Even today, almost a hundred years after he was created, Popeye’s spinach myth is still alive and kicking. Popeye, the American comic character created in 1929, was a rough sailor who, whenever trouble arose, pulled out a can, swallowed spinach – and within seconds his arm muscles swelled and he became as strong as a superhero. The message was clear: Spinach equals strength, spinach equals muscles, spinach equals iron. However, since the days of the comic until today, quite a few nutritional studies have accumulated, and they paint a far more complex picture.
True, spinach is a very nutritious vegetable with many health benefits – but the iron it contains is actually not the main reason to put it on your plate, and certainly not an ideal source of dietary iron. And what is the best way to eat it?
What is not recommended to combine with spinach – and what is?
Spinach and iron – why does it work less well?
Spinach does indeed contain iron, but it is also rich in oxalic acid (oxalates) – compounds that bind to iron and form insoluble complexes in the digestive system. As a result, the availability of iron from spinach for absorption in the body is very low.
Absorption studies have shown that when it comes to non-heme iron, meaning iron from plant sources, the absorption rate from spinach may be particularly low and sometimes even less than 5%. In simple terms: There is iron in spinach, but the body can hardly use it.
What happens when spinach is combined with meat?
Here the story is a bit different. The iron in meat, poultry, and fish is heme iron – a form that is absorbed better by the body and is less affected by absorption inhibitors.
Reviews and absorption studies published in the American Journal of Clinical Nutrition found that the oxalates and polyphenols in spinach do not cancel out the absorption of iron from meat, but they can reduce it to some extent.
According to the data, combining spinach or oxalate-rich vegetables in a meat-based meal may reduce iron absorption from the meat by about 15%–30%. That is, significant iron absorption from the meat still occurs, but it is not optimal.
The good news is that this effect can be moderated. Adding a source of vitamin C – such as red pepper, fresh tomatoes, or lemon juice – can improve overall iron absorption in the meal and reduce some of the inhibition.
The conclusion is clear: There is no reason to avoid combining spinach with meat, but for those who suffer from iron deficiency or anemia, it is better not to base a meat-based meal specifically on spinach as the main vegetable, but rather to include other vegetables or be sure to add vitamin C.
Spinach and calcium – not the enemy people think
Another myth surrounding spinach concerns calcium. Here too, oxalates play a role: They reduce the absorption of calcium from the spinach itself. In other words, spinach is not a good source of bioavailable calcium, even though it contains a respectable amount of calcium on paper.
But – and this is an important but – the oxalates in spinach do not impair the absorption of calcium that comes from other sources in the same meal, such as dairy products. Studies published in the Journal of Nutrition showed that combining spinach with cheese or yogurt does not reduce calcium absorption from dairy foods.
Therefore, a spinach pie with cheeses, an omelet with spinach and cheese, or pasta with cream sauce and spinach are all completely legitimate combinations in terms of calcium.
So what is spinach’s greatest advantage?
This is where lutein comes into the picture – an antioxidant from the carotenoid family, of which spinach is considered one of the richest sources. Lutein is particularly important for eye health, protecting the retina and preventing age-related macular degeneration. Studies published in Archives of Ophthalmology and Nutrients found a link between high lutein intake and a reduced risk of vision impairment with age.
For lutein to be absorbed well, it is important to consume it together with fat. This is where the winning combination comes in: Spinach with eggs, olive oil, avocado, or nuts. Studies in the Journal of Nutrition showed that combining spinach with eggs significantly increases blood lutein levels compared to eating spinach alone.
So Popeye may have built a career on spinach and iron, but nutritional reality is more complex. Spinach is a very healthy vegetable, but not because of its iron. Its real benefits lie דווקא in lutein, folic acid, vitamin K, and vitamin A.
There is no reason to avoid spinach, and no need to be alarmed by “problematic” combinations – it’s simply important to understand what it gives the body, and what it gives less of. As in most areas of nutrition, knowledge allows you to choose correctly – and not rely on myths that are almost a hundred years old.