Heavy Metals in Foods

Cadmium in chocolate, mercury in fish, lead in protein powders and spices, arsenic in grains. Such headlines raise alarms about heavy metals in foods. The immediate reaction may be to eliminate incriminated foods in hopes of avoiding these toxins. However, this approach is flawed.

What’s the difference between heavy metals and essential minerals?

Essential minerals play a role in structure and support systems for the body. For example:

• Calcium is crucial to bone structure and plays a role in heart function
• Iron is important for oxygen transport in the blood
• Zinc is present in enzymes

Problems occur if we ingest too little or too much of these minerals, compromising their ability to perform needed functions.

Heavy metals perform no known functions and are problematic because most accumulate and promote inflammation. Since heavy metals ‘outweigh’ essential minerals, they act as the ‘bully’ and block essential minerals from doing their jobs. Intakes of heavy metals are associated with increased risks of conditions including elevated blood pressure and cholesterol, heart disease, osteoporosis, cancer, cognitive decline and impaired gut and kidney function.

How do heavy metals get into food?

Foods acquire heavy metals from various points between field and fork. Heavy metals enter the environment naturally from rock erosion and volcanic eruptions. Human activities, such as agriculture, mining, smelting, incineration and disposal of old paints, batteries and electrical material may further contaminate the air, water and soil and may add heavy metals to foods.

When it comes to heavy metals, the amount in plants depends on the environment, the type of plant and other conditions. The amount in animals varies with the diet, size and age of the animal. Packaging, processing and cooking can decrease or increase heavy metals in the final food product.

What information is important when evaluating reports about heavy metals?

Many investigative reports list total amounts of heavy metals in food; however, such data may be misleading. This is because heavy metals come in two forms: organic and inorganic, and each impacts the body differently. This makes it important to know the amount of each form, not the total amount, of the heavy metal in foods.

For example:

• Inorganic arsenic has high toxicity, while organic arsenic has little or no toxicity. Fish has high levels of total arsenic, but the source is primarily non-toxic, organic arsenic.
• In contrast, organic forms of mercury have greater toxicity than inorganic mercury.

Note: The use of the word ‘organic’ refers to the metal’s chemical form, not to how it was grown. Thus, organically grown and conventionally grown products may have identical heavy metal content.

Should foods with heavy metals be eliminated from the diet?

Avoiding foods and food groups because they contain heavy metals can cause other problems. Here’s why: 60% of inorganic arsenic in the diet is from vegetables, fruits and juices and 28% is from grains. Avoiding fruits, vegetables and grains would decrease intakes of needed vitamins, minerals, dietary fiber, whole grains and phytochemicals. This strategy would be counterproductive because these foods help minimize the impact of heavy metals.

Many women eliminate fish during pregnancy due to fears of mercury’s adverse effects on fetal development. But research suggests babies of mothers who eat fish during pregnancy have better cognitive and social-emotional development. The Food and Drug Administration (FDA) provides guidance for children and individuals who are pregnant or breastfeeding on how to choose fish that are low in mercury.

What is the best dietary defense to minimize impacts of heavy metals?

Addressing potential harm from heavy metals is best done by regularly eating fruits, vegetables, oily fish, whole grains and foods with dietary fiber. While these foods are recommended as part of a healthful eating pattern, most Americans fall short of recommendations. Diets with attention to variety, and that meet recommendations from the various food groups, help manage the impact of heavy metals.

Following patterns such as the DASH or Mediterranean diet ensure all food groups are included in the right amounts. Focusing on a variety of foods from each food group helps you to get the vitamins, antioxidants, fiber, whole grains and phytochemicals you need. These can help prevent free radicals from doing damage. Another way to minimize heavy metal intake from food is to choose items that are grown in different regions and prepared or processed in a variety of ways. You can do this by checking labels for where products were grown, alternating the types of foods you consume from each food group, and experimenting with different cooking methods.