This was a longitudinal study utilising the Irish Longitudinal Study on Ageing (n 3849 aged ≥ 50 years) and investigated the relationship between blood plasma folate and B12 levels at baseline (wave 1) and incident depressive symptoms at 2 and 4 years (waves 2 and 3). A score ≥ 9 on the Center for Epidemiological Studies Depression Scale-8 at wave 2 or 3 was indicative of incident depressive symptoms. B12 status profiles (pmol/l) were defined as < 185, deficient low; 185 to < 258, low normal; > 258–601, normal and > 601 high. Folate status profiles (nmol/l) were defined as ≤ 10·0, deficient low; > 10–23·0, low normal; > 23·0–45·0, normal; >45·0, high. Logistic regression models were used to analyse the longitudinal associations. Both B12 and folate plasma concentrations were lower in the group with incident depressive symptoms v. non-depressed (folate: 21·4 v. 25·1 nmol/l; P = 0·0003; B12:315·7 v. 335·9 pmol/l; P = 0·0148). Regression models demonstrated that participants with deficient-low B12 status at baseline had a significantly higher likelihood of incident depression 4 years later (OR 1·51, 95 % CI 1·01, 2·27, P = 0·043). This finding remained robust after controlling for relevant covariates. No associations of folate status with incident depression were observed. Older adults with deficient-low B12 status had a 51 % increased likelihood of developing depressive symptoms over 4 years. The findings highlight the need to further explore the low-cost benefits of optimising vitamin B12 status for depression in older adults.

Eggs contain important compounds related to enhanced cognition, but it is not clear if egg consumption, as a whole, has a direct impact on memory decline in older adults. This study aimed to determine whether egg intake levels predict the rate of memory decline in healthy older adults after sociodemographic and dietary controls. We conducted a secondary analysis of data from 470 participants, age 50 and over, from the Biospsychosocial Religion and Health Study. Participants completed a food frequency questionnaire, which was used to calculate egg intake and divide participants into Low (<23 g/week, about half an egg), Intermediate (24–63 g/week, half to 1½ eggs) and High (≥63 g/week, about two or more eggs) tertiles. Participants were administered the California Verbal Learning Test – 2nd Edition (CVLT-II) Short Form in 2006–2007, and 294 of them were again tested in 2010–2011. Using linear mixed model analysis, no significant cross-sectional differences were observed in CVLT-II performance between egg intake levels after controlling for age, sex, race, education, body mass index, cardiovascular risk, depression and intake of meat, fish, dairy and fruits/vegetables. Longitudinally, the Intermediate egg group exhibited significantly slower rates of decline on the CVLT-II compared to the Low egg group. The High egg group also exhibited slower rates of decline, but not statistically significant. Thus, limited consumption of eggs (about 1 egg/week) was associated with slower memory decline in late life compared to consuming little to no eggs, but a dose-response effect was not clearly evident. This study may help explain discrepancies in previous research that did not control for other dietary intakes and risk factors.

Pregnancy and lactation deplete nutrients essential to the neurotransmission system. This may be one reason for the increased risk of depression during the perinatal period. The objective of the present review was to systematically review the literature and summarise evidence on whether blood nutrient levels influence the risk of perinatal depression. PubMed, EMBASE and CINAHL databases were searched for studies of any design. A total of twenty-four articles of different designs were included, representing 14 262 subjects. We extracted data on study population, depression prevalence, nutrients examined, deficiency prevalence, timing of assessment, reporting, analysis strategy and adjustment factors. In all, fourteen studies found associations of perinatal depression with lower levels of folate, vitamin D, Fe, Se, Zn, and fats and fatty acids, while two studies found associations between perinatal depression and higher nutrient levels, and eight studies found no evidence of an association. Only ten studies had low risk of bias. Given the methodological limitations and heterogeneity of study approaches and results, the evidence for a causal link between nutritional biomarkers and perinatal depression is still inconclusive. High-quality studies in deficient populations are needed.