(excerpted from a publication by The Flax Council of Canada)

FLAX - A Complex Food

Flaxseed is a complex food source containing high amounts of alpha-linolenic acid (ALA) - an omega-3 fatty acid - as well as fiber, lignan precursors and other substances that may have an impact on our health.

Lignans are compounds that until recently were thought to be present only in higher plants, but they are now known to be present in the biological fluids of humans and animals. Mam¬malian lignans, primarily enterodiol and enterolactone, are produced from precursors in foods, possibly plant lignans, and by the bacterial flora in the colon. Healthy men and pre¬menopausal women are both able to produce large quantities of mammalian lignans from dietary flaxseed.”’ Some lignans are excreted in the urine, and urinary excretion correlates directly with the amount of plant lignans or lignan precursors in the diet! The biological effect of lignans and related compounds (phytoestrogens) include inhibiting vascular cell proliferation and angiogenesis and acting as an antioxidant, antibacterial, antifungal, and anti-viral agent. They are also estrogen antagonists and play a role in cholesterol homeosta- sis.4

Flaxseed is also complex in its fatty acid composition. The effect of flaxseed oil on various desease states is usually attributed to the high level of ALA, but any observed effects may reflect the particular fatty acid profile of flaxseed oil itself, inluding the amounts of individual fatty acids and their ratio to each other.

CHD PREVENTION: Serum Lipids and Lipoproteins

MILLED FLAXSEED: The fiber content of whole milled flaxseed contributes a substantial cholesterol-lowering effect. Diets containing 50 g milled flaxseed fed to normocholes¬terolemics in addtiion to a self-selected diet lowered total cholesterol by 6% and LDL cholesterol by 9% with no effect on HDL or triglycerides.7 Kidney patients with normal cholesterol levels fed milled flaxseed showed similar effects.’ In moderate hyperlipidemics, similar reductions occur.’ In general, for every 10 g flaxseed incorporated into the diet, there is a 1%’ reduction in total cholesterol and a 1.5% reduction in LDL cholesterol.”

COST/BENEFIT vs DRUG TREATMENT: Cost-benefit comparisons of flaxseed supplementation with lipid lowering drugs is favorable. Flax supplementation may be a cost effective way to keep a large number of hypercholesterolemics from depending on a costly drug treatment for a lifetime. On a population basis, adding small amounts of flax to the diet can shift the population cholesterol curve to the left, keeping millions of people off drug treatment and saving substantial treatment dollars.

CHD PREVENTION: Other risk Factors ALA decreases blood pressure in hypertensives’° and de¬creases the tendency of the blood to form clots.9′12 A recent human intervention study12 indicates that there may also be a protective effect against sudden death from heart attack even at low levels of intake, possibly mediated at the cellular level by preventing arrhythmias and platelet aggregation.

DIABETES
Consumption of milled flaxseed also affects post prandial blood glucose levels. One study showed that bread with 25% flaxseed produced blood glucose responses 28% lower than that of control bread.14 One component possibly responsible for the effect is the mucilage (outer seed coating), although it alone cannot explain the study result. The lower post prandial blood glucose levels were most likely mediated via slowed absorption due to the soluble fiber in flaxseed and other flaxseed com¬pounds that impede starch digestion.

Compared to fish oil (long chain omega-3 fatty acids EPA and DHA), flaxseed oil offers benefits to diabetics. Fish oil decreases triglycerides in diabetics but increases LDL, de¬creases insulin and increases blood glucose levels. ALA from flaxseed lowers triglycerides but doesn’t have the detrimental effects on glucose metabolism or LDL.13

cancer PREVENTION: Lignan Connection
Milled flaxseed is unique among oilseeds because of its exceptionally high concentration of ALA and lignans. ALA comprises 57% of the total fatty acids and the lignan content is 75-800 times that of 66 other plant foods.14 One biological effect of lignans is that they act as an estrogen antagonist.4

BREAST cancer PREVENTION: The anti-estrogen effect of mammalian lignans is important because there is a strong link between a woman’s hormonal profile and breast cancer risk. High levels of estrogen bioactivity increases the risk of breast cancer, and antagonizing estrogen is standard therapy in breast cancer treatment. Mammalian lignan structure is similar to that of phytoestrogens and tamoxifan - an anti-estrogenic drug used in the treatment of breast cancer. Breast cancer appears to be linked to the amount of lignans present in the diet. Urinary excretion of mammalian lignans is lower in breast cancer patients, suggesting lower dietary intake of plant lignan precursors.’ 5

Recent research has begun to shed more light on the link between lignans and breast cancer prevention. Animal studies suggest that the mammalian lignan precursor found in flaxseed is responsible for lowering breast cancer incidence in rats.16,17Fewer tumors were initiated when flaxseed was incor¬porated into the diet, and there was reduced growth of tumors already initiated. When the isolated lignan precursor was tested separately, results suggested that this precursor was responsible for the effect.

ALA in flaxseed may also have a positive effect on breast cancer prevention. An inverse relationship between breast fat tissue levels of ALA and tumor metastasis has been reported.18 Low ALA in breast tissue near the site of cancer positively correlated with increased risk of lymph node involvement and metastasis. In general, animal studies suggest that flax lignans and oil have separate and independent effects on carcinogene¬sis. Both decrease the growth of established tumors but have opposite effects on the development of new tumors16 with the high ALA flaxseed oil correlating with increased number in appearance of new tumors.

COLON CANCER PREVENTION: Colon cancer rates may also be affected by flax consumption. Preliminary animal research suggests that the flax mammalian lignan precursor can affect markers for colon cancer:9

IMMUNE FUNCTION

Dietary factors can affect immune response which can subse¬quently affect disease risk. Some degenerative diseases are due to inflammation (hyperimmune response) such as arthritis, lupus nephritis, and even coronary heart disease. ALA has a wide range of effects that could alter inflammatory and atherosclerotic response:9

Some indices of immune response were inhibited in healthy human volunteers consuming ALA at 6% energy for eight weeks but there was no increased incidence of infections.21 This research suggests that high intake of ALA could have adverse effects in individuals with compromised immune status, but may be of benefit to individuals with auto immune disorders.

LUPUS NEPHRITIS: Lupus Nephritis is an example where flaxseed and/or flax oil can have a beneficial effect. Long chain omega-3 fatty acids have been shown to affect renal disease, leading to research on the therapeutic properties of flaxseed since ALA is known to have anti-atherogenic and anti-inflammatory properties. Platelet aggregation was inhib¬ited and serum creatinine and proteinuria was reduced when 30 g of flaxseed was added to the diet of Lupus Nephritis patients.’ These results suggest that dietary supplementation with flaxseed may be a suitable adjunct treatment for renal disease.

CONCLUSION

In conclusion, it is clear that flaxseed products can have a wide range of biological and metabolic effects in humans and can be useful in the treatment and prevention of disease as well as maintenance of optimal health. Consuming grain products made with flax and consuming animal products, such as eggs, where flax has been used as a feed ingredient can make a substantial contribution to shifting the omega-6/omega-3 ratio of the Western diet, and can supply a significant source of fiber and plant lignans that appear to be useful in treatment and prevention of several diseases.

REFERENCES

1. Lampe,J.W. et al.,Am.J.Clin.Nutr:60:122 (1994)
2. Cunnane,S.C.,et al.,Am.J.Clin.Nutr: 61:62 (1995)
3. Thompson,L.U., in Flaxseed in Human Nutrition ed.by S.C.Cunnane and L.U.Thompson, AOCS Press, Champaign, IL (1995)
4. Setchell,K.D.R.and H.Aldercreutz in Role of the Gut Flora in Toxicity and Cancer ed.by I.R. Rowland, Academic Press London (1988) pp.315- 345
5. Nelson,G.J.and J.G.Chamberlain, in Flaxseed in Human Nutrition ed.by S.C.Cunnane and L.U. Thompson,AOCS Press, Champaign,IL (1995)
6. Chan,J.K.,et al.,Am.J.Clin.Nutr.53:1230 (1991)
7. Cunnane,S.C.,et al.,Br.J.Nutr. 69:443 (1993)
8. Clark,W.F.,et al.,J.Am.ColLNutr.12:501 (1993)
9. Bierenbaum,M.L.,et 12:501(1993)
10. Singer,P.,et al.,./Hum.Hypertens. 4:227 (1990)
11. McDonald,B.J.,et al.,Am.J.Clin.Nutr. 50:1382 (1989)
12. deLogeril,M.,et al.,Lancet,343:1454 (1954)
13. Cunnane,S.C.,et al.,Am.J.Clin.Nutr. 61:62 (1995)
14. Thompson,L.U.,et al.,Nutr.Cancer. 16:43 (1991)
15. Aldercreutz,H.,et al.,J.Steroid Biochem. 25:791 (1986)
16. Serraino,M.,and L.U.Thompson,Cancer Lett. 60:135 (1991)
17. Serraino,M.,and L.U.Thompson, in Flaxseed in Human Nutrition, ed.by S.C.Cunnane and L.U. Thompson, AOCS Press,Champaign,IL (1995)
18. Johnston,P.V.in Flaxseed in Human Nutrition ed. by S.C.Cunnane and L.U.Thompson,AOCS Press, Champaign,IL (1995)
19. Jenab,M.,and L.U.Thompson, Carcinogenesis 17:1343 (1996)
20. Parbtani,A.,and W.K.Clark,in Flaxseed in Human Nutrition ed. by S.C.Cunnane and L.U.Thompson, AOCS Press, Champaign,IL (1995)
21. Kelley,D.S.,et al.,Am.J.Clin.Nutr. 53:40 (1991)

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