What Foods are High in Heavy Metals – Organic vs Conventional?

Organic farming practices involve multiple steps in the whole system, from cultivation to harvesting, with the result being a crop that is cleaner and nutritionally closer to how it may be in a natural environment. We may think of natural environments as those before the Industrial Revolution, when there was less mass production of crops and virtually no pollution.

Fruit and vegetables are particularly susceptible to trace contaminants that accumulate through the soil, including heavy metals. The most concerning of these are lead, cadmium, mercury, and arsenic, because of their toxic effects at low levels. For example, lead and mercury are known to cause problems with learning and cognitive function in children^[1].

Where do Environmental Heavy Metals Contaminants Come From?

As mentioned, heavy metal residues can be found in the air, soil, and water. They originate from the byproducts of many industrial processes^[2], including mining, manufacturing plants that process products and raw materials (e.g., metals), and the burning of fossil fuels (e.g., coal).

Fruits and vegetables are vulnerable to absorbing heavy metals mainly from soil and water supply, because they obtain nutrients from the roots, although it depends on the type of fruit or vegetable. Root vegetables, like carrots and potatoes, are probably more at risk because they grow submerged in the soil.

A Chinese study published in 2017 analyzed the levels of mercury in a variety of fruit and vegetable crops grown nearby to large coal-fired power plants^[3]. They showed a direct relationship between the distance the crops were from the stations and their levels of mercury. This shows that plants can absorb heavy metals, depending on how much they are exposed to.

Heavy Metals In Organic vs Conventional Crops

Organic farming practices are used to reduce the exposure of heavy metals and other contaminants through the use of low-impact growing techniques and supply practices. This aim also involves controlling the location and geography.

A study^[4] by the US Department of Agriculture (USDA) has revealed that of the 5 most popular fruits and vegetables, including tomato, carrots, onions, lettuce, and potatoes, the average amounts of toxic metals were generally lower in organically produced samples than conventionally produced crops. This was especially so for cadmium (40% lower) and lead (32% lower).

Another comprehensive review study^[5] from Europe published in the British Journal of Nutrition also demonstrated that cadmium levels in organic fruits, vegetables, and cereals combined were on average 48% lower than in conventionally grown crops. This study was the largest of its kind, examining results from a total of 343 separate research studies.

Is It Worth Testing for Heavy Metals In Organic Foods?

Despite these improvements, it is still important to verify whether there is heavy metal contamination in organic foods, because there is often a lot of variation. This claim comes from the greater amount of natural differences in how crops grow between farms, districts, countries of origin, seasons, and the use of different sources in a batch.

This contrasts with conventional farming, which generally aims to have little to no variability in the produce, so as to maximize its consistency, for better yields and profit returns.

This guide is for informational purposes only and should not be used to diagnose health conditions or make changes to medical treatments. Always consult with your healthcare professional for advice.