Spices are an essential component of any kitchen to support a healthy diet. They make food more interesting by adding variety and exciting colors and flavors. They can also act as a preservative. Finally, spices and herbs are potent sources of antioxidants, potentially conferring health benefits when used in cooking. However, recent studies have shown they can contain high levels of heavy metals, which can be harmful to health—especially for vulnerable populations. So, how can you enjoy and even benefit from using these basic cooking ingredients while also minimizing your risk of exposure to potentially toxic chemicals?
Sources of heavy metals
Metals exist throughout the environment, and we interact with them every day. Many are even essential for us to consume (in very small amounts) for our body to function properly; iron, copper and zinc, for example, are all important micronutrients to consume regularly. Those with relatively high densities or atomic weights are classified as heavy metals and are not beneficial to consume. While these heavy metals exist naturally in the soil, their relative concentrations vary by location. Anthropogenic (or human-caused) drivers such as soil erosion, coal burning and plastic production have enabled more metals to enter the water and air over time, leading to more integration into growing food crops and other materials made into products for human consumption. And they don’t just enter the food supply during agricultural production—they can also enter our food through processing equipment or packaging. As a result, we may encounter metals through industrial manufacturing, healthcare products, cosmetics and homewares, in addition to our diet. Unfortunately, they are still intentionally used in other consumer products, such as dental fillings and cigarettes.
Health risks of heavy metals
The four heavy metals of greatest concern for human health are lead, arsenic, cadmium and mercury. While minimal amounts of some metals may be tolerable, lead has been determined to have no safe minimum level. In the short term, ingestion of excessive amounts of heavy metals can lead to poisoning, with symptoms including confusion, numbness, vomiting, fatigue, etc. In the long run, metal exposure can also increase the risk of cardiovascular disease, cancer, reproductive failure, kidney disease and more. Children are at particularly high risk due to their developing brains; metals can act as neurotoxicants that impair brain development. Recent research also reveals links with neurodegenerative diseases, like Parkinson’s disease and Alzheimer’s disease, in adults.
While the body can naturally remove some amount of these metals, they can accumulate over the years and be stored in the bone, brain and elsewhere for a long time. Metals in pregnant women’s blood can also accumulate in higher concentrations in their developing fetuses. Therefore, it’s important to minimize human exposure—especially for high-risk populations, such as pregnant women and young children.
The FDA monitors metal levels in our food supply through its Total Diet Study and sets recommended limits in our food; these limits aren’t enforceable, though. Further, many types of food (including baby food) contain dangerous levels that exceed these limits. The limits also don’t account for potential harm from bioaccumulation (or build-up of substances in an organism) or possible synergistic effects.
A Toxic Elements Working Group in the FDA’s Center for Food Safety and Applied Nutrition aims to reduce the public’s exposure by evaluating which products among those it is testing impose the highest risk, which populations are at the highest risk and what policies and actions it should consider to reduce exposure. However, ongoing reports of high metal concentrations in our food and water supply lead many to believe more action is needed. One example of progress comes from New York State, which has just lowered its limits for heavy metals in spices by almost five times to be the lowest in the US. This enables the Department of Health to recall or seize spices with even very small amounts of lead, cadmium or arsenic.
Contamination in herbs and spices
When evaluating exposure to harmful chemicals and making recommendations to patients and the public, health professionals (and especially dietitians) typically focus on foods and beverages consumed frequently and in large amounts—such as water, meat, dairy, grains and salad greens. However, herbs and spices can also contain harmful levels of heavy metals and should be considered as contributors to daily exposure. A 2019 study by the New York City Department of Health and Mental Hygiene, representing 10 years’ worth of data, showed that more than half of all spice samples contained lead, and more than 30 percent had more than the allowable limit for certain food additives. Further, spices sourced from abroad were most at risk of heavy metal contamination—sometimes 25 times higher than domestic varieties—and spices imported from Pakistan, Bangladesh, Nepal and Morocco had the highest concentrations of lead (these also happen to be areas with minimal regulation). While the US produces some of the spices we consume, the majority are imported because they rely on tropical or subtropical climates to grow.
More recently, a widely publicized Consumer Reports study revealed that spices across 126 samples contained concentrations of heavy metals that were detectable and high enough to pose health risks when eaten in regular serving sizes. Herbs—especially thyme and oregano—tended to have higher levels than spices. Further, contaminated samples weren’t restricted to specific brands or non-organic varieties, either. Unfortunately, some spices may be adulterated, with manufacturers adding metals (especially lead chromate) to increase a spice’s weight and color. At least 13 brands of turmeric were recalled in the US between 2011–2017 due to high lead content. Following this increase in recalls, the FDA issued an important alert, allowing ports to detain future shipments from specific importers—especially from companies in Bangladesh and India that were of the greatest concern. As a more extreme example, a 2019 case report by the Southern Nevada Health District showed a two-year-old boy with a blood lead level of 48 μg/dL (compared to a reference range of <5 μg/dL as of October 2021) measured during his routine well-child visit. The high lead concentration was eventually attributed to the turmeric powder in his family’s home. These issues have led many researchers to call for the FDA to establish maximum allowable levels of metals in spices and educate clinicians and public health officials about the consumption of turmeric and other spices and herbs as a potential cause of heavy metal poisoning.
Tips for minimizing your exposure
Want to minimize your exposure and reduce the risk of potential harm from consuming heavy metals? There are several strategies you can use. Certain cooking methods may help to reduce our exposure to heavy metals in herbs and spices. However, the evidence is limited and somewhat contradictory. A better strategy is to minimize the foods that contain these heavy metals in your diet and be aware of potential adverse effects.
When buying herbs and spices, choose ones grown in the US—and especially from reputable sources that have tested their soil or harvested products. The Consumer Reports study consistently recorded the lowest concentrations of heavy metals in the Simply Organic and Penzey's brands; on the other hand, brands like Great Value and Badia typically contained more.
If you’re able, consider growing as many herbs as possible at home (even indoors in pots in the window). Herbs can then be harvested, dried and stored in glass bottles or jars on your spice rack.
Minimize exposure to heavy metals through other parts of your diet by filtering your water, reducing rice consumption (and buying rice grown in California, India or Pakistan, when possible) and eating fish lower on the food chain (limiting large fish like swordfish, orange roughy and tuna), etc.
If you are concerned about exposure to metals, talk with your doctor about having your blood checked. Children should already be checked for lead annually, helping parents know to take corrective action through dietary exposure if the level is concerning.
Consider signing Consumer Reports’ petition to the FDA to limit heavy metals in our food products.
Resources
The full list of resources can be found here.
Christina Badaracco, MPH, RD
Christina is a registered dietitian and author who aims to improve access to healthy and sustainable food and educate Americans about the connections between food and health. She loves to experiment with healthy recipes in the kitchen and share her creations to inspire others to cook.
Christina completed her dietetic internship at Massachusetts General Hospital and earned her Master of Public Health degree from the University of California, Berkeley. Previously, she graduated with a degree in Ecology and Evolutionary Biology from Princeton University, after conducting her thesis on sustainable agriculture and energy in Kenya. She has done clinical nutrition research at the National Institutes of Health, menu planning and nutrition education at the Oakland Unified School District and communications at the Environmental Protection Agency's Office of Water. She has also enjoyed contributing to children’s gardens, farmers markets and a number of organic farms.