risk of nutrient deficiencies if multiple foods are removed without proper guidance.
Why food intolerance testing can be helpful
This is where structured food intolerance testing, such as the Premium Food Intolerance Test by YorkTest, can be a useful starting point. As a practitioner, I’ve seen how helpful it can be for people who feel stuck, overwhelmed or unsure where to begin.
The test is simple to complete at home and provides a clearer picture of which foods may be contributing to symptoms. From a behavioural and psychological standpoint, this clarity is important as it reduces uncertainty, supports motivation, and helps people feel more confident in making changes.
Rather than guessing, individuals can take a more targeted approach, removing specific foods and then reintroducing them in a controlled way, with the support of a nutrition professional from YorkTest.
Living with unexplained symptoms can be exhausting, both physically and emotionally. Food intolerances are real, increasingly recognised, and, importantly, manageable with the right approach.
If you suspect food may be playing a role in how you feel, gathering better information is often the first step. With clearer insight, practical support and a personalised plan, many people find they can dramatically improve their symptoms and quality of life.
