Where the truth lives

If you remember one thing from this chapter: when a wellness claim doesn't trace back to a body on this page, the claim is weaker than it sounds. The bodies below are how the medical, public-health, and nutrition fields actually do their work. They publish their methods, update their conclusions as evidence accumulates, and have institutional reasons to get things right. They're not infallible. They are massively better than 'studies show.'

This chapter is the bookmarks bar you didn't know you needed. Three tiers, ten or so URLs, lifetime utility.

The source hierarchy

Evidence-based medicine organizes sources by how much they synthesize and how broadly they're vetted. From least to most authoritative for a population-level claim:

1. A single case report or anecdote (your aunt got better when she did X)
2. A single observational study (people who do X had fewer Y events)
3. A single randomized controlled trial (we randomly assigned people to X vs Y and X group had fewer events)
4. A systematic review of multiple studies (across 14 trials of X, the average effect was Z)
5. A clinical practice guideline from a peer body (USPSTF, AHA, AASM) synthesizing reviews into a recommendation
6. A government regulatory recommendation (CDC, USDA, FDA) translating guidelines into population-level policy

Wellness-industry content typically operates at level 1 or 2 — a single anecdote or a single study — and claims authority of level 5 or 6. The skill we're building is to recognize what level you're actually reading.

Tier 1 — regulatory and government

These bodies set US health policy. Their recommendations are usually the safest defaults for an individual decision because they survive scrutiny from multiple stakeholders and update as evidence shifts.

• CDC — cdc.gov. Centers for Disease Control and Prevention. Surveillance data (how common is a condition?), vaccine recommendations, prevention guidelines. MMWR (Morbidity and Mortality Weekly Report) is the canonical surveillance journal.
• NIH — nih.gov. National Institutes of Health. Research authority; the umbrella for 27 institutes (NCI for cancer, NIDDK for diabetes, etc.). For supplements: ods.od.nih.gov (Office of Dietary Supplements) has fact sheets on every common supplement.
• FDA — fda.gov. Food and Drug Administration. Drug + device approvals + safety. openFDA (open.fda.gov) is the structured API; DailyMed (dailymed.nlm.nih.gov) is where every prescription label lives in machine-readable form.
• USDA — dietaryguidelines.gov, fdc.nal.usda.gov, myplate.gov. Three sites for three purposes: Dietary Guidelines is the policy doc, FoodData Central has the nutrient breakdown of any food, MyPlate is the consumer-facing translation.
• USPSTF — uspreventiveservicestaskforce.org. US Preventive Services Task Force. The body that publishes grade A/B/C/D/I screening recommendations. If you want to know what's worth getting screened for and at what age, this is the source.
• HHS Surgeon General — hhs.gov/surgeongeneral. Major population-health advisories (loneliness, youth mental health, alcohol).
• WHO — who.int. World Health Organization. Global guideline body; US guidance occasionally diverges but WHO is the international standard.

Tier 2 — peer authority bodies

Clinical societies and review bodies that produce the synthesis underlying tier 1 recommendations. Often more current and more detailed than the tier 1 policy doc that cites them.

• Cochrane Collaboration — cochrane.org. The gold standard for systematic reviews. 'Cochrane Reviews' are exhaustive evidence syntheses on a specific clinical question. Free 'plain-language summaries' on every review.
• NICE (UK) — nice.org.uk. National Institute for Health and Care Excellence. UK guidelines that the US often cribs from. Particularly strong on cost-effectiveness and on health-technology assessment.
• AAP — aap.org. American Academy of Pediatrics. Age-band recommendations from newborn through young adult.
• AHA — heart.org. American Heart Association. Cardiovascular prevention + treatment + nutrition. The source for DASH dietary pattern and for cardiac-rehab guidelines.
• ADA — diabetes.org. American Diabetes Association. Annual Standards of Care — the most-referenced diabetes guideline globally.
• ACSM — acsm.org. American College of Sports Medicine. Exercise-prescription frameworks that operationalize the HHS Physical Activity Guidelines for Americans 2nd ed (2018) recommendation of 150 min/week moderate aerobic activity for clinical prescribing. (The 150-min canonical recommendation originates with HHS PAG, not ACSM.)
• AASM — aasm.org. American Academy of Sleep Medicine. Sleep duration recommendations, insomnia clinical practice guideline, sleep-disorders diagnostic criteria.
• APA — apa.org. American Psychological Association. Treatment guidelines for depression, anxiety, PTSD, eating disorders.

Tier 3 — primary literature (with literacy caveats)

The journals where individual studies and reviews are published. Useful when you want to verify a guideline body's specific source — but reading primary literature well requires the skills covered in chapter 5. Don't substitute primary literature for guideline-body conclusions unless you've built the literacy to interpret it.

• PubMed — pubmed.gov. NIH's index of biomedical literature. ~37 million records, free abstracts, often free full text via PubMed Central. Search syntax matters: use MeSH terms (e.g., 'Diet, Mediterranean'[MeSH]) for precision.
• Cochrane Library — cochranelibrary.com. Full Cochrane reviews + plain-language summaries.
• JAMA — jamanetwork.com. American Medical Association journal. High-impact clinical research. Behind paywall mostly; abstracts free.
• NEJM — nejm.org. New England Journal of Medicine. Similar to JAMA. The CASE RECORDS section (free) is excellent reading for thinking like a clinician.
• BMJ — bmj.com. British Medical Journal. Excellent 'Research Methods & Reporting' essays for understanding study design.
• Lancet — thelancet.com. Family of journals; particularly strong on global health and on population-scale dietary research (the 2019 EAT-Lancet Commission, the GBD studies).

Sources to question (anti-patterns)

When you encounter a wellness claim, run through this checklist. The more of these the source hits, the harder you should look for an independent corroboration from a tier 1 or 2 body.

• Influencer wellness content (especially supplement-affiliated)
• Sites with affiliate links to products being recommended
• Single-study sensationalism without replication discussion
• Before/after photos as primary evidence
• 'One weird trick' / clickbait framing
• Non-peer-reviewed preprints presented without that caveat
• Supplement claims that exploit the DSHEA labeling exemption (supplements legally make 'structure/function' claims that drugs can't, with much lower evidence bars)
• Predatory open-access journals not indexed in MEDLINE
• 'Studies show' without naming the study

Chapter 4 goes into how to actually READ a clinical practice guideline — the grade letters (A/B/C/D/I), the strength-of-recommendation language, the difference between a strong and a conditional recommendation. Chapter 5 covers reading the primary literature behind the guidelines. By chapter 8 you'll have a personal source map identifying which of the bodies above you'll trust for each of your seven dimensions.