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Biomedical subjects

T A Sanders

Publications and source records attributed to T A Sanders.

At least 37 records · Page 2Linked to original sources
PubMed1999

Essential fatty acid requirements of vegetarians in pregnancy, lactation, and infancy.

Long-chain polyunsaturated fatty acids (LCPUFAs) derived from linoleic (18:2n-6) and alpha-linolenic (18:3n-3) acids are required for the normal development of the retina and central nervous system, but the extent to which they can be synthesized from the parent fatty acids is debated. Consuming LCPUFAs markedly increases their proportions in tissue lipids compared with their parent fatty acids. Thus, it has been argued that LCPUFAs must be supplied in the diet. LCPUFAs are generally absent from plant foods, thus it is important find out how essential fatty acid requirements are met by vegetarians. A developing fetus obtains LCPUFAs via selective uptake from its mother's plasma and LCPUFAs are present in the breast milk of vegetarians. There is no evidence that the capacity to synthesize LCPUFAs is limited in vegetarians. However, there are greater proportions of n-6 LCPUFAs and lower proportions of n-3 LCPUFAs in vegetarians compared with omnivores. This difference is probably a consequence of the selection of foods by vegetarians with high amounts of linoleic acid. Although lower concentrations of docosahexaenoic acid (22:6n-3; DHA) have been observed in blood and artery phospholipids of infants of vegetarians, it is uncertain whether their brain lipids contain lower proportions of DHA than do those of infants of omnivores. On the basis of experiments in primates that showed altered visual function with a high ratio of linoleic acid to alpha-linolenic acid, it would be prudent to recommend diets with a ratio between 4:1 and 10:1 in vegetarians and that excessive intakes of linoleic acid be avoided.

Central Nervous System↗
PubMed1998

Faecal pH, bile acid and sterol concentrations in premenopausal Indian and white vegetarians compared with white omnivores.

Faecal bulk, pH, water content, the concentrations of neutral sterols and bile acids and dietary intakes were measured in twenty-two Indian vegetarian, twenty-two white omnivorous and eighteen white vegetarian premenopausal women. Faecal bulk and water content were greater and pH lower in the Indian vegetarians. Total faecal animal sterol and coprostanol concentrations expressed on a dry-weight basis were lower in the vegetarians compared with the omnivores. The faecal sterol concentrations were correlated with dietary cholesterol intake. Primary bile acids were detected in six Indian vegetarians, two white vegetarians and two white omnivores; secondary bile acids were detected in all the white omnivores and vegetarian subjects but not in two of the Indian vegetarians. Total faecal free bile acid and conjugated bile acid concentrations were lower in the white vegetarians compared with the omnivores. Faecal lithocholic acid concentrations were lower in both Indian and white vegetarians. The lithocholic: deoxycholic acid ratio and coprostanol: total animal sterols ratio were significantly lower in the Indian vegetarians compared with the omnivores. Both ratios were positively correlated with faecal pH. Stepwise multiple regression analyses were undertaken in order to identify which nutrients influenced faecal pH, lithocholic and deoxycholic acid concentrations. The intakes of starch and dietary fibre were negatively associated with faecal concentrations of lithocholic and deoxycholic acid. Starch intake alone was negatively associated with faecal pH. The results of this study confirm that diets high in dietary fibre decrease faecal bile acid concentrations and suggest that the complex carbohydrates present in Indian vegetarian diets influence faecal pH and inhibit the degradation of faecal steroids.

Adult↗
PubMed1998

Postprandial effects of an oleic acid-rich oil compared with butter on clotting factor VII and fibrinolysis in healthy men.

BACKGROUND: Factor VII coagulant activity (FVII:c) is associated with an increased risk of fatal ischemic heart disease, is correlated with plasma triacylglycerol concentration, and increases after a meal rich in long-chain fatty acids. OBJECTIVE: We planned to compare effects of meals rich in oleate and butter fat with those of a low-fat meal on FVII:c and fibrinolytic activity. DESIGN: A crossover design was used to compare the postprandial effects on coagulant and fibrinolytic activities in 12 men of 3 high-fat (95 g) meals--high oleate, butter, and oleate + medium-chain triacylglycerols (oleate+MCT)--with an isoenergetic low-fat meal (18 g MCT). The oleate+MCT blend was used to mimic the ratio of long-chain to shorter-chain fatty acids in butter. RESULTS: Neither the amount nor type of fat consumed influenced plasminogen activator inhibitor 1 or t-plasminogen activator activities or D-dimer concentration. FVII:c increased by 12.5% (95% CI: 4.6%, 20.5%) after the high-fat meals at 3 h and by 6.7% (95% CI: 1.6%, 11.7%) at 7 h and changed 7 h after the low-fat meal by -14.3% (95% CI: -3.3%, -25.4%). The responses to the high-fat meals did not differ. Measurements of activated FVII (FVIIa), FVII zymogen, and activated FXII (FXIIa) concentrations made after the low-fat and high-oleate meals showed a significant increase in FVIIa only after the high-oleate meal. CONCLUSIONS: The results of this study confirm that FVII:c falls after a low-fat meal and suggests that postprandial activation of FVII occurs rapidly after a fat-rich meal without involving an increase in FXIIa.

Adolescent↗
PubMed1997

Influence of n-6 versus n-3 polyunsaturated fatty acids in diets low in saturated fatty acids on plasma lipoproteins and hemostatic factors.

Modification of dietary fat composition may influence hemostatic variables, which are associated with increased risk of coronary heart disease (CHD). To address this question, we performed a controlled feeding study on 26 healthy male nonsmoking subjects with diets of differing fat composition. For the first 3 weeks, the subjects were given a diet calculated to supply 30% energy as total fat: 8% as monounsaturated, 4% as polyunsaturated, and 16% energy as saturated fatty acids, respectively (saturated diet). This was followed immediately by two diets taken in random order, each of 3-week duration and separated by an 8-week washout period on the subject's usual diet. Both diets were calculated to supply 30% of energy as fat: 14% monounsaturated, 6% as polyunsaturated, and 8% energy as saturated fatty acids. They both provided 5 g (approximately 1.7% energy) more of polyunsaturated fatty acids than the saturated fat diet; in one diet as long-chain n-3 fatty acids (n-3 diet) and in the other as linoleic acid (n-6 diet). Fasting plasma lipids, lipoproteins, and hemostatic factors were measured on the final 3 days of each dietary period. In a subset of 9 subjects the postprandial responses to a test meal were studied on the penultimate day of each period, each meal having the fat composition of its parent diet. On the n-3 diet compared with the n-6 diet, plasma triglyceride, HDL3 cholesterol, apoprotein AII, and fibrinogen concentrations were lower and HDL2 cholesterol concentration was higher (P = .0001, P = .003, P = .0001, P = .004, and P = .001, respectively). On both the n-3 and n-6 diets compared with the saturated diet, fasting plasma total and LDL cholesterol, apoprotein B, beta-thromboglobulin concentrations, and platelet counts were lower (P < .0001, P < .0001, P < .001, P < .01, and P < .05 respectively) and plasma Lp(a) and von Willebrand factor concentrations were higher (P = .02 and P < .01, respectively). Fasting factor VII coagulant activity (VIIc) was increased and apoprotein AI concentration reduced following the n-3 diet (P = .004 and P = .01, respectively) compared with the saturated diet. Plasma fibrinogen concentration was significantly greater following the n-6 diet than on the saturated diet (P = .02). Postprandially, plasma triglyceridemia was greater on the n-6 diet and lowest on the n-3 diet (P < .001) with the saturated diet being intermediate. Plasma VIIc was increased at 4 hours following the standardized test meals on the n-3 and n-6 diets (both P < .05) but not on the saturated diet. An increased intake of long chain n-3 fatty acids decreases fasting plasma triglyceride and apoprotein AII concentrations and increases HDL2 cholesterol concentrations and results in less postprandial lipemia but leads to an increase in VIIc. An increased intake of linoleic acid may raise plasma fibrinogen concentration. Decreasing the intake of saturated fatty acids reduces plasma LDL cholesterol and apoprotein B without affecting HDL cholesterol concentration independent of the type of polyunsaturated fatty acids in the diet. When advice is given to reduce saturated fat intake, it is important to ensure an appropriate ratio of n-3/n-6 fatty acids in the diet.

Adult↗
PubMed1996

Effects of unsaturated fatty acids on blood clotting and fibrinolysis.

The importance of factors influencing blood clotting and fibrinolysis in preventing coronary events is now established. Modification of these factors is likely to be of more immediate benefit to an elderly population than factors influencing the atherogenic process. Although good evidence shows that intake of long chain fatty acids (> C12) is a major determinant of factor VIIc, little evidence supports the importance of the degree of unsaturation. The role of unsaturated fatty acids in thrombogenesis still remains controversial.

Blood Coagulation↗
PubMed1996

Postprandial activation of coagulant factor VII by long-chain dietary fatty acids.

Factor VII coagulant activity (FVIIc) is associated with an increased risk of fatal ischaemic heart disease (IHD). Several reports have suggested that dietary fat intake or hypertriglyceridaemia are associated with elevated levels of FVII. This study demonstrates that an intake of long-chain fatty acids sufficient to induce postprandial lipaemia in healthy subjects leads to a substantial elevation in both FVIIc and the concentration of FVII circulating in the activated form. Such an increase in FVIIc could not be induced by medium-chain triglycerides. These results suggest that the consumption of a sufficient amount of long-chain triglycerides to induce postprandial lipaemia induces the activation of FVII.

Adult↗
PubMed1995

Vegetarian diets and children.

Although the general health and development of vegan and vegetarian children seem to be normal, there may be subtle differences compared with omnivores. They are at increased risk of iron deficiency, and impaired psychomotor development associated with iron deficiency has been reported in macrobiotic infants. Fortunately, this impairment is not permanent, and follow-up studies have reported higher-than-average intelligence quotients among older macrobiotic children. Several other hazards of vegetarian diets have been identified, including vitamin B12 deficiency, rickets, and a bulky diet that can restrict energy intake in the first few years of life; however, these pitfalls can be avoided easily, and children can be successfully reared on vegetarian diets.

Anemia, Iron-Deficiency↗
PubMed1994

The influence of different amounts of n-3 polyunsaturated fatty acids on bleeding time and in vivo vascular reactivity.

Mesenteric bleeding time, mesenteric vascular reactivity, platelet and erythrocyte lipid fatty acid composition were measured at 2-3 weeks, 5-6 weeks and 11-22 weeks in normotensive Wistar rats, fed on high (6.5% energy) or moderate (1.6% energy) intakes of eicosapentaenoic acid (20:5n-3; EPA) as fish oil, compared with controls fed on a diet devoid of EPA. All diets contained the same level of linoleic acid (4% energy): the moderate- and high-EPA diets also contained 1.1 and 4.4% of the energy as docosahexaenoic acid (22:6n-3) respectively. Moderate, but not high, intakes of EPA increased mesenteric bleeding time. Similar reductions in erythrocyte and platelet arachidonic acid (20:4n-6) occurred in animals fed on either high or low amounts of EPA, but the proportion of EPA increased dose-dependently. At high intakes of EPA the proportion of oleic acid in platelets and erythrocytes was decreased. Blood pressure platelet counts, mesenteric vessel diameter and mesenteric vascular reactivity to vasopressin were unaffected by treatment. High intakes of fish oil led to a slight fall in packed cell volume. In a second experiment bleeding time and mesenteric vascular reactivity to noradrenaline were increased 2-4 weeks after receiving a moderate intake of EPA and these effects persisted 5-21 d after switching to a control diet. A similar increase in vascular reactivity to noradrenaline was observed in animals given indomethacin (6 mg/kg) but not in those given aspirin (20 mg/kg).

Animals↗
PubMed1994

Vegetarian diets and children.

The diets and growth of children reared on vegetarian diets are reviewed. Excessive bulk combined with low energy density can be a problem for children aged < or = 5 y and can lead to imparied growth. Diets that have a high content of phytate and other modifiers of mineral absorption are associated with an increased prevalence of rickets and iron-deficiency anemia. Vitamin B-12 deficiency is a real hazard in unsupplemented or unfortified vegan and vegetarian diets. It is suggested that vegans and vegetarians should use oils with a low ratio of linoleic to linolenic acid in view of the recently recognized role of docosahexaenoic acid in visual functioning. If known pitfalls are avoided, the growth and development of children reared on both vegan and vegetarian diets appears normal.

Anemia, Hypochromic↗
PubMed1994

The influence of maternal vegetarian diet on essential fatty acid status of the newborn.

OBJECTIVES: To evaluate whether a maternal vegetarian diet influences the essential fatty acid status of the newborn and whether this is related to outcome of pregnancy. DESIGN: Dietary intake and the fatty acid composition of plasma phospholipids were determined in 24 South Asian vegetarian and 24 white omnivore non-pregnant premenopausal women randomly selected from the general population of North London. Umbilical cords and cord blood were collected at delivery from 48 South Asian vegetarian women and 98 white omnivores from the same catchment area along with details of antenatal history and the outcome of pregnancy. The fatty acid composition of the cord arteries and that of cord plasma phospholipids were analysed in a subset of 32 pairs of subjects, who were matched for maternal age, gestational age, parity and sex of infant. RESULTS: Intakes of linoleic acid (18:2n-6) expressed as proportion of the dietary energy and the ratio of linoleic to alpha-linolenic acid (18:3n-3) were higher in the vegetarian women, and eicosapentaenoic acid (EPA, 20:5n-3) and docosahexaenoic acid (DHA, 22:6n-3) were absent from their diets. The proportion of linoleic acid, as well as the absolute concentration, was greater and those of EPA and DHA were lower in plasma phospholipids, plasma free fatty acid and total plasma lipids of the vegetarians compared with the white subjects. The proportion of DHA was lower (P > 0.001) but that of docosapentaenoic acid (22:5n-6) was greater (P < 0.001) in cord those from the omnivores. The ratio of 20:3n-9/20:4n-6 was elevated in cord artery but not in cord plasma phospholipids in both groups. Early onset of labour and the duration of gestation was 5.6 days shorter. Birth weight, head circumference and length were lower in the infants born to South Asian vegetarians even after adjusting for maternal height, duration of gestation, parity, gender of infants and smoking habits. Multivariate analysis did not reveal any relationship between the proportions of DHA in plasma or cord artery phospholipids and the birthweight or head circumference of the infants. CONCLUSION: This study demonstrates that vegetarians give birth to infants with less DHA in their plasma and cord artery phospholipids but this did not appear to be independently related to the outcome of pregnancy.

Diet, Vegetarian↗
PubMed1993

The effect of increasing levels of dietary fish oil rich in eicosapentaenoic and docosahexaenoic acids on lymphocyte phospholipid fatty acid composition and cell-mediated immunity in the mouse.

The influence of increasing intakes of fish oil on spleen leucocyte phospholipid fatty acid composition and cell-mediated immunity was studied in the mouse using a popliteal lymph node assay technique. The immune response was suppressed by 160 g fish oil/kg diet, but not by lower doses. The proportion of 20:5n-3 in spleen leucocyte phospholipid increased from 0.14 in the controls to 3.8, 7.2, 8.5 and 9.4% in the animals fed on 25, 50, 100 and 160 g fish oil/kg diet; the proportion of 22:6n-3 increased from 5.1 in the controls to 12.1, 12.2, 12.8 and 12.9% respectively. It is concluded that moderate intakes of fish oil are not immunosuppressive.

Animals↗
PubMed1993

Essential fatty acids, plasma cholesterol, and fat-soluble vitamins in subjects with age-related maculopathy and matched control subjects.

A matched-control study of plasma retinol, alpha-tocopherol, carotenoid, and cholesterol concentrations and the polyunsaturated fatty acid content of plasma and erythrocyte phospholipids was undertaken in 65 elderly patients with age-related maculopathy and 65 control subjects matched for age and sex. Despite the high statistical power of the study and large variations between subjects in the variables under consideration, no significant differences were noted between patients and control subjects. However, several statistically significant differences were noted between male and female subjects independent of their classification with maculopathy or as controls and age: plasma cholesterol, total phospholipids, alpha-tocopherol, and beta-cryptoxanthin concentrations were higher in females than in males. The mean plasma cholesterol concentration for the upper tertile of the whole sample was 7.6 mmol/L. Plasma concentrations of total carotenoids, alpha-carotene, and beta-carotene, but not alpha-tocopherol, were significantly lower in smokers than in non-smokers. The results of this study do not provide any evidence in favor of changing the dietary intake of polyunsaturated fatty acids or fat-soluble vitamins to protect against age-related maculopathy.

Aged↗