Seed oils and the omega-6:omega-3 ratio: what the evidence actually says

Few nutrition topics generate more heat and less light than seed oils. One camp calls them toxic and inflammatory; the other points to trials where linoleic acid — the main omega-6 in sunflower, soybean and rapeseed oil — lowers LDL cholesterol. Both are partly right, and the reason they talk past each other is that the useful number is not the absolute amount of omega-6 you eat, but its balance against omega-3.

The ratio, not the villain

Omega-6 and omega-3 fatty acids compete for the same enzymes that convert them into signalling molecules — some pro-inflammatory, some resolving. Simopoulos (2002, Biomedicine & Pharmacotherapy) argued that ancestral diets ran an omega-6:omega-3 ratio close to 1:1 to 4:1, whereas the modern Western diet sits nearer 15:1 to 20:1. The problem in that framing is rarely that omega-6 is high in isolation — it is that omega-3 is so low that the balance tips hard toward the inflammatory end.

The fix for a bad omega-6:omega-3 ratio is usually not cutting omega-6 to zero — it is eating enough omega-3 to bring the balance back.

Why 'just avoid seed oils' is the wrong lesson

Marklund and colleagues (2019, Circulation) pooled 30 cohorts and found that higher blood levels of linoleic acid were associated with LOWER cardiovascular disease and mortality, not higher. That is hard to reconcile with the 'seed oils are poison' narrative. The more defensible reading of the whole literature is that ultra-processed foods fried and formulated with cheap oils are the issue — the food matrix, not the fatty acid — and that the single most reliable move is to raise marine omega-3 (EPA and DHA) rather than to wage war on a specific cooking oil.

How Misi makes the ratio visible

Most people have no idea what their ratio is, because no ordinary food tracker computes it. Misi's Nutrition Insights includes a dedicated Omega-6:Omega-3 chart that reads the ALA, EPA and DHA content of every ingredient you log against total omega-6, and plots the daily ratio with a target line at 4:1 and a risk line at 10:1. Days built around oily fish drop the ratio sharply; a week of takeaways and no fish shows the line climbing — an honest signal, not missing data.

The practical takeaway

Stop worrying about whether a splash of rapeseed oil in a home-cooked meal is harming you — in the context of an otherwise whole-food diet it almost certainly is not. Spend that attention on the denominator instead: two to three portions of oily fish a week, or a quality EPA/DHA supplement, will move your ratio further and faster than any amount of oil-avoidance.

Misi is a coaching and wellness platform, not a medical service. If you have been advised to follow a specific fat-restricted diet, follow your clinician's guidance.