Flaxseed oil is an oil produced by the seeds of the Linum usitatissimum plant. Flaxseed oil can be used as a food additive, but is often taken directly at higher doses as a nutritional supplement which can cause side effects. As a food additive, flaxseed oil is safe and very healthy if it is used to replace partially hydrogenated oils in recipes or on salads. Flaxseed oil in the quantities taken as a nutritional supplement is far from proven as effective, or safe.
The two most frequently used purposes of flaxseed oil as a nutritional supplement is for the treatment and prevention of rheumatoid arthritis and atherosclerosis. Studies have shown, however, that while slightly effective as a food additive, the amounts taken by most when they take it as a nutritional supplement does not cause any noticeable increase in effectiveness beyond the low doses seen in food preparation and runs the risk of having side effects. Flaxseed oil is also less commonly used as a nutritional supplement to treat anxiety, obesity, and diabetes. No scientific research has shown any effectiveness in any of these conditions.
Flaxseed oil is safe when used as a food additive or as a cooking oil and there will be no side effects. The health benefits of cooking with flaxseed oil greatly increase when it is used to replace most vegetable oils that are partially hydrogenated. For medical or supplemental use, flaxseed oil is safe if taken in lose doses below 25grams a day and for durations less than 2 months. Daily doses great than 25mg can cause diarrhea and individuals taking more than 25grams per day for long durations can experience nutritional and dehydration problems as a result.
One serious potential side effect of flaxseed oil is the possible link between alpha-linolenic acid and prostrate cancer. Flaxseed oil contains large amounts of alpha-linolenic acid, which has a poorly understood relationship with both the development of prostrate cancer in otherwise healthy man, and also the worsening of the cancer in men who already have prostrate cancer. However, this link has only been shown between animal sources of alpha-linolenic acid, which is slightly different than the form found in plants and flaxseed oil.
Another possible side effect of flaxseed oil occurs during pregnancy. Minimal research done has shown that flaxseed oil taken during the second half of pregnancy can result in premature birth. Because flaxseed oil taken as a nutritional supplement should not be taken for very long durations, it is probably best to simply discontinue the use of this supplement during pregnancy anyway. In the same way, flaxseed oil has not been adequately researched in regards to breastfeeding. Because most nutrients are passed directly to the child during breastfeeding, it is likely the baby would have digestion problems if the mother is taking greater than 25mg per day.
Finally, flaxseed oil can cause changing in blood clotting and bleeding. This side effect is serious in persons who already have a disease or condition that affects blood clotting. Also, those about to have surgery should discontinue use for one month prior to the surgery.
As with all nutritional supplements, when taken at levels above 10mg per day, always inform your doctor that you are taking this supplement as it can have serious interactions with other medications and treatments, especially those dealing with cardiovascular health and blood clotting. During pregnancy and breastfeeding, most nutritional supplements should be completely discontinued because in most cases, the effect on the baby has not been tested scientifically.