Flaxseed oil is not inflammatory. It is one of the richest plant sources of alpha-linolenic acid (ALA), an omega-3 fatty acid with well-documented anti-inflammatory properties. Pooled data from randomized controlled trials shows that flaxseed intake significantly lowers two key markers of inflammation in the body. The one exception: if flaxseed oil is heated to high temperatures, it oxidizes rapidly and can produce compounds that work against you.
How Flaxseed Oil Reduces Inflammation
Your body uses omega-3 fatty acids to produce signaling molecules that help resolve inflammation rather than promote it. Flaxseed oil is roughly 50-60% ALA, making it the most concentrated plant source of this particular omega-3. Once consumed, ALA competes with omega-6 fatty acids for the same metabolic pathways, effectively shifting the balance away from pro-inflammatory compounds.
A systematic review and meta-analysis of randomized controlled trials found that flaxseed intake significantly reduced circulating levels of high-sensitivity C-reactive protein (a precise measure of low-grade inflammation) and TNF-alpha, one of the most important inflammatory signaling molecules involved in cardiovascular disease and other chronic conditions. The effect on a third marker, IL-6, was not statistically significant.
The anti-inflammatory benefit was strongest in people who already had elevated inflammation, particularly those with a BMI over 30. In that group, flaxseed lowered TNF-alpha, CRP, and high-sensitivity CRP compared to placebo. For people with lower baseline inflammation, the reductions were smaller and not always statistically meaningful. This pattern makes sense: there’s more room to improve when inflammation is higher to begin with.
Flaxseed Oil vs. Fish Oil
Fish oil contains EPA and DHA, two omega-3 fats that are more biologically active than ALA because the body can use them directly. Your body does convert some ALA into EPA and DHA, but the conversion rate is limited. In healthy young men, about 8% of dietary ALA converts to EPA and 0-4% to DHA. Women convert more efficiently, with roughly 21% reaching EPA and 9% reaching DHA, likely due to the influence of estrogen on the process.
Despite this conversion bottleneck, flaxseed oil holds its own in head-to-head comparisons. A retrospective study of patients with coronary heart disease and type 2 diabetes found that flaxseed oil was actually more effective than fish oil at reducing high-sensitivity CRP and serum insulin levels. Both oils had similar effects on other cardiovascular risk markers. This suggests that ALA’s anti-inflammatory action isn’t entirely dependent on conversion to EPA and DHA; it likely works through additional pathways of its own.
When Flaxseed Oil Can Become Harmful
The same quality that makes flaxseed oil anti-inflammatory, its high ALA content, also makes it extremely fragile. ALA is a polyunsaturated fat with three double bonds in its chemical structure, and each one is a site where oxygen, heat, or light can trigger oxidation. When flaxseed oil oxidizes, it produces peroxides and other breakdown products that can promote inflammation rather than reduce it.
Lab testing confirms that heating flaxseed oil to 180°C (356°F), a typical deep-frying temperature, causes a dramatic increase in oxidation markers and a sharp drop in ALA content. In some regions, flaxseed oil is still used for cooking at temperatures up to 190°C, but this essentially destroys the beneficial fatty acids and creates the opposite of what you’re looking for.
To keep flaxseed oil anti-inflammatory rather than pro-inflammatory:
- Never cook with it. Use it cold, drizzled over salads, mixed into smoothies, or added to food after cooking.
- Store it in the refrigerator in a dark glass bottle. Light and warmth accelerate oxidation even at room temperature.
- Check the expiration date. Rancid flaxseed oil has a bitter, paint-like smell. If it smells off, discard it.
How Much Flaxseed Oil to Use
Clinical trials have used a range of doses, but most of the positive inflammation results come from studies using whole or ground flaxseed at around 30 grams per day (about two tablespoons). In one trial of 120 patients with rheumatoid arthritis, 30 grams of flaxseed daily led to significant decreases in joint pain and morning stiffness after three months compared to controls.
If you’re using flaxseed oil specifically rather than ground flaxseed, you get concentrated ALA but miss out on two other anti-inflammatory components found in whole flaxseed: lignans (plant compounds with antioxidant activity) and soluble fiber. A tablespoon of flaxseed oil provides roughly 7 grams of ALA, which is well above the adequate intake level of 1.1-1.6 grams per day. For general anti-inflammatory purposes, one to two tablespoons of flaxseed oil daily is a reasonable range based on the amounts studied in trials.
Who Should Be Cautious
Flaxseed oil has a mild blood-thinning effect because omega-3 fats can reduce platelet aggregation. If you take anticoagulant or antiplatelet medications, this theoretical interaction is worth discussing with your doctor before adding flaxseed oil to your routine. The risk is not well quantified in clinical studies, but the mechanism is plausible enough that the National Center for Complementary and Integrative Health flags it as a concern.
People with digestive sensitivities may also notice loose stools at higher doses, since concentrated oils can have a mild laxative effect. Starting with a smaller amount and increasing gradually helps you gauge your tolerance.