Vitamin C plays a role in neuronal differentiation, maturation, myelin formation and modulation of the cholinergic, catecholinergic, and glutaminergic systems. This review evaluates the link between vitamin C status and cognitive performance, in both cognitively intact and impaired individuals. We searched the PUBMED, SCOPUS, SciSearch and the Cochrane Library from 1980 to January 2017, finding 50 studies, with randomised controlled trials (RCTs, n = 5), prospective (n = 24), cross-sectional (n = 17) and case-control (n = 4) studies. Of these, 36 studies were conducted in healthy participants and 14 on cognitively impaired individuals (including Alzheimer’s and dementia). Vitamin C status was measured using food frequency questionnaires or plasma vitamin C. Cognition was assessed using a variety of tests, mostly the Mini-Mental-State-Examination (MMSE). In summary, studies demonstrated higher mean vitamin C concentrations in the cognitively intact groups of participants compared to cognitively impaired groups. No correlation between vitamin C concentrations and MMSE cognitive function was apparent in the cognitively impaired individuals. The MMSE was not suitable to detect a variance in cognition in the healthy group. Analysis of the studies that used a variety of cognitive assessments in the cognitively intact was beyond the scope of this review; however, qualitative assessment revealed a potential association between plasma vitamin C concentrations and cognition. Due to a number of limitations in these studies, further research is needed, utilizing plasma vitamin C concentrations and sensitive cognitive assessments that are suitable for cognitively intact adults.

Gastrointestinal (GI) problems affect half of Western populations. Symptoms can vary from frequent reflux to irritable bowel syndrome. The Nutrition Care (NC) Gut Relief Formula contains a combination of herbs and nutrients including curcumin, Aloe vera, slippery elm, guar gum, pectin, peppermint oil, and glutamine shown to benefit the GI system. The 16-week pre-post study tested the hypothesis that the NC Gut Relief Formula would be tolerable and effective in improving GI symptoms and gut health in adults with digestive disorders. A total of 43 participants completed the study. After a control phase, participants took 5 g/d and then 10 g/d of the formula for 4 weeks. GI symptoms and GI health were assessed by a series of validated questionnaires, for example, Leeds Dyspepsia Questionnaire, Bristol Stool Chart, Birmingham IBS Symptom Questionnaire, and by intestinal permeability and gut microbiota profile. The NC Gut Relief Formula significantly improved the frequency and severity of upper and lower GI symptoms by 60%-80%, including indigestion, heartburn, nausea, constipation or diarrhea, abdominal pain, and troublesome flatulence, and significantly improved physical functioning, energy levels, mood, and sleep by 60%-80%. All participants with normal stool, 90% with hard stool, and 66% with soft stool recovered from intestinal permeability, evident by normal lactulose to mannitol ratios. The NC Gut Relief Formula generally improved microbial profile, with a marked increase in Lactobacillus, Clostridium, and Faecalibacterium prausnitzii. Almost half of the participants with upper GI symptoms taking proton pump inhibitors for heartburn no longer required proton pump inhibitors at the end of the study. A third of participants were able to reintroduce food triggers, such as fermentable oligosaccharides, disaccharides, monosaccharides, and polyols garlic, onion, and beans, or reflux-causing acidic/spicy foods, for example, citrus, tomato, and caffeine, in their diet after 3 months without symptom aggravation. The NC Gut Relief Formula significantly improved GI symptoms and associated quality of life over 3 months while reducing intestinal permeability, improving the microbial profile, reducing the need for reflux medication, and enabling the consumption of previous food triggers.

There is increasing evidence that sex differences in the brain may contribute to gender-related behavioral differences, including cognitive function. Literature has revealed gender dimorphisms in cognitive function between males and females. Additionally, several risk factors associated with cognitive decline depend on chronological age. It is well recognized that the process of aging is associated with a decline in cognitive ability and brain function. Various explanations may account for these gender-related cognitive differences and age-associated cognitive changes. Recent investigations have highlighted the importance of vitamin C in maintaining brain health and its association with cognitive function in both cognitively intact and impaired cohorts. The present review explores previous literature that has evaluated differences in plasma/brain vitamin C between genders and during aging. It then assesses whether these age and gender-related differences may affect the relationship between plasma/brain vitamin C and cognition. The purpose of this review was to examine the evidence for a link between plasma/brain vitamin C and cognition and the impact of gender and age on this relationship. Epidemiological studies have frequently shown higher vitamin C plasma concentrations in women. Similarly, aging has been systematically associated with reductions in plasma vitamin C levels. A range of animal studies has demonstrated potential gender and age-related differences in vitamin C brain distribution and utilization. The reviewed literature suggests that gender differences in plasma and brain vitamin C may potentially contribute to differences in gender-associated cognitive ability, particularly while females are pre-menopausal. Additionally, we can propose that age-associated differences in plasma and brain vitamin C may be potentially linked to age-associated cognitive differences, with older cohorts appearing more vulnerable to experience declines in plasma vitamin C concentrations alongside compromised vitamin C brain regulation. This review encourages future investigations to take into account both gender and age when assessing the link between plasma vitamin C concentrations and cognitive function. Further large scale investigations are required to assess whether differences in cognitive function between genders and age groups may be causally attributed to plasma vitamin C status and brain distribution and utilization.

A number of investigations have highlighted the importance of vitamin C in maintaining brain health. Biologically, vitamin C has exhibited roles in neuromodulation, neurodevelopment, vascular support, and neuroprotection. Vitamin C's contribution to cognitive function in both cognitively intact and impaired cohorts has previously been assessed, with little focus on gender variability. The present study explored the interaction between gender and plasma vitamin C on cognitive performance, and the effect of different amounts of plasma vitamin C (adequate/inadequate) on various cognitive tasks by gender. This retrospective analysis was conducted in healthy adults (n = 80, female = 52, male = 28, 24–96 y) with a range of blood plasma vitamin C concentrations. Cognitive assessments included the Swinburne University Computerized Cognitive Assessment Battery (SUCCAB) and 2 pen-and-paper tests, the Symbol Digits Modalities Test (SDMT) and the Hopkins Verbal Learning Test–Revised (HVLT-R). Food-frequency questionnaires were used to elucidate dietary consumption. After adjusting for a number of potential covariates such as age, number of prescribed medications and dose of vitamin C supplementation, results indicated a significant interaction (P < 0.001) between plasma vitamin C and gender on cognitive function, on both the computerized and pen-and-paper assessments. A novel finding was that the performance of males with inadequate plasma vitamin C was poorer on tasks involving components of memory (short/delayed), inhibition, and visual perception, whereas females presenting with inadequate vitamin C were more compromised on tasks involving psychomotor performance/motor speed. Additionally, females with adequate vitamin C concentrations exhibited higher performance than males on tasks involving recall, recognition, attention, and focus. Further larger-scale investigations are required to establish a cause-and-effect relation and to elucidate whether differences in cognitive function between genders may be attributed to plasma vitamin C status. This trial was registered at https://www.anzctr.org.au/Trial/Registration/TrialReview.aspx?id=369440&isReview=true as ACTRN12615001140549.

Vitamin C (ascorbic acid) is a water-soluble vitamin with an array of biological functions. A number of proposed factors contribute to the vitamin’s plasma bioavailability and ability to exert optimal functionality. The aim of this review was to systematically assess plasma vitamin C levels post-surgery compared with pre-surgery/the magnitude and time frame of potential changes in concentration. We searched the PUBMED, SCOPUS, SciSearch and the Cochrane Library databases between 1970 and April 2020 for relevant research papers. Prospective studies, control groups and true placebo groups derived from controlled trials that reported means and standard deviations of plasma vitamin C concentrations pre- and postoperatively were included into the meta-analysis. Data were grouped into short-term (≤7 d) and long-term (>7 d) postoperative follow-up. Twenty-three of thirty-one studies involving 642 patients included in the systematic review were suitable for meta-analysis. Pooled data from the meta-analysis revealed a mean depletion of plasma vitamin C concentration of −17·99 µmol/l (39 % depletion) (CI −22·81, −13·17) (trial arms = 25, n 565, P < 0·001) during the first postoperative week and −18·80 µmol/l (21 % depletion) (CI −25·04, −12·56) (trial arms = 6, n 166, P < 0·001) 2–3 months postoperatively. Subgroup analyses revealed that these depletions occurred following different types of surgery; however, high heterogeneity was observed amongst trials assessing concentration change during the first postoperative week. Overall, our results warrant larger, long-term investigations of changes in postoperative plasma vitamin C concentrations and their potential effects on clinical symptomology.