Cucumbers contain a broad range of vitamins, though most in modest amounts. The standout is vitamin K, which provides about 7% of your daily value in a single half-cup serving with the skin on. Beyond that, cucumbers supply vitamin C, several B vitamins (B1, B5, B6, and folate), vitamin A, and small amounts of vitamin E. They’re not a vitamin powerhouse compared to leafy greens, but their extremely high water content (about 96%, the highest of any food) makes them a hydrating way to pick up a variety of micronutrients with almost no calories.
Vitamin K: The Biggest Contributor
Vitamin K is the nutrient cucumbers deliver most meaningfully. A half-cup of unpeeled cucumber provides roughly 8.5 micrograms, or about 7% of the daily value. That won’t cover your needs on its own, but it adds up when cucumbers are part of a salad or snack rotation alongside other vegetables.
Your body uses vitamin K to produce four of the 13 proteins required for blood clotting, which is why it’s essential for wound healing. It also helps build osteocalcin, a protein that maintains bone strength. Getting consistent vitamin K from vegetables like cucumbers supports both of these processes over time.
B Vitamins and Folate
Cucumbers contain a handful of B vitamins, each in small but real quantities. Pantothenic acid (B5) is the most notable, delivering about 6% of the daily value per cup of peeled cucumber. Folate (B9) comes in at around 5% of the daily value per cup, and vitamin B6 provides about 4%. Thiamin (B1) and riboflavin (B2) are present too, each around 1 to 3% of the daily value depending on whether the skin is left on.
These B vitamins play roles in energy metabolism and cell function. Folate is especially important for anyone who is pregnant or planning to become pregnant, as it supports healthy cell division. Cucumbers alone won’t meet your folate needs, but they contribute to the total you get across a full day of eating.
Vitamin C and Vitamin A
A cup of peeled cucumber contains about 4.3 milligrams of vitamin C, roughly 5% of the daily value. With the skin on, that drops to about 1.5 milligrams per half-cup. Either way, it’s a small contribution compared to citrus fruits or bell peppers, but it’s there. Vitamin C supports immune function and acts as an antioxidant, protecting cells from damage.
Vitamin A shows up mostly through beta-carotene, the pigment your body converts into the active form. A cup of peeled cucumber provides about 5.3 micrograms of vitamin A (around 1% of the daily value), along with small amounts of other carotenoids like alpha-carotene and beta-cryptoxanthin. These are present in trace levels, so cucumbers aren’t a meaningful source of vitamin A the way carrots or sweet potatoes are.
Vitamin E and Antioxidant Compounds
Vitamin E appears in cucumbers only in trace amounts, less than 1% of the daily value per serving. It’s functionally negligible.
That said, cucumbers contain other antioxidant compounds beyond their vitamin content. These include flavonoids, phenolic compounds, and beta-carotene, all of which help neutralize free radicals. Cucumbers also contain a class of compounds called cucurbitacins, which are being studied for various biological effects. These aren’t vitamins in the traditional sense, but they’re part of the nutritional picture.
Why Leaving the Skin On Matters
Peeling a cucumber changes its nutritional profile more than you might expect. Comparing USDA data for peeled versus unpeeled cucumber, the skin contributes meaningfully to several nutrients. Unpeeled cucumber contains more vitamin K, more beta-carotene, and more of the carotenoid pigments lutein and zeaxanthin, which support eye health.
The differences aren’t dramatic for a single serving, but they’re consistent across nearly every vitamin and mineral. Folate, for example, jumps from about 3.6 micrograms in a half-cup of unpeeled cucumber to 18.6 micrograms in a full cup of peeled cucumber, but proportionally, keeping the skin on gives you more nutrients per bite. Vitamin C follows the same pattern. If you don’t mind the texture, eating cucumbers unpeeled is the better nutritional choice.
Key Minerals Alongside the Vitamins
While the search is about vitamins, the mineral content is worth knowing since it rounds out the picture. Cucumbers are a decent source of potassium, with about 181 milligrams per cup (peeled), covering roughly 4% of the daily value. Potassium helps regulate blood pressure and fluid balance, which pairs well with cucumber’s high water content for hydration.
Magnesium comes in at about 16 milligrams per cup (4% DV), supporting muscle and nerve function. Copper provides a surprising 10% of the daily value in a cup of peeled cucumber. Smaller amounts of calcium, iron, zinc, phosphorus, and manganese are also present. None of these are in large doses, but cucumbers deliver a wide spread of trace minerals alongside their vitamin content, making them a useful part of a varied diet rather than a standout source of any single nutrient.