Impact of Watercress Consumption on Antioxidant Defense and Oxidative Stress Among Adults with Different Levels of Exposure to Cigarette Smoke in Chiang Mai, Thailand

Antioxidant intake from natural sources may enhance defense systems against oxidative stress induced by environmental factors such as cigarette smoke. Watercress (Nasturtium officinale) is an abundant source of antioxidants. This study aimed to determine the antioxidant effects of watercress consumption in people exposed to cigarette smoke in Chiang Mai, Thailand. Forty-five participants (15 non-smokers, 15 non-smokers with self-reported exposure to secondhand smoke (SHS), and 15 smokers) aged 20–60 years consumed 60 g of fresh watercress with three meals daily for seven days. Clinical characteristics, lipid profiles, total antioxidant capacity, and oxidative stress markers were evaluated before and after the intervention. After 7 days of watercress consumption, body mass index (BMI) and hip circumference significantly decreased among non-smokers. Watercress consumption reduced total cholesterol and low-density lipoprotein cholesterol (LDL-C) levels in smokers and in SHS-exposed non-smokers; however, high-density lipoprotein cholesterol (HDL-C) significantly decreased in SHS-exposed non-smokers. Catalase activity increased, and malondialdehyde levels decreased in all groups. One of the measures of plasma total antioxidant capacity significantly improved in non-smokers. These findings suggest that watercress consumption may improve lipid profiles and mitigate oxidative stress, and that these beneficial effects differ across people with different levels of exposure to cigarette smoke. However, further studies are suggested to clarify these results.