Six-week supplementation with Chlorella has favorable impact on antioxidant status in Korean male smokers

Abstract

Objective

Chlorella vulgaris is a popular food supplement in Asia and is currently marketed as a nutritional supplement. However, available scientific studies do not support its effectiveness for preventing or treating any disease in humans. Because Chlorella contains numerous nutrients, including antioxidants, it is thought to exert antioxidative functions by scavenging free radicals created by various environmental factors such as smoking. The purpose of this study was to investigate whether 6 wk of Chlorella supplementation to smokers is protective against oxidative damage in a randomized, double-blinded, placebo-controlled trial.

Methods

Fifty-two smokers, aged 20–65 y, were given 6.3 g of Chlorella or placebo every day for 6 wk. Blood samples were drawn at the beginning and after the supplementation. Plasma antioxidant vitamin levels and lipid peroxidation levels were measured. As a marker of oxidative stress, lymphocyte DNA damage was measured.

Results

Chlorella supplementation increased plasma vitamin C (44.4%), α-tocopherol (15.7%), and erythrocyte catalase and superoxide dismutase activities. Although 6 wk of Chlorella supplementation resulted in a significant decrease in lymphocyte DNA damage, as measured by comet assay, placebo supplementation also decreased the measured amount of lymphocyte DNA damage.

Conclusion

Chlorella supplementation resulted in the conservation of plasma antioxidant nutrient status and improvement in erythrocyte antioxidant enzyme activities in subjects. Therefore, our results are supportive of an antioxidant role for Chlorella and indicate that Chlorella is an important whole-food supplement that should be included as a key component of a healthy diet.

Introduction

The World Health Organization ranks cigarette smoking among the 10 greatest risks to health. The adverse health consequences of smoking have been largely attributed to the abundance of free radicals, reactive oxygen species (ROS) and other carcinogens. Smokers are exposed to reactive free radicals that are present in cigarette smoke or caused by smoking [1], [2]. These excess radicals attack normal tissues and cause oxidative damage to lipids, proteins, and DNA, which eventually leads to the pathogenesis of cardiovascular disease and cancer [3], [4], [5], [6]. The single-cell gel electrophoresis assay, also referred to as the comet assay, has been used successfully for evaluating DNA damage and has been suggested as an excellent technique for use with biological markers in the detection, monitoring, and prognosis of chronic degenerative diseases [7], [8]. A demonstration of the usefulness of this technique for evaluating DNA damage during dietary supplementation has been shown in many studies [9], [10], [11]. In this study we utilized the comet assay for detecting and comparing the oxidative DNA damage in peripheral blood lymphocytes before and after supplementation.

In addition to free radicals in smoke depleting plasma antioxidants [5], [12], several studies have reported compromised plasma antioxidant concentrations in smokers [13], [14], [15], [16], [17], [18]. It is still difficult to determine whether this depletion is due to the cigarette smoke exposure or the fact that smokers are typically less health conscious and consume considerably fewer fruits and vegetables. Based on these studies, it is logical that smokers with a greater magnitude of oxidative stress would benefit from increasing antioxidant supplementations or dietary substances with high antioxidant activities (fruits, vegetables, garlic, green tea) containing numerous non-nutritive substances. Most of these dietary supplements have been proven to be safe and are more appropriate than single antioxidant supplements for assessing the effects of bioreactive phytochemicals in the human body.

Chlorella, a type of unicellular green algae, has been a popular foodstuff worldwide, especially in Japan, Taiwan, and Korea. It contains essential amino acids, protein, minerals, vitamins, chlorophyll, and bioactive substances [19], [20]. Administration of Chlorella in animals has demonstrated effects on numerous biochemical functions, such as remarkable antioxidant and anticataract effects in streptozotocin-induced diabetic rats [21] and lowered blood glucose in diabetic animals [22]. Also, anti-inflammatory and immunomodulatory activities have been reported [23]. In addition to producing cytokines and boosting immune function [24], [25], [26], [27], Chlorella can decrease oxidative stress and stress-induced ulcers in mice [28], [29], [30]. In rabbits fed a high cholesterol diet for 10 wk, Chlorella vulgaris showed antilipidemic and antiatherosclerotic actions [31]. These results were also proven in a human study where Okudo et al. [32] demonstrated that Chlorella intake decreases cholesterol levels in patients with hypercholesterolemia. These potential health benefits of Chlorella have been attributed to the effects of specific ingredients in Chlorella, such as minerals, dietary fiber, and a wide range of antioxidants and chlorophylls. Antioxidant activity is considered to play an important role in the protective effects of Chlorella.

The aim of the present study was to evaluate the sensitivity of biomarkers of oxidative damage and to demonstrate the beneficial effects of Chlorella on these biomarkers in a potential risk group of smokers.