Medically Reviewed by Jabeen Begum, MD on September 04, 2023
5 min read

Flaxseed is the seed of the flax plant, which is an annual herb. It has been used as both food and remedy in Mediterranean cultures for thousands of years.

It's a high-fiber food that's probably best known today as a vegetarian source of heart-healthy omega-3 fatty acids. But it contains other healthy nutrients, too. Flaxseed oil, which is made from pressed, dried flaxseeds, shares some, but not all, of flaxseed's health properties.

 Flaxseed can provide many health benefits, such as:

  • Vitamins, minerals, and fiber. It is high in magnesium, which is important for more than 300 different reactions in your body and helps with functions such as bone strength and building your DNA. Flaxseed also supplies a significant amount of choline, which helps your body’s cells communicate with each other.

  • Heart health. Flaxseed has been shown to improve heart health in a number of ways. It's rich in a type of omega-3 fatty acid called alpha-linolenic acid (ALA), which may help lower your risk of heart attack.

Flaxseed is thought to help with several conditions that are risk factors for heart disease. There's good evidence that flaxseed and flaxseed oil may lower cholesterol levels. Some studies also indicate it could help lower blood pressure.

  • Lower risk of cancer. Compounds called lignans have been linked to a lower risk of cancer, especially prostate and breast cancer. Flaxseed is one of the best natural sources of lignans, containing as much as 800 times more than other plants. It's still being studied for its potential to prevent different types of cancer.

  • Digestive health. Flaxseed is often used as a fiber supplement because it has so much dietary fiber. The forms of fiber found in flaxseed improve digestion by helping your intestines process waste more effectively and absorb cholesterol before it makes it to your bloodstream. Flaxseed may also ease constipation.

  • Control blood sugar. If you have type 2 diabetes, adding flaxseed to your diet may help lower your blood sugar levels. But talk to your doctor before using flaxseed, as it may interact with diabetes medications, such as insulin.

  • Stroke prevention. The ALA in flaxseed may help improve cardiovascular health and reduce the risk of stroke.

  • Menopausal symptoms. Research into whether flaxseed could ease menopause symptoms, such as hot flashes, has been inconclusive.

Always talk to your doctor before taking a flaxseed supplement or using flaxseed oil.

Flaxseed is surprisingly rich in protein, providing a healthy, plant-based form to help with muscle rebuilding and hair growth.

It's also an excellent source of:

  • Iron
  • Potassium
  • Folate
  • Magnesium
  • Choline
  • Phosphorus
  • Calcium
  • Niacin

Nutrients per serving

A serving of 4 tablespoons of flaxseed contains:

  • Calories: 148
  • Protein: 6 grams
  • Fat: 10 grams
  • Carbohydrates: 10 grams
  • Fiber: 8 grams
  • Sugar: 0 grams

There is no single recommended dose of flaxseed. But a daily intake of 1-2 tablespoons of ground flaxseed can be a healthy amount. Up to 1 tablespoon of flaxseed oil daily is thought to be a safe and healthy amount. Ask your doctor for advice about how much is right for you.

You can mix flaxseed with liquid or add it to foods, such as muffins or bread. Whole flaxseeds are hard for your body to digest, though. Grinding flaxseed before use helps you get the full benefits of its nutrients. Some people use a small coffee grinder to grind daily doses.

Flaxseed itself is a natural food. It's also sometimes added to foods you can buy, such as breads and cereals. You can also buy ground flaxseed as flour.

Like any other oil, flaxseed oil can be used in salad dressings or dips. But you shouldn't use it for cooking because of its low smoke point (the temperature at which it burns). You can also purchase capsules filled with flaxseed oil.

At normal doses, flaxseed and flaxseed oil seem to be safe. But there are some things to watch out for:

  • Side effects. Flaxseed, but not flaxseed oil, contains soluble fiber. It might cause diarrhea, cramping, gas, and bloating. High doses of flaxseed, especially when not taken with enough water, can cause constipation and, rarely, bowel obstruction. If ground flaxseed or flaxseed oil goes rancid, it may cause cholesterol problems and inflammation.
  • Interactions. If you take any medicines or other supplements regularly, talk to your doctor before you use flaxseed. It may block the normal absorption of medicines. Always take medicines at least 1-2 hours after using flaxseed. Flaxseed and flaxseed oil may also interact with drugs such as blood thinners, NSAID painkillers, hormone treatments, birth control pills, and some medicines for blood pressure, cholesterol, and diabetes. Use caution when taking flaxseed or flaxseed oil with other supplements.
  • Risks. Never eat raw or unripe flaxseed as it could be poisonous. People who have diabetes, bipolar disorder, high triglycerides, bleeding disorders, or prostate cancer should talk to a doctor before using flaxseed or flaxseed oil. Anyone with digestive problems (such as Crohn's disease, IBS, or colitis) or hormone-sensitive diseases such as endometriosis, PCOS, breast cancer, and uterine cancer shouldn't use flaxseed unless instructed by their doctor. Given the lack of evidence about their safety, flaxseed and flaxseed oil aren't recommended for children or women during pregnancy or breastfeeding.

Things to watch out for

Like most seeds and nuts, flaxseed is relatively high in calories. One or two servings of flaxseed per day may help you improve your health without consuming too many calories.