What the Science Supports
Considering how much recognition apple cider vinegar gets as a cure-all, you might think there's tons of research to support those claims. Well, right now, that’s not the case. The scientific literature on humans ingesting vinegar is very, very limited. However, a number of studies into its medicinal uses reveal that there are a few things that scientists have found which could be regarded as health benefits.
It promotes stable blood sugar.
You know that light-headed, low-energy feeling you sometimes get after chowing down on too many refined carbs? That’s your blood sugar spiking—and then crashing down. The acetic acid found in apple cider vinegar (and most other types of vinegars, like white vinegar and red wine vinegar) contains anti-glycemic properties, and studies show that consuming apple cider vinegar before a meal can help keep those kinds of spikes at bay. This could, in theory, have something to do with why people who take apple cider vinegar claim that the stuff boosts their mood and energy. The blood sugar benefits might even spell good news for people with diabetes, though researchers still have more to figure out. If they follow a protocol of drinking some vinegar before every meal for a year or more, does that reduce reliance on insulin medications? Or reduce the progression of their disease? Those questions have yet to be answered. In a review of available studies conducted in 2014, researchers found that while there is some evidence that vinegars can help with hyperglycaemia and obesity, there is no evidence that it positively affects metabolism. You can read the abstract of this review here: Effect and mechanisms of action of vinegar on glucose metabolism, lipid profile, and body weight. Recent studies support the observation that apple cider vinegar is beneficial for managing post-meal blood sugar levels. This can be very helpful for people with diabetes. Keeping it balanced is essential for maintaining good health. You can read the study here:
Vinegar supplementation lowers glucose and insulin responses and increases satiety after a bread meal in healthy subjects.
It can fight bacteria.
Apple cider vinegar has been used to combat infections like ulcers and sores since the time of the ancient Greeks. In fact, there are plenty of studies documenting vinegar’s antimicrobial effects. But just because apple cider vinegar is capable of fighting bacterial infections does not mean that using it to do so is actually a good idea. Because it’s so acidic, pouring it into your ears for an ear infection or using it on open sores or cuts is almost guaranteed to irritate your skin. It’s not safe to use by itself for a sore throat, either, because it could do more harm than good. One should not gargle vinegar either. There have been cases where people have ended up in the hospital because they accidentally choked on it.
It can soothe jellyfish stings.
Weirdly, research shows that if you happen to get stung by a jellyfish, dousing the affected area in apple cider vinegar may help. It can deactivate nematocysts, the sharp barbs that jellyfish use to inject their painful venom. But experts say that warm water can have a similar effect—without irritating your skin the way apple cider vinegar may.
What’s Not So Clear
As for the rest of the miraculous stuff you often hear, most of it is yet to be determined. For now though, the majority of these following claims haven’t been studied.
It improves your skin.
Anecdotally, there are plenty of people who say that applying apple cider vinegar to their faces helps get rid of acne and improve their skin’s texture. People with chronic acne who steam their face with diluted apple cider vinegar, have indeed noticed that within two to three weeks, there’s a difference. And since apple cider vinegar contains antimicrobial properties, it could help acne-prone skin but for now, there aren’t any studies or simply the evidence out there to prove it.
It gets rid of warts.
A handful of studies have shown that putting acetic acid on your skin can destroy wart tissue. But this research used super high concentrations of the stuff (up to 99%). Since apple cider vinegar and other vinegars are only around 5% acetic acid, they wouldn't be nearly strong enough to kill a wart.
It clears up dandruff.
Though an apple cider vinegar rinse might make your hair look shinier, there’s no credible scientific research to support the idea that it can clear up dandruff.
It whitens teeth.
Apple cider vinegar's antibacterial properties could conceivably help get some plaque and germs off of your teeth. However, there isn't evidence to show that apple cider vinegar can whiten teeth. In fact, it’ll probably leave your pearly whites in pretty bad shape. Health practitioners do not advocate whitening your teeth with apple cider vinegar at all. We do not have a lot of acid protection in the mouth, and you don’t want to lose the enamel on your teeth. People who intend to use apple cider vinegar should ensure that it is heavily diluted. 10 parts water to one part vinegar as a safe mixture. In more concentrated doses, apple cider vinegar can erode tooth enamel or burn your mouth and throat. A 2012 study found that drinking one glass of apple cider vinegar each day caused significant tooth erosion. You can read the article here: http://www.ncbi.nlm.nih.gov/pubmed/23373303. It is highly recommended that you rinse your mouth with water afterwards.
The Safe Way to Use Apple Cider Vinegar
Apple cider vinegar's acetic acid contains some beneficial properties, but in high concentrations, acedic acid can be a poison. So if you’re going to drink the stuff or use it on your skin, you’ve got to be careful. Many healthcare practitioners agree that the best way to use apple cider vinegar is in tiny doses. If you’re drinking the stuff, swig a tablespoon diluted in at least eight ounces of water no more than twice a day. And always follow this up with food which can help clear the acid out of your throat faster and prevent irritation. The same principle applies if you want to try using it on your skin. Dilute a tablespoon of apple cider vinegar in a bowlful of hot water and dunk a face towel or rag in the mixture. “You can steam your face with the rag for 12 minutes.
Most of the research on apple cider vinegar has looked at its effects on blood sugar, and those studies seem to pan out. Experts accept that apple cider vinegar has antibacterial properties too—but because vinegar is harsh, it's not the best choice for treating sore throats or wounds (except those jellyfish stings). As for the other stuff, there's no scientific data to support using apple cider vinegar for better skin, less dandruff, or whiter teeth. Furthermore, it might be harmful. If you decide to try using it anyway, proceed with caution. This is an instance where more isn't better!
Taylor, M (Sept 2015) What apple cider vinegar truly can (and can't) do for your health. http://greatist.com/grow/apple-cider-vinegar-benefits
Bowman, J. (Sept 2014) http://www.healthline.com/health/apple-cider-vinegar-diet#3