Diet and nutrition have long been regarded as central to health and longevity. Given the vast variety and complexity of human diets, however, the ongoing challenge has been to identify the specific dietary components with a direct effect on health and mortality. The general consensus is that health gains for chronic disease are most likely from healthy dietary patterns that include adequate consumption of fruits, vegetables, whole grains, nuts, seeds, fibre, and fish and that are low in red and processed meats, sugary beverages, and salt. Yet there remains a parallel interest in other common dietary components that may serve as functional foods. Hot spices are one such example and are the subject of a linked paper by Lv and colleagues.
Among 0.5 million adults in the China Kadoorie Biobank the authors examined the prospective association of self reported consumption of spicy foods with total and cause specific mortality. Over a median of 7.2 years of observation with 3.5 million person years, during which 20 224 deaths occurred, they report a 14% lower risk (95% confidence interval 10% to 18%) in total mortality when comparing those who reported frequent consumption of spicy foods (6 or 7 days a week) with those who reported little consumption of spicy foods (less than once a week). A similar reduction in mortality was apparent even among those who reported consuming spicy foods 3-5 or 1 or 2 days a week compared with those whose consumption was infrequent.
How should we interpret these novel findings and what are their implications for nutritional advice? As the authors acknowledge, a cause and effect relation cannot be inferred from their work. In this prospective study, Lv and colleagues have shown temporality of association, but we need to evaluate additional criteria to judge the strength of evidence. Their findings should be considered hypothesis generating, not definitive, and will undoubtedly encourage further work.
The use of hot spices in food to enhance taste has captured the attention of the popular press as well as food outlets, including supermarkets, restaurants, and fast food shops, fuelling a worldwide trend towards greater consumption. In parallel, there is increasing scientific interest in spicy foods. Many potential benefits have been suggested for chilli or its bioactive compound capsaicin, including but not limited to antimicrobial, anti-oxidant, anti-inflammatory, and anti-cancer properties, a beneficial influence on gut microbiota, and anti-obesity effects through thermogenesis and appetite, energy balance, and weight management.
Future research is needed to establish whether spicy food consumption has the potential to improve health and reduce mortality directly or if it is merely a marker of other dietary and lifestyle factors. The added contribution of spicy food intake to the benefits of a balanced healthy diet and healthy lifestyles also remains to be investigated. However, the current findings should certainly stimulate dialogue, debate, and further interest in research.