Sunday, February 27, 2011

Nutraceuticals: Vinegar

One of the first dietary "supplements"...vinegar.

The term "nutraceutical" was coined by combining "nutrition" and "pharmaceutical" in 1989 by Stephen DeFelice, MD. According to DeFelice, "A nutraceutical is any substance that is a food or a part of a food and provides medical or health benefits, including the prevention and treatment of disease." I plan to start a series on a small number of whole food dietary adjuncts that I think should be adopted nearly universally based on science and anecdote. Whether vegan or "meatitarian" they may be of some value and worth considering adding to the diet. I will start with vinegar.

First off there are whole books on vinegar and it's purported health benefits. I want to keep this post readable, so I'll mostly, not entirely, focus vinegars role in regulating glycemia and insulin. This is of particualr importance to those concerned with Type II Dieabetes management, weight loos, and possibly athletes (vinegar may be implicated in improving glycogen re-synthesis as well). I also try to focus mainly on the scientific research that supports these claims and delve into the possible mechanisms by which vinegar maybe working.

Vinegar has a pretty lengthy track record. Its been reported in the literature that  Hippocrates, the father of medicine used vinegar medicinally to manage wounds as far back as the 5th century BC. Sung Tse, one of the 10th century creators of forensic medicine, preached practice of hand washing with sulfur and vinegar to avoid infection during autopsies (1). According to the Folk Medicine History of Archives many common ailments including poison ivy, croup, and stomach-ache were treated with vinegar. Before the production of glycemic regulating pharmaceuticals (e.g. metformin), vinegar tinctures were commonly consumed by diabetics to help manage their condition (2).

A lot of the more recent research involving vinegar has investigated its effects on postprandial glycemic regulations. In simpler terms, it has looked at the glucose response to a meal with or without vinegar added to the meal, either with the meal, or some extended time before hand; say 5 hours.  In comparison to fasting blood glucose and hemoglobin A1c, postprandial glycemia (PPG) is considered the earliest dysglycemic marker for cardiovascular disease (CVD) and the onset of Diabetes. It has been reported that PPG is linearly related to CVD risk across nondiabetic and diabetic ranges (3). The adverse effects of elevated PPG, even when fasting blood glucose or hemoglobin A1c concentrations are normal, lies in that even acute elevations in blood glucose are implicated  in the formation of free radicals and inflammatory mediators (4).

Several studies have found a relationship of varying degree implicating that vinegar has the ability to 
lower the glycaemic response to a large carbohydrate load (3,5,6,7). However the mechanisms behind the action of vinegar remain unknown for the most part. Earlier investigators in the field speculated that improved glycaemic and insulin responses to a white bread reference meal was probably due to delayed gastric emptying evoked by the vinegar somehow (6). In 2005, Ostman and colleagues also witnessed that the addition of vinegar to a meal based on white bread reduced postprandial responses of blood glucose and insulin, and increased the subjective rating of satiety. Here too, the investigators speculated that the mechanism was impaired gastric emptying or due to  or to the inhibition of digestive enzymes. In cultured Caco-2 cells, the addition of acetic acid, but not other organic acids such as citric or lactic acids, inhibited sucrase, maltase, trehalase and lactase activity (3). However the inhibition of these enzymes in vitro (see here) does not neccessarily mean that the same will occur in humans.

More recent recent research has revealed that vinegar may act through other potential mechanisms, which is what I suspect personally. A 2009 study by Arline Salbe, Carol Johnston (the rock star of vinegar research lol), and colleagues seems to have ruled out the possibility of delayed gastric emptying (8). The researchers suppressed insulin secretion using an oral octreotide/insulin suppression test (OOST) designed to quantify the rate of glucose absorption without the confounding effects of variable glucose clearance due to rising endogenous insulin secretion. The OOST  suppressed endogenous insulin secretion for the first 100 minutes of data collection following the assigned meal. During this time, the  rise of glucose was modestly but significantly (P = .01) greater after vinegar ingestion compared to placebo, suggesting that vinegar does not act to decrease glycemia by interference with enteral carbohydrate absorption.

With gastric emptying ruled out, I would say the best bet is probably that inegar improves insulin sensitivity. A 2004 study also done by Johnston seems to support this. Johnston and fellow researchers found that vinegar improved insulin sensitivity to a high carbohydrate meal in subjects (9). The study included nondiabetic subjects who were either insulin sensitive (controls) or insulin resistant and subjects with type 2 diabetes. Here the subjects recieved a diluted vinegar solution (20 g apple cider vinegar, 40 g water, and 1 tsp saccharine) or placebo drink and, after a 2-min delay the test meal, which was composed of a white bagel, butter, and orange juice for a total of 87 carbohydrates. Blood samples were collected at fasting and 30 and 60 min postmeal for glucose and insulin analyses.

Compared with the placebo drink, vinegar ingestion raised whole-body insulin sensitivity during the 60-min post meal interval in insulin-resistant subjects (34%, P = 0.01, paired t test) and in subjects with type 2 diabetes (19%, P = 0.07). Postprandial fluxes in insulin were significantly reduced by vinegar in healthy subjects as well (% not reported).  I think it is interesting to note that the normal subjects postprandial glucose was not significantly altered but that it took less insulin to regulate the response. So far this is the most solid evidence I have found to support the use of vinegar in improving insulin sensitivity. However there is animal research as well.

A 2001 rat study found that acetic acid feeding enhanced muscle glycogen repletion in rats(10). Any exercise physiology text will read that insulin is antagonistic to glucagon in that it inhibits the breakdown of glycogen and aids in the repletion process. Furthermore two more recent rat studies  have replicated these findings (11 & 12). In fact the most recent of these studies found that the rats fed the acetic acid  had a significantly  lower ratio of insulin to glucagon than the control group at the same point of analyses. Despite this, the acetic acid group had significantly greater liver and gastrocnemius muscle glycogen concentrations. Now granted, I am making some extrapolations here by assuming what worked in rat works for humans, but coupled with the limited direct evidence available, it does appear to strengthen the potential of this mechanism as a possibility.

Lastly, I came across yet another investigation led by Johnston that did not look at insulin directly but found that vinegar ingestion decreased blood glucose response to the same test meal described earlier and improved satiety as well (13). Consumption of vinegar with the high carb test meal was associated with a a reduction of roughly 200-275 Calories throughout the day, sugeesting an improvement in insulin control.

How might one incorporate vinegar?

In order to blind the subjects, researchers typically disguise the vinegar by adding saccahrine and food coloring. Personally I just drink a couple sips of the vinegar straight up followed by water. However other people using vinegar anecdotally are using more palatable concotions such as mixing with honey to make oxymel or mixing it with stevia. In regards to kind and type of vinegar, in the U.S. apple cider vider vinegar is the most commonly used, however it seems coconut, white wine, balsamic, and so forth would work just as well because they all contain the acetic acid. The studies I read were using heinz and claim that the advocation of the "the mother" found in most of the organic, unpasteurized varieties is unsubstantiated. Personally I always buy a brand that includes the mother based on the assumption of it has a long track record, and at the very worst, it probably cant hurt. Depending on one's goals it seems appropriate to have some vinegar with regular meals and/or or peri-workout nutrition.

*Studies in the field have many peculiarities. For example in the investigations  by Johnston et al (3), 10 g of a vinegar in a diluted solution produced significant effects in lowering the glycaemic response to a large carbohydrate load, whereas 20 g did not. In the trial conducted by Ostman et al. (5) there was an observed inverse dose-response relationship between the level of acetic acid (1.0, 1.4 and 1.8 g) and the PPG response to a 50-gram carbohydrate load.

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