1. United Nations (2013) World Population Ageing 2013. New York, NY: Department of Economic and Social Affairs, Population Division. Report No.: ST/ESA/SER.A/348.
2. Lim, SS, Vos, T, Flaxman, AD, et al. (2010) A comparative risk assessment of burden of disease and injury attributable to 67 risk factors and risk factor clusters in 21 regions, 1990–2010: a systematic analysis for the Global Burden of Disease Study 2010. Lancet 380, 2224–2260.
3. Reedy, J, Krebs-Smith, SM, Miller, PE, et al. (2014) Higher diet quality is associated with decreased risk of all-cause, cardiovascular disease, and cancer mortality among older adults. J Nutr 144, 881–889.
4. Selhub, J (2002) Folate, vitamin B12 and vitamin B6 and one carbon metabolism. J Nutr Health Aging 6, 39–42.
5. Li, Y, Huang, T, Zheng, Y, et al. (2016) Folic acid supplementation and the risk of cardiovascular diseases: a meta‐analysis of randomized controlled trials. J Am Heart Assoc 5, e003768.
6. Hooshmand, B, Mangialasche, F, Kalpouzos, G, et al. (2016) Association of vitamin B12, folate, and sulfur amino acids with brain magnetic resonance imaging measures in older adults: a longitudinal population-based study. JAMA Psychiatry 73, 606–613.
7. Andrès, E, Loukili, NH, Noel, E, et al. (2004) Vitamin B12 (cobalamin) deficiency in elderly patients. CMAJ 171, 251–259.
8. Stabler, SP (2013) Clinical practice. Vitamin B12 deficiency. N Engl J Med 368, 149–160.
9. Pfeiffer, CM, Caudill, SP, Gunter, EW, et al. (2005) Biochemical indicators of B vitamin status in the US population after folic acid fortification: results from the National Health and Nutrition Examination Survey 1999–2000. Am J Clin Nutr 82, 442–450.
10. Morris, MS, Jacques, PF, Rosenberg, IH, et al. (2010) Circulating unmetabolized folic acid and 5-methyltetrahydrofolate in relation to anemia, macrocytosis, and cognitive test performance in American seniors. Am J Clin Nutr 91, 1733–1744.
11. Hennessy, A, Walton, J & Flynn, A (2013) The impact of voluntary food fortification on micronutrient intakes and status in European countries: a review. Proc Nutr Soc 72, 433–440.
12. Flynn, MA, Anderson, WA, Burke, SJ, et al. (2008) Folic acid food fortification: the Irish experience. Proc Nutr Soc 67, 381–389.
13. Kelly, F, Gibney, ER, Boilson, A, et al. (2016) Folic acid levels in some food staples in Ireland are on the decline: implications for passive folic acid intakes? J Public Health (Oxf) 38, 265–269.
14. Laird, E, Casey, MC, Ward, M, et al. (2016) Dairy intakes in older Irish adults and effects on vitamin micronutrient status: data from the TUDA study. J Nutr Health Aging, 1–8.
15. Hopkins, SM, Gibney, MJ, Nugent, AP, et al. (2015) Impact of voluntary fortification and supplement use on dietary intakes and biomarker status of folate and vitamin B-12 in Irish adults. Am J Clin Nutr 101, 1163–1172.
16. Kearney, PM, Cronin, H, O’Regan, C, et al. (2011) Cohort profile: the Irish Longitudinal Study on Ageing. Int J Epidemiol 40, 877–884.
17. Whelan, BJ & Savva, GM (2013) Design and methodology of the Irish Longitudinal Study on Ageing. J Am Geriatr Soc 61, Suppl. 2, S265–S268.
18. Lam, JR, Schneider, JL, Zhao, W, et al. (2013) Proton pump inhibitor and histamine 2 receptor antagonist use and Vitamin B12 deficiency. JAMA 310, 2435–2442.
19. Ham, AC, Enneman, AW, van Dijk, SC, et al. (2014) Associations between medication use and homocysteine levels in an older population, and potential mediation by vitamin B12 and folate: Data from the B-proof study. Drugs Aging 31, 611–621.
20. Molloy, AM & Scott, JM (1997) Microbiological assay for serum, plasma, and red cell folate using cryopreserved, microtiter plate method. Methods Enzymol 281, 43–53.
21. Kelleher, BP & Broin, SD (1991) Microbiological assay for vitamin B12 performed in 96-well microtitre plates. J Clin Pathol 44, 592–595.
22. Bailey, RL, Carmel, R, Green, R, et al. (2011) Monitoring of vitamin B-12 nutritional status in the united states by using plasma methylmalonic acid and serum vitamin B-12. Am J Clin Nutr 94, 552–561.
23. Arendt, JF & Nexo, E (2012) Cobalamin related parameters and disease patterns in patients with increased serum cobalamin levels. PLOS ONE 7, e45979.
24. Selhub, J, Morris, MS & Jacques, PF (2007) In vitamin B12 deficiency, higher serum folate is associated with increased total homocysteine and methylmalonic acid concentrations. Proc Natl Acad Sci U S A 104, 19995–20000.
25. Pfeiffer, CM, Sternberg, MR, Hamner, HC, et al. (2016) Applying inappropriate cutoffs leads to misinterpretation of folate status in the US population. Am J Clin Nutr 104, 1607–1615.
26. Herbert, V (1962) Experimental nutritional folate deficiency in man. Trans Assoc Am Physicians 75, 307.
27. Koike, H, Takahashi, M, Ohyama, K, et al. (2015) Clinicopathologic features of folate-deficiency neuropathy. Neurology 84, 1026–1033.
28. Vogel, T, Dali‐Youcef, N, Kaltenbach, G, et al. (2009) Homocysteine, vitamin B12, folate and cognitive functions: a systematic and critical review of the literature. Int J Clin Pract 63, 1061–1067.
29. Peng, Y, Dong, B & Wang, Z (2016) Serum folate concentrations and all-cause, cardiovascular disease and cancer mortality: a cohort study based on 1999–2010 National Health and Nutrition Examination Survey (NHANES). Int J Cardiol 219, 136–142.
30. Pfeiffer, CM, Caudill, SP, Gunter, EW, et al. (2005) Biochemical indicators of B vitamin status in the US population after folic acid fortification: results from the National Health and Nutrition Examination Survey 1999–2000. Am J Clin Nutr 82, 442–450.
31. Clarke, R, Grimley Evans, J, Schneede, J, et al. (2004) Vitamin B12 and folate deficiency in later life. Age Ageing 33, 34–41.
32. Clarke, R, Sherliker, P, Hin, H, et al. (2007) Detection of vitamin B12 deficiency in older people by measuring vitamin B12 or the active fraction of vitamin B12, holotranscobalamin. Clin Chem 53, 963–970.
33. Hannisdal, R, Ueland, PM, Eussen, SJ, et al. (2009) Analytical recovery of folate degradation products formed in human serum and plasma at room temperature. J Nutr 139, 1415–1418.
34. Hoey, L, McNulty, H, Askin, N, et al. (2007) Effect of a voluntary food fortification policy on folate, related B vitamin status, and homocysteine in healthy adults. Am J Clin Nutr 86, 1405–1413.
35. Pfeiffer, CM, Sternberg, MR, Schleicher, RL, et al. (2013) Dietary supplement use and smoking are important correlates of biomarkers of water-soluble vitamin status after adjusting for sociodemographic and lifestyle variables in a representative sample of US adults. J Nutr 143, 957S–965S.
36. Power, SE, Jeffery, IB, Ross, RP, et al. (2014) Food and Nutrient intake of Irish communitydwelling elderly subjects: who is at nutritional risk? J Nutr Health Aging 18, 561–572.
37. Baker, AH & Wardle, J (2003) Sex differences in fruit and vegetable intake in older adults. Appetite 40, 269–275.
38. Billson, H, Pryer, JA & Nichols, R (1999) Variation in fruit and vegetable consumption among adults in Britain. An analysis from the dietary and nutritional survey of British adults. Eur J Clin Nutr 53, 946–952.
39. Bird, JK, Ronnenberg, AG, Choi, SW, et al. (2015) Obesity is associated with increased red blood cell folate despite lower dietary intakes and serum concentrations. J Nutr 145, 79–86.
40. Leahy, S, Nolan, A, O’ Connell, J, et al. (2014) Obesity in An Ageing Society: Implications for Health, Physical Function and Health Service Utilisation. The Irish Longitudinal Study on Ageing. Dublin: Trinity College Dublin.
41. Walmsley, CM, Bates, CJ, Prentice, A, et al. (1999) Relationship between cigarette smoking and nutrient intakes and blood status indices of older people living in the UK: further analysis of data from the National Diet and Nutrition Survey of people aged 65 years and over, 1994/95. Public Health Nutr 2, 199–208.
42. Piyathilake, CJ, Macaluso, M, Hine, RJ, et al. (1994) Local and systemic effects of cigarette smoking on folate and vitamin B-12. Am J Clin Nutr 60, 559–566.
43. Shaheen, MA, Abdel Fattah, NS & El-Borhamy, MI (2006) Analysis of serum folate levels after narrow band UVB exposure. Egypt Dermatol Online J 2, 13.
44. Fukuwatari, T, Fujita, M & Shibata, K (2009) Effects of UVA irradiation on the concentration of folate in human blood. Biosci Biotechnol Biochem 72, 322–327.
45. Borradale, D, Isenring, E, Hacker, E, et al. (2014) Exposure to solar ultraviolet radiation is associated with a decreased folate status in women of childbearing age. J Photochem and Photobiol B 131, 90–95.
46. Lucock, M, Beckett, E, Martin, C, et al. (2016) UV‐associated decline in systemic folate: implications for human nutrigenetics, health, and evolutionary processes. Am J Hum Biol 29, e22929.
47. Rose, RF, Batchelor, RJ, Turner, D, et al. (2010) Narrowband ultraviolet phototherapy does not influence serum and red cell folate levels in patients with psoriasis. J Am Acad Dermatol 62, 710–711.
48. Cicarma, E, Mørk, C, Porojnicu, AC, et al.. (2010) Influence of narrowband UVB phototherapy on vitamin D and folate status. Exp Dermatol 19, 67–72.
49. Cabrera, S, Benavente, D, Alvo, M, et al. (2014) Vitamin B12 deficiency is associated with geographical latitude and solar radiation in the older population. J. Photochem Photobio B 140, 8–13.
50. Juzeniene, A & Nizauskaite, Z (2013) Photodegradation of cobalamins in aqueous solutions and in human blood. J Photochem Photobiol 122, 7–14.
51. Borradale, DC & Kimlin, MG (2012) Folate degradation due to ultraviolet radiation: possible implications for human health and nutrition. Nutr Rev 70, 414–422.
52. Paul, L & Selhub, J (2016) Interaction between excess folate and low vitamin B12 status. Mol Aspects Med 53, 43–47.
53. Pfeiffer, CM, Johnson, CL, Jain, RB, et al. (2007) Trends in blood folate and vitamin B-12 concentrations in the United States, 1988–2004. Am J Clin Nutr 86, 718–727.
54. Sweeney, MR, Staines, A, Daly, L, et al. (2009) Persistent circulating unmetabolised folic acid in a setting of liberal voluntary folic acid fortification. Implications for further mandatory fortification? BMC Public Health 9, 295.
55. van der Zwaluw, NL, Brouwer-Brolsma, EM, van de Rest, O, et al. (2016) Folate and vitamin B12-related biomarkers in relation to brain volumes. Nutrients 9, 8.
56. van Wijngaarden, JP, Swart, KM, Enneman, AW, et al. (2014) Effect of daily vitamin B-12 and folic acid supplementation on fracture incidence in elderly individuals with an elevated plasma homocysteine concentration: B-PROOF, a randomized controlled trial. Am J Clin Nutr 100, 1578–1586.
57. Smith, AD, Kim, YI & Refsum, H (2008) Is folic acid good for everyone? Am J Clin Nutr 87, 517–533.
58. Durda, K, Kąklewski, K, Gupta, S, et al. (2017) Serum folate concentration and the incidence of lung cancer. PLOS ONE 12, e0177441.
59. Bailey, RL, Fulgoni, VL, Taylor, CL, et al. (2017) Correspondence of folate dietary intake and biomarker data. Am J Clin Nutr 105, 1336–1343.
60. Valente, E, Scott, JM, Ueland, PM, et al. (2011) Diagnostic accuracy of holotranscobalamin, methylmalonic acid, serum cobalamin, and other indicators of tissue vitamin B12 status in the elderly. Clin Chem 57, 856–863.