By Dr. Tim Trader, ND, PhD
There is a lot of information in recent times supporting the health benefits of eating fermented foods. They talk about how fermented foods help your digestion and that fermented foods contribute to a healthy digestive tract environment. There is some science that may look at things differently though.
The body’s protection
Starting with the bodily functions, there are ways the body protects itself from invading threats, like pathogenic bacteria. Food borne pathogens are killed by stomach digestive juices like hydrochloric acid and pepsin. (1,2)
This protection does not exclude the beneficial bacteria in the fermented foods as well. When the body is trying to protect itself, it does not determine the difference between good or bad microbes. Its function is to keep anything possible, like viruses, archaea, protists, fungi, and bacteria… that can harm the body from getting in with the food to do some damage and not get in the way of us getting the needed nutrition that we require.
Even probiotic supplements don’t survive digestion, though supplement manufacturers are trying to change this. But that doesn’t solve the problem with fermented foods and the beneficial bacteria it contains, which are not protected in a capsule from complete digestion. (3)
There are studies that do say that a small number of beneficial bacteria (which are also called probiotics) can get through the digestive process. But in reality, it turns out that the bacteria in fermented foods have been killed by the digestive process and what the researchers are finding is the DNA of the bacteria which is left over from digestion is what they are finding in the DNA stool testing that they use to determine which bacteria are in the gut, yet, the testing never ascertains if the bacteria is alive or dead in the digestive tract.
But the probiotics (in capsules or on fermented foods) create metabolites that do survive digestion. (3) Metabolites are the beneficial chemicals that the probiotics supplements and especially the bacteria that the fermented foods produce before being digested. These metabolites like lactic acid and short chain fatty acids do make it through digestion. Lactic acid controls the pathogenic bacteria and keeps them from taking over our digestive system and creating an environment that allows gut bacteria to thrive. The short chain fatty acids are power houses in themselves. They are necessary to help reduce inflammation, which helps with heart disease and diabetes. Short chain fatty acids help with communication of the gut and brain, as well as, short chain fatty acids are essential to heal the never ending damage the gut undertakes in getting nutrients to you after your food has been digested. There is so much more about the metabolite’s health benefits, but that is for another article.
But the bacterium on fermented foods has been shown to never colonize in your gut because they are already dead, so you end up eating the fermented food to keep up the health benefits of the metabolites. Since you don’t have the commensal bacteria to produce metabolites to start with. Once you stop, so do the benefits. Whereas, if you have an abundance of beneficial bacteria already living in your digestive tract, you don’t have to worry about the healthful benefits you are trying to get from the fermented foods because the beneficial bacteria are already there, doing their work in your digestive system producing the metabolites and other needed functions that produce what you need to have a healthy digestive system.
Please understand, you are not replacing beneficial bacteria with fermented foods, but you are helping the gut environment to maintain homeostasis with fermented foods. And you reap the health benefits as long as you do continue to eat fermented foods. Except, there are other problems with fermented foods that are not so beneficial. We can start with the chemicals the fermentation process creates in the development of the fermented foods themselves.
Aldehydes
Let’s begin with Aldehydes and acetaldehydes. Aldehydes are the waste products of the bacteria growing on fermented foods. Aldehydes are a major reason for the taste in fermented foods that makes them different from just eating the same unfermented foods. Typical aldehydes found in fermented foods are, amongst others, formaldehyde and histamines, and then there are acetaldehydes. Yes, these same waist products are made by bacteria in the colon, but the colon is made to deal with the waist products and keeps us from absorbing them into our bodies.
Aldehydes are toxic. (4) Aldehydes are reactive organic molecules that can cause organ damage, inflammation, and acute pain. They can also be mutagenic, cytotoxic, and carcinogenic. The process of fermentation creates aldehydes (5,6,7)
Histamines are an aldehyde. (8,9) You know histamines, they are the inflammatory reaction the body has to toxins and things that don’t belong in the body. When you add more histamines than what your body is making and needs, you have a reaction to normal things in your environment (including food) and a generalized inflammation.
Higher levels of histamine in the body, beyond what the body would normally produce, can cause a variety of symptoms including: itchy skin, flushing, headaches or migraines, nasal congestion, digestive issues like bloating and diarrhea, rapid heartbeat, low blood pressure, and in severe cases, even difficulty breathing due to airway constriction… essentially triggering allergy-like symptoms throughout the body.
Formaldehyde is an aldehyde as well. (10,11) Formaldehyde can be in fermented foods and like histamine, it can cause inflammation and itching, irritation to the eyes, nose and throat, nausea, and coughing. Long term exposure can even cause cancer, lung problems, and allergic reactions.
Acetaldehydes
Acetaldehydes or oxidized ethanol can be very concerning. Acetaldehydes can cause DNA, organ, brain, and nerve damage, as well as a host of uncomfortableness from inflammation for you and your cells. (12,13) Acetaldehydes are toxic to the brain (14,15) and cause nerve damage or otherwise what is called neuropathy. (16)
Vinegar
Another part of fermentation is vinegar. Vinegar is a dilute acetic acid, and it also has traces of aldehydes. Vinegar is either made in the fermenting process or added to reduce spoilage and improper bacterial and mold growth.
Acetic acid is in fermented foods. It is produced by acetic bacteria, or other bacteria that excrete acetic acid as a waste product. (17) When the acetic acid is mixed with other components of the fermentation process, it becomes vinegar. In the digestive system vinegar is an irritant and can be too acidic for the stomach and has to be neutralized. (18) Vinegar can eat away at the mucosa lining of the stomach and create ulcers. (19) Vinegar has been shown to induce cancer. (20) When acetic acid (from vinegar or from fermented foods) gets into our system, it can affect the thyroid, it may even damage the thyroid. Lowering metabolism, body temperature, bone health, nervous system function, and thus muscle function. (21) Vinegar erodes tooth enamel, (22) and vinegar has been shown to induce osteoporosis. (23) Vinegar is not the health promoting product is it made out to be.
Salt
High amounts of salt (sodium) are added to fermented foods to preserve the food from spoilage and to control pathogenic bacteria. (24,25) Fermented foods, especially those of traditional style fermented foods, have been shown to create gastric cancer. Gastric cancer is the third leading cancer in Japan or even higher in some other oriental countries. The high cancer rates are believed to be because of the high salt intake, specifically the high salt content of pickled (fermented) vegetables that are highly consumed in these cultures. (26,27,28,29)
Across the board, high salt intake has been shown to be devastating to health. High salt intake is a major cause of hypertension. (30,31,32) When you have hypertension, heart disease goes right with it. (33) Here is one you may not have suspected, there is connection between high salt intake and osteoporosis. (34,35) High salt intake is also a major contributor to kidney disease. (36) High salt intake kills gut bacteria in your gut (isn’t that opposite the reason to eat fermented foods). (37,38) Consuming salt like most people do, it takes its toll on your overall health and may cause premature mortality (early death). (39)
Glutamate
Then there is glutamate, in some fermented products it is touted as a benefit, a flavor enhancer. You may know it from its popular name in some fermented products, even in seasonings, we know it as MSG (monosodium GLUTAMATE). Which is just salt and glutamate in combination together. Glutamate is produced from lactic acid bacteria which is encouraged to grow in fermented foods. (40,41)
Glutamate is an excitatory neurotransmitter in the central nervous system. Excessive glutamate in the extracellular space can trigger passive and active forms of neuronal death in the nervous system through excessive activation of glutamate receptors. This action has been named excitotoxicity. Excitotoxicity has been implicated in the cause of acute and chronic neurodegenerative disorders. (42) Glutamate is associated with seizures, (43) and neurodegenerative diseases; (44) like ALS, (45) And MS, (46) And autism, (47) Alzheimer’s disease, (48) Parkinson’s disease (49) and a host of other neurodegenerative problems.
Glutamic acid is a normal and a helpful amino acid found in plants. It is used by the body and converted to a neurotransmitter when needed. But when glutamate is dumped into the nervous system it becomes too much for the system and the body. The glutamic acid in plants during fermentation, thanks to lactic acid bacteria, loses a hydrogen bond creating glutamate.
Even fermented dairy has glutamate. (50) Fermented dairy also has acetic acid, (51) and high sodium content. (52) Fermented dairy does not have the fiber to feed the good bacteria. Nor do fermented products like kombucha tea, soy sauce, miso, liquid aminos, or other fermented products, but they all have aldehydes, sodium and glutamate, they just lack the fiber. That is the key, if you feed the bacteria what it needs, they will thrive in your digestive system, and you will get all the health benefits you are looking for.
Fermented foods and cancer
Fermented foods are directly associated with cancers of the digestive system, like colon and esophageal. (53,54,55,56,57) but that’s not all, there are other associations like breast cancer (58) and a general lower mortality (59) not extending health like the many claims about fermented foods that say it does.
A better way
Maybe there is a better way to get our health needs met. If you are still looking for a way to get beneficial bacteria in, then raw fruits and vegetables do have bacteria and there is no need to ferment them. (60) yet, if you cook them, the heat does kill the bacteria. The real situation is that fruits and vegetables are the best source of fiber. (61)
Feed the microbes in your gut the fiber they require and everything you are looking for in the fermented foods will be given to you in abundance. Most people (95% of adults) do not even get the required daily allowances of fiber to start with and so, (62) they look for quick short cuts to do what is needed to feel better.
In ancient times fermentation was how people preserved their fruits and vegetables, but now we have an abundance of fresh produce available year around and all you have to do is to eat more fruits and veggies, it is much easier and more health promoting and actually cheaper than buying expensive fermented products or more time saving then making fermented foods yourself.
References
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3. Survival and therapeutic potential of probiotic organisms with reference to Lactobacillus acidophilus and Bifidobacterium spp
4. Aldehyde toxicity and metabolism: the role of aldehyde dehydrogenases in detoxification, drug resistance and carcinogenesis https://www.tandfonline.com/doi/full/10.1080/03602532.2018.1555587#:~:text=Aldehydes%20are%20generally%20cardiotoxic%20in,with%20macromolecules%20and%20form%20adducts
5. Acetaldehyde Determination in Fermented Food Products by Direct 2,4-Dinitrophenylhydrazine Derivatization, Extraction and High Performance Liquid Chromatography
6. Alcohol and acetaldehyde in African fermented milk mursik – A possible etiological factor for high incidence of esophageal cancer in western Kenya https://pmc.ncbi.nlm.nih.gov/articles/PMC3538938/
7. Biological Risks Associated with Fermented Diary Products, Fruits, Vegetables and Meat: A Critical Review https://www.researchgate.net/publication/312627784_Biological_Risks_Associated_with_Fermented_Diary_Products_Fruits_Vegetables_and_Meat_A_Critical_Review
8. Biogenic Amines in Cheese and other Fermented Foods: A Review https://pubmed.ncbi.nlm.nih.gov/31051616/
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10. Environmental Aldehyde Sources and the Health Implications of Exposure https://pmc.ncbi.nlm.nih.gov/articles/PMC7326653/#:~:text=According%20to%20the%20WHO%2C%20fermented,the%20restaurants%20measured%20%5B72%5D
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12. Metabolic effects of acetaldehyde
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14. Locally-generated Acetaldehyde Contributes to the Effects of Ethanol on Neurosteroids and LTP in the Hippocampus https://pubmed.ncbi.nlm.nih.gov/24455167/#:~:text=Background:%20As%20severe%20alcohol%20intoxication%20impairs%20memory,Neurosteroids%20are%20involved%20in%20this%20LTP%20inhibition
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17. Acetic acid bacteria in fermented foods and beverages https://www.sciencedirect.com/science/article/abs/pii/S0958166917300873
18. Vinegar is a dietary mild irritant to the rat gastric mucosa https://pubmed.ncbi.nlm.nih.gov/3735808/#:~:text=These%20results%20suggest%20that%20dilute,cytoprotection%2C%20mediated%20by%20endogenous%20prostaglandins
19. Evaluation of effects of white vinegar-induced gastric mucosal ulceration in rats Evaluation of effects of white vinegar-induced gastric mucosal ulceration in rats https://www.researchgate.net/publication/375605007_Evaluation_of_effects_of_white_vinegar-induced_gastric_mucosal_ulceration_in_rats_Evaluation_of_effects_of_white_vinegar-induced_gastric_mucosal_ulceration_in_rats#:~:text=The%20results%20of%20this%20study%20reveal%20that,mucosa%20from%20injury%20and%20ulcers%20in%20rats
20. Acetic acid is an oxidative stressor in gastric cancer cells https://pmc.ncbi.nlm.nih.gov/articles/PMC6064817/#:~:text=Acetic%20acid%20can%20cause%20cellular,a%20mechanism%20involving%20oxidative%20stress
21. The influence of a single acetic acid and lactic acid injection on rat normal thyroid tissue https://pubmed.ncbi.nlm.nih.gov/12325474/
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30. Dietary sodium and target organ damage in essential hypertension https://pubmed.ncbi.nlm.nih.gov/11939611/
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33. Sodium Intake and Heart Failure
34. Salt intake, hypertension, and osteoporosis
35. Excessive salt consumption causes systemic calcium mishandling and worsens microarchitecture and strength of long bones in rats https://www.nature.com/articles/s41598-021-81413-2
36. Salt intake and kidney disease
37. High-Salt Diet Induces Depletion of Lactic Acid-Producing Bacteria in Murine Gut https://pmc.ncbi.nlm.nih.gov/articles/PMC8950745/
38. Salt-responsive gut commensal modulates TH17 axis and disease https://pmc.ncbi.nlm.nih.gov/articles/PMC6070150/
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47. The role of glutamate and its receptors in autism and the use of glutamate receptor antagonists in treatment
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49. Molecular Mechanisms of Glutamate Toxicity in Parkinson’s Disease https://www.frontiersin.org/journals/neuroscience/articles/10.3389/fnins.2020.585584/full
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58. Associations between Preserved Foods and Breast Cancer Risk in Hong Kong Chinese Women
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62. Closing America’s Fiber Intake Gap
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