Why the lists disagree with each other
Two things change when a leafy green is cooked. Water leaves the leaf, so a cup of cooked spinach weighs far more than a cup of raw spinach — around 180 g versus 30 g. And carotenoids leach into the cooking water, so the vegetable loses some of what it started with.
USDA reports both per 100 g and per household measure. Lists that quote per-100 g figures for raw vegetables and compare them with per-100 g figures for cooked ones are comparing two different things without saying so. That is how kale acquired a reputation it does not earn once boiled.
The table, per cup cooked
| Food (cooked unless noted) | Lutein + zeaxanthin per cup | Per 100 g | Cups for 10 mg |
|---|---|---|---|
| Spinach, boiled and drained | 20.4 mg (180 g) | 11.3 mg | 0.5 |
| Swiss chard, boiled and drained | 19.3 mg (175 g) | 11.0 mg | 0.5 |
| Collard greens, boiled and drained | 11.8 mg (190 g) | 6.2 mg | 0.85 |
| Kale, boiled and drained | 5.9 mg (118 g) | 5.0 mg | 1.7 |
| Parsley, raw | — | 5.6 mg | ~1.8 cups |
| Romaine lettuce, raw | — | 2.3 mg | ~4.5 cups |
| Sweet corn, cooked | ~1.8 mg | 0.9 mg | ~5.5 cups |
| Egg yolk | 0.25 mg per yolk | — | 40 yolks |
Source: USDA National Nutrient Database (SR Legacy), lutein + zeaxanthin combined. The database does not separate the two carotenoids for most foods.
Cooking helps more than it hurts
The leaching effect sounds bad, and per 100 g the numbers do drop. But what matters is what reaches your blood, not what stays in the leaf. Cooking breaks down cell walls and releases carotenoids from the protein matrix they sit in, which raises bioavailability substantially. Steaming and sautéing avoid the leaching that boiling causes, so they are the better methods if you are eating greens for this specific purpose.
Fat matters more than the cooking method. Lutein is fat-soluble; a study-level summary of the absorption literature puts the effect plainly — the same greens eaten with a few grams of fat deliver markedly more lutein to serum than the same greens eaten fat-free. Olive oil on the spinach is not a garnish, it is part of the dose.
The gap between the table and the plate
Half a cup of cooked spinach a day sounds easy when written down. In practice, national dietary survey data put average adult lutein and zeaxanthin intake in Western countries at roughly 1–2 mg/day — five to ten times below the AREDS2 dose.
That gap is not a failure of willpower. It reflects what people actually eat: green vegetables appear a few times a week, not twice a day, and the portion is a side dish rather than a bowl. A person eating a normal mixed diet does not reach 10 mg without deliberately building meals around it.
So: food, supplement, or both?
If you have intermediate AMD — the group the trial actually studied — food alone is not the intervention that was tested. AREDS2 delivered its nutrients in a single daily dose, consistently, for years. A diet that averages 4 mg on a good week is not the same intervention.
If you are eating for prevention, the honest position is that the trial does not tell us whether supplements help people without AMD, and neither does the food evidence. What both have in common is that they are low-risk. A spinach habit and a supplement are not in competition.
If you do supplement, check what you are actually getting. We read 14 eye supplement panels and measured the lutein-to-zeaxanthin ratio on each — nine land near the trial's 5:1, two are far off it, and one product hides its carotenoids inside an undisclosed blend.