Flaxseed and Flaxseed Oil : Safety, Part 2

by MedlinePlus

(Page 3 of 3)

Taking a large amount of flaxseed ( not flaxseed oil) by mouth may cause obstruction of the intestines, especially when flaxseed is taken with too little fluid. It is recommended that the amount of seed be taken with ten times that amount of water or other liquid. People with narrowing of the esophagus or intestine, ileus, or bowel obstruction should avoid flaxseed ( not flaxseed oil). Individuals with high blood triglycerides should avoid flaxseed and flaxseed oil due to unclear effects on triglyceride levels in animal research. People with diabetes should use caution if taking flaxseed products by mouth, as the omega-3 fatty acids in flaxseed and flaxseed oil may increase blood sugar levels. This increase is reported in one study of adults with type 2 diabetes who were treated with omega-3 fatty acids for one month, but the effect is not reported in another study of people taking flaxseed (50 grams) by mouth.

One study reports that the menstrual period may be altered in women who take 10 grams of flaxseed powder by mouth daily. Due to the possible estrogen-like effects of flaxseed ( not flaxseed oil), it should be used cautiously in women with hormone sensitive conditions such as endometriosis, polycystic ovary syndrome, uterine fibroids, or cancer of the breast, uterus, or ovary. Some natural medicine textbooks advise caution in patients with hypothyroidism, although little scientific information is available in this area. Flaxseed and flaxseed oil may increase the risk of bleeding, based on early studies that show decreased clotting of blood. In human studies, people taking alpha-linolenic acid, a substance present in flaxseed, have bled longer in laboratory tests, but dangerous bleeding problems have not been reported in the available scientific literature. Caution is advised in patients with bleeding disorders, in people taking drugs that increase the risk of bleeding, and in people planning to undergo medical, surgical, or dental procedures. Dosing of blood-thinning medications may need to be adjusted. In animal studies, flaxseed has increased the number of red blood cells.

Several studies in humans report an increased risk of prostate cancer in men taking alpha-linolenic acid (which is present in flaxseed) by mouth. One small study of men with prostate cancer reports that flaxseed supplements do not increase prostate specific antigen (PSA) levels. Until more information is available, men with prostate cancer or at risk for prostate cancer should avoided flaxseed and alpha-linolenic acid supplements.

Pregnancy and Breastfeeding

The use of flaxseed or flaxseed oil during pregnancy and breastfeeding is not recommended. Animal studies show possible harmful effects, and there is little information in humans. Flaxseed may stimulate menstruation or have other hormonal effects and could be harmful to pregnancy.

Interactions

Most herbs and supplements have not been thoroughly tested for interactions with other herbs, supplements, drugs, or foods. The interactions listed below are based on reports in scientific publications, laboratory experiments, or traditional use. You should always read product labels. If you have a medical condition, or are taking other drugs, herbs, or supplements, you should speak with a qualified healthcare provider before starting a new therapy.

Interactions with Drugs

Taking flaxseed ( not flaxseed oil) by mouth may reduce the absorption of other medications. Drugs used by mouth should be taken one hour before or two hours after flaxseed to prevent decreased absorption. Based on one study, flaxseed may provoke mania or hypomania in individuals with bipolar disorder. People taking mood stabilizers such as lithium should use caution. Flaxseed contains alpha-linolenic acid, which may theoretically lower blood pressure. Individuals taking medications to lower blood pressure should use caution when taking flaxseed. Laxatives and stool softeners may increase or enhance the laxative effects of flaxseed. Flaxseed and flaxseed oil can lower cholesterol levels in animals, but studies in humans show mixed results. In theory, flaxseed may increase the effect of other medications that lower lipid (cholesterol and triglyceride) levels in the blood. Hormonal drugs may be affected. Dietary flaxseed may increase the effects of tamoxifen, a medication used to treat cancer. Please do not start flaxseed before discussing with your oncologist and pharmacist.

Although studies report conflicting results, the omega-3 fatty acids in flaxseed and flaxseed oil may increase blood sugar, reducing the effects of diabetes treatments, including insulin and glucose-lowering medications taken by mouth. Flaxseed ( not flaxseed oil) is a rich source of plant lignans. Lignans are sometimes referred to as phytoestrogens and may possess estrogen-like properties. It is not known if flaxseed can alter the effect of birth control pills or hormone replacement therapies. Flaxseed and flaxseed oil theoretically may increase the risk of bleeding, and caution should be used when flaxseed products are taken with drugs that increase the risk of bleeding. Some examples include aspirin, anticoagulants ("blood thinners") such as warfarin (Coumadin ®) or heparin, anti-platelet drugs such as clopidogrel (Plavix ® ), and non-steroidal anti-inflammatory drugs such as ibuprofen (Motrin®, Advil®) or naproxen (Naprosyn®, Aleve®).

Interactions with Herbs and Dietary Supplements

Consumption of flaxseed ( not flaxseed oil) may reduce the absorption of vitamins or supplements taken by mouth at the same time. Therefore, vitamins and supplements should be taken an hour before or two hours after a dose of flaxseed to prevent decreased absorption.

Use caution if combining flaxseed with other mood altering herbs, including St. John's wort ( Hypericum perforatum ), kava ( Piper methysticum ), or valerian ( Valeriana officinalis ). Hormonal herbs and supplements may be affected. Flaxseed contains alpha-linolenic acid, which may theoretically lower blood pressure. Use caution when combining flaxseed with other herbs or supplements that can lower blood pressure. Some examples are aconite/monkshood, arnica, baneberry, betel nut, bilberry, black cohosh, bryony, calendula, California poppy, coleus, curcumin, eucalyptol, eucalyptus oil, ginger, goldenseal, green hellebore, hawthorn, Indian tobacco, jaborandi, mistletoe, night blooming cereus, oleander, pasque flower, periwinkle, pleurisy root, shepherd's purse, Texas milkweed, turmeric, and wild cherry.

Because of the laxative effects of flaxseed, caution should be used when it is taken with other supplements that have laxative effects. Possible laxative herbs include alder buckthorn, aloe dried leaf sap, black root, blue flag rhizome, butternut bark, dong quai, European buckthorn, eyebright, cascara bark, castor oil, chasteberry, colocynth fruit pulp, dandelion, gamboges bark, horsetail, jalap root, manna bark, plantain leaf, podophyllum root, psyllium, rhubarb, senna, wild cucumber fruit, and yellow dock root.

Studies on the effects of flaxseed on blood sugar in people with type 2 diabetes report mixed results. Use caution when combining flaxseed products with supplements that may raise blood sugar levels. These include arginine, cocoa, and ephedra (when combined with caffeine). In theory, flaxseed may contain estrogen-like chemicals. Use caution when combining flaxseed ( not flaxseed oil) with supplements believed to have estrogen-like properties. Possible examples include alfalfa, black cohosh, bloodroot, burdock, hops, kudzu, licorice, pomegranate, red clover, soy, thyme, white horehound, and yucca.

Early studies in humans show that flaxseed and flaxseed oil theoretically may increase the risk of bleeding. Although no reports of dangerous bleeding are available, caution should be used when flaxseed products are taken with herbs and supplements that are believed to increase the risk of bleeding. Multiple cases of bleeding have been reported with the use of Ginkgo biloba , fewer cases with garlic, and two cases with saw palmetto. Numerous other agents may theoretically increase the risk of bleeding, although this has not been proven in most cases. Some examples include alfalfa, American ginseng, angelica, anise, Arnica montana , asafetida, aspen bark, bilberry, birch, black cohosh, bladderwrack, bogbean, boldo, borage seed oil, bromelain, capsicum, cat's claw, celery, chamomile, chaparral, clove, coleus, cordyceps, danshen, devil's claw, dong quai, evening primrose, fenugreek, feverfew, ginger, grapefruit juice, grapeseed, green tea, guggul, gymnestra, horse chestnut, horseradish, licorice root, lovage root, male fern, meadowsweet, nordihydroguairetic acid (NDGA), onion, papain, panax ginseng, parsley, passionflower, poplar, prickly ash, propolis, quassia, red clover, reishi, Siberian ginseng, sweet clover, rue, sweet birch, sweet clover, turmeric , vitamin E, white willow, wild carrot, wild lettuce, willow, wintergreen, yucca.

Interactions with Foods

At high temperatures, for example when cooking, flaxseed oil and powder/flour will degrade. It is reported that eating four eggs per day from chickens fed flaxseed results in elevated serum levels of total omega-3 fatty acids. Long-term effects are not clear.

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