Vitamin D and Smoking
Smokers have consistently lower serum 25(OH)D than never-smokers — roughly 3–5 ng/mL less on average, independent of sun exposure, BMI, and diet. This compounds their well-known bone-density and fracture risk. Quitting partially reverses the vitamin D difference; correcting deficiency is standard care for smokers.
Observational data
NHANES and European cohorts consistently show smokers have lower 25(OH)D. The effect is dose-dependent — heavy smokers (> 20 cigarettes/day) show larger reductions than light smokers. Ex-smokers have intermediate levels; levels rise partially over the years after quitting.
Possible mechanisms
- Increased 25(OH)D catabolism from CYP450 induction by tobacco combustion products.
- Reduced hepatic 25-hydroxylation.
- Reduced physical activity and outdoor time in some smoking populations.
- Lower dietary calcium and vitamin D intake in smokers on average.
- Increased oxidative stress accelerating vitamin D breakdown.
Bone consequences compound
Smoking is an independent risk factor for osteoporosis via multiple mechanisms — direct effects on osteoblast function, altered estrogen metabolism (earlier menopause in women smokers), reduced calcium absorption, and cortisol effects. Combined with vitamin D deficiency, smokers have hip fracture risk ~40% higher than never-smokers. Correcting vitamin D deficiency is one modifiable component in this risk stack.
Passive smoking
Some studies find lower 25(OH)D in non-smokers with significant passive smoke exposure, particularly children. The effect is smaller than active smoking. Reducing household smoking exposure benefits kids on many dimensions including bone health.
Vaping
Data on vaping and vitamin D is limited. Nicotine effects on hepatic metabolism may be similar to smoking; combustion products are absent. Studies to date are inconclusive; the general recommendation is not to vape as a "safer alternative" for vitamin D reasons.
Practical guide
- Smokers: test 25(OH)D and correct any deficiency with standard doses.
- Ensure adequate calcium (1,000–1,200 mg/day) and consider DEXA screening earlier than non-smokers.
- Support smoking cessation — the vitamin D benefit is a small bonus to the many other reasons.
- Quitting resources: nicotine replacement, varenicline, bupropion, counselling, quitlines (US 1-800-QUIT-NOW).