You do not need to log every sip. Write plain water as a rough running tally, and give any other drink its own line with a time, the type and a rough size. Add a short note when a drink had milk, sugar or sweetener in it, was fizzy, or was drunk with a meal or after a symptom began. That is enough to compare one day with another, and it is small enough to keep doing.
Drinks are easy to leave out because they do not feel like “eating”. They can also make two similar days look different, or two different days look the same, when they are missing from the record. This guide is about capturing drinks consistently. It does not say which drinks are good or bad for your digestion, and a diary cannot tell you that.
Why drinks go missing
Drinks are a known weak spot in self-reported records. In a three-day study of young adults aged 18–30 in Australia, published in Nutrients in 2021, participants wore cameras that took a picture every 30 seconds. Water was omitted more often from a smartphone food-record app than it was from the camera images or from a 24-hour recall. The study was about nutrition research rather than digestive symptoms, and it does not show how many drinks any one reader will miss. It does suggest that water is easy to under-record in an app.
Other research is more reassuring about drinks in general. A 2015 cross-sectional study of 190 women in Mexico, aged 18–45 and living with overweight or obesity, compared a 7-day beverage diary with three 24-hour recalls. The two methods gave similar median fluid volumes and a rank correlation of about 0.7 for total fluid. That shows the methods agreed with each other, not that either was accurate, and it applies to one group of women in one trial. Taken together, the studies point to a practical idea: a drinks record can work reasonably well, and it works better when it is written close to the time.
Plain water: keep a tally, not a log
Plain water is usually the most frequent drink and the least informative one to time precisely. Rather than a line each time, try one of these:
- A running tally. “Water: 5 glasses by 18:00, mostly between meals.”
- Containers. “Water bottle (about 750 ml) filled twice at work.”
- A rough band. “Water: a little / usual / more than usual.”
Whichever you choose, write the rule at the top of the diary and apply it every day. If you change the rule halfway through, note the date, so that a change in how you recorded is not mistaken for a change in what you drank.
Make an exception when something about the water is unusual. A large amount drunk quickly, or a big drink taken with a meal, is worth its own line with a time. So is water taken after a symptom began, because the drink then followed the symptom and did not come before it.
Other drinks: one line each
Tea, coffee, squash, juice, fizzy drinks, milk drinks and similar get a short line. A good line has four parts:
- Time. “08:10”.
- What it was. “Tea with milk and one sugar.”
- A rough size. “Mug”, “small glass”, “330 ml can”.
- Anything that stands out. “Fizzy”, “sugar-free”, “drunk with breakfast”, “sipped slowly over an hour”.
A food diary form hosted on the British Dietetic Association’s website asks people to record everything they eat or drink, “including snacks, alcohol, juices, water etc.”. It also asks how a cup of tea was made (how many sugars) and what type of milk was used. Its worked example lists each tea or coffee as its own entry with milk and sugar noted. The form was designed for dietetic assessment, which wants more detail than a personal observation diary needs, so take the structure and not the full level of detail.
Some drinks are closer to a meal than a drink. A smoothie, milkshake, hot chocolate or large latte has several ingredients and may carry real volume. Record these the way you would a mixed meal: the main components, a rough amount and a note on what you are unsure about.
Estimate size in a way you can repeat
Mugs and glasses vary. Rather than convert everything to millilitres, you can pick your own reference sizes and use them every time:
- “Small glass”, “large glass”, “my usual mug”, “takeaway medium”.
- For bought drinks, the size name on the cup or the volume on the bottle or can.
If accuracy matters to you, measure your own usual mug and glass once. For comparison, the US National Health and Nutrition Examination Survey (NHANES) measuring guides describe mug models of 8, 10 and 14 US fluid ounces, each with marked fill levels, to help respondents estimate beverage volume. A personal diary does not need that precision. It needs the same rough scale every day, so that a “mug” on Monday means about the same as a “mug” on Thursday.
Add the details that help you compare
Not every detail is worth writing every time. These are the ones that most often make two entries comparable or different:
- Milk, sugar or sweetener. “Coffee, no milk” and “coffee with a large splash of milk” are different entries.
- Fizzy or still. One word is enough.
- Sugar-free or regular. Write what the label says. If a drink contains a sugar alcohol such as sorbitol, mannitol or xylitol, the label will list it among the ingredients. The BDA’s page on irritable bowel syndrome and diet lists drinks containing those sweeteners among the things it suggests avoiding for people with IBS who have diarrhoea. That page is aimed at people with IBS, and your symptoms may not be IBS. The point for a diary is only that the label detail can be worth capturing.
- With a meal or between meals. “With dinner” or “on an empty stomach” is enough.
- Hot or cold, and how fast. Only when it was unusual.
Where drink advice comes in
You may have seen guidance on fluid, tea and coffee, or fizzy drinks. The NHS says that the Eatwell Guide recommends 6 to 8 cups or glasses of fluid a day, describes this as only a guide, and notes that you may need more if you are ill, physically active or in a hot environment. Water, lower-fat milk and lower-sugar drinks, including tea and coffee, all count. The page was last reviewed in May 2023.
For people with irritable bowel syndrome, the NICE guideline on IBS in primary care includes general advice to drink at least 8 cups of fluid a day, restrict tea and coffee to 3 cups a day and reduce alcohol and fizzy drinks. The BDA’s IBS page similarly suggests limiting alcohol, caffeine and fizzy drinks. That advice is written for people who have a diagnosis, so a reader who has not been told they have IBS cannot assume it applies to them.
A diary does not test any of that advice. It can show what you actually drank on days with and without symptoms, how consistently you recorded it and where the record has gaps. It cannot show that a particular drink caused a symptom. If you are thinking about cutting out a drink or changing how much you drink, the BDA advises people to seek specialist advice if they are struggling or their intake becomes limited.
Reading the drinks when you look back
When you review a few days, use plain questions:
- What did I drink in the hours before the symptom, and was it usual for me?
- Did a similar drink appear on a day without symptoms?
- Did I record drinks as carefully on the days that felt worse as on the days that felt fine?
- Is a missing drink a drink I did not have, or one I did not write down?
The last question matters because a record kept more carefully on bad days can look like a pattern that is not there. The guide to missing symptom check-ins explains how gaps shape what a diary can show, and the guide to telling which meal caused bloating explains why something that came before a symptom is an observation and not a cause.
If you are unwell and cannot drink enough, or if symptoms are persistent, getting worse or worrying you, speak to a pharmacist, GP or NHS 111. A diary is not a substitute for care.
For the rest of the day’s eating, the guide to snacks and nibbling follows the same principle of a short entry and a visible rough guess. If you would like a lower-effort way to capture drinks as well as meals, you can get GutBloom on Google Play.
Sources
- Nutrients (2021) — Using Wearable Cameras to Assess Foods and Beverages Omitted in 24 Hour Dietary Recalls and a Text Entry Food Record App
- BMC Public Health (2015) — Comparing a 7-day diary vs. 24 h-recall for estimating fluid consumption in overweight and obese Mexican women
- British Dietetic Association website — Food diary form
- CDC National Center for Health Statistics — NHANES measuring guides: mugs
- NHS — Water, drinks and hydration
- NICE — Irritable bowel syndrome in adults: diagnosis and management (CG61), recommendations
- British Dietetic Association — Irritable bowel syndrome and diet