Is apple cider vinegar really a miracle cure-all?
It's said to tackle everything from hiccups to colds. But is there any evidence to back up these claims? Resident dietitian Orla Walsh takes a closer look
Apple cider vinegar seems to be increasingly popular. You'd be hard-pushed to go into a health food shop, pharmacy or even a supermarket and not find it displayed prominently on the shelves. At the time of writing this article, when I searched in Google for 'apple cider vinegar', I got nearly 3,500,000 results. But when you search for it in a scientific database, you get fewer than 65.
From a health enthusiast's point of view, it's intriguing. My Google search suggested that apple cider vinegar could be used to treat many conditions and I read about a wide range of supposed benefits, from curing hiccups to alleviating cold symptoms. Then there were some rather unbelievable suggestions that it may help with diabetes, cancer, heart disease and obesity.
From a scientist's point of view, the subsequent investigation for clinical trials leaves you stumped. There have been very few scientific studies on apple cider vinegar. How are there so many claims about a product when so little research has been done? If there was a heap of studies conducted on it that showed no impact whatsoever on the human body, if would be safe to say that it's all a con. But equally, as there are so few studies conducted, it's impossible to say, scientifically speaking, that it stands up to all the wonderful claims that are touted about it.
So what has been shown? There are two prominent areas of research - apple cider vinegar and infection, as well as apple cider vinegar and carbohydrate metabolism.
A study published this year investigated how apple cider vinegar faired against common bacteria such as E coli and staph aureus, as well as the fungus candida. The results were somewhat positive.
Apple cider vinegar did fight the growth of each of these bugs. The amount of apple cider vinegar needed to have an effect did differ with each - but more studies are required to find what clinical therapeutic implications it may have.
A different study from 2015 looked at the antifungal activity of apple cider vinegar on candida, which can cause denture stomatitis, an infection that can occur in the mouth of those that wear dentures. The study didn't look at it in human mouths but rather tested it within the lab. They did compare it to a well-known antifungal medication, which would provide meaningful results. The study showed that apple cider vinegar showed antifungal properties. Therefore it may be a possible therapeutic alternative for people with denture stomatitis.
When research like these two studies is published, it can be harmful when falling into the wrong hands. Someone might read this and assume that apple cider vinegar could therefore help them with their particular ailment. However, case studies have been published which report chemical burns from the inappropriate use of vinegar on and within the body. Therefore, so-called "natural home remedies" not only can be ineffective, but worse, dangerous.
Vinegar is also thought to help reduce the speed at which blood carbohydrate rises. The understanding behind how it actually works is poor. Possible actions that have been suggested include altering the work of enzymes that break down certain carbohydrates into sugar and slowing the emptying of food from the stomach.
A systematic review published in 2017 investigated whether vinegar had any impact on blood sugar levels. The researchers looked at all the trials that report on the effect of vinegar intake on blood sugar levels after someone has eaten. The findings suggested that vinegar can be effective in reducing blood sugar and insulin levels after a meal.
However, when you specifically search for apple cider vinegar and blood sugar control, there were fewer studies conducted. One investigated the effect of water versus apple cider vinegar. There were five people in this study, tested on four different occasions, all one week apart. They received the water on two occasions and the apple cider vinegar on the other two occasions. After they were given either the water or apple cider vinegar, they ate a meal which consisted of mashed potatoes.
Insulin secretion by their bodies was suppressed for the first 100 minutes of the study. Insulin is the hormone in the body that takes the glucose in our blood and brings it into the body's cells. By stopping it doing its job, it allows the blood levels of glucose to rise. What this particular study showed, despite what has been previously shown, is that apple cider vinegar actually increased the rate of which blood glucose rose. Therefore, this study suggests the opposite of what apple cider vinegar is said to do. Although the study was small, it does highlight the need to wait until enough evidence is available before using a product with confidence.
There are many reasons why there may be so many conflicting bits of research on the topic. After damage occurred to a person's food pipe following apple cider vinegar ingestion, a study in 2005 looked at apple cider vinegar tablets. Eight products were tested for pH, component acid content and microbial growth. The researchers found considerable variability between the brands in tablet size, pH, component acid content and label claims. Even more worryingly, they questioned whether apple cider vinegar was in fact an ingredient in the evaluated products.
In summary, it may be best to consider apple cider vinegar as just a tasty condiment at the moment.
Health & Living