Stable consumption of swordfish favors, whereas stable consumption of oily fish protects from, development of postpartum thyroiditis.

PURPOSE: In 236 pregnant women, we showed that selective or predominant consumption of swordfish (group A) was associated with high rates of positivity for serum thyroid autoantibodies (TPOAb and TgAb) throughout day 4 postpartum. In contrast, selective or predominant consumption of oily fish (group B) was associated with TPOAb and TgAb negativity. Rates were intermediate in group C (scanty consumption of swordfish) and group D (consumption of fish other than swordfish and oily fish). Gestational TPOAb positivity is a risk factor for postpartum thyroiditis (PPT), which evolves into permanent hypothyroidism (PH) in about 50% of cases. Purpose of this study was to verify that the different rates of thyroid autoantibodies in the four groups translated into different PPT rates. METHODS: We expanded our previous cohort (n = 412) and duration of follow-up (month 12 postpartum), and measured frequency of PPT and PH. RESULTS: At first timester of gestation, we confirmed the different Ab positivity rates in group A vs. group B (TPOAb = 21.7% vs. 4.7%, P < 0.0001; TgAb = 14.1% vs. 2.4%, P < 0.05). Overall, PPT prevalence was 63/412 (15.3%), but 22/92 in group A (23.9%), 4/85 in group B (4.7%; P < 0.0001 vs. group A), 17/108 (15.7%) in group C, and 16/117 (13.7%) in group D. Approximately half of the PPT women had PH, regardless of fish group. CONCLUSIONS: In conclusion, stable consumption of oily fish (which is enriched in polyunsaturated omega-3 fatty acids) protects from PPT, while stable consumption of swordfish (which is enriched in pollutants) favors PPT. Thus, a dietary prophylaxis of PPT is possible.

Fish consumption and breast cancer risk.

The omega-3 fatty acids, especially long-chain eicosapentaenoic acid (20:5n-3) and docosahexaenoic (22:6n-3) contained in "fatty" fish, have consistently been shown to retard the growth of breast cancer in vitro and in animal experiments. In contrast, studies of the association between fish consumption and breast cancer risk in human populations have not consistently shown inverse associations. However, previous studies have not considered the specific types of fish consumed. Using data from a large, nationwide case-control study conducted in Sweden, we examined the association between consumption of fatty and lean fish and breast cancer risk. Odds ratios (OR) and 95% confidence intervals were computed from unconditional logistic regression models. High consumption of fish was weakly associated with reduced breast cancer risk, and the association was not statistically significant. With multivariate adjustment, the OR for women with the highest consumption (> or =3.5 servings/wk) compared with women with the lowest (virtually none) was 0.88 (95% confidence interval = 0.60-1.29, P for trend = 0.15). When type of fish was examined separately, the association was similar for fatty and lean fish.