The *myth* that spinach is an exceptionally good source of iron originates in 1870. In 1937, German scientists discovered that spinach iron content was 1/10th the claim. The error resulted from a misplaced decimal point.
However, the Spinach Supermyth stuck.

The perpetuation of the Spinach Supermyth has been described as an *academic urban legend*.
See: https://journals.sagepub.com/doi/full/10.1177/0306312714535679

Ironically, spinach contains iron absorption-inhibiting substances (e.g., oxalalic acid), preventing more than 90% of the iron from being used by the human body.

Cartoons perpetuated the Spinach Supermyth, with people following Popeye's dietary advice.
https://www.readersdigest.co.uk/health/health-conditions/medical-myths-spinach-is-full-of-iron

In addition, non-haem form found in spinach is very hard for the body to absorb/use. The better option is here
Cc: @healthcoachkait