Apples and apple-based products in the modulation of cardiometabolic and functional markers: a systematic review of human intervention studies

Apple is one of the most widely consumed fruits worldwide, yet its effects on human health remain the subject of ongoing debate. The aim of the present review was to examine evidence from human intervention studies evaluating the impact of apples and apple-based products on functional and metabolic health markers. A total of 38 studies were included: 13 postprandial interventions, 22 medium- or long-term interventions, and 3 assessing both postprandial and chronic effects. Postprandial studies predominantly investigated the effects of apple consumption on blood glucose levels and plasma antioxidant capacity, whereas medium- or long-term interventions assessed a broader range of biomarkers related to cardiometabolic health, oxidative stress, vascular function, inflammation, and gut function. Overall, the findings suggest that apples and apple-based products may beneficially modulate glycaemia, antioxidant capacity, and vascular endothelial function mainly in short-term interventions, while medium/long-term studies reported an apparent improvement in gut microbiota composition. However, the current evidence remains insufficient to draw definitive conclusions. Additionally, substantial heterogeneity in study design, populations, and products tested limits the ability to generalize results. Nonetheless, apple consumption, consistent with fruit intake in general, represents an important component of a healthy and balanced diet, providing valuable nutrients and bioactive compounds whose intake should be encouraged. Therefore, further well-designed intervention studies, particularly in populations with cardiometabolic risk factors, are warranted to better clarify the role of apples and apple-derived products in human health. Future research should also aim to identify the effective amounts and specific bioactive components responsible for the observed effects, as well as to determine whether these benefits may vary according to the health status of the target population.