Potential of dietary polyphenols for protection from age-related decline and neurodegeneration: a role for gut microbiota?

Many epidemiological studies have shown the beneficial effects of a largely plant-based diet, and the strong association between the consumption of a Mediterranean-type diet with healthy aging including a lower risk of cognitive decline. The Mediterranean diet is characterized by a high intake of olive oil, fruits and vegetables and is rich in dietary fiber and polyphenols - both of which have been postulated to act as important mediators of these benefits. Polyphenols are large molecules produced by plants to protect them from environmental threats and injury. When ingested by humans, as little as 5% of these molecules are absorbed in the small intestine with the majority metabolized by the gut microbiota into absorbable simple phenolic compounds. Flavan-3-ols, a type of flavonoid, contained in grapes, berries, pome fruits, tea, and cocoa have been associated with many beneficial effects on several risk factors for cardiovascular disease, cognitive function and brain regions involved in memory formation. Both preclinical and clinical studies suggest that these brain and heart benefits can be attributed to endothelial vascular effects and anti-inflammatory properties among others. More recently the gut microbiota has emerged as a potential modulator of the aging brain and intriguingly polyphenols have been shown to alter microbiota composition and be metabolized by different microbial species. However, there is a need for well controlled studies in large populations to identify predictors of response, particularly given the vast inter-individual variation of human gut microbiota.

Bioavailability of vitamin D biofortified pork meat: results of an acute human crossover study in healthy adults.

Vitamin D intakes are concerningly low. Food-based strategies are urgently warranted to increase vitamin D intakes and subsequently improve 25-hydroxyvitamin D (25(OH)D) concentrations. This acute randomised three-way crossover study investigated the efficacy of vitamin D biofortified pork derived from pigs exposed to UVB light to increase serum 25(OH)D3 concentrations, compared to a dose-matched vitamin D3 supplement and control pork in adults (n = 14). Blood samples were obtained at baseline and then 1.5, 3, 6, 9 and 24 h postprandially. There was a significant effect of time (p < 0.01) and a significant treatment*time interaction (p < 0.05). UV pork and supplement significantly increased within-group serum 25(OH)D3 concentrations over timepoints (p < 0.05) (max. change 0.9 nmol/L (2.2%) UV pork, 1.5 nmol/L (3.5%) supplement, 0.7 nmol/L (1.9%) control). Vitamin D biofortified pork modestly increased 25(OH)D3 concentrations and produced a similar response pattern as a dose-matched vitamin D supplement, but biofortification protocols should be further optimised to ensure differentiation from standard pork.

Improving vitamin D content in pork meat by UVB biofortification.

Vitamin D deficiency is prevalent worldwide and identification of alternative food-based strategies are urgently warranted. In two studies, 12-week old crossbred pigs (Duroc x (Large White x Landrace)) were exposed daily to narrowband UVB radiation for ∼10 weeks or control (no UVB exposure) until slaughter. In Study 1 (n = 48), pigs were exposed to UVB for 2 min and in Study 2 (n = 20), this duration was tripled to 6 min. All pigs were fed the maximum permitted 2000 IU vitamin D3/kg feed. Loin meat was cooked prior to vitamin D LC-MS/MS analysis. In Study 1, pork loin vitamin D3 did not differ between groups. Study 2 provided longer UVB exposure time and resulted in significantly higher loin vitamin D3 (11.97 vs. 6.03 µg/kg), 25(OH)D3 (2.09 vs. 1.65 µg/kg) and total vitamin D activity (22.88 vs. 14.50 µg/kg) concentrations, compared to control (P < 0.05). Pigs remained healthy during both studies and developed no signs of erythema. Biofortification by UVB radiation provides an effective strategy to further safely increase the naturally occurring vitamin D content of pork loin, alongside feed supplementation.

Impact of cooking on vitamin D3 and 25(OH)D3 content of pork products.

Little is known regarding the impact of cooking on vitamin D content in pork, despite meat being a major contributor to vitamin D intakes. This paper investigated the effect of household cooking (pan-fry/roast/grill/sous-vide/sauté), on the vitamin D3 and 25-hydroxyvitamin D3 (25(OH)D3) concentration/retention in pork loin, mince and sausages. We hypothesised that vitamin D concentrations would be higher in cooked vs raw pork, and retention would differ between products. Cooking significantly increased vitamin D3 (+49 %) and 25(OH)D3 (+33 %) concentrations. All cooked loin vitamin D3 concentrations were significantly lower than mince/sausage. Vitamin D3 retention was > 100 % for all samples (102-135 %), except sauté mince (99 %) which still did not differ significantly from 100 % retention. Sous-vide cooking resulted in the highest vitamin D3 retention (135 %). Likely owing to water/fat loss, household cooking of pork results in favourable retention of vitamin D3 and 25(OH)D3. The type of pork product has greater influence than cooking method.

Anti-cancer properties of phenolics from apple waste on colon carcinogenesis in vitro.

Colorectal cancer is one of the most common cancers in Western countries. The World Health Organisation identifies diet as a critical risk factor in the development and progression of this disease and the protective role of high levels of fruit and vegetable consumption. Several studies have shown that apples contain several phenolic compounds that are potent anti-oxidants in humans. However, little is known about other beneficial properties of apple phenolics in cancer. We have used the HT29, HT115 and CaCo-2 cell lines as in vitro models to examine the effect of apple phenolics (0.01-0.1% apple extract) on key stages of colorectal carcinogenesis, namely; DNA damage (Comet assay), colonic barrier function (TER assay), cell cycle progression (DNA content assay) and invasion (Matrigel assay). Our results indicate that a crude extract of apple phenolics can protect against DNA damage, improve barrier function and inhibit invasion (p<0.05). The anti-invasive effects of the extract were enhanced with twenty-four hour pretreatment of cells (p<0.05). We have shown that a crude apple extract from waste, rich in phenolic compounds, beneficially influences key stages of carcinogenesis in colon cells in vitro.

Diet and cancer: assessing the risk.

Globally, colorectal cancer (CRC) is a leading cause of mortality from malignant disease. Case-control and cohort studies provide strong support for a role of diet in the aetiology of CRC. However to establish causal relationships and to identify more precisely the dietary components involved, intervention studies in human subjects are required. Cancer is an impractical endpoint in terms of numbers, cost, study duration and ethical considerations. Consequently, intermediate biomarkers of the disease are required. This review aims to provide an overview of the intermediate endpoints available for the study of CRC, particularly non-invasive faecal biomarkers. Examples of their use in dietary intervention studies are given.