Health Benefits of Flaxseed - A Historically Revered Food and Resource
The flax plant is exceptionally notable because it has been cultivated since the very beginning of human civilization. It is so versatile that it Latin name, Linum usitatissimum, means “very useful.” For much of human history it was a critical source of fiber for industrial use, and humans have also been consuming the seeds for thousands of years. Industrial uses include production of linen fabrics, rope, and paper. Modern science has confirmed how nutritionally valuable flaxseed is, so its place as a historically-revered plant is clearly deserved.
Health Benefits of Flaxseed
1. Powerful Anti-inflammatory Food with Potential Wound Healing Properties
Numerous studies have conclusively shown that flaxseed can exert anti-inflammatory effects in humans. This makes sense given the Omega-3 fatty acids present along with supportive antioxidants and minerals. A meta-analysis of 32 studies published in 2019 concluded that flaxseed could reduce certain inflammatory biomarkers in humans. The types of studies were extensive and included those using whole flaxseed, flaxseed oil, or flaxseed-derived nutrients.
Interestingly enough, some of flaxseed’s anti-inflammatory properties may derive from a cannabinoid-like compound. Cannabidiol (CBD) from the cannabis or hemp plant has received significant attention in the media for its anti-epileptic, anti-cancer, anti-anxiety, analgesic, and other health properties. In 2012, researchers from Poland reported the discovery of a cannabinoid-like compound apparently similar to CBD, and this compound could reduce inflammation in human cells by modulating expression of genes related to inflammation.
Another study by Polish researchers in 2015 further pointed to the ability of flax fiber extract to inhibit skin inflammation. The in vitro study revealed the extract could inhibit expression of inflammatory cytokines. As importantly, flax fiber was able to increase activity of enzymes called matrix metalloproteinases, which help remodel the extracellular matrix as part of the wound healing process. Ultimately, the flax extract was said to contain components that act as “wound healing activators.”
C-reactive protein (CRP) is one of many biomarkers of inflammation, and a meta-analysis of studies published in the journal Nutrients found that flaxseed or derivative product consumption reduced CRP in obese individuals. While there was no significant effect in other populations, another trial described in the next section found that flaxseed oil reduced CRP in patients with coronary artery disease. Yet another trial described below further demonstrated the ability of flaxseed to reduce pro-inflammatory cytokine levels. Patients with kidney issues have also responded to flaxseed oil treatment by showing lower CRP levels.
Flaxseed may be able to help treat rheumatoid arthritis (RA), one of the most common and painful inflammatory diseases. A 2021 trial in the European Journal of Nutrition found that 30 grams/day of flaxseed for 12 weeks reduced the Disease Activity Score in RA patients. Those who received flaxseed instead of roasted wheat also had stronger decreases in morning stiffness, pain severity, and disease feeling.
Most studies have focused on the consumption of flaxseed, but a randomized controlled trial in the journal Clinical Rheumatology showed that even topical use of flaxseed could provide benefits to patients with hand osteoarthritis. Compared with a hot compress or control, a flaxseed poultice compress applied once a day for a week reduced pain and improved hand function efficiency to a greater extent.
The strong antioxidant profile of flaxseed may be linked to its anti-inflammatory effects. A 2021 meta-analysis of eight trials confirmed the ability of flaxseed to lower levels of an oxidative stress marker called malondialdehyde and increase total antioxidant capacity. The researchers concluded, “Our findings revealed that flaxseed oil supplementation might play a beneficial role in the reinforcement of the antioxidant defense system and amelioration of oxidative stress in adults.”
2. Cardiovascular Health and Diabetes
A tremendous amount of evidence shows how flaxseed can help improve cardiovascular health and manage diabetes. Starting with animal data, a 2020 study with rats revealed several mechanisms by which flaxseed may contribute to the management of Type 2 diabetes. Rats who received flaxseed oil had reduced fasting blood glucose, blood lipids, glycated hemoglobin, and a range of inflammatory cytokines like tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), and interleukin-17A. The endogenous antioxidant superoxide dismutase was also significantly elevated in the treated rats. Furthermore, the flaxseed oil had a positive impact on the gut microbiota, and resulted in higher production of beneficial short chain fatty acids like butyric acid. All of these effects were posited to “potentially contribute to dietary control of diabetes.”
The combination of flaxseed and a citrus-based compound called hesperidin was shown to have beneficial effects on patients with prediabetes in a 2021 study. The treatment group, who received 30 grams milled flaxseed and 1 gram of hesperidin per day (in addition to lifestyle modifications), had greater blood pressure reduction and improvements of inflammation, lipid levels, and glucose homeostasis measures than the control group who only used lifestyle modifications.
Diabetic foot ulcers occur in many patients, and new treatments are needed to fully manage them. A 2017 double-blind, placebo-controlled trial in the Journal of Diabetes and its Complications showed powerful impacts from flaxseed oil (delivering 2,000mg Omega-3 for 12 weeks) on ulcers and other metabolic markers. Those in the treatment group had significant decreases in both ulcer length and depth, the primary outcomes, along with decreases in insulin concentrations, insulin resistance, HbA1c levels, and CRP. There were also increases in insulin sensitivity and total antioxidant capacity in the blood. The researchers theorized these positive metabolic changes influenced the observed wound healing.
Although not related to diabetes, another trial following women with endometrial hyperplasia (abnormally thick lining of the uterus), and which used the exact same dosing and time protocol in the above study, found virtually identical effects from the flaxseed oil supplementation. These included decreased insulin and insulin resistance, along with lower fasting plasma glucose, as well as increases in total antioxidant capacity and the endogenous antioxidant glutathione.
A meta-analysis of controlled trials published in 2015 confirmed the ability of flaxseed to lower blood pressure. The effects of whole flaxseed appeared greater than flaxseed oil, and consumption of the seed for over 12 weeks was also important for maximum effects.
Another meta-analysis from 2021 determined flaxseed could significantly improve lipid parameters among patients with hyperlipidemia (too much fat in the blood, essentially). Based on 14 randomized controlled trials, flaxseed was conclusively determined to reduce total cholesterol, low-density lipoprotein cholesterol (bad cholesterol), and triglycerides. Interestingly, while flaxseed had no effect on the “good” high-density lipoprotein (HDL) cholesterol in patients with diagnosed hyperlipidemia, it did improve HDL in health subjects.
Women diagnosed with polycystic ovary syndrome often causes a host of metabolic abnormalities, which may potentially be alleviated with flaxseed. A 2020 randomized controlled trial compared lifestyle modification alone with the modification plus 30 grams/day of flaxseed powder. Those in the flaxseed group experienced significant reductions in weight, insulin levels, insulin resistance, triglycerides, CRP, IL-6, and leptin. Furthermore, they had better insulin sensitivity and HDL cholesterol, along with higher levels of a fat hormone called adiponectin which may help protect against diabetes and atherosclerosis. Ultimately, adding flaxseed to lifestyle modification was determined to be more effective than modification alone for improving these metrics.
Many people take fish oil, which is rich in long-chain Omega-3 fatty acids, for general and cardiovascular health. While fish oil mainly contains eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) Omega-3s, flax is rich in alpha-linolenic acid (ALA). EPA and DHA are generally more potent forms of Omega-3 that ALA must be converted into by the body. However, a 2019 randomized, placebo-controlled trial in the journal Phytotherapy Research found somewhat similar results between fish oil and flaxseed oil on measures of cardiovascular health in patients with Type 2 diabetes and coronary heart disease. Participants in the trial received 2,000mg Omega-3 from either fish or flaxseed oil for 12 weeks. Both oils were able to reduce insulin levels, and flaxseed oil in particular was associated with significant reductions in high-sensitivity CRP. Yet further, both oils were able to increase total antioxidant capacity in the subjects. This led researchers to conclude that the overall effects of flaxseed oil were similar to fish oil. Therefore, despite fish oil having a supposedly more effective Omega-3 profile, flax still held up.
Another trial published in 2019 by researchers in Iran further showed the benefits of flaxseed consumption for coronary artery disease patients. Those in the flaxseed group, receiving 30 grams/day for 12 weeks, experienced improved flow-mediated dilation, a desired outcome when arteries are not expanding properly due to disease. The flaxseed group also showed lower levels of CRP, IL-6, and TNF-α inflammatory cytokines, indicating an anti-inflammatory effect as well.
Interestingly, although the fats present in flaxseed appear responsible for many benefits, there are clearly other components which produce effects. A 2020 double-blind, randomized trial by Chinese researchers with the Institute of Nutrition and Health at Qingdao University found that adding defatted flaxseed flour to the breakfasts of overweight and obese adults resulted in improved weight loss. Those in the treatment group also experienced lower body mass index (BMI) and triglyceride levels. An anti-inflammatory effect was also observed, since the flaxseed meal was linked with lower levels of the pro-inflammatory cytokine IL-6.
3. Liver Health
Some human evidence indicates that flaxseed could help improve liver health. A 2020 study in the British Journal of Nutrition compared the effectiveness of flaxseed oil and sunflower oil (20 grams/day of either), alongside a low-calorie diet, on metrics of non-alcoholic fatty liver disease (NAFLD). While both oils were effective, flaxseed oil was substantially better at reducing the grade of fatty liver. Flaxseed oil was also able to reduce problematic liver enzymes in the blood, along with blood glucose and fat mass levels.
An earlier study in 2016 examined a higher dose of milled flaxseed, 30 grams a day over 12 weeks, for the treatment of NAFLD. Those who consumed flaxseed in addition to lifestyle modification, rather than lifestyle modification alone, experienced greater reductions in liver enzymes, body weight, insulin resistance, and hepatic fibrosis and steatosis (the accumulation of excess fibrous connective tissue and fat).
4. Gastrointestinal Health
The high amounts of fiber and antioxidants present in flaxseed may make it an especially healthy food for gastrointestinal support. A 2020 randomized controlled trial at Hua Dong Hospital in China compared 50 grams/day of flaxseed flour with 15mL/day of lactulose (a synthetic treatment for constipation) to determine which was more effective at relieving functional constipation. Both treatments were effective, but flaxseed exerted a significantly stronger effect, as evidenced by a greater reduction in the Wexner constipation score and higher defecation frequency per week. Quality of life also improved more in the flaxseed group.
Another randomized controlled trial published in 2018 confirmed the ability of flaxeed, at 20 grams/day for 12 weeks, to decrease constipation symptoms in Type 2 diabetes patients . In addition to that primary endpoint, the flaxseed intervention was also found to reduce weight, BMI, fasting plasma glucose, HbA1C, and cholesterol levels.
Ulcerative colitis (UC) is a form of inflammatory bowel disease which may benefit from flaxseed. A 2021 trial in the International Journal of Clinical Practice gave UC patients 30 grams of ground flaxseed and 10 grams of flaxseed oil per day for 12 weeks. Compared to the control group, the flaxseed group had lower CRP and higher levels of the anti-inflammatory cytokine interleukin-10. Most importantly, their quality of life was better. This led researchers to state that “grounded flaxseed and [flaxseed oil] attenuated systemic inflammation and improved disease severity in UC patients.”
Other Unique Uses
Flaxseed oil may be especially beneficial for women undergoing fibrocystic breast changes, which involve the development of benign cysts and scar-like tissue. A 2021 trial found that administration of flaxseed oil or Vitamin E reduced breast pain in patients with fibrocystic changes, as well as actually decrease the nodules themselves. An earlier trial in 2016 also supported the role of flaxseed for mitigating breast pain.
While there were not many details provided, a 2015 trial in the journal Holistic Nursing Practice reported that three months of flaxseed consumption reduced menopausal symptoms and improved quality of life among women in the trial’s treatment groups.
Shockingly, flaxseed oil can even be used as an eyedrop for treating dry eye disease. While it must be combined with other ingredients to exert efficacy, a 2020 trial suggested that flaxseed oil could be a functional ingredient in eyedrop products.
Patients undergoing dialysis often experience bone resorption (breakdown of bone) and thus are at higher risk of osteoporosis. A 2018 randomized controlled trial found that 6 grams/day of flaxseed oil for 8 weeks may be effective for reducing bone resorption, although since this was based on plasma biomarkers, more research is needed to clarify how effective flaxseed can be for improving bone health.
Another trial in 2017 pointed to further benefits of flaxseed supplementation for dialysis patients. The same dosing protocol mentioned in the study above was used here, and resulted in higher levels of red blood cells, hemoglobin, and other important metrics, while also reducing hepcidin. Too much hepcidin, an iron-regulating hormone, can lead to anemia. This and the above study suggest flaxseed may have powerful regulatory effects for the blood and bones.
There may even be a role for flaxseed as a support for cancer treatment. A 2013 trial in the Journal of Medicinal Food found that giving 147 prostate cancer patients 30 grams/day of flaxseed for 30 days may have impaired prostate cancer cell proliferation, based on lower levels of a cancer marker in tumor tissue. Another similar trial in 2008 further showed the ability of flaxseed to reduce proliferation rates in prostate cancer patients. However, larger scale and longer-term trials are needed to determine the full extent of flaxseed’s benefits.
Summary
The tremendous number of well-designed clinical trials makes it clear that flaxseed can positively impact numerous areas of health. It is easy to add to so many foods like yogurts, salads, or cereals, and is a seamless addition to blended shakes and smoothies. Lately I have been mixing a blend of sprouted flax and chia seed into regular water, which has been surprisingly enjoyable. I do this twice a day, and know that I’m getting a massive quantity of Omega-3 and antioxidants in just a couple minutes. Try it, you may also be surprised at how easy and tasty it is to consume straight.
