How to Track What Foods Make You Feel Bad

Why Food Affects How You Feel

The connection between what you eat and how you feel is well established. The NHS acknowledges that food intolerances, sensitivities, and digestive conditions can cause a wide range of symptoms, from obvious digestive issues to less expected ones like headaches, fatigue, and skin problems.

Unlike food allergies (which involve the immune system and can cause immediate, sometimes severe reactions), food intolerances and sensitivities tend to be subtler. Symptoms can appear anywhere from 30 minutes to 48 hours after eating, which makes them much harder to pin down without careful tracking.

Common reasons food might make you feel unwell include:

• Enzyme deficiencies — such as lactose intolerance, where the body lacks sufficient lactase to digest milk sugars
• Sensitivity to food chemicals — including histamine, caffeine, sulphites, or salicylates naturally present in certain foods
• Digestive conditions — such as IBS, which can make certain foods (particularly high-FODMAP foods) harder to tolerate
• Gut microbiome imbalance — emerging research suggests the balance of bacteria in your gut can influence how you respond to different foods
• Portion size and eating patterns — sometimes it is not the food itself but how much or how quickly you eat it

Common Symptoms to Watch For

Food-related symptoms vary widely from person to person. Here are the most commonly reported ones, along with foods that are frequently associated with them. Remember: these are associations, not diagnoses. Everyone is different.

Notice how broad the timing ranges are. This is exactly why a diary is so valuable — your memory alone is not reliable enough to track a symptom that appeared 18 hours after a particular meal.

How to Start a Food and Symptom Diary

You do not need anything fancy to start. A notebook works, a spreadsheet works, an app works. The key is consistency. Here is what to do:

Step 1: Record everything you eat and drink

Be specific. Not just “pasta” but “wholemeal spaghetti with tomato and basil sauce from a jar, parmesan cheese, glass of red wine.” Include quantities where possible, brand names if relevant, and the time you ate.

Step 2: Record any symptoms

Note what you feel, when it started, and how severe it is. A simple scale works well: mild (noticeable but manageable), moderate (uncomfortable, affects your day), severe (significantly impacts your ability to function). Also note when the symptom passes.

Step 3: Record other factors

Stress, poor sleep, your menstrual cycle, exercise, and medications can all influence how you feel. Noting these helps you distinguish between food-related symptoms and other causes.

Step 4: Be patient and consistent

Track for at least 2–4 weeks before trying to draw conclusions. Some patterns emerge quickly (bloating every time you eat a particular food), while others take longer (skin issues that correlate with dairy consumed 2 days earlier).

What to Look For: Spotting Patterns

After 2–4 weeks of consistent tracking, review your diary and look for:

• Repeated associations — does a particular symptom appear multiple times after eating the same food or food group?
• Consistent timing — does the symptom always appear a similar amount of time after eating?
• Dose dependence — do symptoms get worse with larger portions of a suspected trigger food?
• Absence correlation — on days when you did not eat the suspected food, did the symptom not appear?

Be honest with yourself about what the data shows. Confirmation bias is real — we tend to notice patterns that confirm what we already suspect and overlook data that contradicts it. Let the diary speak for itself.

If you notice a strong pattern, the next step might be an elimination diet where you remove the suspected food for a few weeks and then reintroduce it to see if symptoms return. This is best done with guidance from your GP or a registered dietitian.

How NutraSafe Helps You Track Reactions

Keeping a paper food diary is perfectly valid, but an app can make the process significantly easier:

• Log food quickly — scan barcodes or search the database instead of writing out every ingredient
• Record reactions — NutraSafe’s dedicated reaction tracking lets you log symptoms alongside your food diary with severity ratings and timing
• See patterns visually — review your food and symptom history side by side to spot correlations
• Take it to your GP — having detailed, dated food and symptom records makes GP appointments much more productive
• Track everything in one place — food, calories, nutrients, and reactions all in a single app

NutraSafe can help you track this — the reaction tracking feature is designed specifically for people trying to understand which foods are causing them problems.

When to See Your GP

A food diary is a useful self-help tool, but it is not a substitute for medical advice. See your GP if:

• Your symptoms are severe or getting worse
• You experience difficulty breathing, swelling, or signs of an allergic reaction
• You have unexplained weight loss
• Symptoms persist despite identifying and avoiding suspected trigger foods
• You are considering removing entire food groups from your diet
• You are concerned about nutritional deficiencies

The NHS recommends seeing a GP before starting any restrictive diet, especially if you suspect a food allergy rather than an intolerance. A GP can arrange proper allergy testing and may refer you to a dietitian.

A Gentle Reminder

Tracking food and symptoms can sometimes feel overwhelming, especially when you are already feeling unwell. Here are some things worth remembering:

• Progress, not perfection. If you miss a day of tracking, just pick it up again the next day. Imperfect data is still useful data.
• One thing at a time. Do not try to eliminate five foods at once. Focus on identifying patterns first.
• It gets easier. Logging food feels tedious at first, but after a week it becomes second nature. Most people find it takes less than 5 minutes a day.
• Knowledge is power. Understanding your body’s responses to food puts you back in control. That is a positive thing.

Frequently Asked Questions

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