The nutrients in flaxseed may help lower the risk of diabetes, cancer, and heart disease. For this reason, it is sometimes thought of as a functional food, a food that can be consumed to achieve health purposes.
Flax is one of the oldest fiber crops in the world. It is known to have been cultivated in ancient Egypt and China. In Asia, it has played a role in Ayurvedic medicine for thousands of years.
However, not all of these uses are supported by research.
- Flaxseed has long been thought to offer health benefits.
- It contains fiber, fat, protein, and various minerals and vitamins.
- These nutrients may offer protection against cancer, diabetes, and cardiovascular problems.
- Consuming ground flaxseeds enables the body to absorb the nutrients more effectively.
Flaxseed has been used since ancient times as a food and a medicine, but what does the research say?
The therapeutic and beneficial properties of consuming flaxseed are not yet completely understood, and there is little evidence from high-quality research to confirm its benefits.
However, it contains nutrients which may help prevent a number of health problems.
Possible benefits include helping prevent cancer, reducing cholesterol and blood pressure, and protecting against radiation.
Flaxseed contains omega-3 fatty acids. These are thought to disrupt the growth of cancer cells and to prevent their development. Consuming omega-3 oils may help protect against different types of cancer.
It also contains lignans. Lignans are thought to have antiangiogenic properties. This means they stop tumors from forming new blood vessels. The lignan content of flaxseed is thought to be over 800 times higher than that of other foods.
The lignans in flaxseed may help it protect against a variety of cancers, especially if consumed for life as a part of a healthful diet and lifestyle.
Lowering cholesterol and improving heart health
The fiber, phytosterols, and omega-3 content of flaxseed may help boost heart health. The lignans it contains may help protect against cardiovascular and other chronic diseases.
Phytosterols are molecules that are similar in structure to cholesterol, but they help prevent the absorption of cholesterol in the intestine. Eating foods that contain these nutrients may help reduce the levels of LDL, or "bad" cholesterol, in the body.
In 2010, researchers at the Iowa State University's Nutrition and Wellness Research Center looked at the effect on cholesterol levels in men who consumed at least 3 tablespoons of flaxseed a day, including at least 150 milligrams (mg) of lignans. The men saw a decrease of nearly 10 percent in their cholesterol levels after 3 months. However, it did not have the same effect on women.
Prof. Suzanne Hendrich, who led the Iowa research, suggested that the different may be due to testosterone levels in men, which are lower in women.
Fiber is also thought to help reduce cholesterol and the risk of cardiovascular disease. Flaxseed contains both soluble and insoluble fiber. According to the Mayo Clinic, soluble fiber dissolves to produce a gel-like substance that can help reduce cholesterol and glucose levels.
The American Heart Association (AHA) recommend eating more fiber as part of a heart-healthy diet. One benefit is that it makes you feel full, so you are less likely to overeat.
Omega-3 oils, usually found in oily fish, have been linked to reductions in cardiovascular risk. Some researchers have suggested that flaxseed could offer an alternative to marine sources of omega 3.
Does flaxseed prevent hot flashes?
A study of 188 women, published in the journal Menopause, found that a daily intake 40 g of flaxseed, representing 400 mcg of lignans, improved the symptoms of hot flashes by around half.
However, women taking a placebo also experienced a reduction, and it was not clear that effects were due to the flaxseed. The crushed flaxseed was sprinkled onto cereal, yogurt, or mixed into a drink.
There were hopes that flaxseed could become an alternative or complementary therapy for hot flashes, but the researchers concluded that the study "was not able to provide support for the use of flaxseed in reducing hot flashes more than a placebo."
Improving blood sugar
The lignans and other phytoestrogens are thought to help reduce the risk of chronic diseases, such as diabetes, because of an anti-inflammatory effect.
In a small study published in 2013, scientists gave 25 people 0 g, 13 g or 26 g of flaxseed every day for 12 weeks. The participants had prediabetes, and they were either men with obesity or overweight or women who had undergone menopause.
A study on rats, published in 2016, suggested that compounds found in flaxseed may help reduce the incidence of type 1 diabetes and delay the onset of type 2 diabetes in humans, but more studies are needed.
In 2016, researchers published results of a study in which 99 people with prediabetes were given 40 g, 20 g, or no flaxseed and no placebo each day for 12 weeks. The results indicated that consuming flaxseed powder every day may reduce blood pressure in people with prediabetes, but it does not improve levels of blood sugar and insulin resistance.
The benefits of flaxseed on the symptoms of diabetes remain unclear.
Flaxseed is rich in both soluble fiber, which dissolves in water, and insoluble fiber, which does not dissolve in water.
Insoluble fiber remains in the intestinal tract. It absorbs water and adds bulk to the digestive tract. This helps keep movement through the gut regular.
However, according to the National Center for Complementary and Integrative Health (NCCIH), there is little evidence that flaxseed helps reduce constipation. Consuming it with too little water can make constipation worse and possibly lead to an intestinal blockage.
Too much flaxseed or flaxseed oil can cause diarrhea.
The NCCIH is currently funding studies into whether the nutrients in flaxseed can help with:
Flaxseed has long been used in Ayurvedic medicine for health promotion, prevention, and a range of conditions, many to do with skin health.
A small study published in 2010 suggests that consuming flaxseed oil may help reduce skin sensitivity and roughness and improve skin hydration.
Protecting against radiation
Studies have found that the lignans in flaxseed may help protect against radiation. Scientists gave dietary lignans in flaxseed to mice with lung problems caused by radiation.
The mice that consumed the compounds derived from flaxseed had less inflammation, injury, and fibrosis, and a better survival rate that those that did not.
The researchers suggested that in the future, lignans from flaxseed may be useful for treating lung problems associated with radiation due to accidental exposure or radiation therapy.
Flaxseed is an excellent source of fiber, lignans, and of linoleic and alpha-linolenic acid (ALA), two omega-3 fatty acids that are essential for human health.
According to the United States Department of Agriculture (USDA), a 2.5-gram, or 1-teaspoon, serving of flaxseed contains:
Flaxseeds can be sprinkled on cereal, mixed with yogurt, blended into smoothies, or added to soups.
- 13 calories
- 0.72 g of carbohydrates, of which 0.04 g are sugars
- 0.46 g of protein
- 0.7 g of fiber
- 1.05 g of fat, of which 0.906 g are unsaturated
- 0 cholesterol
- 6 mg of calcium
- 0.14 mg of iron
- 10 mg of magnesium
- 16 mg of phosphorus
- 20 mg of potassium
- 1 mg of sodium
- 0.11 mg of zinc
- 2 micrograms (mcg) of folate
- 0.1 mcg of vitamin K
The USDA also note that flaxseed contains phytosterols. In every 100 g of flaxseed, there are 49.0 mg of phytosterols.
Lignans are also present in large amounts. Lignans are a type of phytoestrogen. Phytoestrogens are estrogen-like chemical compounds with antioxidant qualities. They can reduce levels of free radicals in the body.
Flaxseed is considered a good source of lignans, containing 0.3 g for every 100 grams (g) of flaxseed.
Lignans may help protect against cardiovascular disease and a range of chronic conditions, if consumed for life as part of a healthful diet and lifestyle. However, more research is needed to confirm the exact role they can play.
Omega-3 fatty acids are thought to be beneficial for the heart. They can only be obtained by eating the right foods, as the human body does not produce them.
Flaxseeds should be consumed in ground form, as whole flaxseeds can pass through the digestive tract undigested.
The nutrients in flaxseed may not benefit everyone.
Too much flaxseed can lead to:
- flatulence and bloating
- abdominal pain
- constipation or diarrhea
In people with a bowel obstruction, flaxseed could cause or worsen these symptoms.
Raw and unripe flaxseeds are not suitable for consumption, as they may be toxic. Flaxseed should always be consumed with plenty of fluid.
During pregnancy, women are advised not to consume it, because the phytoestrogens it contains could have an adverse effect. It may not be suitable while breastfeeding.
There is also a chance that the phytoestrogens in flaxseed may interfere with the action of birth control pills or hormone therapy.
The USDA notes that up to 12 percent flaxseed is safe to use in food.
It is not yet clear whether flaxseed does help control diabetes. Anyone who is taking medication for diabetes should check with their doctor before introducing flax seed in your diet, in case an interaction occurs.
Omega-3 fatty acids can increase the risk of bleeding, if used with blood thinners, such as warfarin (Coumadin). Omega-3 supplements or flaxseed products and blood thinners should be used only after discussing with a health professional.
As with any herb or supplement, care must be taken when consuming large amounts. Flaxseed in its natural form is preferable to taking flaxseed as a supplement. Supplements are not monitored Anyone who is considering taking it as an alternative or complementary therapy should first speak to their doctor.