Vitamin U is a term introduced in the early 1950s to identify a compound in cabbage juice. Despite its name, vitamin U is not a true vitamin but rather a derivative of the amino acid methionine (1).

Examples of methionine derivatives often called vitamin U include S-methylmethionine (SMM), methylmethionine sulfonium (SMM), and 3-amino-3-carboxypropyl dimethylsulfonium.

Vitamin U is available not only as a supplement but also found naturally in various foods, particularly cruciferous vegetables like cabbage, broccoli, Brussel sprouts, and kale (1).

Plus, cosmetics companies may add it to certain creams, serums, face masks, and other products.

cabbages on a cutting boardShare on Pinterest
Brett Stevens/Offset Images

Vitamin U is most often advertised as a treatment for stomach ulcers, though it’s also touted to improve digestion, strengthen immune health, protect against food allergies, lower cholesterol, and hasten wound healing.

However, research is limited. Only a handful of these benefits are currently backed by science.

May help stomach ulcers heal

When vitamin U was initially researched in the 1950s, some studies suggested that drinking 1 quart (945 mL) of cabbage juice daily helped gut ulcers heal 4–5 times faster than the standard anti-ulcer therapy available at the time (2, 3, 4).

Yet, researchers couldn’t confirm whether these effects were due to vitamin U or multiple nutrients.

Since then, few studies have examined the topic. To determine whether vitamin U is truly effective against ulcers, more research is needed.

May protect your lungs, liver, and kidneys

Vitamin U may safeguard your lungs, liver, and kidneys from damage.

In an animal study, vitamin U helped reverse some of the liver damage caused by the common anti-seizure medication valproic acid (5).

In another study, rats given vitamin U experienced less severe kidney damage after receiving valproic acid than those given no vitamin U. This substance also appeared to reduce markers of inflammation (6).

Animal research further suggests that vitamin U may help reduce lung damage resulting from epileptic seizures (7).

Still, human studies are necessary.

May lower cholesterol and triglyceride levels

While some evidence supports the notion that vitamin U supplements help reduce cholesterol and triglyceride levels, evidence remains weak.

For instance, one test-tube study suggests that vitamin U may prevent the creation of fat cells and reduce triglyceride levels, but few relevant human studies exist (8).

In an 8-week study, people given 1.5 grams of vitamin U per day experienced no change in triglyceride levels, higher HDL (good) cholesterol, and an almost 10% reduction in total cholesterol. Yet, this study is very dated and included few participants (9).

As such, more human research is needed.

May aid wound healing and skin protection

Vitamin U may offer some protection against the sun’s ultraviolet (UV) rays, as well as expedite wound healing.

Test-tube and animal studies report that applying vitamin U directly to wounds may speed wound closure. Moreover, vitamin U appears to protect against burns and other damage caused by UV rays (10, 11, 12, 13).

Based on these findings, some researchers suggest that certain cosmetics should be formulated with vitamin U.

Yet, a lack of human research means that further studies are necessary.

Vitamin U is likely safe when eaten directly from whole foods. However, little is known about its safety or potential side effects in supplement form.

Therefore, it’s likely safest to rely on vitamin-U-rich foods like cabbage, broccoli, Brussel sprouts, and kale to boost your intake of this compound.

According to the European Chemicals Agency, vitamin U may cause eye, skin, or lung irritation if it comes into direct contact with these organs. Thus, you may want to use caution with skin care products containing this compound (14).

Due to limited research, vitamin U dosage recommendations haven’t been established.

One human study utilized 1.5 grams of vitamin U for 8 weeks (9).

However, this study is dated and didn’t test any alternative dosages or durations. As such, more research is needed.

So far, there have been no reported cases of vitamin U overdose.

An overdose is very unlikely if you consume this compound exclusively from whole foods. Keep in mind that studies have not yet examined the effects of high vitamin U intake from supplements.

This makes it impossible to rule out the possibility of a vitamin U overdose.

As such, more research is needed to understand whether an overdose is possible, the signs and symptoms associated with it, and the safest way to treat it.

There isn’t enough scientific information available to determine whether vitamin U interacts with any other supplements or drugs.

People taking other supplements or medicines should discuss vitamin U with their healthcare provider before trying it.

Vitamin U manufacturers typically recommend that vitamin U supplements or products be stored in a dry, cool area away from direct sunlight.

Products containing this substance may also be refrigerated, though this isn’t necessary.

Vitamin-U-rich foods like cabbage, broccoli, Brussel sprouts, and kale are widely considered safe to eat during pregnancy and breastfeeding.

Yet, little is known about the safety of vitamin U in supplement form. Therefore, you should consider avoiding these supplements if you’re pregnant or breastfeeding.

Foods naturally rich in vitamin U, such as cruciferous veggies, are generally considered safe for most people. However, little is known about the safety of vitamin U supplements for any specific populations.

Until more research is available, those interested in increasing their vitamin U intake should do so through foods rather than supplements.

There aren’t any known direct alternatives to vitamin U. More research would be needed to identify them.