The Buzz about Heavy Metals, Infants, and Young Children
January 2022
Over the last few years, published reports document the presence of heavy metals in certain foods. This is of particular concern when these foods are consumed by infants and young children due to the potential effect of heavy metal exposure on neurological development even at low levels. In April 2021, the U.S. Food and Drug Administration (USFDA) announced their Closer To Zero Action Plan, detailing the actions they will take to reduce the amounts of heavy metals in foods eaten by infants and young children. Lead, mercury, cadmium and inorganic arsenic are the heavy metals targeted in the action plan.
The USFDA held a public meeting on November 18, 2021 that brought in experts to discuss important considerations as the action plan moves forward. Specifically, the panels discussed exposure to toxic elements found in foods and the role of nutrition during the first 1000 days, the most crucial time for growth and development.
Efforts have been made over the past 50 years to reduce heavy metal exposure from the diet. This includes removing lead solder in cans and from gasoline which contaminated soil. These efforts decreased the average exposure to lead in 1-3 year old children by 90%. Similarly, inorganic arsenic levels in rice used in infant rice cereal and in apple juice has decreased in the last decade due to the efforts of the FDA, manufacturers, and the agricultural community.
According to the National Health and Nutrition Examination Survey (NHANES), 87% of the intake by children under 1 year of age (not breastfed infants) is food that is marketed to that age group. Of that, 12.3% is from baby food with the remainder from infant formula. Data from USFDA shows that 83.3% of lead in the diet of children under 1 year of age is from foods marketed to this age group. As children reach 1 year of age and beyond, their diet is comprised primarily of foods the rest of the family is consuming which can also be sources of heavy metals. These data illustrate the importance of a varied diet in assuring nutrient adequacy and minimizing heavy metal exposure.
The first panel of the public meeting spoke to the theme, "The impact of toxic element exposures at different crucial developmental stages for babies and young children."
- The first 1000 days (9 months during pregnancy and the first two years of life) sets the child up for the rest of their life. While the brain is not fully mature until late adolescence, 80% of brain growth occurs in the first 1000 days with the majority of functional maturation occurring before the child turns 2 years old.
- Toxic exposures during this time can have profound effects on cognition and other functions. Lead is the most common example used as it has been studied widely. While lead has a dose dependent effect, science has shown that even low levels of lead in the blood can cause intellectual deficits.
- The young brain is able to adapt to the exposures, especially if occurring in the presence of an enriched environment, but this plasticity comes at a cost given the increased sensitivity to the toxic environment.
- Adverse neurodevelopmental patterns may not show up until several years later in life when it is more difficult to course correct.
- Exposure to heavy metals, poor water and air quality and suboptimal nutrition all impact important neurodevelopmental processes.
The second panel of the public meeting spoke to the theme, "Impacts of toxic element exposure and nutrition at different developmental stages".
- Nutrition in the first 1000 days also sets the foundation for health and development. Elements such as folic acid, iron, iodine, omega-3, calcium, vitamin D, and zinc are all essential for child growth and brain development. These nutritional elements can also help to overcome the effects from toxic elements.
- Breast milk and/or infant formula is the sole source of nutrition for the first months of life. At about 6 months of age, complementary foods are introduced. Balancing nutrient needs and reducing harmful exposures is key to a healthy diet.
- Calcium supplementation reduces maternal BLL and bone uptake of lead. Other studies have shown similar effects with other toxic metals and introduction to iron and zinc through their antioxidant properties.
- There is a relationship between diet, toxic metal exposure and nutritional status. In settings of iron deficiency, a common occurrence in children, the body responds by increasing the transporter for iron. Lead is an opportunist and uses this mechanism to get into the body. The toxicokinetic pathway is similar in that absorption, distribution, metabolism and elimination are similar between toxic metals and nutritional metals.
- Diet may be a source of toxic element exposure, but nutrients may counteract the kinetics to reduce exposure or effect.
- Lastly, many of these elements (toxic and nutritional) travel together in the soil, water and air. While it is important to get the toxic element levels closer to zero, it cannot happen without the possible expense of nutrition.
Ideally, toxic elements would be absent from foods, but there are practical considerations. Fruits, vegetables and grains take up heavy metals from the soil and water as they grow. As one of the best ways to manage exposure is with a varied diet, FDA and partners have begun a consumer information plan to promote a varied diet for all people but, specifically, young children.