As the number of older people is growing rapidly worldwide and the fact that elderly people are also apparently living longer, dementia, the most common cause of cognitive impairment is getting to be a greater public health problem. Nutrition plays a role in the ageing process, but there is still a lack of knowledge about nutrition-related risk factors in cognitive impairment. Research in this area has been intensive during the last decade, and results indicate that subclinical deficiency in essential nutrients (antioxidants such as vitamins C, E and β-carotene, vitamin B12, vitamin B6, folate) and nutrition-related disorders, as hypercholesterolaemia, hypertriacylglycerolaemia, hypertension, and diabetes could be some of the nutrition-related risk factors, which can be present for a long time before cognitive impairment becomes evident. Large-scale clinical trials in high-risk populations are needed to determine whether lowering blood homocysteine levels reduces the risk of cognitive impairment and may delay the clinical onset of dementia and perhaps of Alzheimer's disease. A curative treatment of cognitive impairment, especially Alzheimer's disease, is currently impossible. Actual drug therapy, if started early enough, may slow down the progression of the disease. Longitudinal studies are required in order to establish the possible link of nutrient intake – nutritional status with cognitive impairment, and if it is possible, in fact, to inhibit or delay the onset of dementia.

Studies of Fe absorption in pregnancy often make unfounded assumptions of erythrocyte incorporation. Therefore, we measured the absorption and utilisation of Fe during early and late pregnancy by the erythrocyte incorporation of two stable isotopes. 8·5 mg 57Fe (oral) and 0·5 mg 58Fe (intravenous) were given to five non-pregnant women, to five women in early gestation (12 weeks) and five women in late gestation (36 weeks). The stable isotope ratios in whole blood 14 d later were measured by MS. Together with estimation of body Fe mass, this enabled the calculation of Fe absorption and erythrocyte incorporation. In non-pregnant women, Fe absorption averaged 20·3 (range 10·2–34·3) %. It was not significantly different in early pregnancy (11·8 (range, 4·4–24·8) %), but during late pregnancy Fe absorption increased to 59·0 (range 38·2–77·2) %. All non-pregnant and early-pregnancy subjects had normal Fe status, but two women in late pregnancy had evidence of Fe insufficiency. During early and late pregnancy, mean erythrocyte incorporation was 63·4 (SD 12·1) % AND 71·0 (sd 10·4) % respectively, significantly reduced (P=0·003) compared with non-pregnant subjects (90·1 (sd 6·0) %). Decreased erythrocyte incorporation of absorbed Fe in early pregnancy is compatible with reduced Fe demand and low oral absorption. However, during late pregnancy decreased erythrocyte incorporation associated with high absorption and Fe insufficiency is different from the high erythrocyte incorporation which occurs in non-pregnant Fe-deficient women. This suggests that part of the aetiology of Fe deficiency during pregnancy may be the reduction of Fe utilisation.

The aim of the present work was to estimate volatile fatty acid (VFA) production rate in the rumen of sheep fed two levels of intake using both a tracer (TM; by isotope dilution) and a non-tracer method (NTM; by supplementary infusion) in steady-state conditions. Six wethers received a diet containing 700 g lucerne hay and 300 g ground maize/kg in eight equal meals at 3 h intervals per d. The diet (9·8 MJ metabolizable energy (ME)/kg DM) was offered at 90 % ad libitum consumption (high intake, HI) or 45 % ad libitum consumption (low intake, LI) in a 2×2 crossover design. Each sheep received five intrarumen VFA solutions infused continuously for 24 h at rates of 250 ml and 165 ml/h for the HI and LI respectively. The first infusion, considered as a control treatment (Con), consisted of a solution of [1-13C]propionate (7 mmol/d). The four other solutions were isoenergetic (1·9 MJ ME/kg DM intake) mixtures of unlabelled propionate (C3) and butyrate (C4) at different levels: 0·90 mol C4/kg DM intake; 0·60 mol C4+0·45 mol C3/kg DM intake; 0·30 mol C4+0·90 mol C3/kg DM intake; 1·35 mol C3/kg DM intake. The VFA infusions did not affect rumen fermentation of the basal diet (pH, osmotic pressure, protozoa numbers), and comparable DM digestibility of the diet among the different treatments was observed. Both estimation methods demonstrated a similar increase (1·7-fold) in the rumen VFA production rate of sheep fed at intakes varying between 0·9 to 1·7 times maintenance. Irrespective of the intake level, the rumen production rate of individual VFA was on average 1·5-fold higher when estimated by the TM compared with the NTM. Rumen VFA production rates estimated by the NTM and TM represented 80 % and 120 % ME intake respectively. The difference between NTM and TM estimates seems likely to be caused mainly by overestimation of the VFA production rates by the TM.

Prebiotics are non-digestible food ingredients that target selected groups of the human colonic microflora, thus having the ability to alter the composition towards a more ‘beneficial’ community, i.e. selectively increasing populations of bifidobacteria and/or lactobacilli. In the present study the prebiotic potential of partially hydrolysed guar gum (PHGG) and fructo-oligosaccharides (FOS) in a biscuit was assessed in human volunteers. Fluorescent in situ hybridization using oligonucleotide probes targeting Bacteroides spp., Bifidobacterium spp., Clostridium spp. and Lactobacillus–Enterococcus spp. were used for the bacteriology and total bacteria were enumerated using the fluorescent stain 4′,6-diamidino-2-phenylindole. Thirty-one volunteers consumed daily either three experimental biscuits (providing a total (g/d) of 6·6 FOS and 3·4 PHGG) or three placebo biscuits for two 21-d crossover periods. Bifidobacteria significantly increased in number on ingestion of the experimental biscuits compared with pre-treatment and placebo population levels. Bifidobacterial numbers returned to pretreatment levels within 7 d of the cessation of intake of experimental biscuits. A correlation was observed between the initial faecal bifidobacterial numbers and the magnitude of bifidogenesis, with volunteers who possessed low initial population levels of bifidobacteria experiencing the greatest increase in bifidogenesis. No changes were observed in the other bacterial groups monitored during the trial. Thus, the prebiotic nature of FOS and PHGG was maintained in a final food product as evidenced from the selective increase in bifidobacterial numbers.

The effects of two monounsaturated fatty acid (MUFA)-rich diets, containing virgin olive oil (OO) and high-oleic-acid sunflower oil (HOSO), on development of vascular response from isolated thoracic rat aorta and lipid composition and fatty acid composition were studied and compared with samples from rats fed on a control diet. Dietary MUFA oils were fed for 6 weeks to spontaneously hypertensive (SHR) and Wistar–Kyoto (WKY) rats from 4 weeks of age. The maximum contraction of aortic ring preparations in response to phenylephrine (10-6 M) WAS SIGNIFICANTLY DECREASED IN SHR RATS FED WITH OO (0·81 (sem 0·05) v. 1·18 (sem 0·09) g, P<0·01) and treatment with HOSO did not alter the phenylephrine-induced contractions. The relaxant responses to acetylcholine (10-5 m) were significantly enhanced (30·03 (sem 0·70) v. 18·47 (sem 0·28) %, P<0·001) in the rings from SHR rats treated with OO, and were more pronounced than in WKY rats (P<0·05). In the same way, OO attenuated the dose–response curves induced by phenylephrine (10-8–10-5 m) from SHR rats, accompained with a slower contraction. These results suggest that only the chronic feeding of OO diet was able to attenuate the vascular response of rat aorta. In addition, an increase in phospholipid content (186·7 (sd 3·2) v. 159·1 (sd 11·3) g/kg, P<0·01) and changes in the fatty acid composition of aorta (mainly a decrease in arachidonic acid) could contribute to improving endothelial function. Therefore, the effects can not be attributed exclusively to the content of MUFA (mainly oleic acid). Other components of OO, such as polyphenols, not present in HOSO, may help to explain the vascular protective effect of OO consumption.

A dynamic model was developed to assess insulin sensitivity and pancreatic response in lactating dairy cows. The model is based on a simultaneous analysis of insulin and glucose intravenous tolerance tests. It comprises five compartments corresponding to insulin in portal–hepatic plasma, and insulin or glucose in both systemic plasma and in interstitial fluid. Insulin secretion rate is a sigmoidal function of glucose in plasma. Insulin is cleared from hepatic plasma and from the interstitial fluid. The glucose entry rate is constant and glucose utilization rate is a sigmoidal function of insulin in the interstitial fluid. Six parameters were estimated: two for insulin secretion rate, two for insulin clearance, one for glucose entry rate and one for glucose utilization rate. After integration of the functions, the model yielded a relative estimate of the quantities of insulin secreted and cleared, as well as the glucose entering and utilized during each test. Using an experimental dataset composed of ten pairs of tolerance tests, the explained variations for plasma insulin and glucose concentrations were 96·0 and 98·3 % and standard errors of estimates were 0·032 nmol/l and 0·14 mmol/l respectively. Except in the early stages after injection, residual errors were low. A Jackknife analysis showed that the estimated parameters exhibited low statistical bias. This model simplifies the interpretation of both tests through a simulation based on six common parameters. Compared to a classical analysis of tolerance tests, it may improve the analysis of modifications in the key functions regulating glucose homeostasis in ruminants.

The aim of the present study was to evaluate the effect of diets rich in n-6 and n-3 fatty acids on adipose tissue metabolism. Starting at weaning, male Wistar rats were fed ad libitum, for 8 weeks with one of the following diets: C, rat chow; S, rat chow containing 15 % (w/w) soyabean oil; F, rat chow containing 15 % (w/w) fish oil; SF, rat chow containing 15 % (w/w) soyabean and fish oil (5:1, w/w). Casein was added to the fat diets to achieve the same 20 % (w/w) protein content as in the control chow. Food intake and body weight were measured weekly. The rats were killed by decapitation and the retroperitoneal (RET) and epididymal (EPI) white adipose tissues were removed and weighed. Tissue lipid and protein content, in vivo lipogenesis rate, uptake of diet-derived lipids, in vitro lipolytic rate, adipocyte area, lipoprotein lipase, ATP citrate lyase, and malic enzyme activities were evaluated. Carcass lipid and protein contents were also measured. Energy intake was reduced while carcass lipid content was increased in the three fat-fed groups. However, carcass protein and body weight gains were elevated only with diets F and SF. Lipolysis rate was diminished by diets F and SF, while the uptake of diet-derived lipids was elevated by the diet S in both RET and EPI tissues. These metabolic alterations may have contributed to the increase in in vivo lipogenesis rate in the presence of decreased ATP citrate lyase and malic enzyme activities induced by the three lipid diets. These results indicate that enrichment of the diet with polyunsaturated fatty acids causes changes in adipose tissue metabolism that favour fat deposition. Different metabolic pathways were preferentially affected by each type of fatty acid used.

Red kidney beans (Phaseolus vulgaris) processed to differ in distribution and content of indigestible carbohydrates were used to study hindgut fermentability and production of short-chain fatty acids (SCFA). Bean flours with low or high content of resistant starch (RS), mainly raw and physically-inaccessible starch, were obtained by milling the beans before or after boiling. Flours containing retrograded starch and with a high or low content of oligosaccharides were prepared by autoclaving followed by freeze-drying with or without the boiling water. Six diets were prepared from these flours yielding a total concentration of indigestible carbohydrates of 90 or 120 g/kg (dry weight basis). The total fermentability of the indigestible carbohydrates was high with all diets (80–87 %). Raw and physically-inaccessible starch was more readily fermented than retrograded starch (97–99 % v. 86–95 %; P<0·05). Non-starch glucans were fermented to a lesser extent than RS, but the fermentability was higher (P<0·05) in the case of autoclaved (50–54 %) than boiled beans (37–41 %). The distribution between acetic, propionic and butyric acid in the caecum was similar for all diets, with a comparatively high percentage of butyric acid (approximately 18). However, with diets containing the high amounts of RS, the butyric acid concentration was significantly higher in the distal colon than in the proximal colon (P=0·009 and P=0·047 for the high- and low-level diets respectively), whereas it remained constant, or decreased along the colon in the case of the other diets. Furthermore, the two diets richest in RS also promoted the highest percentages of butyric acid in the distal colon (24 and 17 v. 12 and 12–16 for the high- and low-level diets respectively).

We measured daily dietary Cr intake in southern Spain by sampling duplicate diets for seven consecutive days in different population groups. Cr was determined by electrothermal atomization–atomic absorption spectrometry. The samples were mineralized in a digestion block with HNO3, HClO4 and V2O5. A total of 161 duplicate diets from twenty-three subjects were analysed, and mean levels of Cr intake ranged from 9·39 to 205·16 μg/d. Mean Cr intake (100 μg/d) was similar to levels found for most other countries, and was within the range recommended by the National Research Council for a safe and adequate daily intake (50–200 μg/d). Chromium intake correlated significantly with energy, protein and carbohydrate intake, and with the daily intake of Zn, Fe, Mg, K, Na, Ca and nicotinic acid in the diets analysed.

High intake of fish has been associated with reduced risk of CHD. The high content of n-3 polyunsaturated fatty acids (PUFA) in fish has been suggested to be a protective factor. In addition, fish is the entirely dominating source of methylmercury for the general population, and the concentration of Hg in erythrocytes (Ery-Hg) is often used as an index of fish consumption. Our aim was to study the relationships between a first-ever myocardial infarction, Ery-Hg, activity of gluthathione peroxidase in erythrocytes (Ery-GSH-Px) and plasma concentration of the n-3 PUFA eicosapentaenoic and docosahexaenoic acids (P-PUFA). In a population-based prospective nested case–control study within Northern Sweden seventy-eight cases of a first-ever myocardial infarction were compared with 156 controls with respect to Ery-Hg, P-PUFA and Ery-GSH-Px. Both Ery-Hg and P-PUFA, but not Ery-GSH-Px, were significantly (P<0·0001) higher in subjects reporting high fish intake (at least one meal per week) than in those with lower intake. This finding suggests that Ery-Hg and P-PUFA reflect previous long-term fish intake. Low risk of myocardial infarction was associated with high Ery-Hg or high P-PUFA. In a multivariate model the risk of myocardial infarction was further reduced in subjects with both high Ery-Hg and high P-PUFA (odds ratio 0·16, 95 % CI 0·04, 0·65). In conclusion, there is a strong inverse association between the risk of a first myocardial infarction and the biomarkers of fish intake, Ery-Hg and P-PUFA, and this association is independent of traditional risk factors.

The aim of the present cross-sectional study was to examine the agreement and disagreement between a 7 d diet diary (7DD) and a self-administered machine-readable food-frequency questionnaire (FFQ) asking about diet in the previous year, and to validate both methods with biomarkers of nutrient intake. The subjects were an age- and employment-grade-stratified random subsample of London-based civil servants (457 men and 403 women), aged 39–61 years, who completed both a 7DD and a FFQ at phase 3 follow-up (1991–1993) of the Whitehall II study. Mean daily intakes of dietary energy, total fat, saturated, monounsaturated and polyunsaturated fatty acids, linoleic acid, total carbohydrate excluding fibre, sugars, starch, dietary fibre, protein, vitamin C, vitamin E (as α-tocopherol equivalents), folate, carotenes (as total β-carotene activity), Fe, Ca, Mg, K and alcohol were measured. Serum cholesteryl ester fatty acids (CEFA), plasma α-tocopherol and β-carotene were also measured as biomarkers. Estimates of mean energy intake from the two methods were similar in men, and some 10 % higher according to the FFQ in women. Compared with the 7DD, the FFQ tended to overestimate plant-derived micronutrient intakes (carotenes from FFQ v. 7DD men 2713 (SD 1455) V. 2180 (sd 1188) μg/d, women 3100 (sd 1656) v. 2221 (sd 1180) μg/d, both differences P<0·0001) and to underestimate fat intake. Against plasma β-carotene/cholesterol, carotene intake was as well estimated by the FFQ as the 7DD (Spearman rank correlations, men 0·32 v. 0·30, women 0·27 v. 0·22, all P≤0·0001, energy-adjusted data). Ranking of participants by other nutrient intakes tended to be of the same order according to the two dietary methods, e.g. rank correlations for CEFA linoleic acid against FFQ and 7DD estimates respectively, men 0·38 v. 0·41, women 0·53 v. 0·62, all P≤0·0001, energy-adjusted % fat). For α-tocopherol there were no correlations between plasma level and estimated intakes by either dietary method. Quartile agreement for energy-adjusted nutrient intakes between the two self-report methods was in the range 37–50 % for men and 32–44 % for women, and for alcohol, 57 % in both sexes. Disagreement (misclassification into extreme quartiles of intake) was in the range 0–6 % for both sexes. The dietary methods yielded similar prevalences (about 34 %) of low energy reporters. The two methods show satisfactory agreement, together with an expected level of systematic differences, in their estimates of nutrient intake. Against the available biomarkers, the machine-readable FFQ performed well in comparison with the manually coded 7DD in this study population. For both methods, regression-based adjustment of nutrient intake to mean dietary energy intake by gender appears on balance to be the optimal approach to data presentation and analysis, in view of the complex problem of low energy reporting.

Soya products contain high levels of the isoflavones genistein and daidzein, and their glucosides, and may lower the risk of cardiovascular disease, osteoporosis and cancer. The present cross-sectional study investigated plasma concentrations of daidzein and genistein and their correlations with dietary soya consumption in four groups of twenty premenopausal British women. The women were selected from the Oxford arm of the European Prospective Investigation into Cancer and Nutrition using data from food-frequency questionnaires (FFQ) to guarantee a wide variation in soya consumption, and to investigate the utility of the question related to soya milk consumption compared with the utility of the question related to other soya foods. Dietary intakes of isoflavones were additionally assessed by 7 d food diaries. Plasma concentrations of daidzein and genistein were measured by time-resolved fluoroimmunoassay. Geometric mean plasma concentrations (nmol/l) were for the four groups, which were based on increasing soya intake, 4·9, 8·4, 39·2 and 132 for daidzein and 14·3, 16·5, 119 and 378 for genistein. The Spearman correlation coefficients for plasma isoflavone concentrations with estimated dietary intakes were between 0·66 and 0·80 for the diary-based estimates and between 0·24 and 0·74 for the FFQ-based estimates. The correlations for soya milk intakes were clearly higher than the correlations for intakes of other soya foods. We conclude that both the food diary and the FFQ estimate dietary soya isoflavone intakes sufficiently well to use them in epidemiological studies, and that plasma concentrations of daidzein and genistein in Western women who consumed soya products as a part of their regular diet were close to those in Asian populations.