Common purslane: a source of omega-3 fatty acids and antioxidants

omega-3 fatty acids, alpha-tocopherol, ascorbic acid, beta-carotene and glutathione determined in leaves of purslane (Portulaca oleracea), grown in both a controlled growth chamber and in the wild, were compared in composition to spinach. Leaves from both samples of purslane contained higher amounts of alpha-linolenic acid (18:3w3) than did leaves of spinach. Chamber-grown purslane contained the highest amount of 18:3w3. Samples from the two kinds of purslane contained higher leaves of alpha-tocopherol, ascorbic acid and glutathione than did spinach. Chamber-grown purslane was richer in all three and the amount of alpha-tocopherol was seven times higher than that found in spinach, whereas spinach was slightly higher in beta-carotene. One hundred grams of fresh purslane leaves (one serving) contain about 300-400 mg of 18:3w3; 12.2 mg of alpha-tocopherol; 26.6 mg of ascorbic acid; 1.9 mg of beta-carotene; and 14.8 mg of glutathione. We confirm that purslane is a nutritious food rich in omega-3 fatty acids and antioxidants.

Egg yolk as a source of long-chain polyunsaturated fatty acids in infant feeding

In this paper we compare the fatty acid content of egg yolks from hens fed four different feeds as a source of docosahexaenoic acid to supplement infant formula. Greek eggs contain more docosahexaenoic acid (DHA, 22:6 omega 3) and less linoleic acid (LA, 18:2 omega 6) and alpha-linolenic acid (LNA, 18:3 omega 3) than do fish-meal or flax eggs. Two to three grams of Greek egg yolk may provide an adequate amount of DHA and arachidonic acid for a preterm neonate. Mean intake of breast milk at age 1 mo provides 250 mg long-chain omega 3 fatty acids. This amount can be obtained from less than 1 yolk of a Greek egg (0.94), greater than 1 yolk of flax eggs (1.6) and fish-meal eggs (1.4), or 8.3 yolks of supermarket eggs. With proper manipulation of the hens' diets, eggs could be produced with fatty acid composition similar to that of Greek eggs.

Omega-3 fatty acids in health and disease and in growth and development

Several sources of information suggest that man evolved on a diet with a ratio of omega 6 to omega 3 fatty acids of approximately 1 whereas today this ratio is approximately 10:1 to 20-25:1, indicating that Western diets are deficient in omega 3 fatty acids compared with the diet on which humans evolved and their genetic patterns were established. Omega-3 fatty acids increase bleeding time; decrease platelet aggregation, blood viscosity, and fibrinogen; and increase erythrocyte deformability, thus decreasing the tendency to thrombus formation. In no clinical trial, including coronary artery graft surgery, has there been any evidence of increased blood loss due to ingestion of omega 3 fatty acids. Many studies show that the effects of omega 3 fatty acids on serum lipids depend on the type of patient and whether the amount of saturated fatty acids in the diet is held constant. In patients with hyperlipidemia, omega 3 fatty acids decrease low-density-lipoprotein (LDL) cholesterol if the saturated fatty acid content is decreased, otherwise there is a slight increase, but at high doses (32 g) they lower LDL cholesterol; furthermore, they consistently lower serum triglycerides in normal subjects and in patients with hypertriglyceridemia whereas the effect on high-density lipoprotein (HDL) varies from no effect to slight increases. The discrepancies between animal and human studies most likely are due to differences between animal and human metabolism. In clinical trials eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the form of fish oils along with antirheumatic drugs improve joint pain in patients with rheumatoid arthritis; have a beneficial effect in patients with ulcerative colitis; and in combination with drugs, improve the skin lesions, lower the hyperlipidemia from etretinates, and decrease the toxicity of cyclosporin in patients with psoriasis. In various animal models omega 3 fatty acids decrease the number and size of tumors and increase the time elapsed before appearance of tumors. Studies with nonhuman primates and human newborns indicate that DHA is essential for the normal functional development of the retina and brain, particularly in premature infants. Because omega 3 fatty acids are essential in growth and development throughout the life cycle, they should be included in the diets of all humans. Omega-3 and omega 6 fatty acids are not interconvertible in the human body and are important components of practically all cell membranes. Whereas cellular proteins are genetically determined, the polyunsaturated fatty acid (PUFA) composition of cell membranes is to a great extent dependent on the dietary intake.(ABSTRACT TRUNCATED AT 400 WORDS)

Energy imbalance and cancer of the breast, colon and prostate

In Western societies, energy imbalance is characterized by obesity and sedentary life styles and is associated with increased morbidity and mortality from all causes of cancer, including cancer of the breast, colon and prostate. The interrelationships of energy intake and energy retention, to energy expenditure and physical fitness need further investigation from the physiologic, metabolic, endocrine and genetic aspects of cancer development, since obesity, energy expenditure and cancer have a familial predisposition. The effects of exercise on estrogen and prostaglandin metabolism and their relationship to cancer development require further investigation. Although the exact amount and intensity of exercise that confers benefit is not known, physical activity and physical fitness are inversely associated with all-cause mortality, including cancer. These findings have important public health implications, because about one-third of persons in industrialized societies are quite sedentary, and the prevalence of low physical fitness is quite high. The balance between total energy intake and expenditure may be more important in cancer development than the intake of any given dietary component or energy source. Exercise increases prostacyclin and decreases the aggregation of platelets and possibly decreases the platelet derived growth factors (PDGF). One could speculate that exercise may in turn decrease the probability of developing colon cancer in those who are predisposed to it, since the SIS oncogene is in fact a variant of PDGF.

Summary of the NATO advanced research workshop on dietary omega 3 and omega 6 fatty acids: biological effects and nutritional essentiality

A number of human studies presented at the workshop indicate that the premature infant at birth is biochemically deficient in docosahexaenoic acid (DHA) in both the brain and liver phospholipids, and that DHA is essential for normal visual acuity. The amount of DHA necessary to maintain normal amounts of the liver and brain phospholipids postnatally is 11 mg/kg daily. Elderly patients on long-term gastric tube feedings and others on long-term intravenous fluids and on total parenteral nutrition are particularly prone to deficiencies of alpha-linolenic acid, eicosapentaenoic acid (EPA) and DHA. The amounts estimated to prevent deficiencies in the elderly are 800-1100 mg/d of alpha-linolenic acid and 300-400 mg/d of EPA and DHA combined. Preliminary data indicate that children with malnutrition and mucoviscidosis, women with toxemia, and elderly people have decreased amounts of DHA in plasma phospholipids. The omega 3 fatty acids lower triglycerides and, at high levels, lower cholesterol. The anti-aggregatory, anti-thrombotic and anti-inflammatory properties of omega 3 fatty acids have been confirmed, and a dose-response curve is emerging. Despite the increase in bleeding time, no clinical evidence of bleeding has been noted by the investigators in any of the studies. Clinical trials are necessary in order to precisely define the dose and mechanisms involved in defining the essentiality of omega 3 fatty acids in growth and development and their beneficial effects in coronary heart disease, hypertension, inflammation, arthritis, psoriasis, other autoimmune disorders, and cancer.

Nutritional cancer risks derived from energy and fat

Both animal and human studies indicate that increased caloric intake and increases in body weight and obesity are associated with increased risk of cancer of the breast, endometrium, ovaries, colon, rectum and prostate. Recent animal studies indicate that it is the total caloric intake, rather than the percent of fat in the diet, that is associated with tumorigenesis and carcinogenesis, and that tumor development depends on a complex interaction involving energy intake, energy expenditure, energy retention within the body (body fat vs lean body mass) and body size. Omega-3 fatty acids inhibit tumorigenesis and tumor growth in many cancer models in rodents. Exercise diminishes tumor formation in mice, rats and humans. Exercise delays mortality from all causes, and life-long exercise is associated with decreased cancers of the breast and reproductive system in women, and cancer of the colon in women and men.

Diet and health: scientific concepts and principles conference commentary

The conference concluded that dietary guidelines are needed, but that they cannot apply to everyone in the population nor to the same extent. Furthermore, a mechanism or structure is needed in which the guidelines can be periodically reviewed and updated. In making dietary recommendations, genetic variability, age, sex and body size need to be considered. Survival, extension of life span, relief of selected symptoms and biochemical improvements of risk factors are some of the criteria to be used in assessing the role of diet in health and disease. The most important questions that remain unresolved in the nutritional sciences concern the relation of diet to the development of chronic disease. The science of nutritional epidemiology needs to be strengthened and etiologic research in epidemiology ought to be performed and evaluated with the same standards used in other branches of science. Therefore, there is a need to establish guidelines for the validity of methods in assessing dietary intake and for a minimum acceptable correlation for the reproducibility and repeatability of dietary intake data. Research on the role of genetic variation and nutrition, the metabolic effects of omega-3 fatty acids and their relationship to omega-6 fatty acids, the energy expenditure after weight reduction and improving the scientific base of nutritional epidemiology will enhance the scientific basis of nutrition and our understanding of the role of diet in health and disease.