# Sources & references > The published guidelines and studies behind every number and recommendation in Health Debug — 25 sources from EFSA, FDA, NIH, WHO, AASM, NSF, FIGO and peer-reviewed journals. *2026-10-14T15:32:25Z* The published guidelines and studies behind the numbers and recommendations in Health Debug. Tap one to read it. > Health Debug is a wellness app, not medical advice. It tracks habits; it does not diagnose, treat or prevent any condition. Consult your doctor about your own health. ## Water The health score measures a day's water against 2 litres. Water is logged in 250 ml cups up to 5 litres a day; that is a logging limit, not a target. - **[Scientific Opinion on Dietary Reference Values for water](https://doi.org/10.2903/j.efsa.2010.1459)** Publisher: EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA), EFSA Journal 8(3):1459 · Year: 2010 How Health Debug uses it: Adequate total water intake for adults is 2.0 litres a day for women and 2.5 for men, from drinks and food. The health score uses 2.0 litres, the lower of the two. ## Caffeine The Caffeine Block holds caffeine for the first 90 minutes after you wake. No guideline sets that exact delay: it is Health Debug's own habit rule, based on the research below on the cortisol rise after waking and on caffeine raising cortisol. Your daily allowance is in cups, and you set it. - **[Spilling the Beans: How Much Caffeine is Too Much?](https://www.fda.gov/consumers/consumer-updates/spilling-beans-how-much-caffeine-too-much)** Publisher: U.S. Food and Drug Administration (FDA) · Year: 2024 How Health Debug uses it: Up to 400 mg of caffeine a day is not generally associated with negative effects in most healthy adults. Context for the daily cup allowance you set. - **[The cortisol awakening response (CAR): facts and future directions](https://doi.org/10.1016/j.ijpsycho.2008.03.014)** Publisher: Fries, Dettenborn & Kirschbaum, International Journal of Psychophysiology 72(1):67–73 · Year: 2009 How Health Debug uses it: Cortisol rises sharply after waking and peaks about 30–45 minutes later — the period the Caffeine Block covers. - **[Cortisol responses to mental stress, exercise, and meals following caffeine intake in men and women](https://pubmed.ncbi.nlm.nih.gov/16204431/)** Publisher: Lovallo et al., Psychosomatic Medicine 67(5):734–739 (PubMed) · Year: 2005 How Health Debug uses it: Caffeine raises cortisol; the effect is smaller in people who drink it every day. ## Pre-sleep window The pre-sleep window asks you to stop eating 4 hours before your bedtime. NIDDK and the American College of Gastroenterology advise at least 2–3 hours; Health Debug uses 4 hours, the interval the study below found lowest-risk. - **[Eating, Diet, & Nutrition for GER & GERD](https://www.niddk.nih.gov/health-information/digestive-diseases/acid-reflux-ger-gerd-adults/eating-diet-nutrition)** Publisher: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, NIH) · Year: 2020 How Health Debug uses it: Advises eating at least 3 hours before lying down, and lists foods that commonly trigger reflux: citrus, tomatoes, chocolate, mint, coffee and caffeine, alcohol, spicy and high-fat foods. - **[Association between dinner-to-bed time and gastro-esophageal reflux disease](https://pubmed.ncbi.nlm.nih.gov/16393212/)** Publisher: Fujiwara et al., American Journal of Gastroenterology 100(12):2633–2636 (PubMed) · Year: 2005 How Health Debug uses it: Eating dinner less than 3 hours before bed was linked to much more reflux than leaving 4 hours or more. - **[ACG Clinical Guideline for the Diagnosis and Management of Gastroesophageal Reflux Disease](https://doi.org/10.14309/ajg.0000000000001538)** Publisher: Katz et al., American College of Gastroenterology, Am J Gastroenterol 117(1):27–56 · Year: 2022 How Health Debug uses it: Recommends avoiding meals 2–3 hours before bedtime. ## Focus (Pomodoro) Focus blocks follow the Pomodoro Technique: 25 minutes of work, a 5-minute break, and a longer break after every 4 blocks — 15 minutes in Health Debug. Each break is a prompt to get up from your desk. - **[The Pomodoro Technique for better productivity](https://www.atlassian.com/blog/productivity/the-pomodoro-technique-for-better-productivity)** Publisher: Francesco Cirillo (creator of the technique), Atlassian · Year: 2012 How Health Debug uses it: From the technique's creator: a Pomodoro is 25 minutes, followed by a short break, with a longer break every 4 Pomodoros. - **[Breaking up prolonged sitting reduces postprandial glucose and insulin responses](https://doi.org/10.2337/dc11-1931)** Publisher: Dunstan et al., Diabetes Care 35(5):976–983 · Year: 2012 How Health Debug uses it: In a laboratory study of 19 adults, 2-minute walking breaks every 20 minutes lowered blood sugar and insulin after a meal compared with uninterrupted sitting. - **[WHO guidelines on physical activity and sedentary behaviour](https://www.who.int/publications/i/item/9789240015128)** Publisher: World Health Organization (WHO) · Year: 2020 How Health Debug uses it: WHO advises adults to limit time spent sitting, replacing it with activity of any intensity, and to do 150–300 minutes of moderate activity a week. ## Medication Reminders and the 60-minute logging window follow the schedule you enter. The window is Health Debug's own logging rule. Health Debug does not recommend any medicine or dose; follow your doctor's or pharmacist's instructions. ## Trigger families Foods are marked Safe or Trigger-bearing for the conditions you choose — by what they are, never by amount. The food families come from these NIH dietary pages. - **[Eating, Diet, & Nutrition for GER & GERD](https://www.niddk.nih.gov/health-information/digestive-diseases/acid-reflux-ger-gerd-adults/eating-diet-nutrition)** Publisher: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, NIH) · Year: 2020 How Health Debug uses it: Advises eating at least 3 hours before lying down, and lists foods that commonly trigger reflux: citrus, tomatoes, chocolate, mint, coffee and caffeine, alcohol, spicy and high-fat foods. - **[Eating, Diet, & Nutrition for Irritable Bowel Syndrome](https://www.niddk.nih.gov/health-information/digestive-diseases/irritable-bowel-syndrome/eating-diet-nutrition)** Publisher: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, NIH) · Year: 2017 How Health Debug uses it: Diet guidance for irritable bowel syndrome: fibre, gluten and the low-FODMAP approach, with examples of high-FODMAP foods. - **[Eating, Diet, & Nutrition for NAFLD & NASH](https://www.niddk.nih.gov/health-information/liver-disease/nafld-nash/eating-diet-nutrition)** Publisher: National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK, NIH) · Year: 2021 How Health Debug uses it: For fatty liver disease: limit fats, replace saturated and trans fats, avoid simple sugars (especially fructose in soft drinks and juices) and keep alcohol to a minimum. - **[Gout](https://www.niams.nih.gov/health-topics/gout)** Publisher: National Institute of Arthritis and Musculoskeletal and Skin Diseases (NIAMS, NIH) · Year: 2023 How Health Debug uses it: Foods linked to gout: purine-rich animal foods, alcohol and sugar-sweetened drinks. ## Sleep The default sleep goal is 8 hours, and you can set it between 4 and 12. Adults need 7 or more hours (AASM); 7–9 hours is recommended (NSF). The daily flow counts a night of 6 hours or more, the lower end the NSF says may suit some people. - **[Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the AASM and Sleep Research Society](https://doi.org/10.5664/jcsm.4758)** Publisher: Watson et al., American Academy of Sleep Medicine, J Clin Sleep Med 11(6):591–592 · Year: 2015 How Health Debug uses it: Adults should sleep 7 or more hours a night on a regular basis. - **[National Sleep Foundation's sleep time duration recommendations: methodology and results summary](https://doi.org/10.1016/j.sleh.2014.12.010)** Publisher: Hirshkowitz et al., National Sleep Foundation, Sleep Health 1(1):40–43 · Year: 2015 How Health Debug uses it: Recommends 7–9 hours of sleep a night for adults. - **[How Many Hours of Sleep Do You Really Need?](https://www.thensf.org/how-many-hours-of-sleep-do-you-really-need/)** Publisher: National Sleep Foundation (NSF) · Year: 2026 How Health Debug uses it: Adults need 7–9 hours; an hour or two either side may be appropriate for some people. ## Cycle Cycles are marked irregular when your cycle lengths vary by more than 9 days, following FIGO's definition of a regular cycle. This is an estimate from the dates you log, not a diagnosis. The fertile window is the 5 days before the estimated ovulation day plus the day after; ovulation is estimated 14 days before the next period. Pregnancy weeks count from the first day of the last period (40 weeks), with the second trimester from week 14 and the third from week 28. These are estimates, not a method of contraception. - **[The two FIGO systems for normal and abnormal uterine bleeding symptoms and classification of causes of abnormal uterine bleeding in the reproductive years: 2018 revisions](https://doi.org/10.1002/ijgo.12666)** Publisher: Munro, Critchley & Fraser, FIGO, Int J Gynaecol Obstet 143(3):393–408 · Year: 2018 How Health Debug uses it: A normal cycle is 24–38 days, and cycles are regular when the shortest and longest differ by no more than 7–9 days. - **[Ovulation](https://my.clevelandclinic.org/health/articles/23439-ovulation)** Publisher: Cleveland Clinic · Year: 2026 How Health Debug uses it: Pregnancy is possible from about 5 days before ovulation to 1 day after; most people ovulate about 14 days before their period starts. - **[Timing of sexual intercourse in relation to ovulation — effects on the probability of conception, survival of the pregnancy, and sex of the baby](https://doi.org/10.1056/NEJM199512073332301)** Publisher: Wilcox, Weinberg & Baird, New England Journal of Medicine 333:1517–1521 · Year: 1995 How Health Debug uses it: Conception occurred only from intercourse in the six days ending on the day of ovulation. - **[Pregnancy: Gestation, Trimesters & What To Expect](https://my.clevelandclinic.org/health/articles/pregnancy)** Publisher: Cleveland Clinic · Year: 2024 How Health Debug uses it: Pregnancy lasts about 40 weeks (280 days), counted from the first day of the last menstrual period. - **[How Your Fetus Grows During Pregnancy](https://www.acog.org/womens-health/faqs/how-your-fetus-grows-during-pregnancy)** Publisher: American College of Obstetricians and Gynecologists (ACOG) How Health Debug uses it: The second trimester starts at 14 weeks and the third at 28 weeks. ## Contraception Reminders follow the method and schedule you enter. Health Debug does not choose or recommend a method; ask your doctor or pharmacist. ## Body metrics BMI is your weight in kilograms divided by your height in metres squared. From age 20, it is placed in WHO's adult bands: below 18.5, 18.5–24.9, 25–29.9, 30–34.9, 35–39.9 and 40 or more. Under 20 the number is shown without a band. BMI is a screening measure, not a diagnosis. Health Debug does not estimate body fat, metabolic rate or calorie needs. - **[Nutrition for a healthy life — body mass index (BMI)](https://www.who.int/europe/news-room/fact-sheets/item/nutrition---maintaining-a-healthy-lifestyle)** Publisher: World Health Organization, Regional Office for Europe · Year: 2025 How Health Debug uses it: Adult BMI bands, for adults over 20: underweight below 18.5, normal 18.5–24.9, pre-obesity 25.0–29.9, obesity class I 30.0–34.9, class II 35.0–39.9, class III 40 and above. - **[Growth reference data for 5–19 years (WHO Reference 2007)](https://www.who.int/tools/growth-reference-data-for-5to19-years)** Publisher: World Health Organization (WHO) · Year: 2007 How Health Debug uses it: Between 5 and 19, BMI is judged against age- and sex-specific growth references, not the adult bands — which is why Health Debug shows no band under 20. ## Steps The default daily goal is 10,000 steps; you can set your own between 1,000 and 50,000. - **[Daily steps and all-cause mortality: a meta-analysis of 15 international cohorts](https://doi.org/10.1016/S2468-2667%2821%2900302-9)** Publisher: Paluch et al., The Lancet Public Health 7(3):e219–e228 · Year: 2022 How Health Debug uses it: Across 15 cohorts, the lower risk of death levelled off at about 8,000–10,000 steps a day for adults under 60 and 6,000–8,000 for those 60 and over. - **[WHO guidelines on physical activity and sedentary behaviour](https://www.who.int/publications/i/item/9789240015128)** Publisher: World Health Organization (WHO) · Year: 2020 How Health Debug uses it: WHO advises adults to limit time spent sitting, replacing it with activity of any intensity, and to do 150–300 minutes of moderate activity a week. ## Blood oxygen (SpO₂) The reference range is shown beside your reading for context. Health Debug does not judge the reading. - **[Pulse Oximetry](https://medlineplus.gov/lab-tests/pulse-oximetry/)** Publisher: MedlinePlus, U.S. National Library of Medicine (NIH) · Year: 2024 How Health Debug uses it: A normal blood oxygen level is 95–100%; it can be lower with some lung conditions. ## Health score The health score is Health Debug's own measure of how closely you kept your habits today, not a medical score. Five parts — water, food, caffeine, focus and sleep — are worth 20 points each: water against 2 litres (EFSA), food by meals marked Safe, caffeine by cups taken outside the Caffeine Block, focus against 8 blocks, and sleep against your sleep goal (AASM, NSF). 80 and above is excellent, 60 good, 40 fair. - **[Scientific Opinion on Dietary Reference Values for water](https://doi.org/10.2903/j.efsa.2010.1459)** Publisher: EFSA Panel on Dietetic Products, Nutrition and Allergies (NDA), EFSA Journal 8(3):1459 · Year: 2010 How Health Debug uses it: Adequate total water intake for adults is 2.0 litres a day for women and 2.5 for men, from drinks and food. The health score uses 2.0 litres, the lower of the two. - **[Recommended Amount of Sleep for a Healthy Adult: A Joint Consensus Statement of the AASM and Sleep Research Society](https://doi.org/10.5664/jcsm.4758)** Publisher: Watson et al., American Academy of Sleep Medicine, J Clin Sleep Med 11(6):591–592 · Year: 2015 How Health Debug uses it: Adults should sleep 7 or more hours a night on a regular basis. - **[National Sleep Foundation's sleep time duration recommendations: methodology and results summary](https://doi.org/10.1016/j.sleh.2014.12.010)** Publisher: Hirshkowitz et al., National Sleep Foundation, Sleep Health 1(1):40–43 · Year: 2015 How Health Debug uses it: Recommends 7–9 hours of sleep a night for adults. ## Daily flow The daily flow is Health Debug's own checklist of small daily floors, not medical targets: at least 500 ml of water, 1 logged meal, 2 focus blocks, caffeine within your own cup allowance, the pre-sleep window kept, and a night of 6 hours or more (see Sleep). --- Source: https://healthdebug.com/en/blog/sources