The effect of obesity and dietary habits on oxidative stress in Hashimoto’s thyroiditis

Abstract

Objective: Increased oxidative stress has been described in patients with Hashimoto’s thyroiditis (HT). The aim of the present study was to investigate whether high oxidative stress is further influenced by obesity and dietary habits in euthyroid women with HT.

Methods: Two hundred eighteen consecutive euthyroid women with HT were studied and separated in two groups; 102 with thyroxine replacement and 114 without. For the evaluation of oxidative stress, total lipid peroxide levels in serum (TOS) were measured and recoded as ‘high TOS’ vs ‘medium/low TOS’. The type of food and consumption frequency were recorded. Two binary variables were considered; normal vs low fruit consumption and daily vs sporadic vegetable consumption.

Results: ‘High TOS’ was more frequent in women under thyroxine replacement (31.4% vs 14.7%, OR = 2.7, 95% CI: 1.4–5.2). The prevalence of ‘high TOS’ was higher among overweight/obese women compared to women with normal BMI (30.4% vs 12.5%, OR = 3.1, 95% CI: 1.5–6.4). Low fruit consumption was associated with increased ‘high TOS’ prevalence (30.6% vs 12.9%, OR = 3.0, 95% CI: 1.4–6.2). Sporadic vegetable consumption was associated with increased ‘high TOS’ prevalence compared to daily consumption (29.9% vs 13.5%, OR = 2.7, 95% CI: 1.3–5.7). The examined risk factors were independent and additive in their effect on TOS. At least three risk factors had to be concomitantly present for the likelihood of ‘high TOS’ to be significantly elevated.

Conclusions: Oxidative stress is increased in women with HT under thyroxine replacement. Nevertheless, normal BMI, daily fruit and vegetable consumption, all contribute in maintaining oxidative stress at low levels.

Keywords: oxidative stress; Hashimoto’s thyroiditis; obesity; dietary habits.

Figure 1

Percentage of women with ‘high TOS’ (≥590 μmol/L) depending on the weekly consumption of fruit (A) and vegetables (B). The frequency distributions were tested for significance of linear-by-linear associations using the chi-square for trends statistic. In (A), the light shaded bars denote normal fruit consumption and the dark shaded bars denote low fruit consumption. In (B), the light shaded bars denote daily consumption of vegetables and the dark shaded bars denote sporadic consumption of vegetables.

Figure 2

Percentage of women with ‘high TOS’ (≥590 μmol/L) depending on thyroxine treatment (31.4% vs 14.7%, OR = 2.7, 95% CI: 1.4–5.2, A), BMI (overweight or obese vs normal BMI, 30.4% vs 12.5%, OR = 3.1, 95% CI: 1.5–6.4, B), fruit consumption (low vs normal fruit consumption 30.6% vs 12.9%, OR = 3.0, 95% CI: 1.4–6.2, C) and vegetable consumption (sporadic vs daily vegetable consumption 29.9% vs 13.5%, OR = 2.7, 95% CI: 1.3–5.7, D). The association was checked with 2 × 2 contingency tables reporting the OR with its associated 95% confidence intervals. The level of significance was set at 0.05. TOS, total oxidative status.

Figure 3

Percentage of women with ‘high TOS’ (≥590 μmol/L) depending on the additive presence of risk factors. Chi-square for trends = 29.5, df = 1, P < 0.001. TOS, total oxidative status.