The internet is rife with claims about the health benefits of apple cider vinegar (ACV), leading some to believe it's a magical solution. While ACV isn't a cure-all, it does possess some scientifically supported health benefits.
What is Apple Cider Vinegar?
Vinegar, derived from the French term "vin aigre" meaning sour wine, owes its tartness to acetic acid. The production of ACV involves a two-step fermentation process. First, yeast converts the sugars in apples into alcohol. Then, a bacteria called acetobacter transforms the alcohol into acetic acid. This fermentation process results in the formation of a substance known as the "mother," a combination of yeast and bacteria. While some attribute ACV's effects to the "mother" due to its probiotic content, its importance hasn't been firmly established through research. Beyond probiotics, ACV's vitamin profile is similar to that of apple juice.
Potential Health Benefits of Apple Cider Vinegar
While ACV is touted for various health benefits, it's crucial to examine the scientific evidence behind these claims.
Blood Glucose Levels
Diabetes is a widespread health concern. A small study published in the Journal of the American Association of Diabetes in 2004 investigated ACV's effect on blood glucose levels. Participants consumed a meal consisting of a bagel, orange juice, and butter, followed by either 20 grams of ACV or a placebo. The study revealed that ACV significantly lowered post-meal blood glucose levels.While ACV may help moderately lower blood glucose levels, it's not a substitute for diabetes treatment.
Antimicrobial Properties
A 2005 study explored vinegar's antimicrobial properties by inoculating arugula with Salmonella. The tainted arugula was treated with vinegar, lemon juice, or a combination of both. The results indicated that both lemon juice and vinegar decreased the growth of Salmonella.ACV might offer an additional layer of protection against foodborne illnesses when used on salads, but it should not replace standard food safety practices.
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Weight Loss
The desire to lose weight fuels the demand for weight loss supplements. In a study, participants consumed 15ml of ACV with lunch and dinner (totaling 2 tablespoons) while adhering to a diet with a 250-calorie deficit. The researchers observed a significant reduction in weight among the ACV group. Over 12 weeks, they lost an average of 8.8 lbs, compared to 5 lbs lost by the non-ACV group.ACV may contribute to modest weight loss, but it's not a replacement for a balanced diet and exercise. The participants in the study were on a calorie-restricted diet and they exercised.
Blood Pressure
Despite claims suggesting ACV can control blood pressure, current research lacks sufficient data to support its use as a blood pressure medication.
Anti-Cancer Properties
Some studies suggest that vinegar may possess anti-cancer properties. These studies often involve exposing cultured cancer cells to vinegar or acetic acid. However, these findings cannot be directly translated to treating cancer in humans. A large population study from China found lower rates of esophageal cancer in people who frequently consumed vinegar.ACV is not a cure for esophageal cancer. Reducing the risk of esophageal cancer involves avoiding smoking and excessive alcohol consumption.
Safety and Potential Downsides
ACV is generally considered safe. However, like any supplement, it has potential downsides. The acid in apple cider vinegar may erode tooth enamel. ACV should not replace a healthy lifestyle.
The Bottom Line on Apple Cider Vinegar and Weight Loss
Drinking apple cider vinegar for weight loss seems far-fetched. Apple cider vinegar isn't likely to cause weight loss. Research hasn't proved that this fermented juice made from crushed apples helps people slim down. Some people claim that apple cider vinegar has many healthy effects, such as weight loss. But little research exists to support this claim. Experts haven't found meaningful weight loss or long-term hunger control with use of apple cider vinegar. And many of the studies of apple cider vinegar and weight loss have been small or lacking in other ways. Some small studies suggest that apple cider vinegar may have promise as a weight-loss aid.
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Most people can use commercial apple cider vinegar safely in small amounts. Some studies suggest that it's okay to have up to two tablespoons a day. Research shows that people have used it safely for up to 12 weeks.
Risks of Apple Cider Vinegar Use
Use of apple cider vinegar does have some risks. Apple cider vinegar is highly acidic. It may irritate your throat if you drink it often or in large amounts. Over time, acidic drinks also can weaken the outer layer of teeth, called enamel. In supplement form, an apple cider vinegar tablet that gets stuck in your throat may cause long-lasting pain. This also is due to the acid in the vinegar.
Apple cider vinegar may affect some medicines. These include common high blood pressure treatments called diuretics and the diabetes medicine called insulin. Apple cider vinegar also may affect supplements such as licorice and horsetail. When apple cider vinegar affects these medicines and supplements, levels of a key mineral in the body called potassium may become low.
Effective Weight Loss Strategies
Keep in mind that weight loss takes time and effort. Using a trendy drink or a supplement alone won't help you reach your weight goal. The key is to burn more calories than you take in from food and drinks. So focus on eating a balanced diet and getting more physical activity.
Dietary Supplements for Weight Management: A Broader Perspective
Dietary supplements for weight management include myriad ingredients with thermogenic, lipotropic, satiety, and other metabolic effects. Recently, the safety of this product category has been questioned.
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Common Ingredients in Weight Management Supplements
This review summarizes the safety evidence as well as relevant clinical findings on weight management and metabolic effects of six representative dietary supplement ingredients: caffeine, green tea extract (GTE), green coffee bean extract (GCBE), choline, glucomannan, and capsaicinoids and capsinoids.
Safety of Common Ingredients
Of these, caffeine, GTE (specifically epigallocatechin gallate [EGCG]), and choline have recommended intake limits, which appear not to be exceeded when used according to manufacturers’ instructions. Serious adverse events from supplements with these ingredients are rare and typically involve unusually high intakes. As with any dietary component, the potential for gastrointestinal intolerance, as well as possible interactions with concomitant medications/supplements exist, and the health status of the consumer should be considered when consuming these components.
Metabolic Health Benefits
Most of the ingredients reviewed also improved markers of metabolic health, such as glucose, lipids, and blood pressure, although the data are limited for some. In summary, weight management supplements containing caffeine, GTE, GCBE, choline, glucomannan, and capsaicinoids and capsinoids are generally safe when taken as directed and demonstrate metabolic health benefits for overweight and obese people.
Obesity: A Global Epidemic
Obesity is a global epidemic that is associated with a higher risk of a multiplicity of devastating diseases, including type 2 diabetes mellitus (T2DM) and cardiovascular disease (CVD), among others [1]. The etiology of obesity is complicated, multifactorial, and involves the dysregulation of the body’s energy balance system, mediated by a complex interplay between neural, hormonal, and metabolic pathways, sedentary lifestyle, genetic predisposition, and excess calorie consumption [1,2].
The Challenge of Weight Management
Modest weight loss is considered beneficial to people with overweight/obesity due to its impact on disease risk reduction [3,4,5]. However, successful weight management, which includes not only weight loss but also weight loss maintenance (i.e., limiting weight regain), is challenging [5]. Calorie restriction and increased physical activity are the cornerstones of traditional weight management programs, but often do not lead to significant, sustained weight loss alone [6,7].
The Role of Dietary Supplements
Dietary supplements, particularly those with thermogenic, lipotropic, or satiety properties, are used by many consumers to support dietary and lifestyle programs for weight management. Caffeine and green tea extract (GTE) are commonly used supplements with purported thermogenic properties. Choline and glucomannan represent supplements with expected lipotropic and satiety effects, respectively. Green coffee bean extract (GCBE) and capsaicinoids and capsinoids are newer to the market and becoming popular for weight management support.
Dietary Supplements: Definition and Regulation
The FDA defines dietary supplements as products taken orally that contain dietary ingredient(s) intended to supplement the diet, but not intended to treat, diagnose, mitigate, prevent, or cure diseases [9]. Specifically, these products may make structure and/or function claims associated with a disclaimer stating the claims have not been reviewed by the FDA, although manufacturers are required to maintain supporting evidence [9]. Dietary supplements are also required by the FDA to be manufactured under Good Manufacturing Practices, with mandatory reporting of serious adverse events and FDA notification prior to marketing a new dietary ingredient (NDI), and manufacturers are prohibited from marketing supplements with unsafe ingredients [10].
Evaluating the Evidence for Weight Management Supplements
Given the continued high interest in strategies for successful weight management through diet and lifestyle approaches, as well as recent questions on the safety of products in the dietary supplement weight management category, this review has identified six commonly used components that represent the breadth of the category. The safety evidence for each ingredient is reviewed, and the status of the clinical evidence on the weight management and relevant clinical health benefits are summarized. Given the large body of research for some of these ingredients, this review includes the highest quality evidence, focusing primarily on reports from authoritative sources and published systematic reviews and meta-analyses.
Basing Health and Nutrition Policy on Scientific Evidence
Over the past several decades, much work has been directed on basing health and nutrition policy and recommendations on scientific evidence over expert opinions. Reports from authoritative bodies and government agencies that provide transparency on the scientific evidence review process are among the highest form of evidence for regulatory and policy applications. Within the biomedical sciences, systematic reviews and meta-analyses following established standards, such as PRISMA and MOOSE, and those published in peer-reviewed journals are critical resources [11,12].
Quality of Research Studies
The quality of the research studies included in these reviews is an important factor as well, and randomized clinical trials are the preferred evidence for establishing cause-and-effect relationships [13,14]. In addition, it is important that the science is assessed not only for quality but also for relevance to the key questions. For example, key aspects that authoritative bodies consider when selecting and assessing whether the evidence for decision-making is relevant generally follow the population, intervention, comparator, and outcome (PICO) approach [13,15].
Relevance to Key Questions
In particular, the intervention tested and comparator control should be relevant and practical. Specifically, the form of delivery (supplement vs. food) and intake level (e.g., testing in the range of a typical product) are important to consider when translating science for decision-making [15]. Dietary Guidelines for Americans (DGA) 2020-2025. Discussion of individual clinical trial evidence is included when more recent studies were available and/or no authoritative sources were found. In addition, to provide context around the recommended amounts of the ingredients in products provided to consumers, the Mintel Global New Products Database [16], which monitors worldwide product innovation and new product activity in consumer-packaged goods markets, with data going back to 1996, was searched for products with weight management claims (e.g., slimming, weight and muscle gain) having one or more of the ingredients of interest.
Caffeine: A Closer Look
Caffeine (1,3,7-trimethylxanthine) is one of the most frequently consumed dietary bioactive substances across the globe, is known as a central nervous system stimulant, and is also proposed to increase thermogenesis and fat oxidation [17,18]. Most caffeine intake is from beverage sources, including brewed coffee (56-100 mg caffeine/100 mL), instant coffee and tea (20-73 mg caffeine/100 mL), and cola soft drinks (9-19 mg caffeine/100 mL) [18]. Caffeine is generally recognized as safe (GRAS) for use in cola-type beverages by the FDA [19]. As a supplement, the ODS identifies sources of added caffeine as guarana, kola nut, yerba maté, and other herbs [17].
Caffeine Content in Supplements
A search of the Mintel GNPD found 579 caffeine-containing supplements with weight management claims whereby 164 listed the caffeine content. Of these, 93% recommended intake levels of ≤400 mg/day, with the remaining 7% recommending 400 to 420 mg caffeine/day.
Caffeine Consumption Patterns
Various studies on caffeine intake have been conducted, generally addressing beverage sources. In a summary of data from 18 nationally representative sources, the average caffeine consumption was found to be 23.7 mg/day, 36.6 mg/day, and 83.2 mg/day for infants, children, and adolescents, respectively, compared to 122.1-225.5 mg/day for adults [20]. These authors reported energy drinks contributed little to total caffeine intake across all groups. In another study using data from the 2013-2016 NHANES, those aged 1-80 years who consume caffeine (>1 mg/d) had a mean intake of 195 mg/day, with 14% of those 30-80 years old and only 4.1% of those 13-29 years old having intakes >400 mg caffeine/day [22]. Overall, the consumption of caffeine has remained relatively stable over the past >15 years, with coffee consumers, regardless of age, being the most likely to have higher intakes. having the highest intake (average of 14 mg/day or 0.82 mg/kg/day) [20].
Safety of Caffeine Intake
The safety of caffeine has been the focus of many federal agencies and scientific and non-governmental organizations over the past several decades. In 2003, Health Canada conducted a comprehensive review concluding that an intake of ≤400 mg caffeine/day was not associated with adverse effects in healthy adults [18]. Additionally, Health Canada concluded that the consumption of ≤300 mg/day for pregnant or lactating women as well as those planning to become pregnant, and 2.5 mg/kg/day for children is not associated with adverse effects. Similarly, the EFSA has also indicated that ≤400 mg caffeine/day does not lead to safety concerns for non-pregnant adults, but identified a limit of 200 mg/day for pregnant women [23].
Updated Systematic Review
In 2017, an updated extensive systematic review also found consumption of ≤400 mg/day in healthy adults is not associated with overt, adverse cardiovascular, behavioral, reproductive, and developmental effects, acute effects, or bone status [24]. Additionally, the review found that the consumption of ≤300 mg caffeine/day in healthy pregnant women is generally not associated with adverse reproductive and developmental effects [24]. Limited new data were identified for children (3-12 years old) and adolescents (12-19 years old), and the authors indicated that “there is no evidence to suggest a need for a change from the recommendation of 2.5 mg/kg caffeine/day” [24]. The DGA 2020-2025 addressed caffeine intake and, noting that the FDA has identified ≤400 mg/day of caffeine as the amount not generally associated with dangerous, negative effects, and indicated that caffeine can be consumed ≤400 mg/day [19].
Caffeine Consumption During Pregnancy and Lactation
The DGA also reviewed the evidence of caffeine consumption by pregnant and lactating women. Small amounts of caffeine can pass from the mother to the infant through breast milk, but a review of the evidence indicated that consumption of ≤300 mg/day (equivalent to about 2-3 cups of coffee) by the mother does not adversely affect the infant [19]. No safe limits have been established for children aged 2 years or younger. When used according to the manufacturer’s instructions, most weight management supplements provide caffeine within the recommended amount of ≤400 mg caffeine/day.
Potential Adverse Effects of High Caffeine Intake
However, concern has been raised over the consumption of caffeine at higher intake levels. Acute intake of caffeine > 500 mg/day potentially results in various untoward events such as headache, jitteriness, agitation, anxiety, dizziness, and tinnitus [17,24]. In a review of safety data, the FDA has noted that caffeine metabolism is slowed after consumption of >500 mg, with adverse effects, such as tachycardia, ventricular arrhythmia, and seizures, at consumptions > 1200 mg [25]. Responses are variable and likely depend on individual sensitivity to caffeine, the existence of co-morbidities, and intake of concomitant medications or supplements [24].
Risk of Caffeine Poisoning
Fatality due to caffeine poisoning is rare, and caffeine’s lethal dose is unclear. Reviews by Health Canada, ILSI, and FDA have concluded that there is a potential for death following acute exposures of ~10 g of caffeine for adults and adolescents [18,24,25]. However, due primarily to uncertainty in the estimates of exposure and the high risk of bias (e.g., use of case reports), there is low confidence in this evidence base. The FDA has recognized that pure or highly concentrated powdered and liquid caffeine has the potential to deliver higher amounts and thus has moved to restrict the sale of these highly concentrated items [25]. Consuming 10 g of caffeine from supplements would require ~25-26 servings of the most highly concentrated supplements, and not surprisingly, most case reports of caffeine-induced fatalities have been associated with suicide or abuse [25,26]. Very few reports of fatal caffeine poisoning in children are published [26].
Caffeine and Weight Management
Caffeine has been used as an approach in weight management because of its ability to stimulate both noradrenaline and dopamine secretions, which, in turn, may decrease BW and body fat (BF), as well as increase thermogenesis in brown adipose tissue via an unknown mechanism(s) [27]. A meta-analysis of 13 studies providing 60-4000 mg caffeine/day for 4-36 weeks showed that caffeine intake led to a reduction in BW, BF, and body mass index (BMI), and that this effect is dose-dependent [28]. However, all but three of the 13 included studies provided caffeine with other substances with potential weight loss properties. Of the three with only caffeine, one study in normal weight and one in overweight/obese subjects reported modest weight loss, whereas another in overweight/obese subjects did not. Taken together, there may be a modest effect of caffeine on weight management, but more clinical evidence with caffeine alone is needed for confirmation.
Caffeine and Blood Glucose Levels
Observational evidence suggests that caffeine may be protective against T2DM [29], [30], which has led to further investigations in this area, but results from clinical studies have been mixed. A meta-analysis of seven randomized clinical trials with primarily male normal weight participants consuming caffeine from 3-6 mg/kg [31], and a trial with healthy men and women [32] found significantly decreased insulin sensitivity indexes compared with a placebo, suggesting caffeine might possess a hyperglycemic activity by acutely impairing insulin action in adipose and muscle tissue. The hyperglycemic impact of caffeine may also extend to adolescents [33]; however, more research is needed on the long-term effect of caffeine consumption on glycemic status [29].
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