From mothers and grandmothers we have inherited a lot of knowledge around cooking. One of the bits of wisdom passed down is that spinach should not be reheated. No one really knows why, but people stick to the recommendation because there must be some kernel of truth to it. Or is there not?
Nitrate content in spinach
Spinach is one of those vegetables that accumulate abundant nitrate from the soil during the growing season. Over time, nitrate is bacterially converted to nitrite and then to toxic nitrosamines. Nitrate itself is not harmful to human health. Only after conversion to nitrite can it pose a threat to human health.
Conversion of nitrate into nitrite
The conversion of nitrate into nitrite occurs through bacteria, for example, when food is stored at room temperature for a long time. If, on the other hand, the prepared spinach is stored in the refrigerator, bacterial growth is largely curbed, and so is the formation of nitrite. Thus, in the days of our grandmothers, the recommendation certainly had its meaning, because at that time there was no refrigerator in many households.
Why is nitrite dangerous?
Nitrite can affect our health in two ways:
- Carcinogenic nitrosamines can be formed from nitrite in conjunction with protein breakdown products (known as secondary amines), which occur naturally in many foods and are also formed during digestion.
- High doses of nitrite can hinder oxygen transport in the blood of infants, causing “methemoglobinemia” with cyanosis.
Tips for handling spinach
- Consume spinach as fresh as possible and remove the stems and very large leaf veins when cleaning fresh spinach leaves.
- Thorough washing or blanching can reduce nitrate levels, as nitrate is water soluble.
- Avoid long periods of keeping warm.
- Let the vegetables cool quickly after the first preparation, so that as far as possible no nitrite can develop. For this, it is best to fill the spinach in a clean container around, and put this immediately well covered in the refrigerator for max. 1 day. Then you can reheat the vegetables without hesitation.
- Infants and young children should not eat reheated spinach.
- The recommendations apply equally to all vegetables rich in nitrates, for example, chard, kale, beet, leaf lettuce or arugula.
