The Healthspan Map · Nutrient

Folate (B9)

Linked to getting too little

Where a shortfall of Folate (B9) is linked — 19 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Nutrient or leverDirectionStrengthEvidence typeWhat was foundSource
Folate (B9)Eat enough ofStrongEstablished clinicalFolate deficiency is one of the two most common causes of megaloblastic anemia.Megaloblastic anemia (B12/folate) (opens in a new tab)
Folate (B9)Eat enough ofEmergingRCT / meta-analysisB-vitamin supplementation aids stress/anxiety regulation; supports neurotransmitter synthesis.Young et al. 2019, Nutrients (opens in a new tab)
Folate (B9)Eat enough ofModerateCohort / observationalLow folate (especially with low B12) is associated with cognitive decline and higher Alzheimer risk.Linus Pauling Institute; Huskisson et al. 2007 (opens in a new tab)
Folate (B9)Eat enough ofModerateReview / narrativeLow folate (especially with low B12) is associated with cognitive decline and higher Alzheimer risk.Linus Pauling Institute — Folate (opens in a new tab)
Folate (B9)Eat enough ofModerateReview / narrativeFolate supports DNA synthesis and red-cell formation; deficiency contributes to fatigue and anaemia.Micronutrients for energy/fatigue review (Tardy 2020) (opens in a new tab)
Folate (B9)Eat enough ofModerateEstablished clinicalDeficiency causes neuropsychiatric symptoms including depression and cognitive impairment.StatPearls – Folate (opens in a new tab)
Folate (B9)Eat enough ofEmergingCohort / observationalHigher dietary folate intake is inversely associated with migraine frequency; evidence emerging.Dietary B6/folate-migraine association (via food-migraine review 2024) (opens in a new tab)
Folate (B9)Eat enough ofModerateCohort / observationalFolate supports serotonin/melatonin formation; low folate intake is associated with short sleep.Peuhkuri 2012; NHANES 2005-2016 (opens in a new tab)
Folate (B9)Eat enough ofModerateReview / narrativeFolate supports serotonin/melatonin formation; low folate intake is associated with short sleep.Peuhkuri et al., "Diet promotes sleep duration and quality", Nutr Res 2012 (opens in a new tab)
Folate (B9)Eat enough ofEmergingReview / narrativeFolate deficiency contributes to peripheral neuropathy through the homocysteine/B-vitamin pathway.Nutritional & toxic neuropathy (opens in a new tab)
Folate (B9)Eat enough ofModerateCohort / observationalFolate supports ovulation, embryo quality and IVF success and (with zinc/B12 in one-carbon metabolism) spermatogenesis; preconception folate is standard for neural-tube prevention.Female fertility nutrition review (PMC8634384) (opens in a new tab)
Folate (B9)Eat enough ofEmergingReview / narrativeFolate deficiency causes cheilitis, hair depigmentation and mucocutaneous hyperpigmentation.Folate & skin (opens in a new tab)
Folate (B9)Eat enough ofEmergingRCT / meta-analysisB-vitamin supplementation (>=3 B-group incl. B6/B12/folate) produces a small but significant reduction in stress (SMD 0.23).Young et al. 2019, Nutrients (opens in a new tab)
Folate (B9)Eat enough ofEmergingReview / narrativeFolate supports nerve health and circulation relevant to the auditory system - emerging.Diet & tinnitus (opens in a new tab)
Folate (B9)Eat enough ofEmergingReview / narrativeB-vitamin deficiency (folate/B12/B6) raises homocysteine, associated with AMD; folate supports optic-nerve/retinal health.Retinal/ocular supplements review (PMC9710404) (opens in a new tab)
Folate (B9)Eat enough ofModerateReview / narrativeFolate is required for immune-cell proliferation and the Th1 response.Folate & lymphocytes (opens in a new tab)
Folate (B9)Eat enough ofStrongRCT / meta-analysisLow periconceptional folate causes fetal neural tube defects (spina bifida, anencephaly) and raises preterm birth, growth restriction and miscarriage risk.NIH ODS / USPSTF – Folate (opens in a new tab)
Folate (B9)Eat enough ofStrongRCT / meta-analysisLow periconceptional folate causes fetal neural tube defects (spina bifida, anencephaly) and raises preterm birth, growth restriction and miscarriage risk.Effect of folate intake on health outcomes in pregnancy: a systematic review and meta-analysis, Nutr J 2012 (opens in a new tab)
Folate (B9)Eat enough ofModerateCohort / observationalDeficiency raises homocysteine, contributing to vascular endothelial dysfunction and cardiovascular/stroke risk.StatPearls – Folate (opens in a new tab)

Linked to getting too much

Where an excess of Folate (B9) is linked — 1 sources.In the order the Map holds them: strongest evidence first. That is a statement about the evidence, not about what matters most.
Nutrient or leverDirectionStrengthEvidence typeWhat was foundSource
Folate (B9)Don't overdoModerateCohort / observationalPeople with low B12 plus high folate have lower cognitive test scores and higher homocysteine/MMA; excess folic acid may exacerbate B12-related cognitive decline.Folic-acid–B12 masking review (opens in a new tab)