When healthy adult men replace red meat with legumes for six weeks, their vitamin B12 and iodine levels drop slightly, but remain within normal ranges, suggesting the diet is still nutritionally adequate in the short term.
Evidence from Studies
No evidence studies found yet.
What Would Prove This
Per GRADE and EBM methodology, here is what ideal scientific evidence would look like to definitively prove or disprove this claim, ordered from strongest to weakest.
Whether long-term replacement of red meat with legumes consistently leads to suboptimal vitamin B12 or iodine status across diverse populations, and whether fortification or supplementation mitigates this.
A systematic review and meta-analysis of 15+ RCTs and cohort studies (≥6 months) comparing plant-based diets replacing ≥20% animal protein with meat-based diets, measuring serum holotranscobalamin, urinary iodine, and clinical deficiency rates, with subgroup analysis for fortified food use.
Whether replacing red meat with legumes for 12 months causes clinically significant vitamin B12 or iodine deficiency in healthy adults.
A double-blind RCT of 300 adults aged 25–70, randomized to legume-based or meat-based diets for 12 months, with monthly monitoring of serum holotranscobalamin, urinary iodine, and clinical symptoms, with optional fortified food supplementation as a secondary arm.
Whether individuals who adopt legume-heavy diets over 5–10 years develop vitamin B12 or iodine deficiency more frequently than meat consumers.
A prospective cohort study following 8,000 adults for 10 years, collecting dietary data and annual biomarkers of B12 and iodine status, comparing those who replace ≥20% of red meat with legumes versus those who do not, with clinical deficiency as the primary outcome.
Whether populations with high legume and low meat intake have lower average vitamin B12 and iodine biomarkers at a single point in time.
A national survey measuring serum holotranscobalamin and urinary iodine in 4,000 adults, comparing those consuming ≥150g/day legumes and ≤100g/week red meat to those consuming ≥300g/week red meat and <50g/day legumes.
Whether an individual develops low vitamin B12 or iodine status after switching from meat to legumes.
A case series of 15 individuals who switched from meat to legume-based diets for 6 months, with pre- and post-intervention serum B12 and urinary iodine measurements.