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By Jessica Orner, MD
Family Medicine Physician, Lebanon, PA
Dr. Orner reports no financial relationships relevant to this field of study.
SYNOPSIS: Supplementation with 30 mL of apple cider vinegar combined with a restricted calorie diet may lower body weight, body mass index, and serum triglyceride levels in people with obesity.
SOURCE: Khezri SS, et al. Beneficial effects of apple cider vinegar on weight management, visceral adiposity index and lipid profile in overweight or obese subjects receiving restricted calorie diet: A randomized clinical trial. J Funct Foods 2018;43:95-102.
Apple cider vinegar (ACV) has many uses in today’s society. An online search of ACV will yield more than 17 million results, with articles ranging from food preparation to weight loss to facial toning.1 Although vinegar has been used for centuries as a home remedy, there is a paucity of research supporting many of the claims for ACV.
In a 2009 randomized, controlled trial from Japan, researchers demonstrated that body weight, body mass index (BMI), and serum triglycerides declined significantly in participants with obesity who ingested 15-30 mL of ACV vs. a placebo group.2 The weight management benefits of vinegar are postulated to be due to acetic acid suppressing fat accumulation and appetite suppression due to nausea.
In this randomized clinical trial conducted from October to December 2014, Khezri et al compared the effects of a restricted calorie diet (RCD) combined with 30 mL per day of ACV to a control group who ate only an RCD. The RCD included a 250 kcal/day energy deficit. The primary outcome was dietary modification in response to ACV ingestion.3 Secondary outcomes were anthropometric changes: plasma triglyceride, total cholesterol, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C). The researchers assessed plasma concentrations of neuropeptide-Y (NPY), which is known to stimulate the appetite,4 to determine the effects of ACV on NPY.
The researchers selected participants using convenience sampling from a population at the Specialized Clinic of Nutrition and Diet Therapy in Tehran, Iran. Forty-four overweight or obese adults with BMIs ranging from 27-40 kg/m2 were eligible. Of the eligible participants, two in the ACV group and three in the control group were excluded because of their inability to cooperate or because of conflicts with ongoing medical treatments. Patients also were excluded for regular consumption of ACV within one month prior to the start of the study. The researchers noted that the enrolled subjects did not present with infectious diseases, thyroid disorders, diabetes, or gastrointestinal diseases.3
The intervention was conducted over 12 weeks. The test group received 30 mL of ACV divided into 15 mL at lunch with salad and 15 mL at dinner. Both the control group and the group receiving ACV followed an RCD. The RCD was determined by subtracting 250 kcal from the participant’s estimated energy requirements per day based on the Mifflin-St. Jeor equation, and was designed to provide 55% carbohydrates, 30% fats, and 15% protein. This equation estimates the resting metabolic rate using mass, height, and age. The authors of a 2005 systematic review that compared four predictive equations for resting metabolic rate noted the Mifflin-St. Jeor equation was more likely than other equations to estimate resting metabolic rate to within 10% of measured rates.5
Several measurements were taken at baseline, six weeks, and 12 weeks. These included anthropometric data, physical activity, and an appetite score using the Simplified Nutritional Appetite Questionnaire (SNAQ). A three-day dietary recall was completed at baseline, week 6, and week 12 to estimate caloric intake. This dietary recall provided information about any dietary adjustments that participants made during the trial. Fasting blood samples were collected at baseline and at the end of week 12, measuring triglycerides, total cholesterol, HDL-C, and plasma NPY concentrations. There was no information on adverse events during the study.
There were no significant differences between groups regarding energy intake or physical activity. Both groups reduced their energy intake at the end of the 12 weeks when compared to baseline. However, the reduction for the control group was not significant (P = 0.12). The ACV group significantly reduced dietary energy intake at 12 weeks when compared to baseline (P = 0.01), with a significant decrease in intake of saturated fatty acids and monounsaturated fatty acids (P = 0.03). There was not a significant difference between the groups in protein, carbohydrate, or cholesterol intake.
Both the ACV and control group exhibited a significant reduction in body fat and BMI from baseline (P = 0.001). When comparing the ACV and control groups, there was a significant reduction in hip circumference and body weight, with the ACV group losing an average of 4 kg and the control group losing an average of 2.3 kg. The ACV group had a reduction in plasma triglycerides at week 12 when compared to baseline and the control group (P = 0.001). Concurrently, the control group recorded a significant increase in triglycerides compared to baseline (P = 0.035). There were no statistically significant changes in LDL-C or NPY. Compared to the control group, the ACV group recorded a reduced SNAQ score at the end of 12 weeks (P = 0.04), suggesting a decrease in appetite.
As the popularity of ACV increases, additional research on its effectiveness in weight management is helpful. Khezri et al showed the group consuming ACV and following an RCD reduced body weight, limited saturated fatty acid intake, and recorded lower plasma triglycerides levels compared to the control group following only an RCD. The authors also showed that while the SNAQ score of the control group stayed at approximately 14.5, the ACV SNAQ score decreased to an average of approximately 12.9.
However, there are several concerns. The researchers could not blind the study subjects because of the strong taste and odor of ACV. This introduces the potential for bias related to participants knowing they are in the study group. Also, ACV is postulated to produce health effects from both acetic acid and antioxidation from polyphenolic compounds.6 In this study, the ACV was sourced from traditional medicine stores in Tehran and was prepared by combining 3 kg of apples with 1 kg of white vinegar and storing for 30 days. This differs from other methods, which involve combining apples with sugar and water and allowing them to ferment for six to eight weeks. This difference in processing could lead to changes in polyphenol composition.7 It is unclear if this would affect the overall effects on weight management. Another factor to consider was the sample size and sampling method. The researchers selected participants using convenience sampling. Although this type of sampling is cost-effective and easier than other options, it increases the risk of sampling error and underrepresentation of subgroups in a population. It limits our ability to generalize these results to larger or more diverse populations.
Regarding adverse events, the risk of adding ACV to the diet is likely lower than other weight loss interventions, such as pharmaceutical medication. However, the authors did not provide information on adverse events. ACV can affect tooth enamel and lead to nausea. It would be useful to note the adverse effects in future studies so clinicians can offer patients comprehensive counseling on the risks and benefits of the treatment. Overall, studies addressing these concerns are needed before changing clinical practice to recommend ACV with a restricted diet as a weight management option.
Financial Disclosure: Internal Medicine Alert’s Physician Editor Stephen Brunton, MD, is a retained consultant for Abbott Diabetes, Acadia, AstraZeneca, and Boehringer Ingelheim; and he serves on the speakers bureau of AstraZeneca, Boehringer Ingelheim, Janssen, Lilly, and Novo Nordisk. Peer Reviewer Gerald Roberts, MD; Editor Jonathan Springston; Editor Jason Schneider; Editorial Group Manager Leslie Coplin; and Accreditations Manager Amy M. Johnson, MSN, RN, CPN, report no financial relationships relevant to this field of study.