Keeping a food and symptom journal

The instructions are short and they differ in scope, so each one is here with its owner.

NIDDK, gas in the digestive tract, last reviewed June 2021. Your doctor may ask you to keep a diary of what you eat and drink and your gas symptoms, and the diary can help your doctor or dietitian figure out whether certain foods and drinks could be causing them.

NHS, food intolerance, last reviewed 18 June 2026. You may be asked to keep a food and symptoms diary to help work out what may be triggering your symptoms.

NHS, IBS, last reviewed 17 March 2025. Keep a diary of what you eat and any symptoms you get, and try to avoid things that trigger your IBS.

NHS, food allergy, last reviewed 20 August 2026. The NHS points readers to Allergy UK for guidance on keeping a food and symptoms diary.

Academy of Nutrition and Dietetics, IBS, reviewed April 3, 2026. Recording your daily food intake in a food diary during flare-ups can help you figure out which foods contribute to IBS symptoms.

American Migraine Foundation, Diet and headache control, updated October 2024. Record everything you eat each day, along with any relevant information about your symptoms, such as when you have headache days and migraine attacks. The full headache version of this diary has its own page.

AAAAI and the allergy practice parameter, 2006. When anaphylaxis keeps happening despite avoiding the known food, detailed food diaries, including specific ingredient lists of prepared meals, should be obtained by the patient and reviewed by the physician, along with cofactors such as exercise (Food allergy practice parameter, Ann Allergy Asthma Immunol, 2006). The same document says a food diary may help identify another culprit food (practice parameter, 2006).

American College of Gastroenterology. The ACG's patient pages on IBS and lactose intolerance do not prescribe a diary format. Its IBS page says a dietitian is often helpful when trying diet changes because they can be overwhelming, complicated, limiting and frustrating (ACG, IBS, updated February 2026).

The allergy practice parameter gives the most exact list. The history should cover the suspect food or foods, the time between eating the food and the symptoms, the symptoms themselves, the amount of food needed for a reaction, whether the reaction repeats on earlier or later exposure, cofactors such as exercise, and the time since the last reaction (Food allergy practice parameter, 2006). Its summary adds whether symptoms resolved when the suspect food was removed and how long symptoms lasted, and says this can be augmented by a written recording of dietary intake (practice parameter, 2006).

The gut sources ask about the surrounding picture. For IBS, NIDDK says the doctor asks about family history of digestive diseases such as celiac disease, colon cancer, or inflammatory bowel disease, the medicines you take, recent infections, and what you eat, and checks whether symptoms have come at least once a week in the last 3 months and first started at least 6 months ago (NIDDK, IBS diagnosis, November 2017). For lactose intolerance, the doctor asks about your symptoms, family and medical history, and eating habits (NIDDK, lactose intolerance diagnosis, last reviewed February 2018).

A research diary built for IBS shows what a structured entry can hold. The Food and Symptom Times diary records the time, duration, and severity of abdominal pain, swelling, fullness, and bloating, along with stool type, straining, and urgency, next to the times food was eaten (Wright-McNaughton et al., Clin Transl Gastroenterol, December 2019).

Put together, a useful entry has the food with enough detail to name its ingredients, the time it was eaten, the amount, the symptom, the time it started, how long it lasted, how bad it was, and anything else that day such as exercise or medicine.

The windows differ by what is being tracked, and the sources print different ones. Allergic reactions to food normally occur within minutes of eating, though they can sometimes appear a few hours later (AAAAI, Food allergy). AAAAI's patient handout says symptoms usually happen between a few minutes and two hours after exposure (AAAAI, Food allergy basics, June 2022). The NHS says you may get symptoms straight after eating the food you're allergic to, or days later (NHS, Food allergy, 20 August 2026). For migraine, a food trigger should lead to a headache within 12 to 24 hours at most (AMF, October 2024).

Those spreads are why the diary needs clock times on both the meal and the symptom. A date alone cannot show a two-hour gap or a next-day one.

No source here gives one diary length for every situation. Each gives a period for its own question.

• During flare-ups. The Academy of Nutrition and Dietetics ties the IBS diary to flare-ups (AND, April 3, 2026).
• Several weeks. You may need to change what you eat for several weeks to see if IBS symptoms improve, and a low FODMAP trial runs a few weeks before foods are slowly added back (NIDDK, IBS eating, diet and nutrition, last reviewed November 2017).
• Two weeks. The ACG describes removing lactose from the diet for two weeks to see if symptoms improve, as an alternative when breath testing is not possible (ACG, Lactose intolerance, updated April 2026).
• Four weeks. AMF says to limit a suspected food for four weeks and track headache frequency, severity, and response to treatment in a diary during that time (AMF, Diet and headache control, October 2024).
• Two to three months. An earlier AMF article featuring Dr. Vincent Martin says patients who think a food is triggering their attacks can eliminate it for two to three months to see if avoiding it helps (AMF, Migraine and diet, December 8, 2017).
• Three days. The Food and Symptom Times diary was validated over 3 nonconsecutive days, one of them a weekend day (Wright-McNaughton et al., 2019).

AMF's own two figures disagree, four weeks in 2024 and two to three months in 2017, and both are printed here with their dates. Any removal of a food is a decision for you and your clinician or dietitian, and the diary runs for as long as they set.

The strongest evidence on diaries is about when the entry gets written. In a study of 80 adults with chronic pain, the 40 given a paper diary to fill three times a day for three weeks reported compliance of 90% and actual compliance, measured by a light sensor that logged each time the diary was opened, was 11% (Stone et al., BMJ, May 2002). On 32% of days the diary was never opened, yet entries for those days were reported as complete 92% of the time, and 75% of patients back-filled at least once (Stone et al., 2002). With an electronic diary that stamped the time, actual compliance was 94% (Stone et al., 2002).

The method built on that finding is called ecological momentary assessment. It samples behavior and experience in real time, in daily life, to minimize the recall bias of reports collected later at clinic visits (Shiffman, Stone and Hufford, Annu Rev Clin Psychol, 2008). The IBS diary study makes the same argument for gut symptoms: its authors say real-time scales are likely to be more accurate for symptom occurrence and severity because symptoms are recorded concurrently, which is likely to mitigate recall bias. They also note that the symptoms participants recorded were milder than symptoms reported retrospectively in other studies, which could reflect a milder group or the overreporting found in retrospective studies (Wright-McNaughton et al., 2019).

Self-monitoring, food logging included, has a track record in weight loss. A systematic review in the Academy's journal reports that a significant association between self-monitoring and weight loss was consistently found, and calls the level of evidence weak because of methodological limitations, chiefly homogeneous samples and reliance on self-report (Burke, Wang and Sevick, J Am Diet Assoc, January 2011).

It's important not to cut foods out of your diet without the advice of a GP or dietitian, because you could miss out on vitamins and minerals (NHS, Food intolerance, 18 June 2026). The NHS also says some tests you can buy that claim to diagnose food intolerances are not recommended (NHS, 18 June 2026).

AMF says not to restrict all possible trigger foods for an extended period, because too much concern about avoiding foods may increase stress and make consistent, healthy meals less likely, and it notes that true food triggers are not very common (AMF, October 2024). Dr. Martin's rule of thumb in the earlier article is that a food which seems to correspond with a headache more than half the time may be a trigger (AMF, December 8, 2017).

The dietitian comes up in every gut source. Your doctor may recommend talking with a dietitian (NIDDK, November 2017), a GP may refer you to a dietitian if diet changes and pharmacy medicines are not helping (NHS, 17 March 2025), and a registered dietitian nutritionist can build an individualized eating plan (AND, April 3, 2026).

I keep the diary at the time things happen. You text me the meal when you eat it, a photo works, and I keep it with the clock time and whatever you tell me about the ingredients and the amount. When a symptom shows up, you text me that too, and I keep when it started, how long it lasted, and how bad it was on your scale, next to the meals before it. Once a day I ask how it went so the quiet days get recorded as well, because a diary with only the bad days in it can't show what was different about the good ones.

I never name a trigger food, never tell you to cut something out, and never read a symptom. Before your appointment I hand you the record with the dates and times so your doctor or dietitian works from what happened. When you describe anything on the red-flag lists above, I say so plainly and tell you to call.

No clinician reviewed this page. It restates the NIDDK, NHS, ACG, AAAAI, Academy of Nutrition and Dietetics, and American Migraine Foundation pages and the studies linked below, and those are the documents to trust over anything here.