Does Flaxseed Lower Testosterone? What the Science Says

January 4, 2026 •

3 min read

According to a 2023 meta-analysis of randomized controlled trials, flaxseed supplementation showed no significant effect on total testosterone levels in adults, challenging some earlier reports. This article explores the science behind the claim, examining if flaxseed truly lowers testosterone.

Quick Summary

Recent, comprehensive research indicates flaxseed does not significantly alter total testosterone levels in healthy adults, despite earlier, smaller studies suggesting otherwise due to its lignan content.

Key Points

No Significant Effect on Total T: Recent and larger-scale meta-analyses show that flaxseed supplementation does not significantly lower total testosterone levels in adults.
Lignans are Key: Flaxseed's effect on hormones is primarily due to lignans, plant compounds that act as phytoestrogens.
Context Matters: Effects might be more noticeable in individuals with pre-existing hormonal conditions like PCOS, though recent evidence is mixed.
Prostate Health Benefits: For men, flaxseed is more consistently linked to prostate health benefits, potentially by inhibiting the conversion of testosterone to DHT.
Benefit for Women: For women, flaxseed is known to help balance estrogen levels and can relieve menopausal symptoms.
Benefits Outweigh Risks: For most healthy individuals, moderate flaxseed consumption offers numerous health benefits without causing a significant drop in testosterone levels.

The idea that flaxseed lowers testosterone often arises from its high lignan content. Lignans are phytoestrogens, plant compounds that can act similarly to estrogen in the body, leading to speculation about anti-androgenic effects. However, the actual impact is nuanced and has been refined by recent scientific studies.

The Lignan Connection and Early Research

Lignans, particularly secoisolariciresinol diglucoside (SDG), are converted by gut bacteria into enterodiol and enterolactone. These can interact with sex hormone-binding globulin (SHBG), potentially reducing the amount of free testosterone. This mechanism fueled early studies suggesting a reduction in testosterone.

An earlier study on men with prostate cancer noted a decrease in testosterone levels.
A case study reported a drop in testosterone in a woman with PCOS using flaxseed.
Lignans may also inhibit the enzyme 5α-reductase, which converts testosterone to DHT.

Current Scientific Consensus: Recent Meta-Analyses

More recent and extensive research provides a clearer picture for healthy individuals. A 2023 systematic review and meta-analysis of randomized controlled trials (RCTs) found that flaxseed supplementation did not significantly affect total testosterone, SHBG, or free androgen index in adults. This comprehensive analysis included participants with various health conditions, indicating that flaxseed does not reliably lower total testosterone across diverse adult populations. The inconsistencies with earlier findings may be due to smaller sample sizes, confounding factors, or the relatively weak hormonal effects of lignans compared to the body's natural regulation.

Flaxseed's Hormonal Effects: A Broader View

Flaxseed's impact on hormones appears to differ depending on gender and health status.

Men's Health and the Prostate

While not significantly lowering total testosterone in healthy men, flaxseed may benefit prostate health by potentially inhibiting the enzyme 5α-reductase, which can affect DHT levels.

Women's Health and Estrogen

For women, flaxseed is often beneficial for balancing estrogen, especially during menopause. Its lignans act as weak phytoestrogens, potentially easing symptoms like hot flashes.

Key Considerations for Hormonal Impact

Individual Health: Those with pre-existing hormonal imbalances might experience different effects.
Dosage and Duration: Most studies involve higher doses (30-40g daily) than typical dietary intake.
Diet and Lifestyle: Overall diet and gut health influence how lignans are processed.

Conclusion

Despite earlier reports, the most recent and robust scientific evidence indicates that flaxseed does not significantly lower total testosterone in healthy adults. While lignans can interact with hormone metabolism, their impact is likely minor with typical dietary consumption. For healthy individuals, the many benefits of flaxseed outweigh concerns about testosterone levels. Those with specific hormonal conditions should consult a healthcare provider for personalized advice.

Flaxseed's Effects on Testosterone: A Summary Table


Aspect	Scientific Consensus	Relevant Evidence
Effect on Total Testosterone (Healthy Adults)	No significant effect observed in recent meta-analyses.	Meta-analysis of 10 RCTs found no significant change in total testosterone levels in adults.
Proposed Mechanism (Lignans)	Lignans may weakly bind to testosterone or increase SHBG, reducing free testosterone, but this is not clinically significant for most.	Test-tube studies and earlier research on lignan function suggest potential anti-androgenic effects.
Effects on Specific Conditions (e.g., PCOS)	Early case studies reported reductions, but more robust research shows mixed results.	A 2009 case study reported significant testosterone drop in a woman with PCOS. However, a later RCT included in the 2023 meta-analysis showed no significant effect on sex hormones in women with PCOS.
Effect on Prostate Health (Men)	May benefit prostate health by potentially inhibiting the conversion of testosterone to DHT.	Animal and human trials suggest potential anti-cancer properties and protective effects for the prostate.

For more detailed scientific data, refer to the following resource: The effect of flaxseed supplementation on sex hormone profile: a systematic review and meta-analysis of randomized controlled trials.

Frequently Asked Questions

Yes, for most healthy men, consuming flaxseed as part of a balanced diet will not significantly lower their total testosterone levels. The belief that it does is based on older, smaller studies, while more robust evidence shows no significant effect.

Lignans are phytoestrogens that can bind to sex hormone-binding globulin (SHBG) or inhibit the enzyme that converts testosterone to DHT. While this can have hormonal effects, recent research indicates it does not lead to a significant change in overall testosterone in healthy adults.

Some evidence suggests that flaxseed can have a protective effect on the prostate, possibly by inhibiting the conversion of testosterone into the more potent DHT. This is distinct from a general reduction in testosterone.

Dosage varies between studies, but around 1-2 tablespoons (15-30g) of ground flaxseed daily is a common and safe amount used in research. Always consult a doctor before starting any new supplement regimen.

Ground flaxseed is generally considered more bioavailable, meaning the body can absorb its nutrients, including lignans and omega-3s, more easily than from whole seeds, which may pass through the digestive tract undigested.

No, the feminizing effect is a widespread myth that is not supported by scientific evidence. The amount of phytoestrogens in a normal dietary intake of flaxseed is too small to cause such significant hormonal changes.

Some studies use flaxseed oil, while others use ground seeds, and the results can differ. For example, one 2023 meta-analysis included studies that used either ground flaxseed or flaxseed oil capsules and still found no significant effect on overall sex hormone levels.