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LE Magazine September 2005


High alpha-linolenic acid flaxseed (Linum usitatissimum): some nutritional properties in humans.

Although high alpha-linolenic acid flaxseed (Linum usitatissimum) is one of the richest dietary sources of alpha-linolenic acid and is also a good source of soluble fibre mucilage, it is relatively unstudied in human nutrition. Healthy female volunteers consumed 50 g ground, raw flaxseed/d for 4 weeks which provided 12-13% of energy intake (24-25 g/100 g total fat). Flaxseed raised alpha-linolenic acid and long-chain n-3 fatty acids in both plasma and erythrocyte lipids, as well as raising urinary thiocyanate excretion 2.2-fold. Flaxseed also lowered serum total cholesterol by 9% and low-density-lipoprotein-cholesterol by 18%. Changes in plasma alpha-linolenic acid were equivalent when 12 g alpha-linolenic acid/d was provided as raw flaxseed flour (50 g/d) or flaxseed oil (20 g/d) suggesting high bioavailability of alpha-linolenic acid from ground flaxseed. Test meals containing 50 g carbohydrate from flaxseed or 25 g flaxseed mucilage each significantly decreased postprandial blood glucose responses by 27%. Malondialdehyde levels in muffins containing 15 g flaxseed oil or flour/kg were similar to those in wheat-flour muffins. Cyanogenic glycosides (linamarin, linustatin, neolinustatin) were highest in extracted flaxseed mucilage but were not detected in baked muffins containing 150 g flaxseed/kg. We conclude that up to 50 g high-alpha-linolenic acid flaxseed/d is palatable, safe and may be nutritionally beneficial in humans by raising n-3 fatty acids in plasma and erythrocytes and by decreasing postprandial glucose responses.

Br J Nutr. 1993 Mar;69(2):443-53

Dietary fibre: more than a matter of dietetics. II. Preventative and therapeutic uses.

A nutrition rich in fibre has a preventive effect against constipation, colon diverticulosis, carcinoma of the large bowel and stomach, type 2-diabetes, metabolic syndrome and cardiovascular disease. In case of constipation, diverticulosis and diabetes this effect solely depends on dietary fibre. Regarding carcinomas and cardiovascular diseases, so far unknown factors integrated in or associated with fibre-rich food may also contribute to the preventive effect. Therapy with dietary fibre is indicated for constipation, colon diverticulosis, diarrhea, diabetes, and hypercholesterinemia. The individual dietary fibres differ substance-specifically. Food-integrated dietary fibre such as whole-grain bread, vegetables and fruit have their place in prevention. Dietary fibre preparations such as wheat bran, flax seed or sugar-beet fibre are useful in the treatment of constipation, colon diverticulosis and adiposity. Oat bran is preferentially used in hypercholesterinemia. Purified dietary fibres such as cellulose, guar, psyllium, and beta-glucan have an anti-diabetic, all viscous fibres an anti-lipaemic effect. The therapeutic dosages of dietary fibre preparations are 20-40 g/day and of purified fibres substances 10-20 g/day respectively.

Wien Klin Wochenschr.2004 Aug 31;116(15-16):511-22

Dietary lignan intakes and risk of pre- and postmenopausal breast cancer.

Lignans are plant compounds metabolized in the mammalian gut to produce the phytoestrogens enterolactone and enterodiol. Because estrogens have been linked to breast cancer etiology, lignans could affect breast cancer risk through modulation of endogenous estrogen metabolism or competitive inhibition with estrogen receptors. We examined breast cancer risk and dietary lignan intake in a population-based case-control study of 1,122 women with primary, incident, histologically confirmed breast cancer and 2,036 controls frequency matched to cases on age and county of residence as part of the Western New York Exposures and Breast Cancer (WEB) Study. Diet was assessed with a self-administered 104-item food frequency questionnaire and other relevant data were collected by detailed in-person interviews. Lignans were expressed as the sum of the dietary precursors secoisolariciresinol and matairesinol. Odds ratios (ORs) and 95% confidence intervals (CIs) were estimated by unconditional logistic regression, adjusting for age, total energy and other breast cancer risk factors. Premenopausal women in the highest quartile of dietary lignan intake had reduced breast cancer risk (OR = 0.66; 95% CI = 0.44-0.98). No association was observed between lignan intakes and postmenopausal breast cancer. Our results suggest that dietary lignans may be important in the etiology of breast cancer, particularly among premenopausal women.

Int J Cancer. 2004 Sep 1;111(3):440-3

Flaxseed inhibits metastasis and decreases extracellular vascular endothelial growth factor in human breast cancer xenografts.

Angiogenesis is important in tumor growth, progression and metastatic dissemination. Vascular endothelial growth factor (VEGF) is one key factor in promotion of breast cancer angiogenesis. VEGFs are bioactive in the extracellular space where they become available to the endothelial cells. Phytoestrogens such as lignans have been shown to alter breast cancer incidence and be cancer-protective in rats. We show that supplementation of 10% flaxseed, the richest source of mammalian lignans, to nude mice with established human breast tumors reduced tumor growth and metastasis. Moreover, flaxseed decreased extracellular levels of VEGF, which may be one mechanistic explanation to the decreased tumor growth and metastasis.

Cancer Lett. 2002 Nov 8;185(1):31-7

Essential fatty acids, DHA and human brain.

Essential fatty acids cannot be synthesized in the body but they are required for maintenance of optimal health. There are two classes of polyunsaturated fatty acids (PUFAs)—omega-6 and omega-3. The parent omega-6 fatty acid, linoleic acid (LA) is desaturated in the body to form arachidonic acid while parent omega-3 fatty acid alpha-linolenic acid (ALA) is desaturated by microsomal enzyme system through a series of metabolic steps to form eicosapentaenoic acid (EPA) and decosahexaenoic acid (DHA). But there is a limited metabolic capability during early life to metabolize PUFAs to more active long-chain fatty acids. There is a critical role of EFAs and their metabolic products for maintenance of structural and functional integrity of central nervous system and retina. Most of the brain growth is completed by 5-6 years of age. At birth brain weight is 70% of an adult, 15% brain growth occurs during infancy and remaining brain growth is completed during preschool years. DHA is the predominant structural fatty acid in the central nervous system and retina and its availability is crucial for brain development. It is recommended that the pregnant and nursing woman should take at least 2.6 g of omega-3 fatty acids and 100-300 mg of DHA daily to look after the needs of her fetus and suckling infant. The follow-up studies have shown that infants of mothers supplemented with EFAs and DHA had higher mental processing scores, psychomotor development, eye-hand coordination and stereo acuity at 4 years of age. Intake of EFAs and DHA during preschool years may also have a beneficial role in the prevention of attention deficit hyperactivity disorder (ADHD) and enhancing learning capability and academic performance.

Indian J Pediatr. 2005 Mar;72(3):239-42

The effect of estrogens and phytoestrogenic lignans on macrophage uptake of atherogenic lipoproteins.

The present study examined the effect of estrogens and compounds with estrogenic activity on the uptake of atherogenic lipoproteins into macrophages, thought to be the initiating step in the development of atherosclerotic lesions. Isolated low density lipoprotein (LDL) and lipoprotein(a) (Lp(a)) were radiolabelled with (3)H-cholesterol linoleate, and incubated with J774 macrophages for 24 hours in the presence of pharmacological doses of estrogens and phytoestrogens. At a concentration of 0.1 microM, the estrogen 17beta-estradiol significantly reduced LDL uptake by macrophages by 14% (p < 0.05), but estrone did not have any effect. At 10 microM, both estrogens significantly reduced macrophage LDL uptake, but the phyto-estrogenic-lignans enterodiol and enterolactone had no effect on LDL uptake. Lp(a) uptake into cells was significantly reduced by both estrone and estradiol, and by enterolactone and enterodiol at concentrations of 10 microM (p < 0.01), with enterodiol being most effective. The results of this study suggest that the uptake of these structurally similar lipoproteins is regulated differently. Macrophage Lp(a) uptake appears more phytoestrogen sensitive than does LDL uptake.

Biofactors. 2004;20(3):119-27