Lead is one of several toxic heavy metals that plants can absorb from the environment (the soil, water or air), while growing, and which can contaminate other minerals when they are mined. Sometimes lead is introduced into supplements by its use as a colorant (e.g. lead chromate, which has been added to turmeric powder to make it more yellow) or from other ingredients added to products.
Consequently, supplements and foods such as psyllium, chia seeds, whole turmeric root powder, cinnamon, ginger, ashwagandha root powder, valerian, Echinacea, maca, greens and "whole food" supplements, kelp and seaweed snacks, and green tea leaves all have the potential to be contaminated with lead as well as other toxic metals such as cadmium and arsenic. Plant extracts, as opposed to powders made from whole plant parts, are much less likely to be contaminated as the extraction process helps to remove contaminants. Minerals such as calcium and magnesium may also naturally contain toxic heavy metals such as lead, although this is unlikely today due to improvements in production techniques.
Cocoa and dark chocolate can also contain lead and tend to have even higher levels of cadmium, another toxic heavy metal, which is also in flaxseeds. Because animals and fish can ingest and absorb heavy metals from their environment, products such as canned tuna, herring, and sardines can also be contaminated with heavy metals, particularly arsenic and mercury.
Health concerns and intake limits for lead
In children, infants, and fetuses, even low levels of lead can adversely affect neurobehavioral development and cognitive function. Consequently, lead is of particular concern during pregnancy, as the mother can transfer it to the fetus.
In adults, lead at somewhat higher levels can cause elevated blood pressure, anemia, and adversely affect the nervous and reproductive systems.
The FDA has established maximum daily intakes (i.e., daily limits) for lead from all sources of exposure, called the Interim Reference Levels (IRLs). The limits were reduced by the FDA in 2018: For children, the limit was reduced to 3 mcg from 6 mcg per day. For all adults, it was lowered to 12.5 mcg per day, having previously been 25 mcg for pregnant women and 70 mcg for other adults. According to the agency, the new lower limit for adults helps to protect against possible fetal exposure in women who are unaware that they are pregnant, and against infant exposure during nursing.
The FDA has not established a limit on lead in dietary supplements, leaving the decision up to each manufacturer. Due to its common use by children, in April 2022, the FDA proposed an “action level” limit on lead in apple juice of about 2.4 mcg per cup (8 oz) serving, but double that limit for other fruit juices. (FDA Draft Guidance for Industry 2022).
ConsumerLab.com's testing for lead
Neither the FDA nor any other federal or state agency routinely tests dietary supplements for contamination with lead or other toxic metals prior to sale. For this reason, ConsumerLab tests all supplements containing whole herbs and/or more than 250 mg of minerals for contamination with lead (as well as for cadmium and arsenic). Also tested for heavy metals are all cocoa powders and dark chocolates. ConsumerLab also tests spices for cooking, such as turmeric spice and cinnamon, for heavy metals. ConsumerLab tests for mercury in products where there is contamination concern, such as in canned fish (commonly contaminated) and fish oil supplements (rarely contaminated) and supplements containing spirulina or algae.
When testing for lead, ConsumerLab uses the State of California's Prop 65 limit, above which a warning label is required on products sold in that state (the only state to have such a limit). That limit is 0.5 mcg of lead per daily serving. However, based on settlements of cases of lead contamination in California, which have allowed somewhat higher amounts in products with inherent contamination issues, ConsumerLab allows somewhat higher amounts in products that contain minerals, whole parts of herbs, cocoa (including dark chocolates) and/or for which serving sizes are 5 grams or more.
More details about these limits and how CL tests for lead are found in the How Products Were Evaluated section of each Product Review, accessible here. Any product selected by CL for testing that fails to pass lead testing is noted as "Not Approved" and the amount of lead found is shown in the Review.
In addition the results of its expert testing, ConsumerLab uses only high-quality, evidence based, information sources. These sources include peer-reviewed studies and information from agencies such as the FDA and USDA, and the National Academy of Medicine. On evolving topics, studies from pre-print journals may be sourced. All of our content is reviewed by medical doctors and doctoral-level experts in pharmacology, toxicology, and chemistry. We continually update and medically review our information to keep our content trustworthy, accurate, and reliable. The following sources are referenced in this article: