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By Rebecca L. Fahey, PhD, MD, MBA
Integrative Medicine Epidemiologist, Wheeling, WV
Dr. Fahey reports no financial relationships relevant to this field of study.
SYNOPSIS: A review of the literature to summarize the health benefits of apple ciider vinegar and other common vinegars.
Vinegar has been used in households for more than 10,000 years, as seasoned vinegars for 5,000 years, and is sold in markets across the globe.1 There are two types of vinegars made today: cider vinegar and normal vinegar. Vinegar can be made from many foods. Cider vinegar is made from fruit juices,2 grapes, dates, figs, sugarcane, and apples, while normal vinegar can be made from grains, molasses, coconut, honey, beer, maple syrup, beets, and whey.3 Vinegars also are used in food production, from ketchups and mustard to sauces and mayonnaise. Vinegars contain bioactive compounds, the extra-nutritional constituents found in fruits and vegetables. These bioactive compounds are of many types, such as carotenoids, phytosterols, phenolic compounds, and vitamins C and E.4,5 More specifically, apple cider vinegar also contains organic acids (acetic acid, citric acid, formic acid, lactic acid, malic acid, and succinic acids) and phenolic compounds (gallic acid, catechin, epicatechin, chlorogenic acid, caffeic acid, and p-coumaric acid). All of these compounds instill vinegar with health benefits even when ingested in small amounts, such as acetic acid from vinegar as 0.3% of total food intake or 15-30 mL (1-2 tablespoons) of cider vinegar.6 These health benefits include reducing cholesterol and lipid levels, antioxidant properties, enzyme inhibitors, inhibitors of gene expression, antidiabetic effects,7 reduced blood pressure, prevention of heart disease, and antimicrobial properties.6
Vinegar is made using two biotechnological processes. First, the sugar contained in the food undergoes alcoholic fermentation in the presence of yeast, Saccharomyces cerevisiae, which converts the foodstuff to alcohol.6 Then, the alcohol is converted into acetic acid by acetous fermentation in the presence of acetic acid bacteria (Acetobacter pasterianus and Acetobacter polyoxogenes). The Orleans method (conventional method) and the rapid methods (submerged and generator) are used for producing vinegars.8 The speed of vinegar production is affected by fermentation temperature, pH, yeast strains, sugar, and oxygen concentration.7
Apple cider vinegar has a wide variety of health benefits listed online. Table 1 includes the variety of uses for apple cider vinegar on various health problems. The bioactive compounds and acetic acid in apple cider vinegar and other vinegar varieties contribute to the health benefits of vinegar.4 Bioactive compounds are “extra-nutritional constituents that typically are naturally occurring in small quantities in plant products and lipid-rich foods.”9 Epidemiological research has increased in the area of bioactive compounds because of their beneficial effect on chronic disease treatment and prevention.9 A diet rich in bioactive compounds, including flavonoids, anthocyanin, and others,10 has been shown to have significant health benefits.
Polyphenols prevent lipid peroxidation, hypertension, antiplatelet effects, and anti-inflammatory effects by improving endothelial function, hyperlipidemia, inflammation, DNA damage, and cancer.11 Recent research on antioxidants has shown that they can prevent chronic disease. The most abundant antioxidants in vinegar are polyphenols and vitamins, both with a long history of fighting oxidation.6 The polyphenol pathway is directly correlated with the quality of cider vinegars because polyphenols contribute to the acidity, sharpness, hue, and fragrance12 of the vinegar. Pharmaceutical scientists are researching methods to measure polyphenol amounts in food and measure their antioxidant potential.13 Valuable instruments for measuring the antioxidant levels of different foods are being developed.10 The health benefits depend on both the intake and bioavailability of the substance.14 Several epidemiological studies have found that polyphenols provide protection from cardiovascular disease, cancer, diabetes, infections, aging, dementia, and hypercholesterolemia.15
Antitumor. Black vinegar or brown rice vinegar is used as a condiment in sushi and other Asian restaurants in the United States. Kurosu, traditional Japanese vinegar or black vinegar, contains ethyl acetate, which has superior antioxidative activities,14,16 along with polyphenols, which can inhibit the growth of human cancerous cells.6,14 These additional polyphenols are found in black vinegar — quercetin, catechins (also in apple cider vinegar), isoflavones, lignans, flavones, ellagic acid, resveratrol, and curcumin — and all were tested to show protective effects against cancer sites. These protective effects have been observed in cancer locations of the mouth, the stomach, the duodenum, the colon, the liver, the lung, the mammary glands, and the skin.14
Experiments conducted on rats have shown that ethyl acetate extracts of Japanese black vinegars can prevent azoxymethane-induced colon cancer by increasing enzymes in the liver that prolong the life of the rats.17 Much of the information on the health benefits of fruit vinegars has not been evaluated formally in rigorous clinical trials. However, investigations on polyphenols, especially resveratrol, have shown that the prolonged use of fruit vinegars may lead to protective anticancer outcomes in humans. Future research should focus on the analogous active ingredients of these fruit and black vinegar extracts and their role in tumor necroptosis.
Antiobesity, Anti-lipidemic. It is suggested that humans must consume at least 0.3% of acetic acid daily (1 to 2 tablespoons of vinegar in 8 ounces of water) to reduce serum cholesterol, triglycerides,18 and improve digestion.19 In 2009, Kondo et al studied 155 obese, healthy Japanese subjects who consumed a 500-mL beverage with 15 to 30 mL (1 to 2 tablespoons) apple cider vinegar for 12 weeks. They found that body mass index, visceral fat, waist-to-hip ratio, and triglycerides all decreased at both doses.20 The following triglyceride levels were found: placebo group (1.71 ± 0.50 mmol/L to 1.68 ± 0.67 mmol/L), low-dose apple cider vinegar group (1.70 ± 0.60 mmol/L to 1.39 ± 0.58 mmol/L), and high-dose apple cider vinegar group (1.78 ± 0.55 mmol/L to 1.31 ± 0.54 mmol/L). The acetic acid present in vinegar may down-regulate gene expression in cholesterol synthesis or upregulate gene expression in favor of fatty acid oxidation, thus enhancing lipolysis.21
Beheshti et al performed another study in which 19 hyperlipidemic patients consumed 30 mL (2 tablespoons) of apple cider vinegar twice a day, and they noted reduced cholesterol, low-density lipoprotein (LDL), and triglycerides after eight weeks compared to baseline.22 These studies contrast with a parallel, randomized, double-blind, placebo-controlled eight-week trial on 97 non-diabetic subjects that found no significant differences in high-density lipoprotein, LDL, total cholesterol, triglycerides, or high-sensitivity C-reactive protein. Interpreting these results is difficult because some of the study participants were also taking fish oil and/or statin medications while in the study. More investigations need to be made behind the lipid-lowering potential of apple cider vinegar in carefully constructed clinical trials. Vinegar made from tomatoes has antivisceral properties, and when consumed regularly can reduce the total gut fat and the adipocyte cell size.23,24 Human and animal studies showed that tomato vinegar could be used as an antiobesity and antidiabetic agent24,25 and that consumption of acetic acid reduced serum triglycerides.26
Antidiabetes. Diabetes is a worldwide public health problem.27 Researchers are now looking at vinegars and other bioactive components of foods as an adjuvant treatment for diabetes. The first effect of vinegar on blood glucose levels was published in 1988. When researchers gave rats a solution of 2% acetic acid after a high-glucose meal, the blood glucose levels were reduced.28 A series of human studies ensued on how blood glucose levels are reduced when fruit vinegars are taken after a high carbohydrate meal. (See Table 2.) Vinegar was ineffective in reducing postprandial blood glucose after low-carbohydrate meals,29 possibly because it works on the digestion of food.30 Additional research is needed in this area but apple cider vinegar may reduce glucose during digestion by delaying gastric emptying and/or through the inhibition of enzyme activity thereby influencing carbohydrate absorption.31,32,33
Vinegar can decrease blood glucose after high-carbohydrate meals, increase insulin response, and increase satiety. A systematic review of randomized and non-randomized, controlled clinical trials on diabetic patients who consumed vinegar in therapeutic amounts (4 teaspoons to 2 tablespoons) found a small but significant reduction in mean HbA1c after 8-12 weeks of vinegar administration (-0.39; 95% confidence interval [CI], -0.59 to -0.18; 12: 0%). Other significant findings were a lower pooled mean difference in glucose levels at 30 minutes in the vinegar group.27 Future research should use carefully planned large clinical trials on how vinegar can be used as an adjunct treatment modality for diabetes. A meta-analysis of clinical trials involving vinegar’s effect on postprandial glucose and insulin responses34 confirmed this recommendation.
In the last two decades, vinegar has been shown to decrease blood glucose levels in healthy and diabetic adults.34 In 2017, Shishehbor et al performed a pooled analysis of 11 studies that exposed a significant mean glucose and insulin area under the curve (AUC) in participants who consumed vinegar compared with the control group (standard mean difference, - 0.60; 95% CI, - 1.08 to -0.11; P = 0.01; and -1.30; 95% CI, -1.98 to -0.62; P < 0.001, respectively).35 In the two studies, patients had decreased postprandial glucose and insulin in the vinegar groups. Vinegar can improve the insulin sensitivity of humans and may be used as an adjuvant treatment.35,36
Vinegar is a popular subject in the literature surrounding chronic disease prevention and treatment. Inflammation has been identified as the driving force behind chronic diseases. The antioxidant properties of vinegar, fruits, vegetables, and legumes have been proven effective in the management and prevention of chronic disease.
Apple cider vinegar remedies are advertised widely online as treatments for a variety of health problems. Everything from tablets, pills, drinks, dog rinse cleansers, and traditional vinegars are touted as cures and tonics. There have been a few cases of apple cider vinegar adverse effects in the literature. Investigators examined several types of apple cider vinegar pills on the market after an initial complaint from a patient with pain and difficulty swallowing when an apple cider vinegar tablet had lodged in her throat for 30 minutes. The safety, reliability, and quality of these supplements are in question because of unreliable and erroneous labeling techniques, dosage variability in amounts of active compounds, and the uncorroborated health benefits.37 There is a risk of increased incidence of chemical burns when treating skin disorders, warts, and Mollusca with acetic acid or vinegar.38 The first case of sudden cardiac death due to forced ingestion of 5% acetic acid was published in 2016.39 Individuals have experienced disseminated intravascular coagulation, requiring treatment with fresh frozen plasma and cryoprecipitate,40 as well as hepatic abnormalities41 following the ingestion of acetic acid. It is recommended that vinegar be ingested only in dilute amounts. Many cases of corrosive injuries have taken place when vinegar is ingested undiluted.
Apple cider vinegar is highly acidic. The main ingredient is acetic acid, which can be relatively corrosive. Household vinegar, which is typically 5% acetic acid, should be diluted (1-2 tablespoons) in an 8-ounce glass of water or juice before swallowing.37 Pure, straight apple cider vinegar could damage tooth enamel or the tissues of the mouth and throat.42 The average pH of apple cider vinegar is between 2.5 and 3.0.42 Long-term ingestion of excessive amounts (> 1 to 2 tablespoons in an 8-ounce glass of water) of even diluted acetic vinegar can cause low potassium levels and lower bone density.43 One incident of anaphylaxis from unpasteurized apple cider vinegar (bACV) occurred in a 40-year-old female who drank 30 mL of bACV for two weeks until she developed diffuse urticaria, nausea, vomiting, abdominal pain, and difficulty breathing after the last dose and was treated in the emergency department with injected epinephrine, steroids, and diphenhydramine. A challenge with 15 mL bACV after five minutes showed progressive flushing, groin pruritus, and hives requiring epinephrine, diphenhydramine, ranitidine, and prednisone. Subsequent oral challenge to 15 mL bACV was negative. The patient was advised to avoid bACV and keep epinephrine available.44
It has been theorized that apple cider vinegar may interact negatively with the following medications: antidiabetic medications, digoxin, diuretic drugs, and insulin.
Apple cider vinegar might have additive effects on glucose levels when used with hypoglycemic drugs. Hypothetically, overuse of apple cider vinegar could decrease potassium levels, increasing the risk of toxicity for digoxin, diuretics, and insulin. Physicians should monitor blood glucose and potassium levels closely and medication dose adjustments may be necessary.
Apple cider vinegar has antioxidant, anti-lipidemic, antidiabetic, and therapeutic properties.6 Apple cider vinegar is made from apples by the process of alcohol fermentation and acetous fermentation. Bioactive compounds and acetic acids are the active components in vinegar that are responsible for health benefits. The antidiabetic properties are the most promising because of the backing of several meta-analyses on clinical trials supporting vinegar’s ability to lower postprandial glucose and improve insulin sensitivity. Vinegar has been shown to be helpful in weight loss, decreasing postprandial glucose, and lowering lipid levels.21,22, 23
Definitive studies on vinegar are still surfacing relative to its safety and efficacy. Advise patients to be cautious about their vinegar consumption, and limit the dose to no more than 2 tablespoons daily diluted in 4 to 8 ounces of juice. For weight loss, vinegar might work best when consumed before meals, especially those that are high in carbohydrates. With respect to types of vinegar, the best data are on apple cider vinegar, and some experts recommend organic, unfiltered, unprocessed vinegar, which is cloudy, containing the “mother,” or collection of enzymes and probiotics, possibly indicating a quality product. Future clinical trial research should investigate how vinegar can be used as an adjuvant treatment modality for diabetes and prevention or treatment of other chronic diseases.
Financial Disclosure: Integrative Medicine Alert’s executive editor David Kiefer, MD, peer reviewer Suhani Bora, MD, AHC Media executive editor Leslie Coplin; editor Jonathan Springston; and editorial group manager Terrey L. Hatcher report no financial relationships relevant to this field of study.