Apple Cider Vinegar: Market hype or evidence-based medicine?
Many people are using apple cider vinegar as a component of their health routine. I explore what we do (and don't) know about its clinical relevance.
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Apple cider vinegar (ACV) has risen in prominence as a dietary supplement ingredient in recent years, with consumers spending a whopping $79 million USD on ACV supplements in 2020. But, do the consumer trends follow the science?
In this issue, I examine the evidence behind Apple Cider Vinegar for:
cardiovascular health
atopic dermatitis (eczema)
What is Apple Cider Vinegar (ACV)?
Apple cider vinegar is made through a two-step fermentation process. First, crushed apples are soaked in water and fermented by yeast. This yeast changes the apples' natural sugars into alcohol, a process known as alcoholic fermentation.
Fermentation is a process by which microbes like yeast and bacteria convert sugars and starches into other substances, such as alcohol or acids, often creating distinctive flavors, preserving foods, or producing beverages like wine and beer.
After this, the alcohol is further fermented by bacteria that turn it into acetic acid. This step, called acetic fermentation, gives vinegar its sour taste and strong smell.
As apple cider vinegar ages, it might form a cloudy substance known as the “mother.” This happens because of the acetic acid bacteria, which create a web-like mix of cellulose and acetic acid. Even though the “mother” might not look appealing, many believe it offers health benefits due to its probiotic properties.
Medicinal Uses
ACV has a long history of use as a food, medicine, and preserving agent. The use of ACV has become increasingly popular in recent years, with many people claiming that it can aid in weight loss, regulate blood sugar levels, and improve digestion, “boost” immunity, among other health benefits. While many of these claims are not supported by solid scientific evidence, there is evidence to suggest that ACV may have some health benefits, particularly for blood sugar control and improved digestion.
Clinical evidence
Cardiovascular Disease: Lipid and glycemic profiles
Several clinical studies have been conducted on Apple Cider Vinegar (ACV) to explore its potential in reducing cardiovascular disease risks. A systematic review and meta-analysis of nine randomized clinical trials involving adults revealed that ACV might have positive effects on specific blood markers related to cholesterol and blood sugar levels. The research suggested that ACV consumption could enhance serum levels, particularly benefiting individuals with high initial values.
Although the exact mechanism remains unclear, ACV might enhance various bodily functions, leading to improved health markers. Despite these promising results, the systematic review found that the impact of ACV is more pronounced in certain groups and conditions, with no significant effect in others, such as non-diabetic patients. Furthermore, even though some positive effects were observed with a dosage of 15 ml/day (1 tablespoon per day) of ACV, the correlation between dosage and improvement is still ambiguous and requires additional research.
Atopic Dermatitis (Eczema)
Atopic dermatitis (AD) is a common skin condition affecting both children and adults, causing increased healthcare costs and discomfort. It weakens the skin barrier and alters skin immunity, making the skin more susceptible to bacterial infections, particularly with staph bacteria (Staphylococcus aureus). Current treatments like topical steroids and bleach baths aim to manage these symptoms and reduce staph bacteria on the eczema flares but don't cure the disease.
Given these challenges, there's growing interest in alternative options like apple cider vinegar (ACV) for managing AD. ACV has shown potential in inhibiting Staphylococcus aureus growth in early studies done in lab test tubes. Mouse models treated with a topical vinegar cream have shown modest reduced eczema scores and increased skin hydration. Despite these promising signs, high-quality data supporting ACV's effectiveness for AD treatment is very limited.
In one very small clinical study, including 11 healthy controls and 11 with atopic dermatitis, participants were asked to soak one of their forearms in ACV diluted in water for 10 minutes per day. Samples of the skin microbiome (composition of bacteria on the skin) found on each arm were taken and evaluated. They found no significant change in the skin bacterial microbiome after 2 weeks of ACV soaks, though the treatments made the skin bacterial microbiomes of the eczema subjects more similar to those of healthy controls. However, the clinical significance of this is unknown and the authors conclude that “daily soaks in 0.5% apple cider vinegar are not an effective method of altering the skin bacterial microbiome in atopic dermatitis.”
In another publication by the authors based on the same clinical intervention (11 subjects, 11 healthy controls with 0.5% ACV soaks of their forearms), the authors examined the impact of ACV on the skin pH and integrity of the skin barrier. In atopic dermatitis, the skin barrier is damaged and this is a driving factor in itch, redness, and bacterial colonization of the flare site. Integrity of the skin barrier can be measured with a device that checks for transepidermal water loss.
Major findings: In both groups, there was an increase in transepidermal water loss and a decrease in pH immediately after the ACV treatment, but these changes were not maintained after 60 minutes. In other words, there were no lasting effects observed.
The Takeaway
ACV remains incredibly popular in complementary medicine, both for internal and topical use. Despite its popularity, there is mixed clinical evidence underlying these applications. While laboratory studies suggest that there could be some promising antibacterial properties of relevance to diseases like atopic dermatitis, the one clinical study I could find on ACV soaks demonstrated no lasting benefits.
There are many more clinical studies on the internal use of ACV for mitigation of cardiovascular risk factors, and especially those related to diabetes. Some benefits as measured in blood tests for cardiovascular risk markers were noted for taking a tablespoon of ACV daily in these cases, but the evidence of concrete health benefit is still quite uncertain.
Yours in health, Dr. Quave
Cassandra L. Quave, Ph.D. is a scientist, author, speaker, podcast host, wife, mother, explorer, and professor at Emory University School of Medicine. She teaches college courses and leads a group of research scientists studying medicinal plants to find new life-saving drugs from nature. She hosts the Foodie Pharmacology podcast and writes the Nature’s Pharmacy newsletter to share the science behind natural medicines. To support her effort, consider a paid or founding subscription, with founding members receiving an autographed 1st edition hardcover copy of her book, The Plant Hunter.
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