Please let's not mix haem iron with nonhaem iron. The animal (haem) iron's bioavailability is much higher than the nonhaem iron, whose absorption is regulated by requirements from our body.
This may sound as if I'm disappointed when the opposite is actually true.
You see, there’s something crucial one must consider here and that is the "way". What way is that? Well, as you know I'm sure, there is a vitamin called vitamin a and then there is something called provitamin A carotenoids. The body wants vitamin a as this is the end of the road so to speak. Well, you can eat polar bear liver, which is extremely high in vitamin a, so high in fact that if you eat enough of it you will develop hypervitaminosis A, that's vitamin A poisoning.
Now compare the above with a pro-vitamin A as found in carrots for example (or spirulina). Here, the "way"/pathway has dramatically changed. Here you're providing your body with the bricks, wood, glass, etc to build the house (vitamin A). Here your body is the engineer and you're only the supplier of raw materials. Here the body is a lot smarter than you and I in determining its need and rejecting what it views as being a surplus. You see, the aim is the same, but the "way" going about it is different.
Another critical point to consider (especially as you get older) is cancer and its association with iron. Iron is one of cancer's favourite foods. Again, I'm not speaking of nonhaem iron but the one that comes from red meat especially; hence I consume meat only occasionally (like once a month or so).
Fadi.