Calcium, vitamin D, and bone health

Calcium and vitamin D sources

Dairy is a concentrated calcium source, but it is not biologically required as a food category because nondairy foods and fortified products can provide calcium (NIH ODS, 2026a). NIH lists fortified soy and almond beverages, calcium-fortified drinks, calcium-set tofu, soybeans, and selected greens among nondairy calcium sources (NIH ODS, 2026a). Absorption differs: calcium from dairy and fortified foods is about 30% on average, spinach calcium is less bioavailable because of oxalate, and calcium from lower-oxalate vegetables such as broccoli, kale, and cabbage has bioavailability similar to milk but occurs in smaller amounts per serving (NIH ODS, 2026a). Product labels are necessary because plant-milk fortification is not uniform (NIH ODS, 2026a; NIH ODS, 2026b).

Vitamin D promotes intestinal calcium absorption and supports bone mineralization and remodeling (NIH ODS, 2026b). Few foods naturally contain substantial vitamin D, and fortified foods provide most dietary vitamin D in the United States (NIH ODS, 2026b). A worldwide systematic review found wide variation in population vitamin D status and reported mean 25-hydroxyvitamin D concentrations below 50 nmol/L in 37.3% of included study samples, showing that low status is not confined to vegans (Hilger et al., 2014). Sun exposure, latitude, season, skin pigmentation, age, body composition, malabsorption, and supplement use can all affect status; fortified foods or supplements can be used when intake or status is insufficient (NIH ODS, 2026b).

Evidence in vegan populations

The observational evidence does not support the categorical statement that all vegans have weak bones, but it does identify population-level concerns (Iguacel et al., 2019; Tong et al., 2020). A 2019 systematic review and meta-analysis included 20 studies with 37,134 participants and found lower femoral-neck and lumbar-spine bone mineral density in vegetarian and vegan groups than in omnivores; the vegan subgroup also had a higher fracture rate (Iguacel et al., 2019). In EPIC-Oxford, 1,982 vegans had higher adjusted risks of total and hip fracture than meat-eaters during long follow-up, with associations attenuated but not eliminated after adjustment for body mass index, calcium, and protein (Tong et al., 2020). These studies cannot establish that vegan diet caused the differences because residual confounding, self-selection, body weight, activity, supplement use, and measurement error remain possible (Iguacel et al., 2019; Tong et al., 2020).

Substitution and other bone-health factors

Short randomized evidence supports one narrower claim in the stub: a meta-analysis of 17 trials involving 504 adults found that replacing cow's milk with soy milk did not worsen measured cardiometabolic risk factors and produced modest improvements in several lipid, blood-pressure, and inflammatory markers (Erlich et al., 2024). This evidence concerns intermediate cardiometabolic outcomes, not bone mineral density or fractures, and therefore should not be used as direct proof of bone equivalence (Erlich et al., 2024). Whether a plant milk contributes calcium or vitamin D depends on its fortification (NIH ODS, 2026a; NIH ODS, 2026b).

Bone health is multifactorial (NIH ODS, 2026a; NIH ODS, 2026b; Tong et al., 2020; Massini et al., 2022). In addition to calcium and vitamin D, body weight, protein intake, age, hormones, smoking, alcohol, medication use, falls, and physical activity can influence bone or fracture outcomes (NIH ODS, 2026a; NIH ODS, 2026b; Tong et al., 2020; Massini et al., 2022). A meta-analysis of seven resistance-training studies in 370 older adults found small positive effects at the hip and spine but not the femoral neck, suggesting a modest preventive contribution rather than a complete intervention (Massini et al., 2022).