Seeds (Chia, Flax, Hemp)

•RCT evidence— Flax BP trial; multiple smaller RCTs on lipids

What they bring

• ALA (omega-3 plant precursor): 1 tbsp flax ≈ 2.3 g ALA. Conversion to EPA/DHA is <10% but ALA itself has cardiovascular benefit.
• Lignans (mostly in flax): phytoestrogens with breast and prostate cancer signals.
• Soluble fibre: cholesterol lowering and satiety.
• Magnesium, manganese, phosphorus, zinc.

Evidence

• Blood pressure: Rodriguez-Leyva 2013 showed 30 g/day flaxseed lowered systolic BP by ~10 mmHg in hypertensive patients over 6 months — a remarkable effect size for a food.
• LDL: small but consistent reductions.
• Triglycerides: small reductions.
• Glycaemic response: chia and flax both blunt post-meal glucose.

Practical

• Add 1 tbsp ground flax or chia to oats, yoghurt, smoothies, or baking.
• Hemp seeds (~2 tbsp/day) provide more protein but less ALA than flax.
• Whole flax seeds pass through largely intact — grind fresh in a spice grinder.
• Chia can be eaten whole; soaks into pudding texture.

Cautions

• Very large flax intake (~50 g+ daily) can interfere with absorption of medications.
• Hormone-sensitive cancers: lignan content controversial — modest intake appears protective; very high intake during active treatment warrants oncologist input.
• Anticoagulants: high flax can mildly raise bleeding time.

Related entries

Omega-3, Fiber and the microbiome, Cardiovascular disease.