Linfröolja är en vegetabilisk olja som är rik på omega-3 (den innehåller även omega-6). Denna artikel handlar om huruvida linfröolja har någon positiv inverkan på människor. För att sammanfatta den kort valde jag detta citat: “Medans flertalet studier har visat att fiskolja har en positiv inverkan på personer med reumatoid artrit/ledgångsreumatism, så har inte linfröolja lyckats åstadkomma samma resultat enligt den kliniska studie som finns”.
Linseed and Linseed Oil
- What it is
- Where found
- Helpful for
- Are you deficient?
- Amount to take
- Side effects & interactions
- References
What is it?
Linseed, called linseed in some countries, is a good source of dietary fibre, omega-3 fatty acids, and lignans. Each of these components may contribute to the health effects of eating linseed, but linseed oil contains no fibre and very little lignan.
Like most vegetable oils, linseed oil contains linoleic acid, an essential fatty acid needed for survival. But unlike most oils, it also contains significant amounts of another essential fatty acid, alpha linolenic acid (ALA).
ALA is an omega-3 fatty acid. To a limited extent, the body turns ALA into eicosapentaenoic acid (EPA)—an omega-3 fatty acid found in fish oil—which in turn converts to beneficial prostaglandins. (Prostaglandins are hormone-like substances made in many parts of the body rather than coming from one organ, as most hormones do.)
While fish oil has been shown to have anti-inflammatory activity, an anti-inflammatory effect of linseed oil has not been demonstrated conclusively. Some doctors have argued that, because ALA can be converted to EPA and DHA (the fatty acids found in fish oil), linseed oil should be useful for the same conditions as fish oil. However, the conversion of ALA to EPA and DHA is limited, so that argument may turn out to be incorrect. For example, while numerous studies have shown that fish oils are beneficial for rheumatoid arthritis, linseed oil failed to work for this condition in the only known trial.1 In 1994, a diet purportedly high in ALA was successful in preventing heart disease,2 but this study altered many dietary factors, so ALA may not have been solely responsible for the outcome.3 Linseed oil does not appear to be a good replacement for fish oil for people with elevated triglycerides.4 5 ALA does not reduce excess platelet aggregation (“sticky platelets”), another risk factor for heart disease, the way fish oil does.6 However, linseed oil may help lower cholesterol,7 and research specific to linseed oil indicates that it may also lower blood pressure.8
Linseed is the most abundant food source of lignans, a family of phytochemicals that is drawing the interest of many health researchers.9 10 11 Lignans are not actually present in linseed; rather intestinal bacteria produce them from precursors in linseed.12 13 Lignans have antioxidant activity,14 and test tube and animal research suggests they may also have significant effects on the metabolism and function of the hormone oestrogen.15 16 17
Where is it found?
In addition to its presence in linseed oil, small amounts of ALA are also found in canola, soya, black currant, and walnut oils. Small amounts of lignans are present in a wide variety of foods of plant origin.
Linseed and linseed oil has been used in connection with the following conditions (refer to the individual health concern for complete information):
Rating Health Concerns
3Stars
Constipation (flaxseed)
Systemic lupus erythematosus (flaxseed)
2Stars
High cholesterol (flaxseed)
1Star
Benign prostatic hyperplasia (BPH) (flaxseed oil)
Constipation (flaxseed oil)
Ulcerative colitis (flaxseed)
3Stars Reliable and relatively consistent scientific data showing a substantial health benefit.
2Stars Contradictory, insufficient, or preliminary studies suggesting a health benefit or minimal health benefit.
1Star For an herb, supported by traditional use but minimal or no scientific evidence. For a supplement, little scientific support and/or minimal health benefit.
Who is likely to be deficient?
ALA deficiencies are possible but believed to be rare, except in infants who are fed formula that is omega-3 deficient. Lignan is not an essential nutrient, so deficiencies are not possible.
How much is usually taken?
For promoting bowel regularlity, 1 tablespoon (15 ml) of whole or ground linseed is taken one or two times per day, accompanied by a full glass of water. When used to treat other health conditions, it is used in amounts of 30 to 35 grams (1 to 2 ounces) per day.
Although it is not suitable for cooking, linseed oil (unlike fish oil) can be used in salads. Some doctors recommend that people use 1 tablespoon (15 ml) of linseed oil per day as a supplement in salads or on vegetables to ensure a supply of essential fatty acids. Some conversion of ALA to EPA does occur,18 and this conversion can be increased by restricting the intake of other vegetable oils.19
For those who wish to replace fish oil with linseed oil, research suggests taking up to ten times as much ALA as EPA.20 Typically, this means 7.2 grams of linseed oil equals 1 gram of fish oil. However, even if taken in such high amounts, linseed oil may not have the same effects as fish oil. But, linseed oil will not cause a fishy-smelling burp (a possible side effect of fish oil).
Are there any side effects or interactions?
Linseed oil toxicity has not been reported. However, there is conflicting information about the effect of linseed oil and one of its major constituents, ALA, on cancer risk.
While most test tube and animal studies suggest a possible protective role for ALA against breast cancer,21 22 23 24 25 one animal study26 and a preliminary human study27 suggested increased breast cancer risk from high dietary ALA. Another preliminary human study reported that higher breast tissue levels of ALA are associated with less advanced breast cancer at the time of diagnosis.28 For prostate cancer, a test tube study reported ALA promoted cancer cell growth,29 but preliminary human studies have shown ALA to be associated with either an increased30 31 or decreased risk,32 or no change33 at all.
Advocates of linseed oil speculate that a potential association between ALA and cancer may be due to the fact that meat contains ALA, thus implicating ALA when the real culprits are probably other components of meat. In some studies, however, saturated fat (and therefore probably meat) were taken into consideration, and ALA still correlated with increased risk. The associations between ALA and cancer might eventually be shown to be caused by substances found in foods rich in ALA rather than by ALA itself. However, ALA has been reported to become mutagenic (able to cause precancerous changes) when heated,34 which concerns some doctors.
The effect of ALA as an isolated substance, and of linseed oil on the risk of cancer in humans remains unclear, with most animal and test tube studies suggesting protection, and some preliminary human trials suggesting cause for concern. It is premature to suggest that ALA and linseed oil will either cause or protect against human cancer at this time.
Linseed oil is not suitable for cooking and should be stored in an opaque, airtight container in the refrigerator or freezer. If the oil has a noticeable odour it is probably rancid and should be discarded.
As with any source of fibre, linseed should not be taken if there is possibility that the intestines are obstructed. People with scleroderma (systemic sclerosis) should consult a doctor before using linseed. Although a gradual introduction of fibre in the diet may improve bowel symptoms in some cases, there have been several reports of people with scleroderma developing severe constipation and even bowel obstruction requiring hospitalisation after fibre supplementation.35
Animal research suggests that large amounts of linseed or lignans consumed during pregnancy might adversely affect the development of the reproductive system.36 No studies have attempted to investigate whether this could be a problem in humans.
Allergic reactions to linseed have occasionally been reported, but are considered very uncommon.37 38
At the time of writing, there were no well-known drug interactions with linseed oil.
References
1. Nordstrom DC, Honkanen VE, Nasu Y, et al. Alpha-linolenic acid in the treatment of rheumatoid arthritis. A double-blind, placebo-controlled and randomized study: flaxseed vs. safflower seed. Rheumatol Int 1995;14:231-4.
2. De Lorgeril M, Renaud S, Maelle N, et al. Mediterranean alpha-linolenic acid-rich diet in secondary prevention of coronary heart disease. Lancet 1994;343:1454-9.
3. Rice RD. Mediterranean diet. Lancet 1994;344;893-4 [letter].
4. Kelley DS, Nelson GJ, Love JE, et al. Dietary a-linolenic acid alters tissue fatty acid composition, but not blood lipids, lipoproteins or coagulation status in humans. Lipids 1993;28:533-7.
5. Abbey M, Clifton P, Kestin M, et al. Effect of fish oil on lipoproteins, lecithin: cholesterol acyltransferase, and lipid transfer protein activity in humans. Arterioscler 1990;10:85-94.
6. Wensing AGCL, Mensink RP, Hornstra G. Effects of dietary n-3 polyunsaturated fatty acids from plant and marine origin on platelet aggregation in healthy elderly subjects. Br J Nutr 1999;82:183-91.
7. Chan JK, Bruce VM, McDonald BE. Dietary a-linolenic acid is as effective as oleic acid and linoleic acid in lowering blood cholesterol in normolipidemic men. Am J Clin Nutr 1991;53:1230-4.
8. Singer P, Jaeger W, Berger I, et al. Effects of dietary oleic, linoleic and a-linolenic acids on blood pressure, serum lipids, lipoproteins and the formation of eicosanoid precursors in patients with mild essential hypertension. J Human Hypertension 1990;4:227-33.
9. Thompson LU, Rickard SE, Cheung F, et al. Variability in anticancer lignan levels in flaxseed. Nutr Cancer 1997;27:26–30.
10. Kilkkinen A, Stumpf K, Pietinen P, et al. Determinants of serum enterolactone concentration. Am J Clin Nutr 2001;73:1094–100.
11. Thompson, LU, Robb, P, Serraino, M, Cheung, F. Mammalian lignan production from various foods. Nutr Cancer 1991;16:43–52.
12. Setchell, KD, Lawson, AM, Mitchell, FL, et al. Lignans in man and in animal species. Nature 1980;287:740–2.
13. Borriello SP, Setchell KD, Axelson M, Lawson AM. Production and metabolism of lignans by the human faecal flora. J Appl Bacteriol 1985;58:37–43.
14. Harper A, Kerr DJ, Gescher A, Chipman JK. Antioxidant effects of isoflavonoids and lignans, and protection against DNA oxidation. Free Radic Res 1999;31:149–60.
15. Adlercreutz H, Hockerstedt K, Bannwart C, et al. Effect of dietary components, including lignans and phytoestrogens on enterohepatic circulation and liver metabolism of estrogens and on sex hormone binding globulin (SHBG). J Steroid Biochem 1987;27:1135–44.
16. Orcheson LJ, Rickard SE, Seidl MM, Thompson LU. Flaxseed and its mammalian lignan precursor cause a lengthening or cessation of estrous cycling in rats. Cancer Lett 1998;125:69–76.
17. Kuiper GG, Lemmen JG, Carlsson B, et al. Interaction of estrogenic chemicals and phytoestrogens with estrogen receptor beta. Endocrinology 1998;139:4252–63.
18. Sanders TAB, Roshanai F. The influence of different types of omega 3 polyunsaturated fatty acids on blood lipids and platelet function in healthy volunteers. Clin Sci 1983;64:91.
19. Mantzioris E, James MJ, Gibson RA, Cleland LG. Dietary substitution with alpha-linolenic acid-rich vegetable oil increases eicosapentaenoic acid concentrations in tissues. Am J Clin Nutr 1994;59:1304–49.
20. Indu M, Ghafoorunissa. n-3 fatty acids in Indian diets: comparison of the effects of precursor (alpha-linolenic acid) vs product (long-chain n-3 polyunsaturated fatty acids). Nutr Res 1992;12:569–82.
21. Chajes V, Sattler W, Stranzl A, Kostner GM. Influence of n-3 fatty acids on the growth of human breast cancer cells in vitro: relationship to peroxides and vitamin E. Breast Cancer Res Treat 1995;34:199–212.
22. Munõz SF, Silva RA, Lamarque A, et al. Protective capability of dietary Zizyphus mistol seed oil, rich in 18:3, n-3, on the development of two murine mammary gland adenocarcinomas with high or low metastatic potential. Prostaglandins Leukot Essent Fatty Acids 1995;53:135–8.
23. Thompson LU, Rickard SE, Orcheson LJ, Seidl MM. Flaxseed and its lignan and oil components reduce mammary tumor growth at a late stage of carcinogenesis. Carcinogenesis 1996;17:1373–6.
24. Fritsche KL, Johnston PV. Effect of dietary alpha-linolenic acid on growth, metastasis, fatty acid profile and prostaglandin production of two murine mammary adenocarcinomas. J Nutr 1990;120:1601–9.
25. Cave WT Jr. Dietary n-3 (omega-3) polyunsaturated fatty acid effects on animal tumorigenesis. FASEB J 1991;5:2160–6 [review].
26. Braden LM, Carroll KK. Dietary polyunsaturated fat in relation to mammary carcinogenesis in rats. Lipids 1986;21:285–8.
27. De Stefani E, Deneo-Pellegrini H, Mendilaharsu M, Ronco A. Essential fatty acids and breast cancer; a case-control study in Uruguay. Int J Cancer 1998;76:491–4.
28. Bougnoix P. Alpha-linolenic acid content of adipose breast tissue: a host determinant of the risk of early metastasis in breast cancer. Br J Cancer 1994;70:330–40.
29. Pandalai PK, Pilat MJ, Yamazaki K, et al. The effects of omega-3 and omega-6 fatty acids on in vitro prostate cancer growth. Anticancer Res 1996;16:815–20.
30. Giovannucci E, Rimm EB, Colditz GA, et al. A prospective study of dietary fat and risk of prostate cancer. J Natl Cancer Inst 1993;85:1571–9.
31. Harvei S, Bjerve KS, Tretli S, et al. Prediagnostic level of fatty acids in serum phospholipids: omega-3 and omega-6 fatty acids and the risk of prostate cancer. Int J Cancer 1997;71:545–51.
32. Gann PH, Hennekens CH, Sacks FM, et al. Prospective study of plasma fatty acids and risk of prostate cancer. J Natl Cancer Inst 1994;86:281–6.
33. Schuurman AG, van den Brandt PA, Dorant E, et al. Association of energy and fat intake with prostate carcinoma risk: results from the Netherlands Cohort Study. Cancer 1999;86:1019–27.
34. Shields PG, Xu GX, Blot WJ, et al. Mutagens from heated Chinese and U.S. cooking oils. J Natl Cancer Inst 1995;87:836–41.
35. Gough A, Sheeran T, Bacon P, Emery P. Dietary advice in systemic sclerosis: the dangers of a high fibre diet. Ann Rheum Dis 1998;57:641–2.
36. Tou JC, Chen J, Thompson LU. Flaxseed and its lignan precursor, secoisolariciresinol diglycoside, affect pregnancy outcome and reproductive development in rats. J Nutr 1998;128:1861–8.
37. Alonso L, Marcos ML, Blanco JG, et al. Anaphylaxis caused by linseed (flaxseed) intake. J Allergy Clin Immunol 1996;98:469–70.
38. Leon F, Rodriguez M, Cuevas M. Anaphylaxis to Linum. Allergol Immunopathol (Madr) 2003;31:47–9.
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