Vitamin U - A possible natural alternative to N-acetylcysteine (NAC)

The current coronavirus pandemic has changed our lives forever. One of the hallmarks of coronavirus (COVID-19) infection is acute oxidative stress, and as a consequence, life-threatening damage to the endothelial cells lining our blood vessels. It has been proposed that to counter this oxidative stress one may take N-acetylcysteine (NAC) as part of an array of treatment options that may allay this frightening illness.

Dr Roger Seheult 

Dr Chris Martenson 

N-acetylcysteine (NAC) is a popular supplement invented in the 1960s used primarily to optimize glutathione levels. It is normally used in hospitals in emergency situations to treat overdoses of acetaminophen (e.g. Tylenol), which results in an acute and deadly shortage of glutathione in the liver. When acetaminophen is taken as directed, it is safely metabolized by the liver enzymatically. A small amount is oxidized to form N-acetyl-p-benzoquinone imine (NAPQI), which is highly toxic. NAPQI is detoxified in the liver by conjugation with glutathione. However, in overdoses of acetaminophen, NAPQI levels rise dramatically as the regular detoxification processes are overwhelmed. The liver literally cannot regenerate glutathione fast enough to quench the toxic NAPQI. Extensive liver damage and death often ensues. NAC helps by being quickly converted into cysteine, which enables the production of fresh glutathione.

NAC is also sold as a dietary supplement as a means of optimizing glutathione levels on an everyday basis. Glutathione is the master antioxidant in the human body, responsible for detoxifying compounds in the liver as well as reacting with reactive oxygen species that are harmful in large amounts. Glutathione differs significantly to other antioxidants (such as Vitamin C) in that it is made by humans. Our body makes glutathione from three amino acids - glutamate, cysteine and glycine. Levels can get low when our diet is short of these amino acids. The rate-limiting amino acid is usually cysteine, which the body can obtain from the diet following the digestion of protein, and also enzymatically from methionine. When cysteine levels in the diet are inadequate, glutathione levels in the body become inadequate, resulting in general inflammation. Most chronic illnesses are characterized as having low glutathione levels and restoring glutathione levels may help reduce inflammation, if not actually reverse the underlying problem. 

Vitamin U (S-methylmethionine) is a naturally abundant nutrient found in vegetables and fruits, especially cruciferous (e.g. cabbage, kale) and stalky vegetables (e.g. celery, asparagus). Like NAC, one of the functions of Vitamin U is to facilitate glutathione biosynthesis via its conversion to cysteine. Its use as an alternative to NAC in the treatment of acetaminophen overdose has been proposed and remains under investigation. One of the advantages of Vitamin U is that unlike NAC, Vitamin U is already found in many of the foods available in the fresh market, and is therefore unlikely to cause side effects. 

While Vitamin U should not be used in an emergency situation as its efficacy has not been tested, Vitamin U may serve as an alternative to NAC by those looking for a natural choice to boost their glutathione levels and restore their redox balance on an everyday basis. 

It should be emphasized that any possible overdose of paracetamol/acetaminophen should be treated at a hospital by a doctor and not self-treated with NAC or Vitamin U. 

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 


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.

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

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

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).

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)


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

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)

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

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)


Other references

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

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. 


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.


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.


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.

Cabbage Juice Heals Peptic Ulcers

In the 1940s and 1950s, Dr Garnett Cheney from Stanford discovered that having his peptic ulcer patients drink one liter of fresh cabbage juice every day healed their stomach and duodenal ulcers 3-6 times faster than a bland diet alone. Chronic ulcers disappeared in 1-2 weeks depending on their severity. Dr Cheney was of the opinion that peptic ulcers resulted from a deficiency of a nutritional factor he termed Vitamin U, later identified as the amino acid S-methylmethionine. While cabbages are a particularly rich source of Vitamin U, Cheney found that all raw vegetables, and to a lesser extent, fruit, contain Vitamin U. In addition to healing existing ulcers, Dr Cheney found that Vitamin U also prevented the formation of new ulcers.

Why do we get ulcers? Ulcers result from an imbalance in the digestive system between protective and destructive factors. An alkaline bilayer of mucus containing mucin protects the wall of the digestive tract from harsh elements such as stomach acid, infection by bacteria living in the digestive system, NSAIDs, and dietary factors like high salt and alcohol. In modern times, NSAIDs increasingly contribute to ulcer formation by
 inhibiting the mucus-stimulating function of our body's prostaglandins. When the mucus layer is depleted, these harsh elements irritate the epithelial cells lining the digestive tract causing inflammation and enabling deep infection. 

Ulcers are usually treated with proton pump inhibitors or 
H2 blockers to reduce acid production, antibiotics to treat bacterial infections (particularly Helicobacter pylori in the stomach), antacids to neutralize acid, and mucosal protectants such as prostaglandin mimics. Unfortunately, these only provide a temporary solution to the problem. Ulcers return soon after cessation of treatment. Excessive stomach acid is usually not the root problem, nor is H. pylori infection. Most people with ulcers produce a normal amount of stomach acid, and half the world's population has H. pylori yet remain ulcer-free. These facts indicate that while acid and infection contribute to the formation of ulcers, other factors are at play.

Given the findings of Dr Cheney, it's easy to see that eating a balanced diet rich in sources of Vitamin U is beneficial. But how does Vitamin U work? In later studies, it was shown that Vitamin U has three properties that help maintain a healthy gut.

  1. Stimulating the release of mucin into the mucus layer, thereby protecting the walls from acid and bacterial infection (most important).
  2. Reducing inflammation by acting as a precursor to glutathione, the master antioxidant of the human body via its conversion to cysteine.
  3. Coordinating with other nutrients such as methionine, folate, B12, betaine, choline, SAMe and B6 to supply vital methyl groups required for optimal health.

Increasing the Vitamin U content of one's diet in combination with reducing the intake of foods that deplete the protective mucus layer has been shown to improve ulcerative conditions in the digestive system. A diet rich in fresh vegetables, vegetable juice and fruit, and low in salt, alcohol and sugars is a good approach for restoring the mucus bilayer in most patients.