Spinach

Food · Vegetable · Food, Typed Supps

The Popeye story about spinach and iron is not quite true.

Stage by stage

Intake (Chewing): Breaks down easily since it’s a leafy vegetable with little structural fibre.
Stomach (Digestion begins): Plant cell walls begin breaking down, releasing vitamins and minerals.
Small intestine (Iron absorption limited by oxalates): Spinach’s non-heme iron competes with its own naturally occurring oxalates, which bind iron and reduce how much is actually absorbed.
Bone & immune tissue (Vitamin K & C delivered): Vitamin K supports bone protein function, while vitamin C and other compounds support immune-related processes.

Timing

Pairing with a vitamin C source (like citrus or tomato) improves iron absorption.

Time to effect

Weeks: Regular intake contributes to vitamin K and folate status over time.

Allergens

None of the fourteen major allergens. Derived from what this food is, not from a product label.

Eating patterns

Fits: Vegan, Vegetarian, Pescatarian, Halal, Kosher, Keto, Low-FODMAP, Gluten-free.

In season

March to November in the northern hemisphere, September to May in the southern.

Satiety

The satiety index is measured on 240 kcal servings. At 23 kcal per 100 g that is 1.0 kg of this, which is not a serving anyone eats — so the index has nothing to say about it.

Environmental footprint

0.5 kg CO2e and 108 litres of freshwater per kg, matched to "Other vegetables" in Poore & Nemecek (2018), Science 360.

Cost band

Cheap — roughly £2.5 per kg, as a band midpoint rather than a price.

Key nutrients

Vitamin K
Non-heme iron
Vitamin C
Folate

Nutrition per 100g

Calories: 23.2
Protein: 2.8g
Carbohydrate: 0.7g
of which sugars: 0.7g
Fat: 0.4g
of which saturated: 0g
Fibre: 2.9g
Sodium: 23mg

Food vs. supplement

Spinach’s iron is non-heme and further blocked by its own oxalates — an iron supplement or animal-source (heme) iron absorbs far more efficiently than spinach’s reputation suggests. Pairing spinach with a vitamin C source helps offset this somewhat.

Kitchen tip

Light sauteing in a little oil releases more of its carotenoids than eating it raw, and a squeeze of lemon on top nudges iron absorption upward.

Common myth

“Spinach is one of the best sources of iron.” In reality: Its oxalate content significantly limits how much of its iron actually gets absorbed — red meat, poultry, and seafood provide far more usable iron per serving.