[cbhl]

Some do; some don't.

In my experience, most find a source of protein quickly (tofu, tempeh, peanut butter, chickpeas, quinoa).

But some end up with iron deficiency and may need to take supplements. (Broccoli looks like a comparable source by weight -- 1.1mg per 148g, versus 2.2mg per 85g of beef. But 85g of beef is roughly 3/4 cup by volume, whereas to get the ~300g of broccoli for the same 2.2 mg of iron, you need to eat two stalks or three cups by volume.)

[Legogris]

Spinach is a great source of iron. 2.7mg per 100g. Also high in protein. I think there's a reason Popeye is all about spinach.

[cbhl]

True, but if you're eating raw spinach you need something like nine cups to get your RDA (assuming RDA of 8mg/day, and about 3 cups per 100g). Females 19-50 are told to eat 2x that; pregnant females 3x (27mg/day(!), source: https://ods.od.nih.gov/factsheets/Iron-HealthProfessional/).

If you cook it, then your 300g spinach reduces to something like one and a half cups, but you have to be careful to not lose water-soluble iron to your cooking method. Also, you have to like the texture of wilted spinach.

If you're used to eating half-cup sides of spinach, making spinach your primary iron source is a fairly major change to how you eat.

[pvaldes]

Spinach has oxalic acid that can lead to fragile bones. I wouldn't suggest to eat a lot of it (specially if you are a pregnant woman), unless you take countermeasures to assure a correct calcium intake.