Flaxseed and flaxseed oil are rich sources of an omega-3 fatty acid called alpha-linolenic acid. Research shows that omega-3 fatty acids are good for the heart.

Flaxseed has a lot of fiber. It's also high in substances called lignans that are found in plants. Lignans contain phytoestrogens. Some research suggests that phytoestrogens may help fight cancer. Flaxseed oil does not have fiber or phytoestrogens.

Flaxseed can be used whole or crushed. It also comes in a powder form as meal or flour. It's often mixed with or baked into foods. Flaxseed oil is available as a liquid or as capsules.

People use flaxseed and flaxseed oil to help lower cholesterol and blood sugar and to treat digestive conditions. Some people also take flaxseed to treat inflammatory diseases.

Here's what the research shows about flaxseed and flaxseed oil for the following conditions:

• Heart disease. Some studies suggest that alpha-linolenic acid, which is found in flaxseed and flaxseed oil, might benefit people with heart disease. Some research also suggests that flaxseed and flaxseed oil might help lower high blood pressure, which may help lower the risk of heart disease.
• Cholesterol levels. Several studies have found that taking flaxseed daily can lower total cholesterol and low-density lipoprotein cholesterol, also called LDL cholesterol. LDL is considered the "bad" cholesterol.
• Diabetes. Flaxseed might lower blood sugar in people with type 2 diabetes, but studies are mixed. Flaxseed oil has not been found to help lower blood sugar.
• Cancer. The research is mixed on whether flaxseed or flaxseed oil has an effect on cancer.
• Menopausal symptoms. Research results are mixed when it comes to the use of flaxseed to treat symptoms of menopause, including hot flashes.
• Constipation. Some studies have shown flaxseed to be helpful in easing constipation.

When taken in recommended amounts, flaxseed and flaxseed oil are generally safe to use. But when taken in large amounts and with too little water, flaxseed can cause:

• Bloating.
• Gas.
• Diarrhea.

Do not take flaxseed or flaxseed oil if you're pregnant or breastfeeding.

For some people, flaxseed or flaxseed oil can cause an allergic reaction.

Don't eat raw or unripe flaxseeds.

Flaxseed oil might lessen the blood's ability to clot. Because of this, if you're having surgery, be sure to tell your healthcare team that you take flaxseed oil. You may need to stop taking flaxseed oil before you have surgery.

Flaxseed or flaxseed oil may lead to problems if you're taking the following medicines:

• Anticoagulant and antiplatelet medicines. These medicines lower the blood's ability to clot. Flaxseed also might lessen blood clotting. Because of that, it's possible that taking flaxseed or flaxseed oil along with anticoagulant or antiplatelet medicines might raise the risk of bleeding.
• Blood pressure medicines. Flaxseed may lower blood pressure. So taking flaxseed or flaxseed oil along with medicines that lower blood pressure might lower blood pressure to a level that isn't healthy.
• Diabetes medicines. Flaxseed may lower blood sugar. Taking flaxseed along with diabetes medicines might lower blood sugar too much. The same is true if you take flaxseed along with other medicines that have the potential to lower blood sugar.
• Estrogens. Flaxseed may hinder the effects of estrogen. That means taking flaxseed might lower the effectiveness of birth control pills and estrogen replacement therapy.

Talk to your healthcare professional before you start taking flaxseed or flaxseed oil to make sure it's right for you.