Flax seed and flax seed oil are excellent sources of alpha-linolenic acid, which the body converts to essential omega-3 fatty acids. Flax seed has many health benefits, according to the Cleveland Clinic, including reducing blood triglyceride levels, blood pressure, blood clot formation and inflammatory response. Flax seed contains lignans, a phytoestrogen that protects against certain cancers, and also provides protein, potassium and fiber. You can sprinkle flax seed on cereal, yogurt and salad, and add it to recipes for baked goods. Additionally, you can mix whole or bruised flax seed with liquid and drink it. Some bad side effects are possible with flax seed, but they are primarily associated with consuming large amounts. The Cleveland Clinic says there is no hard-and-fast rule on how much is too much, so you should consult a doctor before using flax products.
Flax seed may have laxative properties, as noted by the U.S. National Institutes of Health. This could lead to abdominal discomfort, an increased number of bowel movements and diarrhea. The NIH recommends that people with diarrhea, irritable bowel syndrome, diverticulitis or inflammatory bowel disease, including Crohn's disease and ulcerative colitis, should not consume flax seed.
Digestive Tract Obstruction
Flax seed may cause obstruction of the esophagus, intestines or bowel if taken in large doses or without enough liquid, warns the NIH. Anyone with narrowing of the esophagus, intestine or bowel, or who already has an obstruction in these areas, should not consume flax seed. Additionally, scleroderma patients should consult with a doctor before using flax seed, according to the University of Michigan Health System. Some scleroderma patients have developed severe constipation and bowel obstruction after beginning fiber supplementation.
Although allergic reactions to flax seed are very uncommon, according to the UMHS, some severe reactions have been reported. Symptoms have included abdominal pain, nausea and vomiting. Life-threatening anaphylaxis also has occurred. Anaphylaxis involves a sudden drop in blood pressure and difficulty breathing.
Effects of a flax seed overdose have been researched in animal studies, according to the NIH. Signs may include shortness of breath, rapid breathing, weakness and trouble walking. A flax seed overdose also may cause seizures or paralysis.
Flax seed may have estrogen-like effects, and women taking flax seed daily may experience changes in menstruation, according to the NIH. The NIH advises that women with hormone-related health conditions be cautious about using flax seed. These conditions include endometriosis, polycystic ovary syndrome, uterine fibroids, and breast, ovarian or uterine cancer. Pregnant women also should not consume supplemental flax seed, as it could stimulate menstruation or cause other hormonal effects that might be harmful to the developing baby.
Effects on Other Health Disorders
Omega-3 fatty acids can increase blood sugar levels, so people with diabetes should be cautious about consuming flax seed, according to the NIH. Flax seed also may elevate the risk of excessive bleeding because it decreases clotting. People with bleeding disorders or taking medications or supplements with blood-thinning effects may need to be cautious about using flax seed supplements. If consuming enough flax seed on a regular basis, these patients may need a change in medication dosage. Another health condition calling for caution with flax seed consumption is bipolar disorder, as flax seed may cause mania in people with this illness.