Influence of Long-Term Fasting on Blood Redox Status in Humans

Abstract

Fasting is increasingly practiced to improve health and general well-being, as well as for its cytoprotective effects. Changes in blood redox status, linked to the development of a variety of metabolic diseases, have been recently documented during calorie restriction and intermittent fasting, but not with long-term fasting (LF). We investigated some parameters of the blood redox profile in 109 subjects before and after a 10-day fasting period. Fasting resulted in a significant reduction in body weight, improved well-being and had a beneficial modulating effect on blood lipids and glucose regulation. We observed that fasting decreased lipid peroxidation (TBARS) and increased total antioxidant capacity (TAC) in plasma, concomitant with a uric acid elevation, known to be associated with fasting and did not cause gout attacks. Reduced glutathione (GSH), glutathione reductase (GR), glutathione peroxidase (GPx) and catalase in erythrocytes did not show significant changes. In addition, reduction in body weight, waist circumference, and glucose levels were associated to a reduced lipid peroxidation. Similar results were obtained by grouping subjects on the basis of the changes in their GSH levels, showing that a period of 10 days fasting improves blood redox status regardless of GSH status in the blood.

Keywords: GSH; antioxidants; oxidative stress; prolonged fasting; redox biomarkers.

Figure 1

The effects of the 10-day fast on the mean levels of redox biomarkers in a group of 109 subjects. There was no change in GSH levels (A). We highlighted 3 subgroups based on the variations in their GSH levels (increase, light blue; decrease, dark blue; unchanged, black) to understand if baseline GSH levels could influence the response to fasting. Catalase (B) levels showed no changes either, while TAC (C) was significantly increased, and TBARS (D) levels were significantly decreased. GR (E) as well as GPx (F) levels were unchanged.

Figure 2

Changes in redox parameters during fasting were associated with changes in clinical parameters. We evaluated associations between the four redox parameters measured in this study (GSH, Catalase, TBARS, TAC) with weight, waist circumference, glucose and uric acid serum levels. The 5 significant associations (A–E) are presented in this figure. Dot plots shows the correlations between the different parameters for pre-fasting (dark blue) and post-fasting (light blue) levels.

Figure 3

Associations between the different redox parameters measured in this study. We evaluated associations between the six redox parameters measured in this study (GSH, Catalase, TBARS, TAC, GR, GPx). The 5 significant associations (A–E) are presented in this figure. Dot plots show the correlations between the different parameters for pre-fasting (dark blue) and post-fasting (light blue) levels.

Figure 4

The beneficial effects of long-term fasting and the findings of the present study. It is established from the literature that fasting leads to a metabolic switch, to decreased reactive oxygen species (ROS) generation at the beginning of fasting and to enhancement of antioxidant defense mechanisms at the end of fasting. This could lead to an increase in health- and life-span and general well-being. In the present study, a 10-day fasting protocol decreased lipid peroxidation and increased total antioxidant capacity in plasma in a pool of 109 participants. Fasting improved the blood redox status of participants in the 3 GSH subgroups regardless the baseline GSH concentration.