Table 2.
Distribution of the RBC nitrogen stable isotope ratio (δ15N)
| Sex | Quartiles of δ15N** | ||||||
|---|---|---|---|---|---|---|---|
| Total | Women | Men | Q1 | Q2 | Q3 | Q4 | |
| No. of participants | 1,073 | 565 | 510 | 262 | 261 | 269 | 281 |
| Mean ± SD (‰) | 9.0 ± 1.5 | 9.1 ± 1.5 | 8.7 ± 1.5 | 7.3 ± 0.3 | 8.2 ± 0.2 | 9.1 ± 0.3 | 11.0 ± 1.1 |
| Maximum | 15.2 | 15.2 | 13.5 | 7.8 | 8.6 | 9.8 | 15.2 |
| Minimum | 6.4 | 6.4 | 6.4 | 6.4 | 7.8 | 8.6 | 9.8 |
| Range (‰) | 8.8 | 8.8 | 7.1 | 1.4 | 0.8 | 1.2 | 5.4 |
Isotope ratios are presented as delta values in “permil” relative to atmospheric nitrogen: δ15N = [(15N/14Nsample − 15N/14Nstandard)/(15N/14Nstandard)] × 1,000 ‰. The relationship between δ15N and EPA follows the linear model: EPA (%RBC fatty acid) = 1.04 × δ15N − 6.7 ‰, as previously described for this population (O’Brien et al. 2009)