What is Apple Cider Vinegar?
Apple cider vinegar has been used by many cultures for thousands of years- as a folk remedy, as a food ingredient and preservative, and for various household cleaning purposes. Reports of the healing properties of apple cider vinegar date to 3300 B.C. In 400 B.C., Hippocrates supposedly used apple cider vinegar as a healing elixir, an antibiotic, and for general health.
Samurai warriors purportedly used a vinegar tonic for strength and power. U.S. Civil War soldiers used a vinegar solution to prevent gastric upset and as a treatment for pneumonia and scurvy.
Apple cider vinegar (ACV) is a vinegar made from apples. The term “vinegar” comes from the French phrase vin aigre, meaning sour wine. To make ACV, apples are crushed into apple must- a freshly made fruit juice which contains the skins, seeds, and stems of the fruits. Then, like all fermented vinegars, it undergoes a double fermentation.
First, it is fermented by yeasts to produce alcohol-producing hard cider. Then the hard cider is fermented by acetobacter bacteria to convert the alcohol to acetic acid, which is the key ingredient of all vinegars. Acetic acid is what gives vinegar its distinctive sour taste and pungent smell. Vinegar is no less than 4% acetic acid by volume.
Raw ACV has something called the “mother.” The mother is a combination of cellulose and a mixture of bacteria used in the second fermentation process. It is what gives the product its cloudy appearance and can also be seen as floating strands.
Eventually, it will settle on the bottom of the bottom. Most commercially produced ACV is filtered and pasteurized which removes the mother and leaves a clear liquid.
Organic or raw ACV retains the mother and will remain cloudy. Aykin et al  examined the mother vinegar produced with apple and pomegranate juices.
They found that “mother of pomegranate vinegar had higher antioxidant capacity and total phenolic substance compared to samples of mother of apple vinegar… gallic acid and chlorogenic acid were dominant phenolic compounds in mother of apple vinegar, whereas gallic acid was the major phenolic compounds in mother of pomegranate vinegar.”
And not all ACV mothers are created equal. A study by Stornik, Skok and Trček  evaluated the microbiota of organic and conventional ACV, and found that the “bacterial microbiota for the industrial production of organic apple cider vinegar is clearly more heterogeneous than the bacterial microbiota for the industrial production of conventional apple cider vinegar.”
Apple cider vinegar has no nutritional value, aside from some calories, with all nutrients at negligible levels. Although a few websites assume that, like apple juice, it contains “vitamins B1, B2, and B6; biotin; folic acid; niacin; pantothenic acid; and vitamin C,” the official USDA website has all those nutrients listed as “0,” except for a small amount of potassium. ACV contains only 3 calories per tablespoon. ACV that retains the mother can contain live bacteria, which may have probiotic properties.
In general, probiotics in fermented foods have been found to be beneficial for health . However, there are no scientific studies that examine whether ACV has microbiota that act in a probiotic in humans. (There is one study of ACV boosting an immune response in carp [yes, the fish], but they are also fed the bacteria as well - so enough said about that!)
Is There any Research?
There are few scientific studies on the effect of ACV on health. A review of PubMed found only 67 articles using the term “apple cider vinegar.” There were no review articles and only one listed as a clinical trial . Limiting the search to the term “vinegar” expands the number of articles to over 45,000, but these include all types of vinegar, including wine vinegars and even onion vinegar !
There is only one trial listed under “apple cider vinegar” on ClinicalTrials.gov on the effects of vinegar on patients with Type 2 diabetes (more on this later).
To put this into perspective, there are over 5000 articles in PubMed on “red wine,” another fermented fruit juice. There are 17 studies on ClinicalTrials.gov.
Does Apple Cider Vinegar Help Regulate Blood Sugar Levels?
Although ACV has been used as a medical tonic for centuries, in the past 30 or so years, researchers have started to evaluate whether ACV influences blood sugar levels. In 1988, Ebihara and Nakajima  first reported the antiglycemic effect of vinegar.
Ogawa et al  did an in vitro study of the effect of vinegar on glucose transport and disaccharidase activity in Caco-2 cells (a cell line used as a model of the intestinal barrier).
They found that acetic acid suppressed sucrase activity. Sucrases are enzymes that convert cane sugar (sucrose) into simple sugars (glucose and fructose). Shishehbor et al  fed both normal and diabetic rats standard animal food containing apple cider vinegar for 4 weeks.
They found that while fasting blood glucose did not change, HbA1c (Hemoglobin A1c – a biomarker of Type II Diabetes or T2D) was significantly decreased by apple cider vinegar in diabetic group (p<0.05). HBA1c measures the amount of blood sugar (glucose) attached to hemoglobin and is felt to represent the average blood sugar over a previous 3-month period.
A few small studies have been done on healthy subjects as well as those with T2D. Östman et al  fed 12 healthy volunteers white wheat bread with or without one of three doses of vinegar.
Fasting blood sugar and a subjective rating of hunger/satiety was obtained before the meal. Blood sugar and insulin levels were obtained at six intervals (between 15 and 120 minutes) after the meal, as was the rating of hunger/satiety.
They found a significant decrease in blood and insulin response in subjects when vinegar was given with bread. However, there was less glucose/insulin response with increasing levels of acetic acid. Satiety increased with increased acetic acid concentration. Subjects were given either a vinegar drink or a placebo drink 2 minutes prior to a meal of bagel, butter, and orange juice.
Johnston et al have published several articles [12-15] on the effect of vinegar on blood glucose in healthy adults, those at risk for T2D, and those with T2D. A 2004 study included nondiabetic subjects who were either insulin sensitive (control subjects, n = 8) or insulin-resistant (n = 11) and 10 subjects with type 2 diabetes.
“Compared with placebo, vinegar ingestion raised whole-body insulin sensitivity during the 60-min post-meal interval in insulin-resistant subjects …and slightly improved this parameter in subjects with type 2 diabetes…
Postprandial fluctuations in insulin were significantly reduced by vinegar in control subjects, and postprandial fluctuations in both glucose and insulin were significantly reduced in insulin-resistant subjects.”
In a 2010 randomized crossover study with 38 healthy volunteers, participants were divided into 4 trial groups. All participants were fed a standardized meal on the evening before testing. They then underwent an overnight fast (>10 hr.) and a 2-hour glucose testing after eating a bagel and juice test meal.
Post-prandial glucose levels (PPG- blood sugar after eating) were compared. I’ve summarized their results in the table below.
|1. Do small amounts of vinegar (2-20 g) possessed antiglycemic effects?||10 g (2 teaspoons) of 5% acidity vinegar reduced PPG after 2 h by 23% compared to placebo (p = 0.05).” This amount of vinegar is roughly equivalent to the amount the present in a serving of vinaigrette dressing.|
|2. Does the antiglycemic effects persisted for 5hr after consumption?||Vinegar given with the meal decreased PPG by 19% compared to placebo, but vinegar given 5 hr. before the test meal did not.|
|3. Does the antiglycemic effect depend on the form of carbohydrate eaten?||The antiglycemic property of vinegar is related to starch (complex carbohydrate) digestion as using the single sugar dextrose did not reduce PPG|
|4. Does whether a “vinegar pill” possessed antiglycemic effects in individuals with Type II diabetes?||Sodium acetate does not appear to possess antiglycemic properties.|
The 2013 study was done on adults at-risk for T2D. They ingested either a vinegar drink or a control pill twice a day for 12 weeks. Fasting blood sugar was measured daily, and insulin and HBA1c were measured in week 0 and 12. Although the fasting glucose level was reduced in the vinegar group compared to controls, insulin and HbA1c did not vary between groups.
They also did fasting hydrogen breath tests at week 12. A hydrogen breath test (or HBT) is used as a diagnostic tool for small intestine bacterial overgrowth and carbohydrate malabsorption. The vinegar group had a 19% higher hydrogen level than the control- suggesting an increase in colonic fermentation, and possible carbohydrate maldigestion.
Several studies have documented that vinegar ingestion reduces the glucose response to a complex carbohydrate load in healthy subjects and those with Type 2 Diabetes, however, the mechanisms by which this occurs are not yet understood and the number of human studies is small.
The long-term effects on HbA1c have not yet been determined. Larger studies are needed to decide whether vinegar will be a helpful adjunct therapy for those with diabetes or at risk for it.
Does Apple Cider Vinegar Enhance Weight Loss?
Vinegar has been promoted as a natural appetite suppressant, primarily by promoting satiety (feeling full). Some have suggested that it increases satiety by delaying stomach emptying. Liljeberg and Björck  used paracetamol as a marker of gastric emptying in subjects given vinegar with a starch, protein and fat test meal.
They concluded that, based on lower paracetamol levels after the test meal with vinegar, the mechanism is probably due to a delayed gastric emptying rate. The main concern with this article is whether paracetamol itself might influence gastric emptying itself.
A few articles were done with rats and mice. Beh et al  found that obese mice fed Nipa vinegar (produced through the fermentation of Arenga pinnata palm sap) or synthetic acetic acid in their diet reduced food intake and body weight, possibly by “altering lipid metabolism, inflammation and gut microbe composition.”
Bouderbala et al  used 3 groups of Wistar rats. One fed a standard diet, the other two given a high-fat diet. Half the high-fat diet group was also fed ACV.
Rats in the high-fat vinegar group have a highly significant decrease (P<0.001) in body weight and food intake, as well as a very significantly difference in anthropometric parameters: BMI (P<0.01), chest circumference and abdominal circumference (P<0.001).
In human studies, the most commonly cited article on the effect of ACV on weight is by Kondo et al . According to the authors: “The subjects [155 in number] were randomly assigned to three groups of similar body weight, body mass index (BMI), and waist circumference.
During the 12-week treatment period, the subjects in each group ingested 500 ml daily of a beverage containing either 15 ml of vinegar, 30 ml of vinegar, or 0 ml of vinegar.
Bodyweight, BMI, visceral fat area [the fat that surrounds the internal organs], waist circumference, and serum triglyceride levels were significantly lower in both vinegar intake groups than in the placebo group.”
Östman et al  used a subjective rating of hunger/satiety pre- and post-meal in patients (see section above). Patients rated themselves more satiated when the meal included ACV than without it. Satiety increased with increasing ACV levels.
Kherzi et al  did a randomized study (which was not blinded because the smell of vinegar gave it away) of 39 Iranian adults divided into two groups. Both groups were put on a calorie-restricted diet (CRD) and half also received 30 ml (1 oz.) of vinegar/day divided between lunch and dinner for 12 weeks.
Both groups had significant weight loss, but those given ACV also had a significant decrease in body weight, BMI and hip girth compared to the control group. It should be noted that lean body mass was also significantly decreased in the ACV group compared to their baseline, meaning not all weight loss was due to fat loss.
However, one study, by Darzi et al , points out the “ingestion of vinegar significantly reduced quantitative and subjective measures of appetite, which were accompanied by significantly higher nausea ratings…These effects are largely due to poor tolerability following ingestion invoking feelings of nausea. On this basis, the promotion of vinegar as a natural appetite suppressant does not seem appropriate.” I agree.
Although there is some evidence of weight loss with ACV ingestion, the numbers are small, especially in human subjects. In addition, it is not clear whether the poor tolerability of ingestion of larger amounts of ACV is one cause of decreased intake. Larger placebo-controlled, double-blinded studies are needed.
Does Apple Cider Vinegar Help Lower Cholesterol?
As with the weight loss issue, most of the scientific evidence suggesting that ACV can lower cholesterol comes from animal studies. In the study by Beh mentioned above , mice fed a high-fat diet lead to a higher serum lipid profile.
Treatment with synthetic acetic acid vinegar or nipa vinegar “exhibited statistically significant (p < 0.05) lower serum total cholesterol, triglyceride (TG), low-density lipoprotein (LDL) and higher high-density lipoprotein (HDL) (p < 0.05) relative to the untreated obese group.”
I found only four papers which looked at the effect of ACV on lipid profiles in humans. Two were already mentioned above. Kondo  found that triglyceride (TG) levels began to decrease from week 4 in both the low and high dose ACV groups. The low dose group also had significantly lower total cholesterol levels at 12 weeks.
Kherzi  found that plasma TG concentrations were significantly reduced in the ACV group compared to their baseline and in comparison to the control group (p=0.001). HDL (high-density lipoprotein- “the good cholesterol”) level was also significantly increased in the ACV compared to the control group.
Although total cholesterol significantly decreased in the ACV group compared to baseline, LDL levels did not significantly change.
Beheshti et al  looked at 19 patients with high blood lipids. Participants were asked not to modify their diet or physical activity pattern, however, they agreed to consume 30ml of ACV twice a day for eight weeks. There was no placebo control.
“There were significant reduction in the serum levels of total cholesterol (p < 0.001), triglyceride (p = 0.020), and LDL (p = 0.001) after eight weeks of consuming apple cider vinegar and with increased HDL levels but the trend was not statistically significant (p = 0.200).”
In contrast, Panetta et al  conducted a randomized placebo-controlled clinical trial to determine the effects of apple cider vinegar intake in 114 non-diabetic subjects. Subjects consumed 30 ml of ACV/day for 8 weeks. They found no significant difference in HDL-C, LDL-C, triglycerides, or total cholesterol.
A review by Petsiou et al  points out the main limitation of this study is that the group of subjects was mixed, with one-third being on a statin and/or fish oil treatments.
Most of the evidence of the impact of ACV on lipids is in animal studies and a few human studies with important limitations. Larger, long-term, randomized, blinded, placebo-controlled studies are necessary.
Does Apple Cider Vinegar Improve Skin Health?
Most of the argument for ACV improving skincare centers around its antibacterial and antifungal  properties. Vinegar has been used from the time of Hippocrates (460-377 BC) for cleaning ulcerations and sores.
Johnston and Gaas  point out that most of the antimicrobial properties of vinegar have been documented in the context of food preparation and that experts advise against using vinegar preparations for treating wounds.
There are no scientific papers which specifically examine the effect of ACV on the skin. I found one paper on the helpful effect of zinc oxide and citric acid on Propionibacterium acnes , a skin bacterium linked to acne; another on the topical application of lactic acid/lactate lotion as a preventative treatment for acne .
There is a small amount of citric acid in ACV (there’s a lot more in lemon juice). This is by no means the same as ACV which is primarily acetic acid.
There is no scientific evidence that ACV improves skin health.
Does Apple Cider Vinegar Reduce Blood Pressure?
There are three scientific papers that look at the effect of ACV on blood pressure- two of them in rats. Our friends Kondo et al (see above) are the authors of two of the three studies.
In the rat study, Kondo  reported a significant reduction in systolic blood pressure (about 20mm of mercury) in spontaneously hypertensive rats (SHR) fed either acetic acid, ACV compared to controls who received the same diet with water.
They suggest that the reduction in blood pressure may be caused by a “significant reduction in renin activity and the subsequent decrease in angiotensin II.” The renin-angiotensin (RAA) system is a group of related hormones that act together to regulate blood pressure. The renin-angiotensin system, which works together with the kidneys, is the body's most important long-term blood pressure regulation system.
Honsho et al , using a beverage made from red wine vinegar and grape juice, examined the effect of the drink on the blood pressure of anesthetized rats. They induced an elevated blood pressure with the addition of angiotensin I. This effect was diminished when the rats were given the vinegar beverage.
The previously mentioned Kondo paper  that examined the weight and lipid profile effects of ACV also looked at blood pressure in the 155 subjects of the study. They found a significant decrease in the systolic blood pressure at 8 and 12 weeks, but only in those subjects who received high doses of vinegar. The “P- value” of that significance was <0.05, which is the lowest limit at which a finding is considered significant.
There is insufficient evidence to support the use of vinegar to control blood pressure.
Does Apple Cider Vinegar Relieve Symptoms of Acid Reflux?
Gastroesophageal reflux (GER) happens when your stomach contents come back up into your esophagus. Stomach acid that touches the lining of your esophagus can cause heartburn, also called acid indigestion, or acid reflux. Gastroesophageal reflux disease (GERD) is a more serious and long-lasting form of GER and is diagnosed when GER occurs more than twice a week for a few weeks.
GER and GERD happen when your lower esophageal sphincter (the muscle that acts as a valve between your esophagus and stomach) becomes weak or relaxes when it shouldn’t, causing stomach contents to rise up into the esophagus. The lower esophageal sphincter becomes weak or relaxes due to certain things, such as
- increased pressure on your abdomen from being overweight, obese, or pregnant
- certain medicines, including those to treat asthma, calcium channel blockers for high blood pressure, antihistamines, sedatives, and antidepressants.
- smoking, or inhaling secondhand smoke
- hiatal hernia (A condition in which the upper part of your stomach pushes upward into your chest through an opening in your diaphragm.)
I’ve seen a few of the websites (which will remain nameless) that promote the use of ACV in the treatment of acid reflux using the argument that GER or GERD is caused by low stomach acid, and adding the acid of ACV will improve GER. Not so, say experts like the Cleveland Clinic who list citrus fruits, as well as vinegar, as possible triggers for GERD.
There is only one paper that comes up when you search for “apple cider vinegar and acid reflux.” The paper, by Brown et al  is entitled “Effect of GutsyGum™ A Novel Gum, on Subjective Ratings of Gastro Esophageal Reflux Following A Refluxogenic Meal.” GutsyGum™, a chewing gum developed to alleviate the symptoms of GER contains calcium carbonate, with a proprietary blend of licorice extract, papain, and apple cider vinegar (GiGs®).
The study was a double-blind, placebo-controlled- crossover study with 24 participants with a history of GER. Participants completed questionnaires at regular intervals (up to four hours) following a meal (designed to induce reflux) followed by GutsyGum™ or a placebo gum. Significant improvement (based on questionnaire scores) was found in those chewing GutsyGum™ vs. placebo for heartburn and acid reflux.
Pain, nausea and belching symptoms tended lower, but were clinically insignificant.
There is insufficient evidence to recommend the use of ACV in the treatment of acid reflux. To the contrary, for many people, it might cause acid reflux.
Is Apple Cider Vinegar Safe?
Apple cider vinegar has been used as a condiment and food ingredient for thousands of years, so overall, it can be considered safe. However, there are some reports in the literature of adverse reactions to vinegar, a few of which will be outlined here:
- The acidity of undiluted ACV may destroy tooth enamel when sipped orally. Either dilute it before drinking or drink some water afterward.
- Acidic foods or liquids like vinegar may exacerbate acid reflux.
- Apple cider vinegar should be used cautiously in patients with low potassium levels and patients taking potassium-lowering medications.
- Theoretically, long-term oral use of apple cider vinegar can decrease potassium levels, increasing the risk of toxicity of cardiac glycoside drugs such as digoxin (Lanoxin). Long term use may also add to the potassium-lowering effects of insulin, laxatives, and diuretics such as furosemide (Lasix).
- ACV can delay gastric emptying in patients with diabetes, especially in those with previous gastroparesis (slow stomach emptying). 
- Chung  cited a case where a 39-year-old woman drank one tablespoon of white vinegar in order to ‘soften’ crab shell stuck in her throat (apparently a folklore remedy in China). Endoscopy revealed inflammation of the oropharynx and second-degree caustic injury of the esophagus extending to the first part of the stomach.
Johnston et al  have one of the few studies which focused on the safety of ACV. Twenty-seven patients with Type II Diabetes were randomly divided into three groups who received commercial vinegar pills (REF- 30 mg of acetic acid daily), pickles (PCK-approximately 1,400 mg of acetic acid daily), or vinegar (VIN- 2,800 mg of acetic acid daily) while continuing their normal diet for 12 weeks.
Fifty to 56% of those in the PCK or VIN groups reported at least one adverse event (acid reflux, burping, flatulence or change in bowel habits) compared to the reference (REF) group, only 11% of who reported adverse effects.
Although, for the most part, ACV can be considered a safe food, certain individuals or circumstances may want to limit or carefully monitor its use.
Apple cider vinegar can be a tasty addition to your salad, but I wouldn’t expect it to cure all that ails you. Studies have shown some promise that ACV can affect blood sugar levels in healthy people and those with and at risk for diabetes. However, the study sizes are small and limited to no more than 3 months in duration.
The other health claims have even fewer scientific studies to support them. Larger scale, long-term clinical trials are needed before definitive health claims can be made.