A common fungicide used on leafy vegetables could make people fat

Obesity is on the rise globally. World Health Organization forecasts 2.3 billion overweight adults in the world by 2015 and greater than 700 million of them to be obese. In the UK, as in most industrialised nations, obesity is increasing. Figures show that 62.8% of UK adults (aged 16 or over) were overweight or obese as are 30.3% of children (aged 2-15). A recent report released by the NHS (National Child Measurement Programme) indicates that in the UK 1 in 3 of primary school children in the last year are overweight/obese.

The health implications of obesity are enormous. Studies suggest that obesity could have a causal effect or increases the risk of  several diseases, notably type 2 diabetes, heart disease,  liver disease, and selected cancers. Three major factors that influence obesity are diet, environmental factors and physical activity.

Several studies have shown that maternal diet and exposure to environmental agents has a crucial effect not only on the health of the woman, but also on foetal and child health. Our earlier post looked at how exposure of pregnant mothers to pesticides can leadto obesity in children and put them at risk for heart disease. We also discussed one study where maternal exposure of phthalates make their way to the offspring and can have detrimental effects.

Chemicals that increase either the number of fat cells in an organism or the amount of fat stored in those cells and promote weight gain are called obesogens. Notable culprits are environmental agents such as bisphenol A, phthalates, organophosphate pesticides etc. Some scientists hypothesise that the obesity epidemic that is seen could have links to the increased exposure  to pesticides.

Triflumizole (TFZ) is an imidazole fungicide that is used during the cultivation of  many green leafy vegetables.Whilst TFZ is not classified as toxic, its effect on development is unknown. A recent study by researchers in California shows that this fungicide promotes adipogenesis (the process by which precursors of fat cells become fat cells) in laboratory experiments with human and mouse cells in culture and also in animal models. They found that stem cells that have the potential to develop into bone, cartilage, or fat cells,  upon treatment with the fungicide, ended up as fat cells. The researchers also observed that levels of genes related to obesity increased with treatment of both human and mouse cells. Exposure with the fungicide also resulted in fat accumulation. More interestingly, exposure of pregnant mice with the fungicide at very low doses (roughly 400 fold below the levels that show no observed adverse effect ) increased mass of fat depot (where fat tissue is stored) but were not shown to increase body weights. The study further showed that blocking PPAR gamma (Peroxisome Proliferator Activated Receptor gamma)  pathway using a specific antagonistic drug, stopped the differentiation into fat cells  suggesting that that  TFZ acts through this receptor. PPAR is found in the nucleus of the cell ( hence called nuclear receptor)and functions as a transcription factor (that which switches on  genes and controls the levels). Interestingly other nuclear receptors include the receptors for estrogen, thyroid hormone, retinoic acid, Vitamin D etc. These receptors have also been shown to interact with each other. It appears that TFZ could also be grouped under ‘endocrine disruptor’  (hormone disruptor). 

Very little information exists about the exposure and the levels of TFZ in humans. The scientists suggest that further studies that monitor the levels of TFZ and its metabolites in humans must be carried out to decipher the role of the chemical’s potential influence on obesity. However one fact is clear that TFZ is now in the list of potential new obesogens. Eating green leafy vegetables is good for health, but this maxim only holds true when it is  pesticide/fungicide free.

PS- TFZ is also licensed for used on a variety of fruits and vegetables in the US (Personal communication with Dr. Blumberg, one of the authors of this study). 

Reference:
Li, X., Pham, H., Janesick, A., & Blumberg, B. (2012). Triflumizole is an Obesogen in Mice that Acts through Peroxisome Proliferator Activated Receptor Gamma (PPARγ) Environmental Health Perspectives DOI: 10.1289/ehp.1205383