Recently there has been reports stating that supplementation with synthetic beta-carotene caused an increase in lung cancer in women who had ever smoked (including current and former smokers). It is possible that chemicals in cigarette smoke reacts with beta-carotene, causing the formation of compounds that have deleterious effects on human health. Such a toxic interaction has previously been demonstrated between beta-carotene and alcohol: supplementation with beta-carotene increased the severity of ethanol-induced liver disease in rats.
The best way to consume beta-carotene is by eating fruits and vegetable, which contain a wide array of different carotenoids. Supplementation with beta-carotene by itself might deplete other carotenoids that have health benefits.
Terry Pfau DO, HMD