Overview of Rickets (Stuff You Missed in History Class — episode: "Rickets")
This episode traces the history, biology, social drivers, and eventual cure of rickets — a childhood bone-mineralization disease caused by vitamin D deficiency. The hosts explain how rickets emerged in written and archaeological records, how physicians misinterpreted it for centuries, the parallel discoveries that identified sunlight and cod liver oil as effective treatments, and how the identification of vitamin D and food fortification dramatically reduced its prevalence in the 20th century. The episode also covers modern risk factors and why rickets still occurs today.
Key takeaways
- Rickets is caused primarily by vitamin D deficiency leading to poor calcium absorption and defective bone mineralization in growing children; the adult equivalent is osteomalacia.
- Classic signs: bowed legs, spinal deformities, “rickety rosary” (knobs at rib–cartilage junctions), weak/deformed limbs, delayed/decaying teeth.
- Two empirically discovered cures preceded the discovery of vitamin D: cod liver oil (rich in vitamin D) and sunlight/UV exposure.
- Historical increases in rickets in 16th–19th century Europe were likely driven by urbanization, industrial air pollution, reduced sun exposure, dietary changes, and climate factors (Little Ice Age).
- By the 1920s–30s, research showed both UV light and dietary vitamin D prevented and cured rickets; vitamin D was isolated and food fortification and supplementation led to a sharp decline.
- Rickets persists today in pockets due to malabsorption conditions, exclusive breastfeeding without supplementation, limited sun exposure, high melanin skin (needs more sun for same vitamin D), and possibly lifestyle/sunscreen patterns.
Biology and causes
- Vitamin D (D3 synthesized in skin via UVB acting on cholesterol) is converted in the body into a hormone that enables calcium absorption and bone mineralization.
- Sources of vitamin D:
- Sunlight (UVB) — requires direct sun (blocked by glass, clothing, heavy smog).
- Diet — fatty fish (salmon, tuna, sardines), egg yolks, wild mushrooms; cod liver oil is a concentrated source.
- Fortified foods — in many countries (e.g., milk, some cereals, juices); policies vary by region.
- Risk modifiers:
- Latitude/season, atmospheric pollution, indoor living reduce UVB exposure.
- Melanin: darker skin synthesizes less vitamin D from the same sun exposure → higher sun needs.
- Infants: breastmilk typically lacks sufficient vitamin D — supplementation is recommended for exclusively breastfed infants.
- Medical malabsorption (celiac disease, inflammatory bowel disease, cystic fibrosis) can cause rickets.
Historical timeline and important studies
- Earliest archaeological evidence: 5,000-year-old skeleton in Scotland (2013). Roman-era skeletons also show childhood rickets.
- Early written references:
- Possibly described by Soranus of Ephesus (1st–2nd century CE) regarding infant care.
- Named and described clinically in the 17th century: Daniel Whistler (1645 MD thesis) and Francis Glisson (1650 treatise) provided systematic clinical descriptions.
- 16th–17th centuries: Rising mentions in artwork and accounts across Europe; often linked to urban settings and certain wells/springs used as remedies.
- 18th–19th centuries:
- Cod liver oil used empirically in northern coastal communities as a general medicine; noticed to help rickets.
- Jedrzey Sniadecki (1822) proposed sunlight as a cure — noted rickets was rare in sunnier regions.
- John Snow (1857) proposed alum in cheap flour might bind phosphorus and impair bone mineralization.
- Monkeys in glass enclosures (London Zoological Society) developed rickets rapidly — hinting at UV-deprivation.
- Late 19th–early 20th centuries:
- Debate: sunlight vs. cod liver oil as the key cure.
- 1912: Casimir Funk coins “vitamines” (vitamins) — deficiency theory gains traction.
- 1918–19: UV lamp treatments (Dr. Hulczynski) showed systemic benefit from local UV exposure.
- Hess & Unger (NYC): cod liver oil prevented/resolved rickets in a high percentage of treated infants (noted ethical issues by modern standards).
- 1921–22: Harriet Chick and team in Vienna: randomized-like nursery study showed cod liver oil and sunlight both prevented/treat rickets; indoor babies developed rickets and improved with outdoor exposure, UV lamps, or cod liver oil.
- Early 1920s: vitamin D isolated and named (Elmer McCollum coined “vitamin D”); synthetic production followed, enabling fortification.
- Result: widespread fortification and supplementation in the 1920s–30s led to dramatic declines in rickets in many countries.
Social, environmental, and medical context
- Urbanization/Industrial Revolution: more people (including children) worked and lived indoors; coal pollution and smog reduced UVB exposure.
- Class observations: early physicians (e.g., Whistler) noted rickets in both wealthy (due to wet-nursing/indoor infants) and poor (due to malnutrition / poor living conditions) populations; associations were initially misinterpreted.
- Racist misuse: higher rickets prevalence in Black communities (due to melanin and sun exposure at northern latitudes) was sometimes misused to justify racist claims rather than understood biologically.
- Public health response: fortification of milk/foods and infant vitamin D supplementation policies helped eliminate much of the disease in many regions, though not uniformly.
Modern relevance and prevention
- Still remains a public health issue in parts of the world and in at-risk groups.
- Prevention and treatment:
- Ensure adequate dietary vitamin D (fortified foods, supplements where needed).
- Vitamin D supplementation recommended for exclusively breastfed infants.
- Sensible sun exposure (accounting for skin type, latitude, season) balanced with skin cancer prevention.
- Treat underlying malabsorption or metabolic causes if present.
- Recognize signs early (bowing, rib changes, delayed dentition) and evaluate vitamin D/calcium status.
- Sunscreen nuance: lab studies show sunscreen blocks vitamin D synthesis, but real-world application is imperfect; low outdoor time and indoor lifestyles are often larger contributors to deficiency.
Notable insights and historical ironies
- Effective treatments (cod liver oil, sunlight) were in use long before vitamin D was identified — empirical cures preceded mechanistic understanding.
- The disease became particularly documented and visible during periods of social/industrial change (Little Ice Age, industrial smog), underscoring how environment and lifestyle shape nutrition-linked diseases.
- Animal cases (e.g., zoo monkeys in glass enclosures) provided compelling evidence for the role of UV exposure.
Practical recommendations (for general readers)
- Check that exclusively breastfed infants receive vitamin D supplementation per pediatric guidelines.
- Be mindful of risk factors: dark skin living in high latitudes, limited outdoor time, heavy air pollution, or medical conditions affecting absorption.
- Discuss testing and supplementation with a healthcare provider if you suspect deficiency or see signs in a child (growth delay, bowed legs, dental problems).
- For policymakers/clinicians: fortification, public health education about supplementation, and targeted screening for high-risk groups remain effective prevention tools.
If you want a quick reference: rickets = vitamin D deficiency → poor calcium absorption → soft/poorly mineralized bones in growing children. Treat/prevent with vitamin D (sunlight, cod liver oil/dietary sources, supplements/fortified foods) and address underlying causes.