Apple cider vinegar (ACV) is promoted in the world of alternative medicine for the prevention and treatment of countless ailments. These claims vary in how extreme they are – from boosting weight loss, to improving digestion and even reducing the risk of cancer. This article will explore the science related to the most common health claims related to ACV.
ACV is created by fermenting apples with yeast to produce alcohol. This cider then undergoes a further fermentation step in order to convert the alcohol to acetic acid, which is one of the key components in vinegar (1).
ACV is mainly water, as it contains little to no fat, carbs or protein in a typical portion. It does contain a small amount of potassium, but one tablespoon only provides about 8-11mg of potassium which is 0.2 – 0.3% of an adult’s daily requirements. ACV can also naturally contain small amounts of antioxidants (2, 3).
Ordinary vinegar contains about 4% acetic acid, whereas ACV usually contains 5-6% acetic acid (4). Many of the claimed health benefits of ACV are related to acetic acid.
Organic cold-pressed ACV which is cloudy in appearance contains crushed pieces of apple called ‘must’. Within the must there is a substance known as ‘the mother’ of vinegar, which is a combination of yeast and bacteria (4). Therefore this type of SCV falls into the category of a fermented food which contains probiotics (beneficial bacteria). However, it is unclear whether this actually impacts our health, as the bacteria may not survive digestion and make it to the gut alive.
One of the most common claims about ACV is that it promotes weight loss.
There aren’t many studies which focus specifically on ACV and weight loss. There is some evidence that vinegar in general may promote weight loss due to its impact on: appetite, insulin function and metabolism (5).
A small study in 2018 found that consuming two tablespoons of ACV along with a 250 kcal deficit per day for 12 weeks led to a significant reduction in visceral fat (fat which surrounds organs in our abdomen) and an average weight loss of 4kg, as compared with 2.3kg weight loss in the control group (who followed a 250 kcal deficit per day without consuming ACV) (6).
Similarly, a study from 2009 found that consuming ordinary vinegar with a meal may reduce appetite and participants consumed 200 – 275 less calories at the meal (8). However, this study didn’t monitor whether this impacted weight over time.
A Japanese trial of obese adults found that consuming one or two tablespoons of vinegar per day led to lower: body weight, waist circumference and visceral fat (7). Some animal studies have also found that acetic acid may lead to reductions in body fat (5, 9).
Overall, there are some interesting findings related to vinegar and weight loss. However, there is a lack of human data – especially in terms of studies which focus specifically on ACV and weight loss.
The study mentioned above, which compared adults who consumed a daily 250 kcal deficit with or without ACV, also found that the ACV group had significantly better cholesterol and lower triglyceride levels after 12 weeks (6). Beyond this, there isn’t much evidence specific to ACV and heart disease in humans.
There are a few human studies which found significant improvements in markers of heart disease in relation to various types of vinegar (7, 10). There are also a number of animal studies which have found that consuming ACV may improve measures of heart health, such as: cholesterol levels, triglyceride levels and blood pressure (11, 12, 13). However, other studies have found no improvement in these markers related to vinegar consumption (14).
There is a possible role related to vinegar consumption and heart health. But the current evidence base is contradictory, and lacking in human studies – especially in relation to ACV specifically.
Some studies have found that consuming vinegar with a meal which contains carbohydrates may help with regulating blood glucose levels after following the meal (15, 16, 17). These results have been echoed in a few animal-based studies (18, 19).
For example, a small study from America found that consuming 20g of ACV (roughly one and a half tablespoons) with a carbohydrate-containing meal improved the body’s response to insulin (insulin sensitivity) by 34% (20).
Another small study found that consuming two tablespoons of ACV per day for 3 days reduced fasting blood glucose levels by 6% in those with fasting levels above 7.2 mmol/l and by 0.7% in those with average fasting levels below 7.2 mmol/l (21).
Suggested reasons for these findings include (22):
- Increased secretion of the hormone glucagon like peptide 1 (GLP-1) in the gut
- Changes in glucose metabolism related to an increase in the activity of the enzyme 5’adenosine monophosphate-activated protein kinase (AMPK)
- Less free fatty acid in the blood
- Increased blood flow in the body
- Increased feelings of fullness when eating (as discussed above under Weight Loss)
Furthermore, two small studies have found that consuming ACV slowed the release of food from the stomach (23, 24). Although this can be beneficial in stabilising blood glucose levels, it could also increase the risk of developing dangerously low blood glucose levels (hypoglycemia) for those who take medication in order to control their blood glucose.
It is important to highlight that most of the human studies in this area have been very small, often containing around 10 participants, with short follow-up periods.
Overall, there is some interesting research which suggests that consuming vinegar or ACV with a meal containing carbohydrates may help in the management of blood glucose levels. However, there are definite limitations to this research and there is much stronger evidence in support of established medical and lifestyle interventions for the prevention and management of diabetes.
Most of the messages related to ACV and cancer are related to the alkaline diet. This is based on the fallacy that the pH level of our body can be influenced by our diet, which in turn can impact our health. There is no robust research which supports the use of the alkaline diet in the prevention or treatment of cancer, and this approach can actually be harmful due to a higher risk of nutritional deficiencies (25). For more information on the alkaline diet, check out this post.
Furthermore, no studies have specifically investigated the impact of ACV on cancer in humans. A study from 2014 found that acetic acid (the main active component in ACV) killed tumour cells in a petri dish (26). Similarly, a study involving stomach cancer in mice found that surgically applying acetic acid straight onto a cancerous ulcer (rather than consuming this) killed the tumour (27). Although these are interesting results, they can not be directly applied to humans at this stage so further research is needed.
Currently, there is no evidence to support the use of ACV in the prevention or treatment of cancer. Promoting non-medical cancer ‘cures’ can be extremely harmful as it may dissuade some people from life-saving cancer treatment, and this is actually illegal in the UK under The Cancer Act.
As discussed above, organic cold-pressed ACV may contain probiotics, but it isn’t clear whether this has any impact on our gut health. Although apples contain prebiotic fibre (i.e. food for probiotics) most of this is removed in the process of making ACV. Check out this post for more information about probiotics.
As mentioned in the Diabetes section of this article, two studies have found that ACV may slow down the rate that food leaves the stomach (23, 24). This can lead to unpleasant gut issues, such as: bloating, nausea and vomiting. The highest risk of this occurring is in those who already have issues with delayed gastric emptying, for example those who suffer with gastroparesis.
It is claimed that ACV can help in the management of heartburn or reflux by increasing the acidity of the stomach or increasing the amount of stomach acid. Again, there is no human research to support this claim, and in fact there have been some case reports of throat burning related to drinking ACV (28).
It is also a myth that ACV can help to reduce gas by providing enzymes to help with digestion. A study investigating the impact of ACV in fish found that digestive enzyme activity was enhanced (29). However, there is no convincing scientific evidence in humans to back up this claim. Furthermore, the enzymes found in ACV differ to those needed for human digestion. In addition, no studies have found that ACV is helpful in the management of gut conditions such as IBS or IBD.
Therefore, there is no strong evidence to suggest that taking ACV improves gut health or alleviates digestive issues.
ACV is often touted as a way of “boosting your immune system”. This concept is flawed as although we want to support our immune system, ‘boosting’ this via dietary changes isn’t possible and would most likely be harmful if it were to occur.
As ACV is acidic it can kill bacteria and fungi when this has been tested in laboratory studies (30, 31). Although this suggests that ACV may have applications as a cleaning agent, it doesn’t tell us how this impacts the human body when consumed. In fact, no human trials have investigated the impact of ACV on our immune system.
There are also some studies in fish and shrimp which found possible benefits to the immune system (32, 33). However, these studies can not be directly applied to humans.
Similar claims exist about the anti-inflammatory effect of ACV (34, 35). Again, this is based on a few animal studies. One study based in rats in the 1980s actually found worse inflammatory outcomes, as measured by rheumatoid arthritis symptoms, in the group who consumed ACV (36).
Overall, there is currently no convincing evidence that ACV leads to improvements in our immune system. For more information about how diet impacts our immune system, check out this article.
One of the main side-effects from regularly consuming ACV is a higher risk of tooth erosion due to its acidity (37, 38). For example, a case study of a 15 year old from 2012 found that drinking a glass of ACV per day led to severe tooth decay (39).
There have been reports of ACV burning the skin and the throat, particularly in children (28, 40).
As ACV may delay the release of food from the stomach, this could contribute to gut issues for those who already have slow gastric emptying – for example in cases of gastroparesis (23). There have also been some reports of nausea related to consuming ACV (41).
A case report from 1998 reported that a young woman who had been 250ml of ACV every day for 6 years developed low potassium levels and osteoporosis (42). However, no trials have investigated these outcomes in relation to ACV.
ACV may interact with medications which act on potassium or blood glucose levels – so you may need to speak to your doctor before regularly consuming ACV.
With the exception of tooth erosion, there is a low risk of harm from ACV overall. However, this depends on how high the dose is and how regularly this is consumed.
There is some interesting research that supports a possible role for vinegar in relation to the management of blood glucose levels and in promoting feelings of fullness when consumed with a meal. However, these findings are not very robust and there isn’t much evidence which specifically focuses on ACV. There is also a possible role in relation to ACV and heart dícese, although human research on this topic is sparse and conflicting overall.
ACV has antibacterial and antifungal properties when used outside of the human body, but there are no human studies about whether it is beneficial for our immune system. Furthermore, there is no strong evidence to support claims that ACV is useful in relation to cancer or digestive health.
The main risk related to regularly consuming ACV is an increased likelihood of tooth erosion. This risk can be reduced by consuming no more than two tablespoons of ACV per day, rinsing your mouth after consuming this or consuming it as part of a meal rather than a drink by itself.
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