Table 4.
Summary risk estimates for association between alpha linolenic acid (ALA) and risk of cancer mortality in adults aged ≥18 years
| No of effect sizes | Pooled relative risk (95% CI)* | I2 (%)† | P values | ||
|---|---|---|---|---|---|
| Heterogeneity‡ | Meta-regression | ||||
| Highest v lowest comparison | |||||
| Dietary ALA intake: | |||||
| Overall | 10 | 1.06 (1.02 to 1.11) | 3.8 | 0.40 | |
| Study location | |||||
| US | 8 | 1.06 (1.00 to 1.12) | 18.6 | 0.28 | 0.70 |
| Western countries§ | 10 | 1.06 (1.02 to 1.11) | 3.8 | 0.40 | |
| Eastern/Mediterranean countries | 0 | - | - | - | |
| Sex | |||||
| Men and women | 3 | 0.94 (0.77 to 1.14) | 57.8 | 0.09 | 0.25 |
| Men | 5 | 1.10 (1.00 to 1.21) | 0 | 0.79 | |
| Women | 2 | 1.10 (1.01 to 1.19) | 0 | 0.79 | |
| Follow-up duration (years) | |||||
| ≥10 | 7 | 1.07 (1.01 to 1.13) | 18.7 | 0.28 | 0.08 |
| <10 | 3 | 0.91 (0.72 to 1.14) | 0 | 0.94 | |
| Dietary assessment tools | |||||
| Food frequency questionnaire | 8 | 1.07 (1.02 to 1.13) | 7.1 | 0.37 | 0.26 |
| Food recall or record | 2 | 0.89 (0.68 to 1.15) | 0 | 0.94 | |
| Adjustment for energy | |||||
| Yes | 8 | 1.06 (1.01 to 1.12) | 20.2 | 0.27 | 0.51 |
| No | 2 | 0.93 (0.65 to 1.33) | 0 | 0.77 | |
| Adjustment for BMI | |||||
| Yes | 8 | 1.06 (1.01 to 1.12) | 21.3 | 0.26 | 0.64 |
| No | 2 | 0.96 (0.66 to 1.39) | 0 | 0.66 | |
| Adjustment for other nutrients¶ | |||||
| Yes | 6 | 1.06 (0.99 to 1.13) | 38.5 | 0.14 | 0.57 |
| No | 4 | 1.01 (0.85 to 1.19) | 0 | 0.83 | |
| Adjustment for trans fatty acids | |||||
| Yes | 5 | 1.07 (1.00 to 1.14) | 40.5 | 0.15 | 0.29 |
| No | 5 | 0.98 (0.85 to 1.13) | 0 | 0.84 | |
| Health status** | |||||
| Healthy | 6 | 1.06 (1.02 to 1.11) | 0.5 | 0.41 | 0.28 |
| Unhealthy | 4 | 0.94 (0.77 to 1.15) | 0.2 | 0.39 | |
| Tissue ALA levels: | |||||
| Overall | 4 | 0.93 (0.86 to 1.01) | 0 | 0.39 | |
| Linear dose-response association | |||||
| Dietary ALA intake (per 1 g/day increase) | |||||
| Overall | 8 | 1.03 (0.98 to 1.08) | 51 | 0.04 | |
| Study location | |||||
| US | 7 | 1.03 (0.97 to 1.09) | 57.3 | 0.02 | 0.83 |
| Western countries§ | 8 | 1.03 (0.98 to 1.08) | 51 | 0.04 | |
| Eastern/Mediterranean countries | 0 | - | - | - | |
| Sex | |||||
| Men and women | 3 | 0.96 (0.85 to 1.07) | 64 | 0.06 | 0.31 |
| Men | 3 | 1.05 (0.98 to 1.13) | 13 | 0.31 | |
| Women | 2 | 1.10 (1.03 to 1.17) | 0 | 0.96 | |
| Follow-up duration (years) | |||||
| ≥10 | 6 | 1.04 (0.98 to 1.10) | 58 | 0.03 | 0.02 |
| <10 | 2 | 0.95 (0.86 to 1.06) | 0 | 0.93 | |
| Dietary assessment tools | |||||
| Food frequency questionnaire | 6 | 1.04 (0.98 to 1.10) | 58 | 0.03 | 0.27 |
| Food recall or record | 2 | 0.95 (0.86 to 1.06) | 0 | 0.93 | |
| Adjustment for energy | |||||
| Yes | 7 | 1.03 (0.98 to 1.09) | 56.2 | 0.03 | 0.60 |
| No | 1 | 0.96 (0.79 to 1.16) | - | - | |
| Adjustment for BMI | |||||
| Yes | 6 | 1.03 (0.97 to 1.09) | 63.3 | 0.01 | 0.74 |
| No | 2 | 0.98 (0.83 to 1.17) | 0 | 0.56 | |
| Adjustment for other nutrients¶ | |||||
| Yes | 5 | 1.03 (0.97 to 1.10) | 70.1 | 0.01 | 0.67 |
| No | 3 | 0.99 (0.89 to 1.11) | 0 | 0.84 | |
| Adjustment for trans fatty acids | |||||
| Yes | 4 | 1.04 (0.97 to 1.10) | 74 | 0.009 | 0.30 |
| No | 4 | 0.98 (0.90 to 1.06) | 0 | 0.89 | |
| Health status** | |||||
| Healthy | 5 | 1.04 (0.99 to 1.10) | 53 | 0.07 | 0.22 |
| Unhealthy | 3 | 0.94 (0.79 to 1.11) | 40.4 | 0.18 | |
| Tissue ALA levels (per 1 SD increase): | |||||
| Overall | 2 | 0.99 (0.88 to 1.11) | 0 | 0.83 | |
BMI=body mass index; RBC=red blood cells; SD=standard deviation.
Obtained from random effects model.
Inconsistency—percentage of variation across studies due to heterogeneity.
Obtained from Q test.
Includes studies from the US.
Studies that controlled for at least one of dietary nutrients, including lipids, vitamins, and minerals.
Studies that recruited apparently healthy adults (without a previous diagnosis of cancer, cardiovascular disease, or any other chronic diseases) were included in the healthy subgroup, and studies that recruited participants with at least one chronic disease were included in the unhealthy subgroup.