Safety and side effects of apple vinegar intake and its effect on metabolic parameters and body weight: a systematic review

Introduction Apple vinegar (AV) has been proclaimed to have different health benefits, such as a weight loss, the ability to lower blood glucose levels, and reducing the risk of heart diseases. Studies on animals have demonstrated effects of AV consumption, deepening our knowledge of the beneficial effects and side effects. Aim The aims of this study were to evaluate the evidence of the effect of AV on metabolic parameters and body weight in humans, furthermore, to evaluate the safety and side effects of ingesting AV, and additionally to evaluate the evidence of the effect of AV on metabolic parameters, safety, and side effects of AV from studies performed on animals (mammals). Methods A systematic literature search was performed. The databases PubMed (MEDLINE), PsycInfo (Ebsco), CINAHL (Ebsco), and Embase (Ovid) were searched for relevant articles. Primary outcomes were glycated hemoglobin, postprandial glucose, and synonyms for blood glucose. Secondary outcomes were waist circumference, visceral fat, high-density lipoprotein, low-density lipoprotein, triglycerides, and total cholesterol. Studies performed on humans and animals were included. The included studies performed on humans were quality assessed for risk of bias using a version of the Cochrane Collaboration's tool. Results A total of 487 papers were identified in the literature search. Of these, 13 studies performed on humans and 12 studies performed on animals were included. There may be beneficial health effects from the consumption of AV. The risk of side effects when ingested in recommended quantities and in recommended ways seems inconsiderable. Conclusion Due to inadequate research of high quality, the evidence for the health effects of AV is insufficient. Therefore, more large-scale, long-term clinical studies with a low risk of bias are needed before definitive conclusions can be made.