Food intolerance: why it’s rarely just one food

When symptoms flare, most of us instinctively look for one food to blame. It might be dairy, gluten, eggs, tomatoes or food additives. Sometimes it is a specific food, particularly in true allergies. But in the majority of cases I see in clinic, ongoing symptoms are not caused by one single ingredient in isolation. They are related to overall load.

A child might tolerate a particular food one day and seem to react to it the next. An adult might eat the same meal they have always eaten and suddenly experience bloating, headaches or fatigue. The food itself has not necessarily changed. What has changed is the body’s capacity to tolerate what it is being exposed to.

Cumulative load matters

I often explain this to clients using the idea of a bucket. Throughout the day and week, different things fill that bucket. On their own, many of these are manageable but together they can become too much. When the bucket is only partly full, the body copes well. When it becomes overloaded, symptoms appear. The food that gets blamed is often simply the final addition that caused the bucket to overflow.

Many factors can contribute to cumulative load, including:

• food additives and preservatives
• natural food chemicals such as salicylates and amines
• histamine
• stress and poor sleep
• illness or infection
• hormonal fluctuations
• environmental exposures

This was something I learnt first hand with my own daughter. When she was younger, she began experiencing persistent stomach pains, skin rashes and weight loss. At first, we searched for a single obvious culprit, focusing on things like gluten and dairy. But cutting those things out didn’t seem to make a big difference.

Eventually, we discovered that she was reacting to salicylates, which are naturally occurring plant chemicals found in many fruits, vegetables, herbs and spices. Salicylates tend to be higher in colourful foods such as berries, tomatoes and certain herbs, and they are also present in some food additives and flavourings. For most people they are completely harmless, but in sensitive individuals they can contribute to symptoms when overall load is high. When we reduced our daughter’s salicylate load and supported her gut health, her symptoms settled.

That experience shaped how I now approach food intolerance with families. It reinforced the importance of looking at the bigger picture before cutting everything out.

Tolerance is not fixed and often shifts in perimenopause

A common comment I hear from women in their 40s is, “I’ve never had a problem with this food before and now I can’t tolerate it.” Gluten is frequently mentioned, but it could also be wine, chocolate, tomatoes or spicy food.

Perimenopause is a time of significant hormonal fluctuation, particularly in oestrogen and progesterone. These shifts can influence gut motility, microbiome balance, immune reactivity and inflammatory pathways. Oestrogen also interacts with histamine, meaning that as hormones fluctuate, histamine responses can become more pronounced. If gut barrier integrity is compromised or stress levels are high, tolerance thresholds can drop even further.

Factors that commonly reduce tolerance during this life stage include:

• fluctuating oestrogen and progesterone levels
• increased stress and disrupted sleep
• changes in gut microbiome composition
• altered gut motility and bloating
• increased inflammatory load
• nutrient deficiencies

When the system is under strain, foods that were once well tolerated may suddenly contribute to bloating, headaches, joint pain, skin flares or fatigue. It does not automatically mean someone has developed a permanent intolerance. Often, it reflects a temporary lowering of the threshold in the context of hormonal and physiological change.

Why over-restriction often backfires

When symptoms persist, the instinct is often to remove more and more foods. As someone who has experienced food intolerances, I can completely understand this response but it is not an approach I recommend as it can create a restrictive eating pattern that is stressful and nutritionally inadequate.

Excessive restriction can:

• reduce fibre intake and microbiome diversity
• increase the risk of nutrient deficiencies
• increase anxiety around food
• make social situations more stressful
• lower resilience further

Rather than eliminating an ever-growing list of foods, it is usually more effective to gently reduce overall load while strengthening the foundations that support tolerance. This might mean improving the quality of high-frequency foods, reducing the amount of additives consumed each day, increasing protein and fibre intake, supporting iron status, and prioritising sleep and stress management.

In most cases, the goal is not to create a perfectly “clean” diet, but to reduce overall load enough that symptoms settle and the body can cope again.

When you step back and look at the bigger picture, it becomes possible to reduce symptoms without drastic elimination, and without turning food into a constant source of worry.