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Health risk: iodine content of sushi leaves too high


Pollutants: Sushi leaves can harm your health

Fresh fish, vegetables and rice: Sushi is considered a healthy fast food. However, the algae leaves in which the other ingredients are wrapped are often contaminated with unhealthy pollutants such as lead and arsenic. In addition, the iodine content is often too high.

Table algae are particularly widespread in Asian cuisine. In this country, they are primarily known as a component of sushi. Algae provide numerous nutrients and often contain large amounts of iodine. The trace element is vital, but it can be harmful in high doses. In addition, algae leaves are often contaminated.

Algae leaves for food and food supplements

As the Federal Office for Consumer Protection and Food Safety (BVL) writes in a current communication, dried algae leaves are often used in salads, soups and vegetable dishes or as a component in food supplements.

Large-leaf seaweed such as seaweed are used here. Well-known varieties are, for example, the brown algae Wakame and Kombu as well as the red algae Nori, whose leaves are used to cover sushi.

According to the experts, however, some marine algae tend to absorb and accumulate pollutants, such as heavy metals or other environmental contaminants.

For this reason, the food surveillance authorities of the federal states examined dried algae leaves in 2013 as part of a nationwide monitoring program. This program was repeated five years later.

Pollutants in high concentrations

In 2018, 165 samples of dried seaweed were examined for various chemical elements. According to the BVL, cadmium, lead, arsenic and aluminum were particularly high concentrations.

For the heavy metal cadmium, there is currently a statutory maximum level of 3.0 milligrams per kilogram (mg / kg) of dried algae for use in food supplements. However, this value was exceeded in every tenth sample of seaweed examined.

As in 2013, comparatively high lead contents were determined. In about ten percent of the samples with the highest lead contents, these ranged from one to ten mg / kg.

No maximum permissible maximum level for lead in seaweed has yet been set. According to the BVL, the introduction of such a maximum legal salary is planned and is the subject of current advice on consumer health protection.

High average arsenic levels

The arsenic results also largely confirmed the findings of the previous monitoring program.

The algae samples examined have high average arsenic contents of around 25 mg / kg, but almost exclusively in the organically bound form, which has not yet been adequately investigated with regard to its health risk.

According to the Federal Institute for Risk Assessment (BfR), the inorganic arsenic compounds in particular are considered to be health problems.

In addition, inorganic arsenic was detected in 42 percent of the samples, however, the findings at 0.1 mg / kg are only slightly above the laboratory analytical detection limit and thus at a very low level.

Analyzes of uranium

It was also found that the average aluminum content of the investigated algae leaves, at around 100 mg / kg, was at a similar level as five years earlier.

According to an exposure assessment by the BfR, however, the tolerable weekly oral intake of 1 mg / kg body weight specified for aluminum is only used to a very small extent by a maximum of 0.15 percent.

Based on the current level of knowledge, a health risk cannot be assumed due to the small amount to be consumed.

The uranium analyzes carried out for the first time in 2018 showed high concentrations, but according to the BfR the exhaustion rate of the tolerable daily intake of 0.6 μg / kg body weight is only a maximum of 0.19 percent. A health risk is therefore not to be expected with regard to the measured uranium findings.

Too much iodine can harm health

In addition to the potentially toxic chemical elements, the trace elements iodine, zinc, selenium, manganese and copper have also been investigated, and their absorption in small amounts is necessary to maintain human health.

With excessive intake, these elements can also have negative health effects.

Although iodine is indispensable for the build-up of thyroid hormones, an excess of iodine can lead to an iodine-induced overactive or underactive thyroid gland.

The BfR therefore recommends 0.5 mg iodine per day for Germany as the maximum intake. In a toxicological risk assessment, the BfR indicates that iodine is absorbed to a dangerous extent if algae products with an iodine content of over 20 mg / kg are consumed.

For reasons of preventive health protection, products with an iodine content above the maximum tolerable upper limit of 20 mg / kg are warned that excessive iodine intake can lead to disorders of thyroid function, as well as information on the iodine content and the maximum amount consumed.

In the monitoring carried out in 2018, iodine levels of over 20 mg / kg were measured in around three quarters of all algae samples. However, eight percent of these samples had no warnings or consumer information.

Because such products are likely to damage health, they must not be placed on the market under the general provisions of food law.

In order to avoid a health risk of an excess supply of iodine, according to the BVL it is recommended to only buy those seaweed products that contain clear information on the iodine content and the maximum consumption.

The trace elements zinc, copper, selenium and manganese were also detected in relatively high amounts. With these, however, taking into account the maximum tolerable daily intake values, no health risk can be assumed. (ad)

Author and source information

This text corresponds to the requirements of the medical literature, medical guidelines and current studies and has been checked by medical doctors.


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