Apple Cider Vinegar
Apple cider vinegar may provide some health benefits when taken with meals, such as reducing glucose spikes and suppressing appetite. That being said, the magnitude of the benefits is unclear, and excessive vinegar consumption may damage the gastrointestinal tract.
Last Updated:September 28, 2022
1.
Background information
1.1
History
The production and use of vinegars is ancient, likely dating back to roughly the origin of alcoholic beverage production due to the resulting transformation of alcohol to acetic acid when exposed to air.[1] The purposeful production and use of vinegar dates back to at least 5000 BC when it was used in Mesopotamia for pickling food and flavor. It was derived from date palm sap, date wine, grapes, and beer.[2] The Bible, both the Old and New Testament, make references to vinegar, and it was commonly used in the Bronze Age East Mediterranean area.
When it comes to health, there’s an early mention from ancient Assyria, recommending its application to treat water, blood, or puss in the inner ear.[3] Hippocrates, around 400 B.C advised that it be consumed and also used as a dressing for wounds, which persisted with the ancient Romans.[2] Vinegar has been used as the base of a supposed prophylactic to the Black Plague and has had a role more recently as a general battlefield antiseptic.
The origin of apple cider vinegar is unknown, but given the close relationship between alcoholic beverage production and vinegar, it seems reasonable to place it anywhere and anytime cider was made from apples, with the same uses as other vinegars.
Vinegar is ancient, dating back thousands of years. It has been used to preserve food, for flavor, as a dressing for wounds, and for various niche medical purposes throughout history.
1.2
Sources
Any vinegar is the result of a two-part fermentation of carbohydrates into ethanol, largely by the yeast Saccharomyces cerevisiae, and then to acetic acid by acetic acid-producing bacteria, largely of the acetobacter genus.[4] A vast variety of vinegars exist because the use of any carbohydrate-rich raw material produces a different type of vinegar with phytochemical properties reflecting that raw material.[5] Thus, vinegars derived from apples contain many constituents of apples in small quantities, along with acetic acid and other products of fermentation. The distinction between cider vinegars and regular vinegars is a small one, but is essentially the difference between starting with juice (cider) and starting with crushed, whole apples.
Vinegar is produced through the fermentation of ethanol to acetic acid via bacteria. A wide variety of carbohydrate-containing foods can produce a wide variety of vinegars, with phytochemical characteristics reflecting the raw material.
1.3
Properties
One study found that apple vinegar made from Florina apples with the classic Orleans method contained 3.9% acetic acid after 28 days and 9% after 48 days of acetic fermentation. It also contained 1.5 and 7 g/L of carbohydrates, and 0.47 and 0.8 g/L of malic acid.[6]
Another study found the following (g/l, mean + SD) in a sample of 11 apple vinegars:[7]
Acetic acid: 56.7 ± 12.8. Lactic acid: 2.02 ± 1.50. Citric acid: 0.157 ± 0.378. Tartaric acid: ND (not detected). Malic acid: 0.086 ± 0.195. Succinic acid: 0.135 ± 0.157.
mg/L:
Gallic acid: 4.02 ± 2.34. Catechin: 82.6 ± 46.0. Epicatechin: 17.9 ± 13.9. Chlorogenic acid: 6.63 ± 6.83. Caffeic acid: 1.37 ± 1.18. Cis-p-coumaric acid: 0.033 ± 0.108. Trans-p-coumaric acid: 0.947 ± 0.714. Ferulic acid: 0.066 ± 0.213.
The paper also listed many other compounds.
Another study found that the total phenolic content of apple cider vinegar varied considerably depending on production method, from 416.95 mg/L to 908.595.[8] Individual phenolic compounds (mean + SEM, mg/L) are shown below.
Gallic acid: 0.05 ± 0.05 to 1.00 ± 0.31. Catechin: 0.80 ± 0.15 to 1.00 ± 0.35. Epicatechin: 0.70 ± 0.10 to 2.00 ± 0.75. Caffeic acid: 0.56 ± 0.06 to 1.00 ± 0.15. Chlorogenic acid: 2.40 ± 0.72 to 18.67 ± 2.77. p-coumaric acid: 0.05 ± 0.01 to 0.07 ± 0.00.
The highest levels of phenolic compounds were produced by the surface method which included maceration, and the lowest was found with the common submersion method, though the submersion method yielded the highest level of epicatechin.
Another study evaluated the phenolic composition of 7 different apple cider vinegars and found (mg/L)[9]:
Gallic acid: 0.35 ± 0.02 to 16.72 ± 0.18 with one sample not containing detectable concentrations. Vanillic acid: 0.06 ± 0.04 to 3.44 ± 0.07 with 4 samples not containing not containing detectable concentrations. Caffeic acid: 0.04 ± 0.00 to 3.03 ± 0.02 with 3 samples not containing detectable concentrations. Chlorogenic acid: 0.83 ± 0.02 to 26.42 ± 0.62. p-Coumaric acid: 0.09 ± 0.00 to 0.33 ± 0.28 with 4 samples not containing detectable concentrations. Ferulic acid: 0.03 ± 0.00 to 0.24 ± 0.01 with 3 samples not containing detectable concentrations. Catechin: 2.05 ± 0.02 to 37.55 ± 0.61 with 5 not containing detectable concentrations. Epicatechin gallate: 0.77 ± 0.34 with 6 samples not containing detectable concentrations. Phlorizin: 1.76 ± 0.14 to 10.10 ± 0.13 with 4 samples not containing detectable concentrations.
Apple cider vinegar is a rich source of acetic acid, and a source of other acids such as citric and lactic acid, and malic acid. The composition of apple vinegars can be affected by a number of factors in the chain of production, including the type of apples used, the species of bacterial cultures used, and the duration of fermentation. Apple cider vinegar contains many of the phenolic and other phytochemical constituents of apples, in small quantities.
1.4
Variants and Formulations
The methods and apple varieties used to produce apple cider vinegar will to some extent determine its contents. Apple cider vinegar can be taken on its own, in capsules, or in the form of tablets.
2.
Safety
2.1
Side Effects and Adverse Events
Vinegar’s acidity can be corrosive to skin. There is one report of a 14-year-old-girl who suffered chemical burns to her nose from using apple cider vinegar as a home recipe for nevi (moles).[10] In a study in in which forearms were submerged in apple cider vinegar frequently, there was only one reported case a severe reaction out of 22 participants, though a majority of participants did note some skin irritation.[11] It’s possible that there are individual differences in the resilience of skin, that her use of apple cider vinegar was more frequent and of a longer duration, or that facial skin is more sensitive than that of the forearms.
Tooth enamel erosion has been noted in one report due to swishing of apple cider vinegar in the mouth.[12] Vinegar in general, due to its acidic nature, can cause enamel erosion, however it’s unclear what risk diluted apple cider vinegar poses when quickly consumed.
A 48-year-old woman taking apple cider vinegar tablets for the purpose of weight loss reported esophageal pain and difficulty swallowing after a tablet became lodged in her throat for 30 minutes.[13]
Nausea has been noted with oral doses of vinegar in general.[14]
A higher rate of gastric cancer has been associated with increased pickled food consumption.[15] It’s unclear if vinegar itself is the primary cause, but due to its potential to damage tissue with sustained contact, it’s plausible that excessive vinegar consumption would be a factor.
It may be possible to damage sensitive tissue and tooth enamel with excessive use of apple cider vinegar, especially when contact is prolonged.
3.
Effects on the Digestive System
Digestion in hypochlorhydria
While it may be tempting to think that a lack of natural stomach acid could be remedied by consuming vinegar during meals, the efficacy of vinegar hasn’t been tested, and it’s unclear if vinegar will work as intended.
Gastroesophageal reflux disease
In a randomized, double-blind, crossover study, 14 participants who reported heartburn related to GERD were assigned to consume a meal of 250 g of chili (control group) or chili with an antacid, 20 ml of apple cider vinegar during the meal, or 20 ml after a meal, with one week between test days.[16] 11 participants completed the trial, but 3 of those didn’t have heartburn during the trial and didn’t follow protocol, leaving 7 for analysis.
It’s generally unclear from this small study what the effects of vinegar on GERD-related heartburn are.
Symptoms after vinegar mixed into the chili weren’t notably different than during the control meal, and vinegar after the meal coincided with somewhat reduced heartburn symptoms, but the difference compared with the control meal wasn’t statistically significant. Symptoms were roughly at their greatest at the end of the 2-hour post meal period (the end of recording), and at that time, both vinegar conditions and control were roughly the same. The antacid outperformed vinegar, but the difference also wasn’t statistically significant. When considering only the 3 participants who didn’t respond to antacids, symptoms were somewhat lower during both vinegar conditions than control and antacids, but the difference wasn’t statistically significant. Symptoms were also at their highest and comparable between both vinegar conditions and control at the end of the 2-hour testing period, suggesting that if there is a reduction by vinegar, it’s in the early period after eating, given a single dose.
4.
Effects on Body Composition
In one study, 72 white male albino rats were divided into 6 equal groups, with half being part of each designed period of 8 or 11 weeks.[17] One group consumed a standard laboratory diet containing 3143 calories per kg of food while the other two consumed a high-fat diet containing 4493 calories per kg of food and 22% fat. One high fat group received 0.6% of its diet as apple cider vinegar with 5% acetic acid. In both periods, the rats received apple cider vinegar only after 2 weeks, making the treatment duration 6 and 9 weeks, respectively.
During the 6-week period, total body weight was higher in the high fat groups than the control group. The high-fat group that didn’t receive apple cider vinegar weighted (mean + SEM) 272.5 ± 7.19 g while the apple cider vinegar group weighted 259.5 ± 7.57,g the difference being statistically significant. The group that didn’t receive apple cider vinegar had a total food intake of 121.75 ± 5.91 g/d while the apple cider vinegar group consumed 103.08 ± 6.14, the difference being statistically significant.
In the 9-week period, total body weight was higher in the high fat groups than the control group. The group that didn’t receive apple cider vinegar weighed 302.33 ± 11.07 at the end while the apple cider vinegar group weighed 281.41 ± 8.87, the difference being statistically significant. Food intake was 123.75 ± 4.75 g/d and 119.66 ± 7.96 g/d, respectively.
In a randomized, double-blind, placebo-controlled trial,175 overweight participants were assigned to a 500 ml beverage containing 0, 15, or 30 ml of apple vinegar daily for 12 weeks.[18] All subjects were given dietary advice but ultimately made their own food choices. At the end of the 12th week, the placebo group didn’t lose any weight or body fat, but the apple vinegar groups had seen a statistically significant reduction in weight and body fat area, body fat ratio, and waist and hip circumference as compared with placebo. The higher dose group saw a somewhat higher reduction than 3-day food diaries were taken and it was estimated that the apple vinegar groups reduces their total energy intake more than the placebo group, but there were no statistically significant differences.
In a randomized, unblinded, controlled trial, 44 overweight/obese participants were assigned to follow a low-calorie diet (250 calories below energy requirements, 55% carbohydrate, 30% fat, 15% protein) or the same low-calorie diet with 30 ml of apple cider vinegar daily for 12 weeks, divided into 15 ml servings at lunch and dinner.[19]
The 3-day dietary recall found a somewhat higher reduction in calories in the apple cider vinegar, the difference not being statistically significant. The primary outcome was the change in body composition, and the apple cider vinegar group saw a greater reduction in body weight by about 1.7 kg on average, which was statistically significant between groups. Measures of lean body mass from bioelectric impedance analysis found that a considerable amount of that difference (1.1 kg) was lean body mass, and the rest was body fat, the change for both separately not being statistically significant. Subjective assessments of appetite decreased more in the apple cider vinegar group. Neuropeptide Y was increased more in the apple cider vinegar group, but the difference wasn't statistically significant.
Evidence is lacking, but apple cider vinegar incorporated into food seemed to suppress food intake and body weight gain in rats and overweight humans.
Fat oxidation
One study found that acetic acid increased mRNA levels for PPAR-alpha, acetyl-CoA oxidase, carnitine palmitoyltransferase-1, UCO-2, and decreased them for fatty acid synthase (though the difference wasn’t statistically significant) in the livers of mice, suggesting an increase in fatty acid oxidation.[20] This coincided with a reduction in body weight during high-fat feeding, and was reversed by AMPK silencing, suggesting a core role of AMPK. Another study in rats found that pomegranate vinegar increased AMPK phosphorylation and also increased mRNA levels for PPAR-alpha and carnitine palmitoyltransferase-1, though not clearly for UCP-2.{PMID:24180378] There was also a significant reduction in sterol regulatory element-binding protein 1. This coincided with weight loss independently of calorie intake.
Satiety
In addition to the apple cider vinegar-specific studies in humans previously mentioned, other studies suggest reduced food intake after consuming vinegar. In one study, 12 healthy participants with normal BMIs consumed meals of white bread only or with 18, 23, and 28, g of 6% acetic acid white vinegar in a crossover manner, at least one week apart.[21] Subjective satiety scores for 2 hours after the vinegar-containing meal were lowest when consuming the smallest amount of vinegar and highest when consuming the most. In another study, 20 g of apple cider vinegar reduced subsequent food intake by about 200 to 275 calories by the end of the day when taken, though this wasn’t statistically significant, and the authors didn’t report an effect during a low glycemic index meal.[22] This suggests that lowering glycemic index may be the main mechanism by which acetic acid may improve satiety after meals. Other studies corroborate this by observing a reduced gastric emptying rate after consumption of apple cider vinegar and greater satiety during meals when consuming vinegar.[23][14]
However, it’s not clear if this phenomenon is consistent, since another study failed to find a reduction in the rate of carbohydrate absorption from mashed potatoes with 20 ml of apple cider vinegar..[24] It should be noted, however, that the oral octreotide/insulin suppression test used to test carbohydrate absorption is of unknown accuracy.
While an increase in fatty acid oxidation is possible, it hasn’t be tested in humans. Effects on satiety, on the other hand, are a more plausible reason for any body fat reduction due to acetic acid consumption.
5.
Effects on Glucose Metabolism
5.2
Blood Glucose and Insulin
In a randomized, controlled trial, 70 participants with type 2 diabetes were assigned to 20 ml of apple cider vinegar (5% acetic acid) split between lunch and dinner daily or no intervention for 4 weeks.[29] Fasting glucose was reduced by roughly 10 mg/dl in the apple cider vinegar group, while it was greatly increased in the control group, the difference being statistically significant. Insulin on the other hand was reduced equally in both groups. Food records didn’t suggest that there was a notable difference in energy intake, which lends more credence to the idea that apple cider vinegar had an intrinsic effect on glucose tolerance. When it comes to measures of insulin resistance, there were no statistically significant differences but there was a greater reduction in HOMA-IR in the apple cider vinegar group.
In a randomized, double-blind, placebo-controlled trial,175 overweight, healthy participants were assigned to a 500 ml beverage containing 0, 15, or 30 ml of apple vinegar daily for 12 weeks [18] All subjects were given dietary advice but ultimately made their own food choices, and the result was greater weight loss in the apple cider vinegar group, so it’s unclear what the unique effect of apple cider vinegar was. Despite this, there were no statistically significant differences between groups for fasting glucose, insulin, HbA1c or HOMA-IR, though the participants didn’t have elevated glucose levels to begin with, so this study can’t be applied to type 2 diabetics.
In an uncontrolled trial in women with polycystic ovary syndrome, 15 g of apple vinegar was consumed after dinner for 90-110 days and insulin resistance as HOMA-IR was reduced in most participants.[30]
When it comes to the effects of apple cider vinegar on post-meal glucose and insulin concentrations, one study found an effect of 20 ml on a high glycemic index (bagel, butter and orange juice) meal and a nonsignificant lower levels on a low glycemic index meal (chicken and rice) in healthy participants.[22] However, in another small study, there didn’t appear to be much of an effect of 20 ml apple cider vinegar as compared with a placebo during a meal of mashed potatoes in healthy participants.[24] Interestingly in yet another study, while glucose levels were lower after 20 ml of apple cider vinegar and a meal of a bagel, butter, and orange juice in all groups, they were the highest in insulin resistant but nondiabetic participants, followed by diabetic participants and healthy participants.[31]
Although apple cider vinegar is distinguished from other types of vinegars by its phytochemical contents, its effect seems to be common to vinegars, and acetic acid, as other types also reduce glucose and insulin levels after meals.[32]
Current evidence, while not robust, suggests a modest beneficial effect of apple cider vinegar on both fasting and postprandial glucose. Effects on insulin levels are unclear.
5.3
Glycation
In a randomized, double-blind, placebo-controlled trial, 114 nondiabetic participants were assigned to either 30 ml of apple cider vinegar or 30 ml of a 1.7% balsamic vinegar solution for 8 weeks.[33] The apple cider vinegar group saw a small reduction in HbA1c of -0.07% −0.15, 0.01, 95% CI (p=0.08 compared with baseline), and no change in the placebo group.
It’s unclear how apple cider vinegar would impact HbA1c in diabetics, but a reduction in blood sugar levels makes it plausible that there would be an effect.
6.
Effects on Cardiovascular Health
6.1
Hemodynamics
In a randomized, controlled trial, 70 participants with type 2 diabetes were assigned to 20 ml of apple cider vinegar (5% acetic acid) split between lunch and dinner daily, or no intervention for 4 weeks.[29] The control group say a greater reduction in systolic blood pressure (mean + SD, 131.70 ± 11.56 to 126.45 ± 25.16) than the apple cider vinegar group (125.89 ± 10.88 to 124.65 ± 8.71), though the difference wasn’t statistically significant, and the control group started off with notably higher blood pressure. For diastolic blood pressure, the control group saw a reduction from 88.18 ± 15.48 to 85.43 ± 9.15, which was also not statistically significant. Homocysteine was increased somewhat by the control group and was slightly reduced in the apple cider vinegar group, the difference not being statistically significant.
In another randomized, double-blind, placebo-controlled trial,175 overweight participants were assigned to a 500 ml beverage containing 0, 15, or 30 ml of apple vinegar daily for 12 weeks.[18] After 12 weeks, the high dose group saw a statistically significant reduction in systolic blood pressure compared with the placebo group, while the low-dose group saw a smaller, nonsignificant reduction. For diastolic blood pressure, there were no statistically significant differences after 12 weeks, though there was a very slight reduction in the apple cider vinegar groups and none in the placebo group. It should be noted that this is the same study from the body composition section that found greater weight loss in the apple cider vinegar groups than the placebo group, and so some of these effects may be due to weight loss.
30 ml of apple cider vinegar daily might reduce blood pressure modestly, but much more research is needed.
6.2
Blood Lipids and Lipoproteins
In a randomized, double-blind, placebo-controlled trial, 114 nondiabetic participants were assigned to either 30 ml of apple cider vinegar or 30 ml of a 1.7% balsamic vinegar solution for 8 weeks.[33] The primary outcome was the change in HDL-C, and the apple cider vinegar group say an increase of 1.14 −0.47, 2.75, 95% CI mg/dl while the placebo group saw a change of −1.06 −3.05, 0.92, 95% CI, neither change was statistically significant compared with the respective group baseline numbers. Total cholesterol and LDL were slightly reduced more in the placebo group, triglycerides were slightly increased, none of which were statistically significant compared with baseline for either group. Interestingly, the placebo group say a reduction in HS-CRP of −0.50 −0.94, −0.05, 95% CI mg/L, which was statistically significant, while the apple cider vinegar group say an increase of 0.15 −0.27, 0.57, 95% CI which wasn’t statistically significant.
In another randomized, double-blind, placebo-controlled trial,175 overweight participants were assigned to a 500 ml beverage containing 0, 15, or 30 ml of apple vinegar daily for 12 weeks.[18] After 12 weeks, there were no statistically significant differences in between the groups for LDL, HDL or HDL, while the low dose and high dose groups say a statistically significant reduction greater reduction than the placebo group for triglycerides and the low-dose group say a statistically significant reduction in total cholesterol compared with placebo, and the high dose group say a greater, nonsignificant reduction. Four weeks after ceasing supplement, the reduction in triglycerides was mostly retained in the low-dose group but not the high dose group. It should be noted that this is the same study from the body composition section that found greater weight loss in the apple cider vinegar groups than the placebo group, and so some of these effects may be due to weight loss.
In a randomized, unblinded, controlled trial, 44 overweight/obese participants were assigned to follow a low-calorie diet (250 calories below energy requirements, 55% carbohydrate, 30% fat, 15% protein) or the same low-calorie diet with 30 ml of apple cider vinegar daily for 12 weeks, divided into 15 ml servings at lunch and dinner.[19]
There was a statistically significant greater reduction in triglycerides, very little change in total cholesterol, a slightly greater increase in HDL and an increase in LDL while the control group saw a reduction, the difference not being statistically significant.
There has been very little research, but so far it doesn’t seem like apple cider vinegar notably influences blood lipids in humans.
7.
Effects on Aesthetics
7.1
Skin
One study had 11 patients with atopic dermatitis and 11 healthy controls dip one arm in dilute apple cider vinegar (0.5% acetic acid) and the other in tap water for 10 minutes at the first visit, for 10 minutes per day, for the following 14 days, and for 60 minutes again after the 14 days.[11]
Transepidermal water loss (TEWL) was increased in healthy subjects and those with atopic dermatitis somewhat more after soaking with ACV than with water, with the difference persisting for 15 minutes before returning to baseline and parity with the water-soaked arm. Skin pH was reduced by ACV in both healthy subjects and those with atopic dermatitis, with the pH almost returning to baseline after 60 minutes in the atopic dermatitis group, and not yet returning to baseline at 60 minutes in the healthy group. After 14 days of daily soaking, there was no difference in transepidermal water loss in either group, and pH was unaffected, though somewhat but nonsignificantly lower in the healthy control group. 73% of participants reported skin discomfort from ACV, mostly mild, and one reported severe skin irritation.
It’s unclear if apple cider vinegar by itself has an effect on skin moisture. Generally, the vast majority of skincare claims involving apple cider vinegar are untested.