Apple Cider Vinegar holds the title for the most popular type of vinegar throughout natural health communities. There are dozens of claimed apple cider vinegar benefits. It's common in food flavoring and preservatives, and it has decades of use as a folk remedy for various ailments. But is it as useful as everyone claims it to be?
What is Apple Cider Vinegar?
Apple cider vinegar is juice from crushed apples that has been fermented. It is a pale-yellow color and can come in either a pasteurized form or an unpasteurized, raw form that contains what is known as “the mother” of vinegar. It contains pectin from the apples, Vitamin C, Vitamin B1, Vitamin B2 and B6, niacin pantothenic acid, and folic acid.  The vinegar contains between 5 and 20-percent acetic acid, trace elements, minerals, amino acids, water, flavorings, and plant-based antioxidants called “polyphenols”. [2, 3]
Apple cider vinegar is made through a natural fermentation of aged apple juice which initially makes the alcohol-containing hard apple cider. If it is not collected for hard apple cider, the liquid will undergo a second fermentation which breaks the alcohol into acid and creates vinegar. 
Apple Cider Vinegar History
The name vinegar comes from the French “vin aigre” which means “sour wine”. The use of apple cider vinegar goes back as far as 420 BC as a natural and effective wound disinfectant and treatment. In the late 18th century, there are writings from US physicians including the use of apple cider vinegar for treatment of poison ivy, croup, stomach ailments, and more. Today, it has popular use by the health community and people who like natural solutions to everyday health issues. [3, 5]
How is ACV made?
Apple cider vinegar undergoes multiple steps to turn from apples into vinegar. First, the sugar in the apples is fermented by yeasts and produces alcohol-containing “hard” apple cider. The bacteria and microorganisms remaining from the first fermentation use the alcohol in a second process in which the alcohol is oxidized into acetic acid (or vinegar). The bacteria which turns the alcohol into acetic acid is called acetobacter. [3, 6]
What is Apple Cider Vinegar Made of?
The most common types of bacteria in apple cider vinegar are acetic acid bacteria and lactic acid bacteria. Acetic acid bacteria contain mostly Acetobacter and Komagataeibacter, with Komagataeibacter in a larger quantity at the end of the oxidation process. The lactic acid bacteria consist of two generas: Lactobacillus and Oenoncoccus. Oenococcus has the highest concentration of the lactic acid group. A smaller concentration of bacteria found in apple cider vinegar is Gluconobacter. 
Some of the Lactobacillus in apple cider vinegar has been gene sequenced and is known to contain Lactobacillus collinoides, Pediococcus parvulus, O. oeni, and in smaller concentrations L. casei and P. ethanolidurans. 
Organic apple cider vinegar contains a different constituent profile than conventional apple cider vinegar. Conventional apple cider vinegar also contains some yeasts that survive within acetic acid. Organic apple cider vinegar is considered a more heterogenous mixture of bacteria because conventional ACV only contains two species of bacteria versus organic ACV’s four species of bacteria.
- Organic apple cider contains:
Acetobacter pasteurianus: 71.90%
Acetobacter ghanensis: 12.50%
Komagataeibacter oboediens: 9.35%
Komagataeibacter saccharivorans: 6.25%
- Conventional apple cider vinegar contains:
Acetobacter pasteurianus: 66.70%
Komagataeibacter oboediens: 33.70%
Saccharomycodes ludwigii 
The raw, organic, unpasteurized form of apple cider vinegar has been the focus of health communities because it does contain a better variety of bacteria. The major difference between conventional ACV and raw ACV is the lump at the bottom of the raw bottle known as “the mother”.
The “mother of vinegar” comes from a substance made of cellulose and acetic acid bacteria which develops on fermenting liquids containing alcohols. The “mother of vinegar” is formed by the bacteria Acetobacter aceti and was also known as Mycoderma aceti when first discovered. 
The “mother’s” acetobacter uses the oxygen in the air and the alcohol produced by fermentation to oxidize the alcohol into acetic acid, or vinegar. It is often added to liquids that are already alcoholic to further produce vinegars. It may also form in conventional vinegar if any non-fermented sugar or alcohol is present. 
The “mother of vinegar” is safe to consume and many raw ACV enthusiasts recommend shaking the bottle vigorously, so the sediment formed by the “mother” is mixed into the vinegar and you consume some of it with each use. It can also be removed with a strainer or just left at the bottom of the bottle. 
Some people believe that all apple cider vinegar is a probiotic. Since only the “mother” is still present in raw ACV that has not been pasteurized, it is the only form of ACV that can be considered a probiotic. It retains beneficial bacteria and pectin from the apples, which is a prebiotic. Pectin is a starch found in fruits, vegetables, and their skins. Pectin is often included in the capsules of probiotics to enrich the effectiveness of the probiotics. To be classified as a prebiotic, it has to meet several criteria, and studies have demonstrated that pectin increases the growth of several beneficial strains of bacteria, such as Bifidobacteria and Lactobacillus, which are both present in the gastrointestinal tract. 
How to Incorporate Apple Cider Vinegar Safely into Your Diet:
Never drink apple cider vinegar without diluting it first because it is very strong.
Since it is so acidic, it will impact your dental health. Speak with your dentist about if using Apple Cider Vinegar is a good idea for you.
Apple Cider Vinegar Side Effects
Apple cider vinegar can potentially have negative interactions with diuretics and insulin. This can lead to dangerously low potassium levels or blood sugar levels if you mix them. Some of the medications you want to avoid mixing with apple cider vinegar include:
- Tolbutamide and others 
Delayed Stomach Emptying
Apple cider vinegar slows down the rate that food leaves your stomach and digestive tract. In turn, this slows down how fast it absorbs into the bloodstream. For people that have gastroparesis, this can cause it to worsen or flare. Side effects may include bloating or abdominal pain. 
Tooth Enamel Erosion
Drinking apple cider vinegar undiluted can damage the enamel on your teeth. One study showed that teeth that are immersed in apple cider vinegar for four hours can experience between 1 and 20-percent enamel loss. This can lead to tooth decay and cavities if you don't dilute it and remove any residue. [33, 34]
Burning of Throat Tissue
Undiluted apple cider vinegar has the potential to cause tissue burns in your throat. This is especially true for children, and one study even suggested that apple cider vinegar be kept in a childproof container. Another study showed a woman who experienced burns after an apple cider vinegar tablet got stuck in her throat. [35, 36]
As apple cider vinegar is very acidic, a few reports have demonstrated that putting even a few drops of pure apple cider vinegar on your skin to clear up acne or to help clean open wounds can cause irritation or slight burns on your skin. 
Who Should Avoid Taking Apple Cider Vinegar
Though this isn't a fully inclusive list, Apple Cider Vinegar should be avoided by children and women who are pregnant or nursing. Those who are taking potassium supplements should consult with their healthcare practitioner before beginning apple cider vinegar supplementation.
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