Spinach: Nutrition Facts, Health Benefits, and the Most Vitamin K-Dense Leafy Green Available

Spinach is one of the most nutrient-dense foods on earth by almost any measure. At just 23 calories per 100g cooked, it provides 411% of daily Vitamin K, 58% of Vitamin A, 41% of manganese, 37% of folate, 21% of magnesium, 20% of iron, 19% of copper, and 14% of Vitamin E — a spread of vitamins and minerals that very few foods can match at this calorie level. Understanding what those figures mean — including the honest caveats around spinach’s iron and calcium — is what makes this page genuinely useful rather than just impressive-looking.

Spinach Nutrition Facts (per 100g, cooked)

USDA’s figures for fresh spinach, boiled and drained, without salt. The sodium is naturally present in spinach.

Spinach Nutrition Facts (per 180g serving — approximately one cup cooked)

Cooking shrinks spinach dramatically — a large bag of raw leaves wilts down to just a cup or two:

A single cup of cooked spinach provides 740% of daily Vitamin K and more than a full day’s Vitamin A for just 41 calories — one of the most remarkable nutrient-to-calorie ratios of any food in this collection.

Vitamins in Spinach (per 100g, cooked)

Multiple standouts: Spinach’s vitamin profile at 23 calories per 100g is genuinely outstanding. Vitamin K at 411% DV is one of the highest figures of any food — more than four times the daily requirement in 100g. Vitamin A at 58% DV — from beta-carotene rather than preformed retinol — supports vision, immune function, and healthy skin and mucous membranes. Folate at 37% DV supports DNA synthesis and red blood cell formation, and riboflavin (18% DV), Vitamin E (14% DV), and B6 (14% DV) round out an exceptional vitamin profile.

Minerals in Spinach (per 100g, cooked)

Multiple standouts: Manganese at 41% DV supports bone formation and the MnSOD mitochondrial antioxidant enzyme. Magnesium at 21% DV is involved in hundreds of enzyme reactions, including energy (ATP) production. Iron (20% DV) and copper (19% DV) work together — copper is needed for the body to use iron properly. Potassium (466mg per 100g) supports blood pressure regulation. Spinach’s iron and calcium come with important absorption caveats, covered below.

Fresh vs Frozen Spinach (per 100g, boiled)

Frozen spinach is a convenient, affordable option that’s slightly more concentrated — more fiber, Vitamin K, and Vitamin A per 100g in USDA’s data — though it has less Vitamin C, folate, and iron than fresh. Both are excellent choices.

Vitamin K at 411% DV: Spinach’s Most Extraordinary Figure

This deserves explanation, because 411% of a daily requirement in a 23-calorie food is genuinely unusual.

Vitamin K comes in two main forms. Spinach provides Vitamin K1 (phylloquinone) — the plant form, concentrated in green leaves, where it plays a role in photosynthesis.

In the body, Vitamin K has two important jobs:

Blood clotting — Vitamin K is needed to activate clotting factors II, VII, IX, and X, along with proteins C and S, in the liver. Without enough Vitamin K, these proteins can’t work properly and blood doesn’t clot normally.

Bone and blood vessel health — Vitamin K activates osteocalcin, a protein that helps bind calcium into bone, and matrix Gla protein (MGP), which helps prevent calcium from building up in artery walls. Low Vitamin K intake has been associated with lower bone density in observational studies; the evidence on artery calcification is strongest for Vitamin K2 from animal and fermented foods rather than the K1 in leafy greens.

Practical note for anyone on warfarin: Vitamin K counteracts warfarin, a blood-thinning medication. People taking warfarin don’t need to avoid spinach, but they should keep their Vitamin K intake consistent — eating similar amounts from week to week rather than making sudden large changes — and talk to their doctor before changing their diet.

Vitamin A: The Hidden Beta-Carotene

Spinach’s 58% DV of Vitamin A per 100g cooked comes from beta-carotene — an orange pigment hidden in spinach by the much larger amount of green chlorophyll. Beta-carotene is a provitamin A: the body converts it to retinol, the active form of Vitamin A, as needed. For beta-carotene in food, about 12µg provides 1µg of Vitamin A activity, which the “RAE” figure above already accounts for.

This differs in important ways from the preformed Vitamin A in animal foods:

No toxicity risk — unlike preformed retinol from liver or supplements, beta-carotene from food doesn’t cause Vitamin A toxicity, because the body converts less of it when its stores are adequate.

Fat helps absorption — beta-carotene is fat-soluble, so eating spinach with a little fat — olive oil in a sauté, avocado in a salad, or eggs in an omelette — substantially improves how much is absorbed. This is the most practical tip for getting the most Vitamin A from spinach.

Cooking helps too — cooking softens the plant cell walls that hold beta-carotene in raw spinach, making more of it available for absorption.

The Iron Question: What Spinach Actually Delivers

Spinach’s iron has been famous, then famously “debunked,” then partly rehabilitated. The full story is worth telling accurately.

The Popeye Myth and the “Decimal Point” Myth

Popeye, who first downed spinach for strength in the early 1930s, did a lot to cement spinach’s reputation as a strength food. You may also have heard that spinach’s iron reputation came from an 1870s decimal-point error that recorded 35mg of iron instead of 3.5mg. That story is itself a myth — researchers who went looking for the supposed error couldn’t find it in the historical record.

How Much Iron Does Spinach Really Have?

USDA lists 3.57mg of iron per 100g of boiled spinach (20% DV). Figures vary considerably between samples, though: USDA’s newer analysis of raw mature spinach found about 1mg per 100g. Spinach is a reasonable plant source of iron, but not an exceptional one.

The Oxalate Problem

The more important caveat is oxalic acid — a natural compound in spinach (and in rhubarb, chard, and some other plants) that binds iron and calcium in the gut and reduces how much is absorbed.

Studies have found that very little of the iron in spinach is absorbed — typically only a few percent — lower than from many other plant foods, and far lower than the roughly 15–35% of haem iron absorbed from meat and fish.

The Honest Picture

Spinach does contain useful non-haem iron — oxalate reduces, but doesn’t eliminate, its contribution. A few strategies help:

Pair it with Vitamin C — eating spinach with Vitamin C-rich foods such as tomatoes, lemon juice, or bell peppers helps convert iron into the form that’s easier to absorb.

Separate it from large amounts of dairy — calcium reduces iron absorption when eaten at the same meal, so it helps to have big servings of dairy at a different time if you’re relying on spinach for iron.

Boil and drain — boiling spinach and discarding the water removes a good share of the soluble oxalate.

Spinach calcium is affected even more — only about 5% of spinach’s calcium is absorbed, compared with around 30% from dairy. Despite its headline figure, spinach isn’t a practical calcium source — dairy, fortified foods, canned fish with bones, or calcium-set tofu are far better.

The bottom line: spinach’s iron and calcium contributions are real but modest. Its Vitamin K, Vitamin A, folate, manganese, and magnesium are the nutrients that really make it stand out.

Dietary Nitrates: Spinach’s Performance Secret

This is one of the less-known facts about spinach, and it’s directly relevant to athletic performance.

Spinach is one of the richest vegetable sources of dietary nitrate, along with beetroot, rocket (arugula), and other leafy greens. Its nitrate content varies widely with growing conditions, but is often comparable to beetroot. When you eat nitrate, bacteria in your mouth convert some of it to nitrite, which the body can then turn into nitric oxide (NO) — especially in low-oxygen conditions such as hard-working muscle.

What Nitric Oxide Does

Nitric oxide relaxes the walls of blood vessels, widening them and improving blood flow. In exercising muscle, research has found:

A lower oxygen cost of exercise — studies by researchers in Sweden and the UK found that dietary nitrate — given as nitrate salts or, most famously, beetroot juice — reduced the amount of oxygen needed for a given amount of work. In other words, muscles became more efficient.

Better exercise tolerance — in many studies, this improved efficiency translated into better endurance performance, though the effects are smaller and less consistent in highly trained athletes.

Possible effects on muscle power — animal research suggests nitrate may also improve how muscle fibers handle calcium, which could help muscle force, though this is less established in people.

Where Spinach Fits

Most nitrate performance research has used beetroot juice. Studies have shown that eating nitrate-rich vegetables, including spinach, raises blood nitrite levels in the same way, but the performance evidence for spinach specifically is still limited. Still, for athletes who want a whole-food source of nitrate, spinach offers it alongside an outstanding range of vitamins and minerals at almost no calorie cost.

Health Benefits of Spinach

Vitamin K for Bones and Blood

At 411% DV per 100g, regular spinach eaters can easily meet their Vitamin K needs for normal blood clotting and for the activation of osteocalcin in bone. Higher Vitamin K intake has been associated with better bone density in observational research.

Vitamin A for Immune and Barrier Health

At 58% DV per 100g (105% per cup cooked), spinach’s beta-carotene supports immune function, the mucous membranes that form the body’s first line of defense, skin health, and night vision — the wide range of tissues that depend on Vitamin A, which acts by switching on and off hundreds of genes.

Folate for DNA Synthesis and Red Blood Cells

At 37% DV per 100g (66% per cup cooked), spinach is one of the best vegetable sources of folate, needed for DNA synthesis in rapidly dividing cells, red blood cell formation, and — alongside B6 and B12 — keeping homocysteine levels in check.

Magnesium for Energy and Muscle Function

At 21% DV per 100g (37% per cup cooked), spinach is one of the more magnesium-rich vegetables — supporting energy production, muscle contraction and relaxation, and normal nerve function.

A Broad Antioxidant Profile

Spinach contains a wide range of antioxidant compounds: beta-carotene, Vitamin E (which protects cell membranes), Vitamin C (which helps regenerate Vitamin E), flavonoids such as kaempferol and quercetin (which have anti-inflammatory effects in laboratory studies), and lutein and zeaxanthin, which protect the eyes.

Eye Health: Lutein and Zeaxanthin

Spinach is one of the richest dietary sources of lutein and zeaxanthin — the carotenoids, discussed on the corn page, that build up in the macula of the eye, where they help filter blue light. Higher intakes have been associated with lower risk of age-related macular degeneration and cataracts in observational studies. As with beta-carotene, eating spinach with some fat improves their absorption.

Cardiovascular Support

Spinach supports heart health in several ways: its potassium (466mg per 100g) and magnesium help regulate blood pressure, its dietary nitrates can help relax blood vessels and modestly lower blood pressure, and diets rich in leafy greens are consistently associated with lower cardiovascular risk in large population studies.

Spinach for Athletes and Active People

Nitrates for Performance

As detailed above, spinach’s nitrates support nitric oxide production, which may reduce the oxygen cost of exercise. Most performance research has used concentrated beetroot juice taken about 2–3 hours before exercise; a generous serving of spinach as part of a meal a few hours before training is a reasonable whole-food way to add nitrate, though the effect of spinach alone hasn’t been well studied.

Magnesium for Training Demands

Athletes lose some magnesium through sweat. Spinach’s 21% DV per 100g (37% per cup cooked) contributes to the magnesium that supports energy production and muscle function.

Iron for Endurance Athletes

Despite the oxalate caveat, spinach eaten with Vitamin C-rich foods adds some useful non-haem iron for endurance athletes managing their iron status — and its copper (19% DV) helps the body use iron. For athletes who struggle with iron, though, spinach shouldn’t be relied on as a main iron source.

Vitamin K for Bone Health Under Training Load

Athletes placing repeated stress on their bones benefit from consistent Vitamin K intake alongside calcium, Vitamin D, and protein. Regular spinach eaters can easily meet their Vitamin K needs.

A Low-Calorie Nutrient Booster for Any Meal

At 23 calories per 100g, spinach adds almost no calories. A large handful in scrambled eggs, a smoothie, a stir-fry, or alongside any protein adds substantial Vitamin K, Vitamin A, folate, magnesium, and manganese without affecting macronutrient targets.

Raw vs Cooked Spinach: What Changes

Raw and cooked spinach differ in several practical ways:

Raw Vitamin C figure from USDA’s newer Foundation Foods analysis of raw mature spinach.

The practical conclusion: both raw and cooked spinach are excellent. Raw keeps the most Vitamin C and folate. Cooked makes carotenoids easier to absorb, reduces oxalate, and lets you eat far more spinach per serving. For iron and calcium, boiled and drained spinach is the better choice.

Practical Ways to Include Spinach in Your Diet

Sautéed with garlic and olive oil — the classic preparation. The olive oil helps you absorb spinach’s fat-soluble Vitamins K and E, beta-carotene, and lutein. A big handful wilts down in a couple of minutes and goes with almost any meal.

Blended into smoothies — raw spinach blends into fruit smoothies with very little effect on flavor — an easy way to add it to breakfast.

In scrambled eggs or omelettes — a classic combination: the fat in the yolk helps absorb spinach’s fat-soluble vitamins, and the eggs add complete protein and choline.

In soups and stews — a large handful stirred in during the last couple of minutes adds a lot of nutrition with little change in flavor.

As a salad base — raw baby spinach with an olive oil dressing (for carotenoid absorption), tomatoes (Vitamin C for iron absorption), nuts (Vitamin E), and a protein source makes a simple, very nutritious salad.

Frozen spinach — convenient, cheap, and nutritious, as the table above shows. It’s slightly lower in Vitamin C, folate, and iron than fresh, but richer per 100g in Vitamins K and A and fiber.

Pre-workout green smoothie — blending spinach with beetroot juice, banana, and water combines two nitrate-rich foods in a convenient pre-training drink.

Potential Considerations

Warfarin and Vitamin K consistency — as noted above, people taking warfarin should keep their spinach intake consistent rather than varying it dramatically. Steady, moderate amounts are fine; sudden large increases or cutting it out completely are the patterns to avoid.

Oxalate and kidney stones — spinach is one of the highest-oxalate foods, so people with a history of calcium oxalate kidney stones are usually advised to limit it. For people without kidney stones, the oxalate in normal amounts of spinach isn’t a meaningful concern.

Calcium caveat — as detailed above, spinach’s calcium is poorly absorbed because of oxalate, so it isn’t a practical calcium source.

Iron caveat — as detailed above, pairing spinach with Vitamin C and having large servings of dairy at a different time improves the iron you absorb.

Nitrates and babies — because of its nitrate content, spinach and other high-nitrate vegetables aren’t recommended for babies under about 3 months, and health authorities advise caution with large amounts for infants under 1 year. This isn’t a concern for older children or adults.

Nutrient data: USDA FoodData Central, SR Legacy — spinach, cooked, boiled, drained, without salt (FDC ID 168463). Comparisons: frozen spinach, boiled, without salt (SR Legacy, FDC ID 169288), and raw mature spinach (Foundation Foods, FDC ID 1999633). % Daily Values use the FDA’s current Daily Values.