In my last post, I addressed the first of two questions raised by a reader in response to a newsletter circulated by a representative of Biotics Research Canada, citing articles from Dr. Lawrence Wilson and Dr. Mark Hyman. In that post, I addressed the question of whether we should avoid animal protein in order to optimize an important health-related process known as methylation. In this post, I will address the question of whether we should avoid kombucha and other fermented foods because their content of chemicals known as aldehydes makes them toxic.
This idea comes from the article by Dr. Wilson, which states that fermented foods such as kombucha, kimchi, and most fermented grains contain aldehydes that are “quite toxic for the liver.” Wilson allows, by contrast, yogurt, kefir, miso, and “most good quality cheeses” as “safe to eat in moderation.” Following the links in the article reveals that Wilson uses as a prototypical example the acetaldehyde content of kombucha.
Googling “kombucha acetaldehyde” without the quotes reveals that this concept has been discussed on many different websites and is quite controversial within the diverse array of alternative health communities, with more speculation and opinion being circulated than hard evidence. I am afraid that hard evidence in this area is wanting; what I will provide in this post is not hard evidence, but rather some context and perspective that seems to be missing in the other posts I have read on this topic.
Dr. Wilson’s article links back to another article of his, “Kombucha Tea – Please Avoid This Poison,” which links in turn to another article of his, “Aldehyde Poisoning,” which contains the references he uses for his information about aldehydes. These references are primarily about aldehyde toxicity, not about the concentration of acetaldehyde in kombucha, nor about the degree to which acetaldehyde in kombucha is absorbed into the human body, nor on any negative health effects that directly result from drinking kombucha. Although I have not searched exhaustively, I did peruse the literature and I was unable to quickly locate anything that actually reports the concentration of acetaldehyde in kombucha, let alone the degree to which acetaldehyde is absorbed from kombucha into the human body. If you know of any such evidence, please post it in the comments.
In perusing the literature, I did find articles reporting the contents of ethanol (the alcohol we drink in alcoholic drinks) and acetic acid. These articles are easy to find by keyword searching, but can also be found listed in the Body Ecology article, “4 Surprising Reasons to Ditch Kombucha.” I believe the likely reason that articles have reported the content of ethanol and acetic acid without reporting the content of acetaldehyde is probably because kombucha does not contain very much acetaldehyde, and this would be one reason it could be very hard to measure. And indeed, I would not expect kombucha to contain very much acetaldehyde. For the same reasons I would hold this expectation, I would also expect that for most people who consume kombucha in the manner in which it is typically consumed the acetaldehyde content is nothing to worry about.
Let us back up a moment and discuss what an aldehyde actually is. The picture below depicts acetaldehyde in two different ways. This will help us discuss aldehydes in general as well as acetaldehyde in particular.
The figure on the left emphasizes the bonding patterns of the specific atoms within acetaldehyde. The figure on the right emphasizes the arrangement of the atoms in space and realistically depicts the proportion of space taken up by each atom. The key feature that makes acetaldehyde an aldehyde is that one of the carbons (C) is double-bonded to oxygen (O) and on one side is only bound to a hydrogen atom (H). On the right, carbons are shown in black, hydrogens are shown in gray, and the oxygen is shown in red. This pattern is called an aldehyde group.
The reason that aldehydes have the potential for toxicity is because their aldehyde groups make them highly reactive, and while some of the reactions they engage in may actually be helpful to us, many of them may be harmful to us. Let us briefly consider why they are so reactive. All of these atoms are balanced by positive and negative charges. Positive and negative charges are attracted to one another and when they are fully balanced within a molecule the molecule tends to be relatively inert. When carbons and hydrogens are bound to one another, they share electrons and share those electrons relatively equally between one another. By contrast, when carbon is bound to oxygen, oxygen holds on to the shared electrons much more tightly than carbon does. Electrons carry negative charges, so this makes the oxygen relatively more negatively charged and the carbon relatively more positively charged. Thus, most of the acetaldehyde molecule is inert but the separation of charge between the carbon and oxygen allows the relatively positively charged carbon to be strongly attracted to negative charges within other molecules.
Many molecules contain both carbon and oxygen and these include even fats, proteins, and carbohydrates. What makes the aldehyde group unique is that on one side there is only a hydrogen atom. You can see in the picture above on the right that hydrogen is the smallest atom. Were there any larger atom in its position, that larger atom would get in the way of any molecules that would want to react with acetaldehyde. Since the aldehyde group has nothing in the way except this measly hydrogen atom, it is free to react with any of the molecules to which it is attracted, regardless of whether such a reaction would be helpful for us or harmful to us.
For this reason acetaldehyde, and aldehydes in general, have a high potential for toxicity. But they are no more toxic to us than they are to the microorganisms that make them. These microorganisms, just like us, make aldehydes primarily as intermediates between one thing and another. These microorganisms, just like us, try to avoid these intermediate aldehydes from accumulating. If they did not, they too could suffer from the toxicity risk that aldehydes pose.
In kombucha, most of the acetaldehyde is made by acetobacter. Acetobacter makes it as an intermediate in the two-step conversion of ethanol to acetic acid. If one follows up any of the references on this matter listed in the Body Ecology posts that I linked to above, one will find that these sources describe kombucha as primarily an acetic acid ferment. Kombucha can become alcoholic, but the kombucha that is sold commercially in stores is consistently low enough in ethanol to be considered nonalcoholic. Home ferments can reach 1% or 2% ethanol, but this is significantly less alcoholic than what most people would consider alcoholic drinks. If someone ferments kombucha for too long, it becomes like vinegar because of its high acetic acid content; it does not become strongly alcoholic. Regardless, because acetaldehyde is toxic to acetobacter, the sum of ethanol and acetic acid will always greatly prevail over acetaldehyde, whose concentration will always be small.
We humans, just like acetobacter, convert ethanol in a two-step process first to acetaldehyde and then to acetic acid. Because acetaldehyde is toxic to us, we make it only as an intermediate and do not let its concentration accumulate. Most acetaldehyde in our bodies will be from the ethanol be consume. If we experience a rise in the amount of acetaldehyde that passes through our bodies from drinking kombucha, it will most likely predominantly result from the ethanol in the kombucha rather than the acetaldehyde, simply because there is presumably much more ethanol in the kombucha then there is acetaldehyde. This risk, then, would be quite low when the kombucha is fermented in the typical manner that results in a low concentration of ethanol, and it would always be far lower with kombucha than with typical alcoholic drinks.
Some people are more vulnerable to this than others. It is thought that one reason many Asians have a low tolerance for alcohol is because they are more likely to be genetically predisposed to convert ethanol to acetaldehyde more quickly than they convert acetaldehyde to acetic acid.
But ethanol is hardly the only precursor to an aldehyde within the human body. In fact, the production of aldehyde intermediates is a universal feature of energy metabolism.
The bulk of our energy supply is generally met by utilizing fatty acids or carbohydrates for fuel, depending on our diet and whether we are in the fed state or the fasting state. In order to burn carbohydrates for energy, we first split glucose in half to form glyceraldehyde. Glyceraldehyde is a potentially toxic aldehyde. We therefore quickly convert it to pyruvate, which is almost half of a glucose molecule but has the potentially dangerous aldehyde group removed.
When we burn fatty acids we make ketone bodies. These include acetone, which is the principal ingredient in paint thinner and nail polish remover and is responsible for “ketone breath.” When we are burning fatty acids, it is partly because the supply of glucose is low, and this generally means that we need to synthesize new glucose to meet the needs of red blood cells and certain cells within the brain that are unable to use fatty acids or ketone bodies. Although we primarily make glucose from amino acids during these conditions, we can also make it from acetone. Doing so requires us to make pyruvaldehyde (also known as methyloglyoxal) as an intermediate. Pyruvaldehyde is a potentially toxic aldehyde. We therefore quickly convert it to pyruvate, which we can use to make glucose.
For further information and references about these topics please see these other posts of mine.
I therefore agree that drinking kombucha could increase the flux of aldehydes through the body, but I do not see it as intrinsically any more dangerous than meeting our essential caloric needs by consuming carbohydrates and fat. The main problem is that in any of these pathways things can go wrong. When energy metabolism becomes dysfunctional, when we have deficiencies in the nutrients needed to support these pathways, or when we have genetic predispositions to tolerate certain dietary factors poorly, the aldehydes may accumulate instead of being quickly metabolized to other safer molecules. This could allow them to have toxic effects.
I personally see the practical implications of this material as follows:
- If you feel flushed and uncomfortable when you drink kombucha, or if drinking it gives you a hangover, I would avoid drinking kombucha and other even slightly alcoholic drinks. You may be producing acetaldehyde from the alcohol at a faster rate than you convert the acetaldehyde to acetic acid. Alternatively, if this is true but you nevertheless really enjoy kombucha, I would use it with a level of moderation that allows you to get enjoyment without risking negative effects that you don’t think are worth enduring in order to get that enjoyment. I do not see any difference between considering kombucha in this case, and considering other drinks that contain alcohol.
- If you quantify your performance on some health-related issue, athletic performance for example, and you find that drinking kombucha seems to hurt this performance, then I would impose a level of moderation on kombucha consumption that is needed to continue meeting your performance goals.
- If you currently drink kombucha, have no health problems, and feel that you are meeting all of your goals that relate in any way to the performance of your body, then I would continue to drink kombucha without dwelling on it any further.
- If you do not currently drink kombucha, and you’re thinking of starting, as long as you do not have a particular reason to avoid even slightly alcoholic drinks, I would try it without worrying too much about any of this.
It is easy to find information about the benefits of kombucha all over the Internet. I do not think any of this is invalidated by the concern about aldehydes, nor do I think it makes much sense to single out kombucha or other fermented foods for this concern. The bullet points above are not meant to suggest that there is anything particularly risky about drinking kombucha; everyone is different, however, so with anything it is always advisable to try to listen to your body and take into account how it responds.🖨️ Print post
Christina Fritz says
If kombucha is out, should we consider kefir to be okay or a substitute for those looking for pro-biotics in another form?
Chef Jemichel says
So glad that I first read the comments on this at the Daily Lipid as the main retort there gave me a great “heads up” on this article – sparing me from needless anxiety about good old kombucha – a long-time fermented tea drink that I have been making and drinking consistently for over fourteen years with great enthusiasm along with many other blessings!
I make my own kombucha and drink 64 oz a day. It seems to help my digestion. I feel better drinking it.
Tom Jeanne says
Chris, I don’t put much weight on the easy-to-find information on the Internet that suggests kombucha is beneficial, but I like the rest of your summary. Your biochemical reasoning is impeccable, though what we still need is empirical evidence of aldehyde content in various formulations of kombucha.
On that note, given the wonderful wildness of homebrewed kombucha, with local strains of bacteria and fungi playing a role, I worry about fungal toxins. Aflatoxin, which typically is a contaminant of cereal grains in poor storage conditions, is one of the most potent carcinogens known. It doesn’t seem unreasonable to worry about Aspergillus or another toxin-producing fungi growing on kombucha, especially if the initial ferment is in warm conditions. The last few batches I made had various tastes ranging from interesting to alcoholic to weird…. I don’t know if I should try to acquire a taste or dump them–precautionary principle would say the latter, even though I would admit the potential for a high risk toxin is probably low.
WILL BOYDEN says
I have BEEN DRINKING FARM KOMBUCA FORT TWO YEARS WITH NO COMPLAINTS from THE LOCAL WAPF CHAPTER
have YOU HAD ANT COMPLAINTS OR HEADS UP FROM ANYBODY?
THERE ARE MANY MOLECULES OF GOOD QUALITY WATER IN A GOOD WELL COOLED CONTAINER OF KOMBUCHA THAT
WIL GREATLY REDUCE THE RISK OF ALDEHYDE ATTRACTION OF AN ANTIGEN ETC
THAKS FOR YOUR STRUCTURAL ANALYSIS.
And he advises drinking dairy products. Pure nonsense from your typical SAD advocates.
Chris – Thank you so much for the article. Is there any concern with the aldehyde content of raw sauerkraut? My kraut ferments in the high 60’s to low 70’s temperature range of my apartment. I think Dr. Wilson advises minimal to no consumption of kraut. I welcome any insight you might have.
Excellent information. My wife and I have just starter making kombutcha and drinking it nearly every day. Appreciate clarifying this issue.
I’ve heard this mentioned before elsewhere but no one ever explained the details, thanks!
I believe kombucha is toxic and has contributed to my fatty liver disease, pre-diabetes and other health problems including IBS. Acetic acid is the main culprit for the and its role in diabetes, metabolic syndrome, obesity crisis etc. Most fermented products and alcohol will have this effect.
there is plenty of information since the 1950s onwards on the acetate connection
Eating pickles and fermented products is much like drinking alcohol, which is converted to acetate in the body.
Now we know the association of alcohol and the pot belly, and metabolic syndrome.
Now, the other major culprit working in conjuction with the acetic acid is the high levels of fructose in kombucha from the sugar. The following article makes the link between fructose and fatty liver disease.
You mentioned in your discussion, that ketones can’t be used/metabolised by the brain ? did I read that correctly ? refer to Dr David Perlmutter’s work on Ketone metabolism by the brain and Epilepsy
(USA Research Neurologist )
He did not say the brain as a whole cannot use ketones. What he did say is “…and certain cells within the brain…”
Chef Jemichel says
Thank you Chris!
What I hear you present here corresponds to another reading: “Aldehydes are produced and dealt with as a bi-product to metabolism.”. I appreciate the “context and perspective” that you offer as I found these elements lacking in articles from Dr. Lawrence Wilson.
The long standing history of kombucha consumption is also part of my perspective. I suspect that much of the aldehyde toxicity issues occur due to compromised digestion as a result of modern day diets with apparent alterations occurring in the metabolic processes. I imagine that illustrations of the metabolic process showing where aldehydes are not being converted properly could make a great reference in this respect!
 M Baird – JANUARY 23RD, 2017 @
Brandon Lutz says
If you’re worried about aldehyde, take molybdenum. It literally has saved my life. Candida creates aldehyde as a toxic byproduct so treating Candida is important if you suspect that you have it.
I think you have a lot of knowledge but there is a skill in knowing how to explain it to the average person. A lot of your writing is either too long or goes over our heads (have spoken with others about this). We want to understand but we can’t. Just something to keep in mind.
When my stomach is uneasy from eating the questionable things in restaurants these days, drinking kombucha definitely helps me feel better.
I had a horrible experience with home-made kombucha. Previously drank some and ok, but this time it was overly fermented. I was violently ill, as it seemed to explode inside me.
Although not diagnosed w/ candida, its possible I had some buildup. I went to bed and the next morning I woke up and as strange as it sounds, I looked in the mirror and my face had fallen. The dura had torn or something and I developed a CSF leak, maybe a couple of leaks. That was 16 months ago and I am still recovering and looking for effective medical care. since then I have learned that the leak is related to a connective tissue disorder – which is genetic . Over the months that followed 6-8 of my teeth on my upper jaw broke off. I don’t understand all the chemical reactions etc.. but want to tell everyone to avoid home-made kombucha. I do feel like I was poisoned.
I was poisoned by kombucha as well. I wish people would exercise more caution in consuming this beverage, store-bought or homemade, and really reflect on how it is interacting with their biology. Those who drink kombucha daily tend to be addicted (I was). It is not necessary for health.
There is virtually nothing in the world that some guru online isn’t going to proclaim unsafe. When it comes to diet, the advice out there by well-meaning people is endless and often hopelessly inconsistent.
Dr. Wilson seems to have very extreme views and rigid ideas about what’s OK to consume. Since virtually nobody on earth could adhere to anything close to his diet, and since so many things according to him are toxic, we as a species should be much less healthy than we are. His views on collateral topics such as sex are REALLY out there. I would consider the source before believing him that some kimchi or a tomato is going to poison you.
Does and extra long fermentation time for home kombucha result in more or less of the acetaldehyde?