Table 4.
Adjusted odds ratios (95% confidence intervals) of colon and rectal cancers by quartile levels of plasma polyunsaturated fatty acids (PUFA) and desaturase indices in n-6 PUFA) synthesis pathway, The Singapore Chinese Health Studya
| 1st (low) | 2nd | 3rd | 4th (high) | P trend | |
|---|---|---|---|---|---|
| Colon cancer | |||||
| n-3 PUFAs | |||||
| α-Linolenic acid (18:3) | 1.00 (Referent) | 0.56 (0.32–1.00) | 0.64 (0.37–1.11) | 0.41 (0.23–0.73) | 0.005 |
| Eicosapentanoic acid (20:5) | 1.00 (Referent) | 1.06 (0.60–1.86) | 1.18 (0.69–2.02) | 0.93 (0.54–1.62) | 0.931 |
| Docosahexaenoic acid (22:6) | 1.00 (Referent) | 1.47 (0.83–2.62) | 1.32 (0.74–2.34) | 1.11 (0.59–2.07) | 0.855 |
| n-6 PUFAs | |||||
| Linoleic acid (18:2) (LA) | 1.00 (Referent) | 0.63 (0.35–1.13) | 0.52 (0.29–0.93) | 0.43 (0.23–0.82) | 0.008 |
| γ-Linolenic acid (18:3) (GLA) | 1.00 (Referent) | 0.62 (0.33–1.15) | 0.68 (0.36–1.27) | 0.54 (0.30–1.00) | 0.085 |
| Dihomo-γ-linolenic acid (20:3) (DGLA) | 1.00 (Referent) | 0.81 (0.45–1.43) | 0.80 (0.44–1.46) | 0.54 (0.29–1.00) | 0.060 |
| Arachidonic acid (20:4) (AA) | 1.00 (Referent) | 1.36 (0.78–2.37) | 2.18 (1.16–4.08) | 1.52 (0.82–2.81) | 0.111 |
| n-6 PUFA desaturase indices (DI) | |||||
| GLA:LA ratio (for Δ6 DI) | 1.00 (Referent) | 1.09 (0.60–1.98) | 1.19 (0.66–2.13) | 0.61 (0.33–1.10) | 0.140 |
| AA:DGLA ratio (for Δ5 DI) | 1.00 (Referent) | 1.28 (0.70–2.31) | 2.77 (1.53–5.03) | 2.51 (1.39–4.53) | <0.001 |
| AA:LA ratio (for total n-6 PUFA DI) | 1.00 (Referent) | 2.90 (1.52–5.55) | 1.28 (0.69–2.37) | 3.53 (1.82–6.85) | 0.006 |
| Rectal cancer | |||||
| n-3 PUFAs | |||||
| α-Linolenic acid (18:3) | 1.00 (Referent) | 1.00 (0.50–2.03) | 1.38 (0.66–2.91) | 1.70 (0.84–3.43) | 0.087 |
| Eicosapentanoic acid (20:5) | 1.00 (Referent) | 1.07 (0.52–2.20) | 0.64 (0.31–.35) | 0.89 (0.42–1.91) | 0.516 |
| Docosahexaenoic acid (22:6) | 1.00 (Referent) | 0.79 (0.38–1.66) | 0.63 (0.30–1.31) | 0.72 (0.32–1.66) | 0.349 |
| n-6 PUFAs | |||||
| LA (18:2) | 1.00 (Referent) | 0.88 (0.44–1.75) | 1.64 (0.78–3.44) | 1.15 (0.51–2.58) | 0.394 |
| GLA (18:3) | 1.00 (Referent) | 1.43 (0.65–3.14) | 1.43 (0.72–2.84) | 1.59 (0.75–3.34) | 0.232 |
| DGLA (20:3) | 1.00 (Referent) | 0.76 (0.39–1.51) | 0.94 (0.44–2.01) | 2.36 (1.02–5.44) | 0.068 |
| AA (20:4) | 1.00 (Referent) | 0.86 (0.40–1.82) | 1.93 (0.86–4.31) | 1.44 (0.63–3.27) | 0.200 |
| n-6 PUFA DIs | |||||
| GLA:LA ratio (for Δ6 DI) | 1.00 (Referent) | 1.14 (0.56–2.31) | 1.05 (0.54–2.03) | 1.47 (0.65–3.34) | 0.476 |
| AA:DGLA ratio (for Δ5 DI) | 1.00 (Referent) | 0.66 (0.31–1.37) | 0.56 (0.26–1.21) | 0.68 (0.33–1.42) | 0.366 |
| AA:LA ratio (for total n-6 PUFA DI) | 1.00 (Referent) | 1.24 (0.57–2.72) | 1.98 (0.88–4.46) | 1.08 (0.50–2.32) | 0.711 |
a Odds ratios are adjusted for body mass index (<20, 20–24, 24–28, ≥28 kg/m2), smoking (never, light, heavy), education level (none, primary, ≥secondary), alcohol use (none, <7, ≥7 drinks/week), weekly physical activity (yes, no), history of diabetes (yes, no), and use of nonsteroidal anti-inflammatory drugs (NSAIDs) (yes, no)