Mouth ulcers and Vitamin U

Summary - Mouth ulcers result from a breach of the mucous layer that protects the lining of the mouth and an underlying inability to repair the mucous layer quickly. Taking Vitamin U in the form of fresh vegetable juice and/or supplements is a great way to naturally heal mouth ulcers. Talk to your doctor or dentist.

Mouth ulcers (aphthous ulcers or stomatitis) are small, painful, circular sores that form in the lining of the mouth. They are very common. Right this minute, 1-2% of people have a mouth ulcer. Over a lifetime, about half of the US population will get at least one if not many. They mainly afflict teenagers. Ulcers normally heal spontaneously in one to two weeks, although they can reoccur many times. Recurrent ulcers indicate an underlying health problem. Sores in the corner of the mouth or outside the mouth are not ulcers and should be treated differently.  

Why do I have a mouth ulcer? 

The lining of your mouth is covered by a thin layer of mucus. The main purposes of this mucus is to protect the lining of the oral cavity from physical and chemical damage, infection, and to help digest food. Mouth ulcers develop when the protective mucus layer is breached and the body shows a delayed repair response with non-specific oral bacteria infecting. The integrity of the mucus layer is a function of constructive vs destructive factors. 

Destructive factors

Biting your mouth while eating or from a nervous habit is probably the most common way ulcers start. Physical or chemical damage from food is another very common cause - 

• Crusty food like bread or toast
• Crispy food like chips
• Salty food like pretzels
• Sweet food like candy
• Sticky food like cookies
• Sour food like vinegar
• Hot food like coffee

Abrasive, salty and hot foods/drinks physically damage the mouth. Sour foods/drinks chemically burn the mouth instantly. Sweet and sticky foods burn slowly by feeding oral bacteria, which metabolize sugars to produce corrosive acids. 

Drugs are another destructive factor. Alcohol is oxidized by oral bacteria to acetaldehyde, which is toxic and a carcinogen (Tagaino et al, 2019). Some acetaldehyde is even produced from sugar by oral bacteria. Acetaldehyde is also found in cigarette smoke (Sprince et al, 1975). As with peptic ulcers, NSAIDs like aspirin inhibit prostaglandin E2 synthesis which reduces mucin secretion. People swishing aspirin in their mouth to quell inflammation are actually slowing down ulcer healing (Slomiany and Slomiany, 2000).

Poor dental hygiene is yet another destructive factor. Harsh brushing makes tiny holes through which corrosive agents can meet the cell surface. Ineffectual or nonexistent brushing leaves food and bacteria in position to generate more organic acids and acetaldehyde.

Constructive factors

The major factor protecting the mouth is mucus. There are five kinds of mucin produced in the mouth - MUC5B and MUC7 being the most important (Frenkel and Ribbeck, 2015). MUC5B is a very long protein rich in serine and threonine amino acids to which glycans attach. These glycans attract water to form a gel and gives your mouth that slippery feeling. The protein overall looks likes a bottle brush with one end attached to the cell. MUC7 is similar, but is unattached and therefore flows freely aiding in formation of the soft bolus from food. MUC5B proteins form polymers via disulfide bonds. Cysteine is unusually common in MUC5B and is essential for disulfide bond formation.

A shortage of many dietary factors have been suggested to cause mouth ulcers. Examples include vitamin B9 (folate), vitamin B12, vitamin C, vitamin E, selenium. All play a role in antioxidation, and it makes sense that these nutrients are low in ulcers as the environment shows signs of oxidative stress (elevated malondialdehyde and depressed glutathione)(Arikan et al, 2009). 

Despite this speculation, however, the evidence has been inconclusive. There are certainly some patients who respond well to supplementation with one or another of these micronutrients. However, many times mouth ulcers occur in people with no apparent deficiency and/or supplementation has no effect. Considering that some of these micronutrients work in some cases, it's possible that they help in an indirect way, or that chronic mouth ulcers are indicative of a systemic redox imbalance. For example, chronic ulcers are more prevalent in those with other problems in their digestive tract (Brailo et al, 2007).

Can Vitamin U help heal and prevent mouth ulcers?

The use of Vitamin U to treat or prevent mouth ulcers has undergone little investigation (Kato and Takayasu, 1961). Vitamin U has been shown to be a useful treatment for gum disease (Sulym, 2016), and sulfur compounds like cysteine are effective in quenching the damaging effects of acetaldehyde in the mouth, particularly when combined with vitamins B1 and C (Sprince et al, 1975; Syrjanen et al, 2016).

The fact that Vitamin U has been shown to heal and prevent peptic ulcers by stimulating the release of mucin suggests that it may also have this function in other parts of the digestive tract which also secrete mucin (Watanabe et al, 2000). One can't help but wonder whether mouth ulcers have a similar etiology to its more dangerous relatives. If this is indeed the case, one may speculate as to whether Vitamin U or a metabolic derivative could have this effect on the release of mucin from not only the mouth or other parts of the alimentary canal, but even other epithelial tissues, including the lungs, trachea, nose and eyes.  

Vitamin U may also support mucosal function in indirect ways. Firstly, Vitamin U yields cysteine, which is the rate-limiting component of glutathione, the master antioxidant that fights oxidative stress. Secondly, the relatively large amount of cysteine required to tether mucin to the epithelial tissue means that extra cysteine in the form of Vitamin U may prove useful. Thirdly, much of the glycans that attach to mucins are themselves sulfated, requiring more sulfur. 

Many people, especially those whose diet is low in the sulfur amino acids methionine and cysteine, have limited antioxidant capacity due to having low levels of glutathione. For those people, alternative sources of sulfur amino acids like Vitamin U are an important alternative source. Drinking freshly-made vegetable juice or taking Vitamin U supplements in combination with the cessation of destructive practices will probably help clear up your current mouth ulcer and help prevent future ulcers.

Vitamin U complements H2 blockers

Summary - H2 blockers are drugs used to reduce stomach acid in people who have pain due to stomach ulcers. Vitamin U in the form of fresh vegetable juice or supplements can be used alongside H2 blockers to speed up the restoration of the protective mucous bilayer.

The human stomach is a very acidic environment. The pH of a correctly-functioning stomach is 1.5 - 3. The acidity of gastric juice is due to hydrochloric acid (HCl), which is produced by parietal cells in the upper parts of the stomach (fundus and cardia). Parietal cells produce acid using enzymes called proton pumps (H+/K+ ATPase), which use the energy derived from the hydrolysis of ATP to pump H+ into the stomach. It is the protons (H+) that cause acidity. 

The parietal cells pump acid into the stomach in response to signal molecules binding receptors. There are numerous kinds of receptors that respond to different stimuli, either positively or negatively. The most important for acid production are the H2 histamine receptors. Protein in food is broken down in the stomach by acid and the enzyme pepsin to form peptides. These peptides stimulate the release of the hormone gastrin from G cells in the stomach and duodenum. Gastrin stimulates the release of histamine from ECL cells. Histamine binds receptors in the base of parietal cells where it stimulates the movement of proton pumps to the apical surface, where they pump acid into the stomach cavity (lumen). This acid accelerates this whole cycle, breaking down more proteins in food by hydrolysis as well as activating pepsin.

H2 blockers bind to the H2 receptors, which stops histamine from binding. If histamine can't bind, the levels of acid in the stomach remain fairly low and the corresponding pH relatively high. (H2 blockers are often referred to as H2 antagonists because they block the binding of histamine without itself stimulating the function of the receptor, an important distinction from agonists). 

H2 blockers were invented in the 1960s and have to a large extent been superseded by proton pump inhibitors due to the latter's more potent acid-suppressing abilities. Commonly used H2 blockers include omeprazole (e.g. Prilosec), famotidine (e.g. Pepcid) and cimetidine (e.g. Tagamet). Ranitidine (e.g. Zantac) was the most prescribed drug in the US during the 1980s, but the FDA has recently banned its sale due to carcinogenic impurities. 

Stomach ulcers and gastroesophageal reflux (GERD) are conditions characterized by pain caused by stomach acid coming into direct contact with the lining of the stomach and esophagus, respectively. Contrary to popular opinion, these conditions are rarely caused by excessive production of stomach acid. In fact, the acidity in the stomach of those with stomach ulcers is typically low (i.e. relatively high pH). GERD is caused by normal stomach acid coming into contact with the esophagus, an organ that is not designed to withstand such exposure. Unlike the stomach, the esophagus is not coated with a protective alkaline mucous bilayer and is very sensitive to contact from even small amounts of gastric juice.

One unfortunate problem with taking H2 blockers for stomach ulcers is that they reduce the secretion of mucin (Ichikawa et al., Diebel et al). So while they reduce pain by reducing the amount of acid produced, they also increase the risk of pain by weakening the mucous bilayer. 

Vitamin U is a nutrient abundant in vegetables and fruit that stimulates the secretion of mucin in the stomach. As fresh vegetables and fruit have been a major component of our diet for a very long time, it is reasonable to conclude that dietary Vitamin U plays an important role in the maintenance of optimal stomach function. 

Can Vitamin U be combined with H2 blockers? 

Considering Vitamin U stimulates mucin secretion and H2 blocker reduce it, one may wonder whether Vitamin U can be taken with H2 blockers to negate the negative effects. The evidence suggests yes. In 2009, Ichikawa et al. showed that co-administration of Vitamin U with famotidine reversed the mucin-blocking effects of famotidine without affecting the acid-suppression effects. These results suggest that Vitamin U can add another level of protection to the gut in those taking H2 blockers.

Considering these findings, drinking fresh vegetable juice daily or taking Vitamin U supplements may help restore your mucous bilayer, ease discomfort and heal your ulcers.

Vitamin U may help combat the ulcergenic effects of NSAIDs

Summary - Taking NSAIDs increases the risk of you developing stomach ulcers by inhibiting your natural protective system. There are several measures you can take to help get rid of stomach ulcers due to NSAIDs -

    1) reduce the dose

    2) change the NSAID to one less irritating 

    3) counteract with other drugs

    4) switch from NSAIDs to other pain relievers

    4) take Vitamin U

Vitamin U in the form of fresh vegetable juice or supplements can be used in combination with other measures to combat ulcers. However, Vitamin U will not counteract all of these negative effects as NSAIDs are powerful drugs. If you have an ulcer and are taking NSAIDs, talk to your doctor as there may be a solution.

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Stomach ulcers result from an imbalance between protective and destructive factors. There are several destructive factors including infection with Helicobacter pylori, overproduction of stomach acid, overeating salt, alcohol and sugar, and taking NSAIDs. Ulcers often result from a combination of these factors. The focus of this post is the role NSAIDs play in causing your ulcer.

NSAIDs (Non-Steroidal Anti-Inflammatory Drugs) are widely used to reduce pain and inflammation. The most commonly taken NSAIDs are aspirin (e.g. Bayer), ibuprofen (e.g. Advil, Motrin), naproxen (e.g. Aleve), mefenamic acid (e.g. Ponstal), diclofenac (e.g. Voltaren), piroxicam (e.g. Feldene). A more complete list is linked here.

NSAIDs reduce inflammation and pain by inhibiting the enzyme COX-2. COX-2 is part of your body's inflammatory response. A certain amount of inflammation is good and necessary for healing. However, too much inflammation causes pain and further damage, which is why we take NSAIDs.

How do NSAIDs cause stomach ulcers? 

In addition to inhibiting COX-2, NSAIDs also inhibit the related enzyme COX-1, albeit to a lesser extent. COX-1 catalyzes the same reaction as COX-2, that being the synthesis of prostaglandins from arachidonic acid. However, COX-1 and COX-2 have different functions due to their different expression patterns. COX-1 is expressed throughout the body continuously, in contrast to COX-2 which is only expressed during inflammation. In the gastrointestinal tract, the continuous production of prostaglandin E2 catalyzed by COX-1 stimulates mucin production. Mucin forms a mucus bilayer in the stomach that protects the lining against corrosive agents such as stomach acid. The inadvertent inhibition of COX-1 by NSAIDs reduces mucin production, leaving the stomach wall vulnerable. To compound the problem, NSAIDs also have a multitude of other negative effects including increasing the production of stomach acid and increasing oxidative stress (Matsui et al, 2011), which for people with an ulcer will cause more discomfort and make the ulcer worse.

Fortunately, not all NSAIDs inhibit COX-1 equally. Some NSAIDs are more ulcergenic than others. For example, some of the early NSAIDs like aspirin are notorious for upsetting the stomach. More recently, scientists have developed NSAIDs that don't inhibit COX-1 as much as their predecessors and while still inhibiting COX-2 strongly, so-called COX-2 inhibitors, e.g. celecoxib (Celebrex). Consequently, these newer NSAIDs may reduce ulcer formation while still providing pain relief elsewhere in your body. If you have an ulcer and are taking NSAIDs, talk to your doctor about alterative NSAIDs. Be warned that these new generation NSAIDs are not without other side effects.

 

Can Vitamin U help?

The short answer is probably. Vitamin U is a naturally-occurring nutrient found in all vegetables, fruit and grains. One of its functions is to stimulate the secretion of mucin onto the walls of the stomach. How it does this is not well understood, but it is doesn't seem to have anything to do with COX-1/2 and prostaglandins. As a result, Vitamin U can be used to counteract the mucus-depleting effects of NSAIDs.

Are there any studies supporting the use of Vitamin U to counteract the ulcergenic effects of  NSAIDs?

Yes. In 1993, Salim reported the findings of a clinical trial in which Vitamin U was found to accelerate healing of patients hospitalized for erosive gastritis (bleeding from the stomach) caused by NSAID intake. Erosive gastritis is a common precursor to stomach ulcers. The majority of the patients had been taking NSAIDs for either osteo- or rheumatoid arthritis for less than 3 months. The NSAIDs used included diclofenac, piroxicam, mefenamic acid, naproxen and ibuprofen. The double-blind study found that the patients who received 4 x 500 mg of Vitamin U (DL-methylmethionine sulfonium chloride) per day had significantly less bleeding than the negative controls. Similarly to Vitamin U, patients given the sulfhydryl amino acid L-cysteine were also found to have significantly reduced bleeding, demonstrating the action of Vitamin U is likely via its conversion to a sulfhydryl. Endoscopies performed two days after treatment revealed significantly greater healing in those who were given either Vitamin U or cysteine. Of the 57 patients who were not treated with either Vitamin U or cysteine, 4 died from their condition. In contrast, there were no fatalities in those who were treated with either of these compounds. 

Currently, it is standard medical practice in cases of erosive gastritis to get the patient to stop taking NSAIDs, or at least take less irritating types, and/or to suppress stomach acid production. For a person who is taking NSAIDs for arthritic pain, reducing the amount of NSAIDs taken is clearly not desirable. Switching to less irritating NSAIDs is an option. Talk to your doctor.

Suppressing acid production will reduce irritation of the stomach, but at what cost? Unless you are producing too much stomach acid (a rare condition), reducing stomach acid will have side effects. The major role of stomach acid is to digest protein in our food. Dietary protein must be unraveled then enzymatically chopped up by pepsin to produce peptides. Without an acidic environment, protein passes through to the duodenum half digested. Enzymes in the duodenum that further digest protein into tiny peptides or amino acids can only do so much, leaving a significant portion of protein to pass into the colon. Consequently, low stomach acid can result in inadequate protein absorption as well as colonic fermentation (smelly gas). Furthermore, long-term suppression of stomach acid production promotes the growth of Helicobacter pylori, a known carcinogen (more).

While the results of this clinical trial are promising, Vitamin U is not infinitely powerful. There is only a certain amount Vitamin U can do to reverse or prevent damaged induced by NSAIDs. Large doses of NSAIDs will probably damage the stomach faster than Vitamin U can reverse this damage. However, these findings suggest that Vitamin U may be of some use in counteracting some of the negative effects caused by NSAIDs. Drinking freshly-made vegetable juice on a daily basis provides Vitamin U as well as other beneficial nutrients such as folate. 

Vitamin U and acne, dandruff and eczema

Acne, dandruff and eczema are skin conditions the origins of which are often idiosyncratic and mysterious. However, one characteristic shared by all three conditions is low glutathione levels. Glutathione is by far the most important antioxidant in the human body, yet we absorb little of it from our food- that's why our body makes it. 

There are three main causes of low glutathione - 

1. A medical condition that drains large amounts of glutathione

2. A genetic block that prevents the biosynthesis or regeneration of glutathione

3. Not enough glutathione precursors in our diet

Identifying the root cause of your skin condition is an important first step in the healing process. However, this is easier said than done. Often we just don't know why these conditions happen. Sometimes they can break out suddenly and worsen quickly, particularly under stress. At other times, symptoms can persist chronically for years.

Irrespective of the root cause, restoring your glutathione levels is a vital part of this rebalancing act. Glutathione is a tripeptide comprised of cysteine, glutamate and glycine. Of these amino acids, cysteine is most commonly in short supply. If glutathione levels are low due to dietary factors, it is usually due to a shortage of cysteine. Cysteine is found in protein, especially that derived from animals. Cysteine is also made from methionine, again abundant in animal proteins. These sulfur amino acids are also plentiful in grain proteins. However, some people find that meat/dairy/grain are inflammatory for other reasons like hormones or allergens. 

Vitamin U is S-methylmethionine, a soluble nutrient abundant in vegetables and fruit that is converted into methionine by the enzyme BHMT2. There have not been any direct studies into whether Vitamin U has any effect on these three conditions, whether taken internally in the diet or as a supplement, or when applied topically as an active component of a lotion. However, taking Vitamin U can help restore glutathione levels which are low in the tissues affected by acne, dandruff and eczema, so it is quite likely that increasing your intake of Vitamin U will help with these conditions, especially in combination with the identification and removal of triggers of these conditions in you. 

A glass of freshly-made vegetable juice every day is an excellent way to boost your Vitamin U intake along with a slew of vitamins and minerals essential for good skin health.

Food sources of Vitamin U

Vitamin U is produced by all flowering plants (angiosperms). Pretty much any vegetable and fruit we eat comes from a flowering plant, so pretty much anything we eat that comes from a plant has some Vitamin U, at least before it is processed. In fact, the only plants or plant-like organisms that don't make Vitamin U are conifers, ferns, mosses, algae and fungi.

In general, vegetables belonging to the Brassicacea family are the best source of Vitamin U. This family includes cabbages, kale, broccoli, kohlrabi, collards and turnips. Other vegetables such as spinach, asparagus and celery also produce abundant amounts of Vitamin U. Fruit are also good sources, but not as good as vegetables. In general, there is more Vitamin U in the leaves and stalks than in the fruit, roots and seeds. Grains seem to have little when fresh, but Vitamin U is made during sprouting. Animal products have little to no Vitamin U as it is not synthesized nor stored in significant amounts in animals.

Several studies have measured the concentration of Vitamin U in various foods. Tables listing some of these results are included below. Many factors affect the amount of Vitamin U in a given vegetable. These factors include storage conditions, storage duration, harvest time, regional variations and species variations. For example, cabbages have more Vitamin U during spring and summer when freshly harvested, with the nutrient slowly degrading with storage. After six months in the fridge, the concentration drops by one third, with faster losses at room temperature. In contrast, when barley is germinated for making beer, the amount of Vitamin U rises over time, affecting the flavor of the end product. In some cases, there are varieties of fruit that produce less Vitamin U. Oranges that have been selected to produce less Vitamin U are used to make juice because Vitamin U breaks down with extended storage and pasteurisation to form dimethyl sulfide, a compound that negatively affects the taste of the product (Sakamoto et al https://pubmed.ncbi.nlm.nih.gov/8987599/.) 

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Song, Ji-Hoon, Hae-Rim Lee, and Soon-Mi Shim. 2016. “Determination of S-Methyl-L-Methionine (SMM) from Brassicaceae Family Vegetables and Characterization of the Intestinal Transport of SMM by Caco-2 Cells.” Journal of Food Science 82 (1): 36–43.

https://www.ncbi.nlm.nih.gov/pubmed/27883364

Food (Vitamin U concentration (mg/kg dry weight))

Radish (129-139)
Cabbage (535)
Kimchi cabbage (89-116)
Broccoli (150-350)

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Scherb, J., Kreissl, J., Haupt, S. & Schieberle, P. Quantitation of S-methylmethionine in raw vegetables and green malt by a stable isotope dilution assay using LC-MS/MS: comparison with dimethyl sulfide formation after heat treatment. J. Agric. Food Chem. 57, 9091–9096 (2009).

https://www.ncbi.nlm.nih.gov/pubmed/19754146

Food (Vitamin U concentration (mg/kg wet weight))

Celery (176)
Kohlrabi (124)
Leek (94)
Beetroot (89)
Cabbage (81)
White asparagus - Peru spears (161)
White asparagus - Peru stalks (86)
White asparagus - Germany spears (252)
White asparagus - Germany stalks (68)
White asparagus - Greece spears (113)
White asparagus - Greece stalks (101)
Green asparagus - Peru spears (234)
Green asparagus - Peru stalks (109)
Green asparagus - Germany spears (94)
Green asparagus - Germany stalks (53)
Green asparagus - Mexico spears (134)
Green asparagus - Mexico stalks (64)
Tomato (2.8)
Commercial orange juice (0.9)
Commercial strawberry juice (1.8)

Freshly-squeezed orange juice (1.2)
Barley - unprocessed (0.9)
Barley - after 4 days of germination (24)

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Kim, G.-H. Determination of Vitamin U in Food Plants. Food Sci. Technol. Res. 9, 316–319 (2003).

https://www.jstage.jst.go.jp/article/fstr/9/4/9_4_316/_pdf

Food (Vitamin U concentration (mg/100g dry weight))

Spinach (45.2)
Pak-choy (34.3)
Kale (23.4)

Sumssukbujaengi - a wild korean leafy vegetable (19.8)
Leaf mustard (19.6)
Bud of aralia (19.3)
Broccoli (18.9)
Asparagus (18.7)
Sanmanul - a wild garlic (14.4)
Crown daisy (11.1)
Burdock (11.0)
Celery (8.3)
Komchi (4.7)
Wasabi (4.7)
Chamchi - a wild korean plant (4.0)
Shepherd’s purse (3.4)
Garlic (2.8)
Onion (2.7)
Green onion (2.6)
Laver (2.2)
Nurukchi (0.8)
Green tea (0.1)
Ginger (not detected)
Seaweed (not detected)
Red chilli (not detected)
Miscellaneous wild korean vegetables (not detected)

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Kovatscheva, E. G. & Popova, J. G. [S-Methylmethionine content in plant and animal tissues and stability during storage]. Nahrung 21, 465–472 (1977).

https://www.ncbi.nlm.nih.gov/pubmed/927476

Food (Vitamin U concentration (mg/kg wet weight))

Cabbage (50-104)
Kohlrabi (81-110)

Turnip (51-72)
Tomato (45-83)

Celery (38-78)

Leeks (66-75)
Garlic leaves (44-64)

Beet (22-37)
Raspberries (27)
Strawberries (14-25)

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Other references

1. 100-600 mg/kg dry weight (Bourgis et al and references within.)

  

https://pubmed.ncbi.nlm.nih.gov/10449582/

How much Vitamin U do you need to heal ulcers?

Summary - Hospitalized peptic ulcer patients were cured by drinking cabbage juice containing 42-162 mg of Vitamin U per day for 7-10 days when eating a bland diet and getting bed rest.

A recommended dietary allowance (RDA) for Vitamin U has not been established by the US National Academy of Medicine. However, an estimate of how much Vitamin U you could try can be made by calculating the amount of Vitamin U used in Dr Cheney's studies. Cheney healed ulcer patients with 1 liter of cabbage juice per day over 7-10 days. At the time, Cheney didn't know exactly how much Vitamin U was in the juice. He just knew this much juice in combination with a bland diet and rest was enough. In more recent years, Vitamin U was identified as S-methylmethionine, and there have been several studies in which the amount of this amino acid has been quantified in cabbages. From these studies we can approximate how much supplemental Vitamin U is required to heal ulcers.

In 2003, Kim reported 26-46 mg/100 g of dry weight, which given that a cabbage is ~92% water, works out as 21-37 mg/kg of fresh cabbage. In 2009, Scherb and others found that cabbages have 81 mg of Vitamin U per kg of fresh cabbage. In 2017, Song et al determined that cabbages contain 50 mg/kg of Vitamin U. So we can estimate that there is roughly 21-81 mg Vitamin U per kg of cabbage.

Why this variation? There are several probable explanations. One possibility is that different parts of the cabbage were analyzed by the various researchers. Kim found that the concentration of Vitamin U in the core, middle and outside leaves varied by 2-fold, with the middle leaves having the most. Scherb found that vegetables grown in different countries had different amounts of Vitamin U, suggesting that some of the variation may be due to geography. Another possibility is that the cabbages were not all of equal freshness or picked at the same time of the year. In an older study, Kovatscheva and Popova noted that cabbages lose 62% of their Vitamin U during six months of storage without refrigeration and 34% with refrigeration. Cabbages harvested in spring /summer have the highest Vitamin U content. Finally, it is possible that the various extraction procedures used in the studies resulted in slightly different yields of Vitamin U. 

1 liter of juice is typically extracted from about 2 kg of cabbage. Cheney arrived at 1 liter from prior studies in which various volumes of cabbage juice were given to guinea pigs subjected to chemically-induced ulceration. 100% of the guinea pigs responded to the guinea-pig equivalent of 720 ml of juice. The volume used in the clinical study was rounded up to 1 liter to take into consideration variations in body weight and unexpected factors. 

Taking all this data together, it can be estimated that 1 litre of juice contains 42-162 mg of Vitamin U, which probably represents a maximum daily requirement.

Issues with drinking 1 liter of cabbage juice

In the 1940s and 1950s, Stanford doctor Garnett Cheney healed his peptic ulcer patients by having them drink 1 liter of cabbage juice daily for a couple of weeks. Cabbage juice is not only rich in Vitamin U, but is also rich in folate, vitamin C, vitamin K and potassium among other nutrients. It's well worth trying this treatment for peptic ulcers rather than taking supplements. However, there may be some drawbacks. 

Taste

Many people find cabbage juice to be distasteful. The chemicals responsible for this bitterness are called isothiocyanates. These compounds are produced in the cabbage when the leaves are physically damaged during chewing or juicing. Glucosinolates are enzymatically converted by myrosinases to form the bitter isothiocyanates. Some people are lucky in that can't taste isothiocyanates all that well so they can readily drink cabbage juice. One way to prevent the formation of isothiocyanates is by boiling unbroken cabbage leaves before juicing to kill the enzymes. That's why boiled cabbage has a mild taste compared to raw cabbage. However, the problem with this approach is that Vitamin U is also unstable to boiling, negating any beneficial effects. 

One solution is to drink the one liter of juice as 4 cups throughout the day instead of all at once. Another solution is to mix in better tasting vegetables that contain Vitamin U such as celery. Cheney used mixes containing a 3:1 cabbage-to-celery to good effect.


Gas

A second issue is gas. Cabbage has a significant amount of raffinose, a sugar that is notorious for producing gas when eaten. The human small intestine lacks the enzyme required for the digestion of raffinose. Unfortunately, some types of bacteria in our large intestine do have such an enzyme and will ferment raffinose quite readily to form gases. These gases produced in the colon have only one way out and will cause bloating and discomfort until discharged. Ingesting one liter of cabbage juice will cause problems for most people. In principle, a possible solution is to treat the cabbage juice with Beano before drinking it. Beano is basically alpha-galactosidase, an enzyme that will break down raffinose into sucrose and galactose, both of which we can easily break down and absorb. I'm not sure whether anyone has tested this idea, though taking Beano along with the juice as recommended should help. Drinking several cups spread throughout the day should also reduce bloating.


Smell

A third issue is smell. Fresh cabbage juice smells fine - old juice does not. Vitamin U is degraded to homoserine and dimethylsulfide by enzymes found in cabbage. Dimethylsulfide has a disagreeable sulfur odor a little like that found in rotten eggs, though without the toxicity. These enzymes don't work as quickly as myrosinases, but leaving cabbage juice sitting around for a few hours will allow plenty of time for dimethylsulfide to form. Putting the juice in the fridge will slow the reaction somewhat, but after 24 h the juice still tastes terrible. Even if a person could stomach the old juice, there would not be much point as by this stage most of the Vitamin U would have been degraded. Cabbages also have other compounds that contain sulfur that when broken down produce disagreeable odors. The solution is to drink cabbage juice fresh before it has had a chance to go off.