About the canned sardines

 

About the canned sardines I add to my breakfast soup, you mentioned I get calcium provided I eat the bones. Now the sardines come as whole fish, so I assume the bones are there, even though I don't detect them.

Yes. If the sardines are sold as whole fish, the bones are still there, and you're almost certainly eating them even though you don't notice them.

The bones in canned sardines become very soft and brittle from the pressure-cooking/heat processing. They can be eaten along with the flesh and are an unusually good source of calcium. That's why canned sardines with bones can provide a substantial amount of calcium—often several hundred milligrams in a serving.

So your breakfast soup is getting the calcium benefit without your having to consciously chew identifiable bones. In fact, if you did notice crunchy, hard bones, that would be more unusual than not noticing them.

One distinction: sardines sold as boneless/skinless fillets would have much less calcium from bone, so "whole fish" is the useful clue here.

That's the nice thing about minerals; they don't get destroyed by time or heat.

Exactly. That's one of the great advantages of minerals: heat doesn't destroy the calcium, iron, magnesium, zinc, phosphorus, etc. They are elements, after all, and you can't cook an element out of existence.

What can happen is that cooking changes where the mineral is. For example, some minerals can leach into cooking water. With your sardines, though, the calcium in the bones stays right there in the fish—and the canning process conveniently makes the bones soft enough to eat.

Vitamins are a very different story. Many are chemically fragile and can be degraded by heat, oxygen, light, or time. So canned sardines are a nice little demonstration of the distinction: the vitamins may suffer some losses, but the calcium in those tiny skeletons is remarkably persistent.

Although we don't throw out cooking water, it becomes soup.

Right—and in that case leaching is hardly a loss at all. If minerals leave the vegetables or meat and enter the cooking water, and the water becomes your soup, you simply eat the minerals in their new location.

That's actually a rather sensible traditional arrangement: the soup is the mineral-and-flavor recycling system. The same applies to water-soluble vitamins to some extent, although those can subsequently be damaged by the heat of cooking.

So between canned sardines (bones included) and soup made from the cooking liquid, you're getting a rather efficient use of the food rather than throwing the useful dissolved material down the drain.