Heavy metals are normally present in nature: in soil, water and the atmosphere. But they can also be displaced from their storage sites through certain industrial processes, waste incineration, car traffic and agricultural practices, thus contaminating the environment and food. Man can thus be exposed through the air and the ingestion of contaminated water or food (to date, food exposure seems to be the most relevant). Since these metals have the ability to bind to the cellular structures in which they are deposited, preventing their correct functioning, if they accumulate over time in the body they can damage the brain, liver, kidneys and bones, causing chronic diseases as well as irritation phenomena , intoxications, up to a carcinogenic action. Therefore, the regulatory authorities for the protection of public health have established in individual countries maximum values for some contaminants, including heavy metals, present in food products, providing legal limits for some types of food.
Above all, cereals and derivatives, vegetables, potatoes, crustaceans and molluscs, and fish contain heavy metals. But now a new American study from the University of Tulane University has found that even some soft drinks such as fruit juices, plant-based milks and sodas can contain levels of heavy metals dangerous to health. Researchers specifically analyzed 60 types of drinks and found that they contained levels of arsenic, cadmium and lead, exceeding the standards for drinking water set by the EPA (US Environmental Protection Agency) and WHO ( World Health Organization). A fact to reflect on if we consider that drinks such as fruit juices, plant-based milks (e.g. almond and oat milk), carbonated drinks, energy drinks and teas are widely consumed globally, and largely by children (the fruit juices). “It is surprising that there are so few studies on toxic and essential substances found in soft drinks,” said lead author of the study, Tewodros Godebo. “These findings create important awareness and prompt new analyses.” The results of the study were published in the Journal of Food Composition and Analysis.
The American study
Researchers at Tulane University in Louisiana purchased 60 soft drinks (available throughout the United States) from supermarkets and retail stores in New Orleans, including single and blended juices, plant milks, sodas and teas. They measured 25 different toxic metals and trace elements in these drinks, and found that five of the 60 drinks they tested contained levels of a toxic metal exceeding federal standards for drinking water. In particular, they found arsenic levels above the standard of 10 micrograms/litre in two mixed fruit juices. While a cranberry juice, a mixed carrot and fruit juice and an oat milk had cadmium levels above the standard of 3 micrograms/liter.
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Fruit juices and plant-based milks are the most dangerous drinks
In total, 7 of the 25 elements the researchers measured in their study exceeded drinking water standards in some beverages, including nickel, manganese, boron, cadmium, strontium, arsenic and selenium, while lead was detected in more than 93 % of 60 samples tested, although most contained levels below 1 microgram per litre. The highest level (6.3 micrograms/liter) was found in a lime sports drink, although it still falls below the standards for drinking water set by the EPA and WHO. Overall, the blended fruit juices and plant-based milks, including oatmeal and almond milks, contained higher levels of toxic metals than the other beverages analyzed in the study.
Children are at the greatest risk
The soft drinks sampled are usually consumed by an adult in smaller quantities than water, so the health risks are likely to be low. The youngest are at greater risk because they consume more of these drinks, especially fruit juices. Therefore, parents should avoid giving their children drinks such as mixed fruit juices or plant-based milks in large quantities. Arsenic, lead and cadmium are known carcinogens and well known to cause internal organ damage and cognitive impairment in children, especially during early brain development.”
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Cadmium and arsenic: how they damage the body
Cadmium is a metal found in high concentrations in the air, water and soil. The main source of human exposure is diet. Being able to mimic the behavior of essential elements, such as calcium, it crosses the biological membranes within our body, and once absorbed, it is deposited in the tissues of organs such as the liver, kidneys and intestines, remaining there for a long time time (it takes between 10 and 30 years to eliminate 50% of the absorbed cadmium). Its main adverse effects are: toxicity on the kidneys as it accumulates inside them and demineralization of the bones with effects also on the metabolism of calcium and vitamin D. Arsenic is also a natural metal that can be easily found in drinking water and in foods (particularly in fish and seafood). Long-term exposure to high levels can lead to skin disorders, an increased risk of diabetes, high blood pressure and several types of cancer.
Lead: how it damages the body
Lead is also a natural metal, present above all in milk and dairy products, meat, cereals and legumes, vegetables, fish products but also in water. The quantity accumulated in the body due to polluted areas and production processes is added to the ‘food route’. Once absorbed this metal is carried by the blood and distributed to the brain, liver and kidneys and bones, where it persists for over 30 years. In adults, chronic exposure causes damage to almost all body systems: haematopoietic, cardiovascular, renal, endocrine, gastrointestinal, immune, reproductive and nervous systems. But for children the risks are more serious. In the stage of brain development (from the formation of the fetus) exposure has a neurotoxic effect with irreversible damage, even at low levels. It can also cause progressive hearing loss, chronic fatigue and sluggishness, learning disabilities and reduced IQ.
Future research perspectives
According to the researchers most of these elements found in the drinks presumably come from contaminated soil. “Therefore – said Godebo -, regulations and environmental controls are fundamental to reduce its presence, in order to limit the levels to which humans are exposed. However – he continues -, in toxicity it is the dosage that often makes the difference, therefore if the consumption of these drinks is moderate, there is no alarm”.
The researchers’ next step will now be to conduct a risk analysis based on the data collected to learn about the impacts of toxic metal uptake by children and adults. “We are keen to continue exploring what is in our beverages and foods sold to consumers,” Godebo concluded.