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/

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.

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.

References

https://www.ncbi.nlm.nih.gov/pubmed/18104715

https://www.ncbi.nlm.nih.gov/pubmed/10719747

https://pubs.acs.org/doi/pdf/10.1021/ja01630a032