Effect of dietary phytate and microbial phytase on mineral and trace element bioavailability- a literature review

Phytic acid (PA) is the main phosphorus storage compound in cereals, legumes and oil seeds. In human populations where phytate-rich cereals such as wheat, maize and rice are a staple food, phytate may lead to mineral and trace element deficiency. Zinc appears to be the trace element whose bioavailability is most influenced by PA. Furthermore, several studies in humans as well as in monogastric animals clearly indicate an inhibition of non-haem iron absorption at marginal iron supply due to phytic acid. In fact PA seems to be, at least partly, responsible for the low absorption efficiency and high incidence of iron deficiency anaemia evident in most developing countries, where largely vegetarian diets are consumed Microbial phytases have provided a realistic means of improving mineral availability from traditionally high-phytate diets. In fact it has been consistently shown that Aspergillus phytases significantly enhance the absorption of calcium, magnesium and zinc in pigs and rats. Furthermore there are a few studies in humans indicating an improvement of iron bioavailability due to microbial phytase.

Influence of habitual diet on antioxidant status: a study in a population of vegetarians and omnivores

Background: Antioxidant status can be used as a biomarker to assess chronic disease risk and diet can modulate antioxidant defence. Objective: To examine effects of vegetarian diet and variations in the habitual intakes of foods and nutrients on blood antioxidants. Subjects and Setting: Thirty-one vegetarians (including six vegans) and 58 omnivores, non-smokers, in Northern Ireland. Design: A diet history method was used to assess habitual diet. Antioxidant vitamins, carotenoids, uric acid, zinc-and ferric-reducing ability of plasma (FRAP) were measured in fasting plasma and activities of glutathione peroxidase (GPX), superoxide dismutase ( SOD) and glutathione S-transferase (GST) and level of reduced glutathione (GSH) were measured in erythrocytes. Results: Vegetarians had approximately 15% higher levels of plasma carotenoids compared with omnivores, including lutein (P <= 0.05), a-cryptoxanthin (P <= 0.05), lycopene (NS), alpha-carotene (NS) and beta-carotene (NS). The levels/activities of all other antioxidants measured were similar between vegetarians and omnivores. Total intake of fruits, vegetables and fruit juices was positively associated with plasma levels of several carotenoids and vitamin C. Intake of vegetables was positively associated with plasma lutein, alpha-cryptoxanthin, alpha-carotene and beta-carotene, whereas intake of fruits was positively associated with plasma beta-cryptoxanthin. Intake of tea and wine was positively associated with FRAP value, whereas intake of herbal tea associated positively with plasma vitamin C. Intakes of meat and fish were positively associated with plasma uric acid and FRAP value. Conclusions: The overall antioxidant status was similar between vegetarians and omnivores. Good correlations were found between intakes of carotenoids and their respective status in blood.

Carbon and nitrogen isotopic ratios of urine and faeces as novel nutritional biomarkers of meat and fish intake

Purpose Meat and fish consumption are associated with changes in the risk of chronic diseases. Intake is mainly assessed using self-reporting, as no true quantitative nutritional biomarker is available. The measurement of plasma fatty acids, often used as an alternative, is expensive and time-consuming. As meat and fish differ in their stable isotope ratios, δ13C and δ15N have been proposed as biomarkers. However, they have never been investigated in controlled human dietary intervention studies. Objective In a short-term feeding study, we investigated the suitability of δ13C and δ15N in blood, urine and faeces as biomarkers of meat and fish intake. Methods The dietary intervention study (n = 14) followed a randomised cross-over design with three eight-day dietary periods (meat, fish and half-meat–half-fish). In addition, 4 participants completed a vegetarian control period. At the end of each period, 24-h urine, fasting venous blood and faeces were collected and their δ13C and δ15N analysed. Results There was a significant difference between diets in isotope ratios in faeces and urine samples, but not in blood samples (Kruskal–Wallis test, p < 0.0001). In pairwise comparisons, δ13C and δ15N were significantly higher in urine and faecal samples following a fish diet when compared with all other diets, and significantly lower following a vegetarian diet. There was no significant difference in isotope ratio between meat and half-meat–half-fish diets for blood, urine or faecal samples. Conclusions The results of this study show that urinary and faecal δ13C and δ15N are suitable candidate biomarkers for short-term meat and fish intake.

Effect of processed and red meat on endogenous nitrosation and DNA damage

Haem in red meat (RM) stimulates the endogenous production of mutagenic nitroso compounds (NOC). Processed (nitrite-preserved red) meat additionally contains high concentrations of preformed NOC. In two studies, of a fresh RM versus a vegetarian (VEG) diet (six males and six females) and of a nitrite-preserved red meat (PM) versus a VEG diet (5 males and 11 females), we investigated whether processing of meat might increase colorectal cancer risk by stimulating nitrosation and DNA damage. Meat diets contained 420 g (males) or 366 g (females) meat/per day. Faecal homogenates from day 10 onwards were analysed for haem and NOC and asso- ciated supernatants for genotoxicity. Means are adjusted for differ- ences in male to female ratios between studies. Faecal NOC concentrations on VEG diets were low (2.6 and 3.5 mmol/g) but significantly higher on meat diets (PM 175 ± 19 nmol/g versus RM 185 ± 22 nmol/g; P 5 0.75). The RM diet resulted in a larger pro- portion of nitrosyl iron (RM 78% versus PM 54%; P < 0.0001) and less nitrosothiols (RM 12% versus PM 19%; P < 0.01) and other NOC (RM 10% versus PM 27%; P < 0.0001). There was no statis- tically significant difference in DNA breaks induced by faecal water (FW) following PM and RM diets (P 5 0.80). However, PM re- sulted in higher levels of oxidized pyrimidines (P < 0.05). Surpris- ingly, VEG diets resulted in significantly more FW-induced DNA strand breaks than the meat diets (P < 0.05), which needs to be clarified in further studies. Meats cured with nitrite have the same effect as fresh RM on endogenous nitrosation but show increased FW-induced oxidative DNA damage.