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 any meaningful measure. At just 23 calories per 100g cooked, it provides 411% of daily Vitamin K, 315% of Vitamin A, 37% of folate, 21% of magnesium, 39% of manganese, 20% of iron, 14% of Vitamin E, and 14% of copper — a spread of vitamins and minerals at this calorie level that no animal food and very few plant foods can match. Understanding what those figures mean mechanistically — and addressing the honest caveats around spinach’s iron specifically — is what makes this page genuinely useful rather than just impressive-looking.

Spinach Nutrition Facts (per 100g, cooked)

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

Cooking reduces spinach volume dramatically — roughly 500g of raw spinach yields approximately 180g cooked:

A single cup of cooked spinach provides 740% of daily Vitamin K and over five times the daily Vitamin A requirement at 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 extraordinary standouts: Spinach’s vitamin profile at 23 calories per 100g is genuinely extraordinary. Vitamin K at 411% DV is the highest figure in this collection for any food — more than four times the daily requirement in 100g. Vitamin K activates osteocalcin for bone mineralization and matrix Gla protein for preventing arterial calcification, making it essential for both bone density and cardiovascular health. Vitamin A at 315% DV — from beta-carotene rather than preformed retinol — supports vision, immune function, skin cell differentiation, and mucosal integrity. Folate at 37% DV supports DNA synthesis and red blood cell formation. Vitamin E at 14% DV and B6 at 12% DV round out a vitamin profile without parallel in the leafy green category.

Minerals in Spinach (per 100g, cooked)

Multiple standouts: Spinach’s mineral profile matches its extraordinary vitamin profile. Manganese at 39% DV supports bone matrix formation and the MnSOD mitochondrial antioxidant enzyme. Magnesium at 21% DV supports over 300 enzymatic reactions including ATP production. Iron at 20% DV and copper at 14% DV work in complementary roles — copper through ceruloplasmin is required for iron metabolism, making their co-occurrence in spinach nutritionally fitting. Calcium at 10% DV and potassium at 466mg per 100g contribute to bone health and blood pressure regulation respectively.

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

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

Vitamin K exists in two primary forms with distinct functions. Spinach provides Vitamin K1 (phylloquinone) — the plant form concentrated in leafy greens where it plays a role in photosynthesis.

In the human body, Vitamin K1 is essential for two independently important functions:

Blood clotting — Vitamin K activates the gamma-carboxylation of clotting factors (II, VII, IX, X, and proteins C and S) in the liver. Without adequate Vitamin K, these proteins cannot achieve the structural form required for their clotting function, impairing the entire coagulation cascade.

Bone and vascular health — Vitamin K activates osteocalcin — the protein that directs calcium into bone mineral — and matrix Gla protein (MGP), which prevents calcium from depositing in arterial walls. Low Vitamin K status is associated with both reduced bone mineral density and increased arterial calcification — two problems that are simultaneously relevant to cardiovascular and skeletal health.

The 411% DV figure reflects both how much Vitamin K1 is concentrated in green leaves specifically (it’s a chloroplast constituent) and how relatively modest the official daily requirement is set. Most nutrition researchers believe current Vitamin K recommendations may be set conservatively, with higher intakes associated with additional bone and cardiovascular benefits in prospective research.

Practical note for anyone on anticoagulant medication: Vitamin K directly antagonizes warfarin’s mechanism of action. People taking warfarin must maintain consistent Vitamin K intake rather than making sudden large changes — this doesn’t mean avoiding spinach, but it does mean eating it consistently rather than varying greatly week to week.

Vitamin A at 315% DV: The Beta-Carotene Source

Spinach’s 315% DV of Vitamin A comes entirely from beta-carotene — the orange plant pigment that in spinach is masked by the larger quantities of chlorophyll present. Beta-carotene is a provitamin A: the body converts it to retinol (the active form of Vitamin A) as needed, with conversion efficiency around 1:12 by weight (12µg of beta-carotene produces approximately 1µg of retinol).

This conversion-based mechanism differs importantly from preformed Vitamin A in animal foods:

No toxicity risk — unlike preformed retinol from liver or supplements, beta-carotene excess cannot cause Vitamin A toxicity because the conversion slows down as retinol status becomes adequate. The body is self-regulating.

Fat-soluble absorption — beta-carotene is fat-soluble and requires dietary fat for absorption. Eating spinach with even a small amount of fat — olive oil in a sauté, avocado in a salad, eggs in an omelette — dramatically improves beta-carotene bioavailability compared to eating it plain without fat. This is the single most practically important bioavailability fact for maximizing spinach’s Vitamin A contribution.

Cooking increases bioavailability — cooking ruptures plant cell walls and breaks down the protein-carotenoid complexes that hold beta-carotene in raw spinach, making significantly more beta-carotene available for absorption from cooked spinach than raw.

The Iron Question: What Spinach Actually Delivers

Spinach’s iron has been famous — and then famously debunked — and then partially rehabilitated. The full story is worth telling accurately.

The Popeye Myth and Its Origins

Popeye’s spinach-eating superstrength was loosely inspired by spinach’s genuinely high iron content (20% DV per 100g), which has been known since the 19th century. A frequently repeated claim that spinach’s reputation as an iron source was based on a decimal point error in an 1870 study (attributing 35mg rather than 3.5mg of iron per 100g) is itself a myth — this error never appears in the historical record. Spinach genuinely is iron-dense by vegetable standards.

The Oxalate Problem

The legitimate nuance about spinach’s iron is oxalic acid — a naturally occurring compound in spinach (and rhubarb, chard, and several other plants) that forms insoluble calcium oxalate and iron oxalate crystals when it encounters dietary calcium and iron in the digestive tract. These crystals reduce the absorption of both minerals.

Research has confirmed that the iron in spinach specifically is absorbed at significantly lower efficiency than the iron in, for example, lentils, despite spinach containing more iron per 100g. Estimates of spinach iron absorption run at approximately 1–5% — considerably lower than the typical 2–20% for non-haem iron from most plant foods, and dramatically lower than 25–35% for haem iron from meat.

The Honest Picture

At 20% DV per 100g raw and cooked, spinach genuinely contains meaningful non-haem iron — the oxalate issue reduces but does not eliminate its iron contribution. The practical strategies that enhance non-haem iron absorption generally also apply:

Pair with Vitamin C — consuming spinach alongside Vitamin C-rich foods (tomatoes, lemon juice, bell peppers) converts ferric iron to ferrous form that can be absorbed despite oxalate competition, significantly improving iron uptake.

Don’t pair with dairy at the same meal — calcium competes with iron for absorption; combining spinach with large amounts of dairy in the same sitting reduces iron absorption from both foods.

Cooking reduces oxalate content — boiling spinach and discarding the water removes a meaningful proportion of oxalates, improving mineral bioavailability from cooked versus raw spinach for those specifically managing iron or calcium intake from spinach.

Spinach calcium is similarly affected — the same oxalate concern applies to spinach’s calcium (10% DV per 100g). Spinach calcium bioavailability is estimated at only around 5%, substantially lower than dairy calcium. Spinach is not a practical calcium source despite its headline figure — dairy, fortified foods, or sardines are far more bioavailable calcium sources.

The bottom line: spinach’s iron contribution is real but modest relative to the headline figures; the Vitamin K, Vitamin A, folate, manganese, and magnesium contributions are far more practically significant because oxalate does not meaningfully impair those.

Dietary Nitrates: Spinach’s Performance Secret Most People Haven’t Heard Of

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

Spinach is one of the most concentrated natural sources of dietary nitrates — inorganic compounds that undergo a biological conversion process in the body. When dietary nitrate is consumed, bacteria in the mouth reduce it to nitrite, which is then further reduced to nitric oxide (NO) in the bloodstream under the low-oxygen conditions found in exercising muscle tissue.

What Nitric Oxide Does

Nitric oxide is one of the most potent endogenous vasodilators in the body — it relaxes smooth muscle in blood vessel walls, causing them to widen and reducing the pressure required to push blood through them. In exercising muscle specifically:

Reduced oxygen cost of exercise — multiple well-controlled studies, including several conducted by the Karolinska Institute, have found that dietary nitrate supplementation (typically from beetroot juice, but also from other nitrate-rich vegetables including spinach) reduces the amount of oxygen required to produce a given amount of mechanical work. Muscles become more metabolically efficient — they produce the same power output for less oxygen expenditure.

Improved exercise tolerance — the reduced oxygen cost translates to improved performance in submaximal exercise, with subjects able to sustain effort for longer before reaching their VO₂ max ceiling.

Enhanced muscle contractility at low oxygen — nitric oxide specifically improves calcium handling in muscle fibers under the hypoxic conditions of intense exercise, potentially enhancing force production when oxygen is limited.

The Spinach Advantage

Spinach contains approximately 250–450mg of nitrate per 100g — comparable to beetroot, which has been far more extensively studied for this effect but is nutritionally inferior to spinach in virtually every other dimension. Research specifically on spinach nitrates has confirmed the same nitric oxide conversion pathway and preliminary evidence of similar performance benefits.

For athletes seeking whole-food nitrate loading before training or competition, spinach is arguably the most nutritionally comprehensive vehicle available — delivering the nitrate dose alongside extraordinary Vitamin K, Vitamin A, folate, magnesium, and manganese at negligible caloric cost.

Health Benefits of Spinach

Vitamin K for Bone Density and Arterial Health

At 411% DV per 100g, regular spinach consumption ensures vitamin K sufficiency for both osteocalcin-directed calcium incorporation into bone and MGP-mediated prevention of arterial calcium deposition. Population research has found higher dietary Vitamin K intake associated with both higher bone mineral density and lower coronary artery calcification scores — two independent benefits operating through the same activation mechanism.

Vitamin A for Immune and Epithelial Health

At 315% DV of provitamin A beta-carotene per 100g, spinach supports immune cell differentiation, mucous membrane integrity (the first line of defense against pathogens), skin cell turnover, and night vision — the broad range of functions that Vitamin A as a transcription factor regulates across almost every tissue type.

Folate for DNA Synthesis and Red Blood Cell Health

At 37% DV per 100g (66% per cup cooked), spinach is one of the better whole-food folate sources available, essential for DNA synthesis in all rapidly dividing cells, red blood cell formation, and the methylation cycle that regulates homocysteine levels alongside B6 and B12.

Magnesium for Energy, Muscle, and Stress Resilience

At 21% DV per 100g (37% per cup cooked), spinach is one of the more magnesium-dense vegetables available — contributing meaningfully to ATP production, muscle contraction and relaxation, and the HPA axis regulation that governs the body’s stress response.

Exceptional Antioxidant Profile

Spinach contains an unusually broad spectrum of antioxidant compounds working through different mechanisms: beta-carotene quenches singlet oxygen, Vitamin E neutralizes lipid peroxidation radicals in cell membranes, Vitamin C regenerates oxidized Vitamin E, flavoring including kaempferol and quercetin inhibit NF-κB inflammatory signalling, and lutein and zeaxanthin specifically protect macular tissue from light-induced oxidative damage in the eyes.

Eye Health: Lutein and Zeaxanthin

Spinach is one of the most concentrated dietary sources of lutein and zeaxanthin — the carotenoids discussed on the corn page that selectively accumulate in the macula of the eye and form the “macular pigment” that filters damaging blue light and quenches phototoxic free radicals. Research has found higher dietary lutein and zeaxanthin intake associated with significantly reduced risk of age-related macular degeneration (AMD) and cataracts. Fat consumption alongside spinach dramatically enhances lutein and zeaxanthin absorption, the same mechanism that applies to beta-carotene.

Cardiovascular Support

Multiple mechanisms: Vitamin K preventing arterial calcification, magnesium and potassium (466mg per 100g) contributing to blood pressure regulation, dietary nitrates promoting vascular dilation and endothelial function, and folate managing homocysteine — spinach’s cardiovascular benefits are genuinely multi-layered.

Spinach for Athletes and Active People

Nitrate Loading for Performance

As detailed above, spinach’s dietary nitrate content supports nitric oxide production in exercising muscle, reducing the oxygen cost of submaximal exercise and potentially improving endurance performance. For athletes seeking a whole-food approach to nitrate loading before competition or hard training sessions, 200–300g of spinach consumed 2–3 hours before exercise provides a meaningful nitrate dose in a nutritionally complete vehicle.

Magnesium for Training Demands

Athletes lose meaningful magnesium through sweat. Spinach’s 21% DV per 100g (37% per cup) contributes to replenishing the magnesium that supports ATP production and the muscle contraction/relaxation cycle that every training session depends on.

Iron for Endurance Capacity

Despite the oxalate caveat, spinach consumed with Vitamin C-rich foods provides meaningful non-haem iron for endurance athletes managing iron status. The manganese (39% DV) works alongside iron in the MnSOD enzyme system, and copper (14% DV) activates ceruloplasmin needed for iron metabolism — all three relevant to maintaining the iron status that oxygen transport depends on.

Vitamin K for Bone Resilience Under Training Load

Athletes placing repeated mechanical stress on bone through weight-bearing exercise benefit from consistent Vitamin K intake for osteocalcin activation. Spinach’s extraordinary 411% DV makes adequate Vitamin K status essentially guaranteed for regular spinach eaters.

A Calorie-Free Nutrient Amplifier for Any Meal

At 23 calories per 100g, spinach is essentially a nutrient delivery vehicle with no meaningful caloric cost. Adding a large handful to any meal — in scrambled eggs, a smoothie, a stir-fry, alongside any protein — adds extraordinary Vitamin K, Vitamin A, folate, magnesium, and manganese to that meal without affecting macronutrient targets in any practical way.

Raw vs Cooked Spinach: What Changes

This is a meaningful comparison because raw and cooked spinach have genuinely different nutritional profiles in several important respects.

The practical conclusion: both raw and cooked spinach are excellent choices. Raw maximizes Vitamin C and folate. Cooked maximizes carotenoid and lutein/zeaxanthin bioavailability, reduces oxalates, and allows dramatically more spinach to be consumed per serving by reducing bulk. For anyone optimizing iron or calcium contribution from spinach specifically, cooked spinach with water discarded is the better preparation.

Practical Ways to Include Spinach in Your Diet

Sautéed with garlic and olive oil — the classic preparation. The olive oil increases fat-soluble vitamin absorption (Vitamin K, beta-carotene, lutein). A large handful wilts to a small portion in under 3 minutes and can be added to almost any meal.

Blended into smoothies — raw spinach blends seamlessly into fruit smoothies with minimal flavor impact. A large handful adds the full vitamin and mineral profile to a breakfast drink in a way that’s almost undetectable by taste.

Added to scrambled eggs or omelettes — spinach and eggs is a classic combination; the fat in the yolk enhances spinach’s fat-soluble vitamin absorption, and the eggs’ choline and complete protein combine naturally with spinach’s micronutrient density.

In soups and stews — a large handful stirred into any soup in the last 2 minutes of cooking adds substantial nutrition with minimal flavor change.

As a salad base — raw baby spinach with olive oil-based dressing (fat for carotenoid absorption), alongside tomatoes (Vitamin C for iron absorption), nuts (additional Vitamin E), and a protein source is one of the most nutritionally complete simple salad constructions possible.

Frozen spinach — nutritionally equivalent to fresh for most purposes (frozen at peak nutrition shortly after harvest), more convenient, and considerably cheaper. The one exception is Vitamin C, which degrades somewhat in frozen storage — for Vitamin C specifically, fresh is marginally better.

Pre-workout green smoothie — blending spinach with beetroot juice, banana, and water before training combines spinach’s dietary nitrates with beetroot’s well-studied nitrate dose for a research-supported pre-exercise nitric oxide strategy.

Potential Considerations

Warfarin and Vitamin K consistency — as noted above, people taking warfarin must maintain consistent spinach intake rather than varying dramatically, since Vitamin K directly affects warfarin’s activity. Consistent moderate inclusion is fine; sudden large increases or total elimination are the patterns to avoid.

Oxalate and kidney stones — people with a history of calcium oxalate kidney stones are typically advised to limit high-oxalate foods including spinach, as dietary oxalate contributes to urinary oxalate that can promote crystal formation. For people without kidney stone history, oxalate in spinach at normal dietary amounts is not a meaningful concern.

Calcium bioavailability caveat — as detailed, spinach calcium is poorly absorbed due to oxalates. Spinach is not a practical calcium source regardless of its headline figure; dairy, sardines, or fortified foods provide far more usable calcium per serving.

Iron bioavailability caveat — as detailed, Vitamin C co-consumption and avoiding calcium-rich foods at the same meal significantly improves iron absorption from spinach.

Thyroid and goitrogens — spinach contains goitrogenic compounds at low concentrations, similar to other leafy greens. At normal dietary intake, this is not a meaningful concern for people with normal thyroid function; those with existing thyroid conditions may wish to discuss leafy green consumption with their doctor, though cooking largely neutralizes spinach’s goitrogen content.