Trans Fat Index optimal range and reference range

Compiled by Alina Radu, founder of Sera, from the published sources below · Last reviewed November 9, 2026

Sera's bands for Trans Fat Index:

Optimal 0 – 1 %; sufficient 1 – 2 %; out of range below 0 or above 2 %.

Evidence grade: Functional / longevity target. A narrower target in common use in functional, integrative, preventive and longevity practice. It is not a universally validated diagnostic range.

At Sera's last range review a change to this band was proposed and held, because the evidence for it was thin, so the band is unchanged. The note below says where it matches published intervals and where it does not.

All units

Unit	Optimal	Sufficient	Out of range
%	0 – 1	1 – 2	below 0 or above 2

What the evidence says

The one fatty acid with no requirement and no beneficial level, so lower is unambiguously better and public-health guidance is unambiguous with it. One caveat on the figure: WHO's 1% is a share of total dietary ENERGY, while this band is a share of membrane fatty acids — the same number attached to a different quantity, so the guidance supports the direction rather than the exact edge. Levels have fallen sharply where partial hydrogenation was banned, so a raised value now usually points at imported processed or fried food. The 1% edge has peer-reviewed support as a red cell figure: a Health Canada analysis of the Canadian Health Measures Survey compares against a proposed threshold of 1% of total red cell fatty acids. It is a proposed research threshold and not a guideline one. The 2% edge has no source.

Assay: Results differ meaningfully between platforms and methods. Compare against the interval printed by the issuing laboratory before acting on a borderline value.

Sources

Proportions of trans fatty acids in erythrocytes of Canadian adults before the prohibition of partially hydrogenated oils in foods: results from the Canadian Health Measures Survey 2012-2015 — Demonty I, Nguyen L, MacFarlane AJ, et al. — The American Journal of Clinical Nutrition, 2024 · Peer-reviewed publicationNationally representative Canadian survey, 4,025 adults: mean total red cell trans fat 0.59% of total fatty acids, described as low against a proposed threshold of 1% above which cardiovascular risk may be higher. Matches Sera's optimal upper edge of 1%.
Red Blood Cell Fatty Acid Patterns from 7 countries: Focus on the Omega-3 Index — Schuchardt JP, Cerrato M, Ceseri M, et al. — Prostaglandins, Leukotrienes and Essential Fatty Acids, 2022 · Peer-reviewed publicationMean red cell levels measured by one laboratory method in 17 cohorts (Italy, Spain, Germany, Canada, United States, Japan, Korea; 167,347 people). Cohort means only: the paper gives no percentiles or reference interval. Total trans means: 0.59% in Canada, 0.66% in Italy, 0.96% in the German LURIC cohort, 0.77% to 0.91% in US laboratory cohorts from 2011 to 2019, and 2.10% to 2.70% in older US cohorts. Shows that 1% now separates current from pre-ban levels; does not support the 2% edge as a threshold.
REPLACE action package and guideline on saturated and trans-fatty acid intake — World Health Organization, 2023 · Government / public-health guidanceEstablishes that industrially produced trans fat should be eliminated from the food supply, and that total trans fat intake should stay below 1% of total energy. Read the quantity carefully: that is a DIETARY INTAKE threshold, not a red cell membrane percentage. Sera's band edge is a different measurement that happens to share the figure, so the source supports the direction — lower is unambiguously better, with no beneficial level — rather than the exact edge.

What Trans Fat Index measures

The combined share of industrially produced trans fatty acids in red blood cell membranes.

There is no beneficial level and no requirement, which makes this the one fatty acid where lower is unambiguously better. Levels have fallen sharply in countries that banned partial hydrogenation, so a raised value now usually points at imported processed food or fried food eaten out.

Related fatty acids markers

See Trans Fat Index in the full list of biomarker ranges

This page is a reference for practitioners, not medical advice. Sera's bands are practitioner targets for structured review, not diagnostic thresholds, and Sera does not diagnose or recommend treatment. Read a result alongside the interval printed by the issuing laboratory and the client's history and symptoms. Range set: Sera Production, version 1.0, last reviewed November 9, 2026.