It is well established that nutrition is vitally important to maintain health and to promote longevity. In addition to the macronutrients a well-balanced diet provides, fruits and vegetables contain a variety of small molecules known as phytochemicals, which can act in a quasi-pharmaceutical manner affecting a multitude of biological pathways. The consumption of grapes has long been thought to impart health benefits, and numerous studies have attempted to uncover the phytochemicals responsible for this; however, the search for one or more specific molecules responsible for the putative benefits of dietary grapes has remained elusive. In light of this, Dave, et al., have focused their research efforts on the consumption of whole grapes. Their findings, reported in the journal Foods, provide evidence that dietary supplementation with grapes has the potential to improve the quality and duration of life.
To interrogate the potential health benefits of the entire range of phytochemicals found in grapes, researchers supplemented the diets of mice with a whole grape powder. The amounts added to the experimental diets of mice studied would equate to a 150 lb. person eating 40 to 45 grapes per day. Experimentally, the diet having the most profound benefit when supplemented with powdered grapes was a high-fat diet designed to replicate the Western diet, which is known to increase the risk of obesity, cardiovascular disease, cancer, and various metabolic disorders. Mice on this diet are subject to metabolic dysregulation, resulting in a lifespan reduction of roughly one-third and the onset of multiple pathologies, e.g., diabetes and non-alcoholic fatty liver disease (NAFLD).
NAFLD is increasingly prevalent in Western cultures and an ever-growing issue globally as more regions adopt a Western diet. It is characterized by an excess accumulation of fat in the liver, leading to cellular damage and impaired function and a dramatic increase in the risk of developing liver cancer. In this recent study, large amounts of powdered grapes added to a high-fat diet altered the expression of genes involving lipid metabolism in the liver and abrogated the development of NAFLD. It is thought that one or more compounds found in grapes elicit a change in hepatic lipid metabolism, preventing deleterious fat accumulation. Surprisingly, these findings seem specific to the liver, as mice supplemented with grape powder were heavier than their non-supplemented counterparts, likely due to the accumulation of fat in depots other than the liver. This is consistent with other findings, suggesting that the detriment of increased adiposity is dependent on the type of and region where fat is accrued.
In addition to the liver-specific benefits, mice on the grape-supplemented high-fat diet exhibited a significant extension of lifespan when compared to mice on a high-fat diet alone. It is unclear whether changes in liver metabolism and the prevention of NAFLD are responsible for ameliorating the shortened lifespan caused by chronic consumption of a high-fat diet or if additional mechanisms are responsible.
Interestingly, there is growing evidence that NAFLD is correlated with increases in the severity of Alzheimer’s disease and the risk of developing dementia. Furthermore, there is evidence of a potential shared mechanism underlying both NAFLD and Alzheimer’s disease. The authors do note observed changes in both gene expression and behavior of mice fed a grape-supplemented high-fat diet consistent with prolonged preservation of brain function and plan to pursue these findings further.