Association between seafood intake and the risk of thyroid cancer
A meta-analysis
Abstract
Abstract:Background: Previous observational epidemiological studies such as case-control studies and cohort studies have reported inconsistent results regarding the associations between seafood intake and the risk of thyroid cancer. Materials and methods: We searched PubMed and EMBASE in August 2021 using keywords related to seafood intake and thyroid cancer. A pooled odds ratio (OR) or relative risk (RR) with its 95% confidence interval (CI) was calculated. Results: We included 17 observational studies with 13 case-control studies and 4 cohort studies, which included 4,309 thyroid cancer patients among 599,161 participants. In the random effects model meta-analysis of all 17 studies, we found that there was no significant association between seafood intake (highest vs. lowest intake) and the risk of thyroid cancer (OR or RR, 1.01; 95% CI: 0.86 to 1.19; I2=51.4%). Although the associations were not statistically significant, subgroup meta-analyses by study design showed opposite findings: seafood intake decreased the risk of thyroid cancer in case-control studies (OR or RR, 0.94; 95% CI: 0.74 to 1.19; I2=60.6%; n=13) but increased in cohort studies (OR or RR, 1.14; 95% CI: 0.97 to 1.35; I2=0.0%; n=4). Conclusion: The current meta-analysis of observational epidemiological studies found that that overall, there was no significant association between seafood intake and the risk of thyroid cancer. However, given that cohort studies give us a higher level of evidence than case-control studies, further prospective cohort studies are warranted to confirm the association between them.
References
1 Global cancer statistics 2020: GLOBOCAN estimates of incidence and mortality worldwide for 36 cancers in 185 countries. CA Cancer J Clin. 2021;71(3):209–49.
2 . Worldwide thyroid-cancer epidemic? The increasing impact of overdiagnosis. N Engl J Med. 2016;375(7):614–7.
3 . Cancer epidemiology and prevention. 4th edition. Oxford: Oxford University Press; 2018.
4 . Risk factors for thyroid cancer: an epidemiological review focused on nutritional factors. Cancer Causes Control. 2009;20(1):75–86.
5 . Role of dietary iodine and cruciferous vegetables in thyroid cancer: a countrywide case-control study in New Caledonia. Cancer Causes Control. 2010;21(8):1183–92.
6 Obesity and thyroid cancer risk among U.S. men and women: a pooled analysis of five prospective studies. Cancer Epidemiol Biomarkers Prev. 2011;20(3):464–72.
7 . Iodine deficiency. Endocr Rev. 2009;30(4):376–408.
8 . Iodine-deficiency disorders. Lancet. 2008;372(9645):1251–62.
9 . Even mild iodine deficiency during gestation may impair brain function in children. JAMA. 2013;309(23):2428.
10 A pooled analysis of case-control studies of thyroid cancer. VI. Fish and shellfish consumption. Cancer Causes Control. 2001;12(4):375–82.
11 Dietary iodine and thyroid cancer risk in French Polynesia: a case-control study. thyroid. 2012;22(4):422–9.
12 . Dietary factors and thyroid cancer risk: a meta-analysis of observational studies. Nutr Cancer. 2014;66(7):1165–78.
13 . Dietary factors affecting thyroid cancer risk: a meta-analysis. Nutr Cancer. 2015;67(5):811–7.
14 . The relationship between iodine intake and the risk of thyroid cancer: A meta-analysis. Medicine. 2017;96(20):e6734.
15 Relationship between iodine levels and papillary thyroid carcinoma: A systematic review and meta-analysis. Head Neck. 2017;39(8):1711–8.
16 The Newcastle-Ottawa Scale (NOS) for assessing the quality of nonrandomised studies in meta-analyses [cited 2021 Aug 10]. Available from: http://www.ohri.ca/programs/clinical_epidemiology/oxford.htm
17 . Quantifying heterogeneity in a meta-analysis. Stat Med. 2002;21(11):1539–58.
18 . Meta-analysis in clinical trials. Control Clin Trials. 1986;7(3):177–88.
19 Diet and the risk of papillary and follicular thyroid carcinoma: a population-based case-control study in Sweden and Norway. Cancer Causes Control. 1997;8(2):205–14.
20 . Norwegian case-control study testing the hypothesis that seafood increases the risk of thyroid cancer. Cancer Causes Control. 1993;4(1):11–6.
21 . Thyroid cancer: reproductive factors, previous diseases, drug intake, family history and diet. A case-control study. Eur J Cancer Prev. 1994;3(6):481–8.
22 Iodine and thyroid cancer risk among women in a multiethnic population: the bay area thyroid cancer study. Cancer Epidemiol Biomarkers Prev. 2001;10(9):979–85.
23 . An epidemiologic study of thyroid cancer in Hawaii. Cancer Causes Control. 1990;1(3):223–34.
24 . Lifestyle and other risk factors for thyroid cancer in Los Angeles county females. Ann Epidemiol. 2002;12(6):395–401.
25 . Benign thyroid disease and dietary factors in thyroid cancer: a case-control study in Kuwait. Br J Cancer. 2002;86(11):1745–50.
26 . A case-control study of thyroid cancer in women under age 55 in Shanghai (People’s Republic of China). Cancer Causes Control. 1993;4(5):431–40.
27 Risk factors of thyroid cancer among women in Tokai. Japan. J Epidemiol. 1996;6(3):140–7.
28 Prospective study of seaweed consumption and thyroid cancer incidence in women: the Japan collaborative cohort study. Eur J Cancer Prev. 2016;25(3):239–45.
29 Consumption of fish is not associated with risk of differentiated thyroid carcinoma in the european prospective investigation into cancer and nutrition (EPIC) study. J Nutr. 2017;147(7):1366–73.
30 . Prospective investigation of poultry and fish intake in relation to cancer risk. Cancer Prev Res (Phila). 2011;4(11):1903–11.
31 Seaweed consumption and the risk of thyroid cancer in women: the Japan public health center-based prospective study. Eur J Cancer Prev. 2012;21(3):254–60.
32 . High default rate in thyroid cancer management in Ibadan, Nigeria: a need for health insurance. Afr J Med Med Sci. 2012;41 Suppl:105–9.
33 Dietary habits and thyroid cancer risk: A hospital-based case-control study in Sicily (South Italy). Food Chem Toxicol. 2020;146:111778.
34 . Identification of thyroid cancer risk factors incidence in urban and rural areas. Pakistan. Pak J Pharm Sci. 2020;33(6):2607–10.
35 . Avoiding bias in observational studies: part 8 in a series of articles on evaluation of scientific publications. Dtsch Arztebl Int. 2009;106(41):664–8.
36 A comparison of prospective and retrospective assessments of diet in the study of breast cancer. Am J Epidemiol. 1993;137(5):502–11.
37 . Iodine and cancer. Thyroid. 2001;11(5):483–6.
38 . Role of iodine in metabolism. Recent Pat Endocr Metab Immune Drug Discov. 2017;10(2):123–6.
39 . Follicular thyroid carcinoma in a country of endemic iodine deficiency (1994–2013). J Thyroid Res. 2018;2018:6516035.
40 . Prevalence of goitre in school children of Chamarajanagar district, Karnataka, India. J Clin Diagn Res. 2013;7(12):2807–9.
41 The epidemiology of thyroid carcinoma. Crit Rev Oncog. 1993;4(1):25–52.
42 . Plasma inorganic iodide, a chemical regulator of normal thyroid function. Endocrinology. 1948;42(6):468–71.
43 . Control of thyroid hormone secretion in normal subjects receiving iodides. J Clin Invest. 1973;52(2):528–32.
44 . The effect of iodide on serum thyroid hormone levels in normal persons, in hyperthyroid patients, and in hypothyroid patients on thyroxine replacement. Clin Endocrinol (Oxf). 1992;36(6):573–8.
45 . The association between serum TSH concentration and thyroid cancer. Endocr Relat Cancer. 2009;16(4):1065–72.
46 . Iodine excess and hyperthyroidism. Thyroid. 2001;11(5):493–500.
47 Association of high iodine intake with the T1799A BRAF mutation in papillary thyroid cancer. J Clin Endocrinol Metab. 2009;94(5):1612–7.
48 . Thyroid cancer, thyroiditis and dietary iodine: a review based on the Salta, Argentina model. Endocr Pathol. 2008;19(4):209–20.
49 Changing trends of incidence and prognosis of thyroid carcinoma in lower Franconia, Germany, from 1981–1995. Thyroid. 2004;14(2):141–7.
50 . Variability of iodine content in common commercially available edible seaweeds. Thyroid. 2004;14(10):836–41.
51 . Effects of kelp supplementation on thyroid function in euthyroid subjects. Endocr Pract. 2003;9(5):363–9.
52 . Suppression of thyroid function during ingestion of seaweed “Kombu” (Laminaria japonoca) in normal Japanese adults. Endocr. 2008;55(6):1103–8.
53 . Thyroid cancer in Denmark 1943–2008, before and after iodine supplementation. Int J Cancer. 2012;131(10):2360–6.