Heavy Metals in Food

Lead, cadmium and co. occur naturally in the earth. But we increase the values ​​greatly. And that can be dangerous.

Some soils are contaminated by the Romans

There are many heavy metals – such as iron, copper, lead, cadmium, chromium, mercury, uranium, silver, gold or platinum. They occur naturally in the rocks of the earth’s crust – and also end up in the soil and groundwater through weathering and erosion. But the large mass of heavy metals that we have in our soil today comes from somewhere else: through industry and road traffic, we produce fine dust that is deposited on the soil over time.

Although we now use unleaded petrol, the abrasion from tires and brakes also releases lead and other heavy metals. They are also found in fertilizers and pesticides used in agriculture. The problem: Some of them are poisonous – and can get into our food via the soil. The next problem: Heavy metals are difficult to break down. Some of what is still stored in the ground today was brought in there centuries ago. In the Sauerland, for example, some soils are heavily contaminated with lead – from lead mining by the Romans.

Vegetables, lettuce and mushrooms are particularly contaminated – for example cadmium

How much heavy metal can food contain without harming us? The European Commission sets this in maximum levels for the individual foods, but these are revised downwards from time to time. An example: In 2009, a report by the European Food Safety Authority showed that our bodies are almost three times more sensitive to cadmium than previously thought.

Five years later, the EU Commission lowered the maximum cadmium levels for some foods. But not for everyone. This may be corrected again in 2018. This would be particularly important for food plants that absorb a particularly large amount of cadmium. This is because it varies from plant to plant. Leafy vegetables such as spinach and chard or lettuce are among the top cadmium intakes. Therefore, as a precaution, you should always wash them thoroughly and remove the outer leaves.

Celery and forest mushrooms are also frequently contaminated with cadmium (cultivated mushrooms, on the other hand, are much less). Oil seeds such as sunflower seeds or linseed also contain a particularly large amount of cadmium compared to other crops. Experts therefore recommend not eating more than 20 grams of flaxseed a day – that’s about two tablespoons. Wheat also absorbs a lot of cadmium.

The heavy metal is of course also absorbed by animals via plants. There, innards such as (beef) kidneys are often more heavily loaded. Apples, beans, peas, cucumbers, broccoli, pumpkins, peppers, types of cabbage, zucchini or tomatoes, on the other hand, only absorb little cadmium. By the way: tobacco also contains cadmium. This is particularly dangerous because the heavy metal is particularly easily absorbed through the lungs when smoking.

Homegrown vegetables can also contain heavy metals

If you grow it yourself, you don’t get any state food control. The allotment gardener can decide for himself whether to use fertilizer or pesticides with heavy metal content. But vegetables and lettuce grown in a garden that’s near a busy road, an industrial area, or in the middle of a big city can still be so heavily contaminated with heavy metals that eating them is potentially unhealthy.

Experts therefore recommend allotment gardeners to shield the vegetable beds from the road with biological air filters such as hedges if the garden soil is polluted. Or create raised beds with pollutant-free potting soil. However, cheap potting soil is not always cadmium-free.

Heavy metals can harm our body – but they can also be beneficial

Heavy metals are not inherently toxic. It depends on the heavy metal and the dose. But some of them, like cadmium, lead or mercury, can make us sick even in small amounts. Cadmium, for example, weakens the immune system, cardiovascular and nervous systems, bones and the filter function of the kidneys. Lead poisoning begins with diarrhea, exhaustion, headaches and body aches and, depending on the dose, can be fatal.

And mercury also attacks the central nervous system. But there are also heavy metals that our body urgently needs – as trace elements. Zinc, which is found in tomatoes and oatmeal, for example, is important for building muscle. And we need copper, for example from nuts, for cell respiration. But the same applies here: it depends on the dose.

We’re not going to get rid of heavy metals anytime soon

It is virtually impossible to get the heavy metals out of the ground again. Because in addition to the numerous heavy metals that are already there, new ones are added every day. Complex renovations, in which the floor is completely replaced, are very expensive and usually only take place if there is an immediate danger to the population due to extremely high soil pollution.

The alternative: so-called protection and restriction measures. This means that if fields are heavily contaminated with cadmium, the authorities recommend that farmers grow plants that hardly absorb cadmium – and avoid those that absorb a lot of cadmium. Specifically: rye instead of wheat. Or beans instead of spinach. In addition, farmers can bind the heavy metals in the soil so that they can no longer be absorbed by the plants. The trick: You put lime on the field – this changes the PH value of the soil. But both methods have a catch: the heavy metals remain untouched in the soil.