Does your body absorb heavy metals? Bioavailability explained

Even at the high end, these absorbed quantities are so microscopic they’re not even visible to the human eye. A single grain of salt weighs about 60 mcgOpens in a new tab — that’s about 566 times heavier than the amount of lead absorbed from any of the foods above.

What’s more, a portionOpens in a new tab of the small amount your body absorbs is processed and excreted through stool and urine. For example, most of the arsenicOpens in a new tab your body absorbs is converted into a less harmful form by the liverOpens in a new tab and 70-80% is cleared out within a week. 

How Food Protects You From Heavy Metal Absorption 

Your body doesn't passively soak up whatever you eat. Many whole foods contain nutrients and compounds that bind, block, or escort heavy metals out of your system.

Selenium: Counteracts mercury

Selenium is a mineral that binds strongly toOpens in a new tab mercury. When these two nutrients are ingested together, less toxic mercury-selenium complexesOpens in a new tab are formedOpens in a new tab, which are harder to absorb and easier to eliminate.

Selenium may also play a role in demethylationOpens in a new tab, the process that converts methylmercury (the more absorbable form) into inorganic mercury, which is largely excreted. This is an active area of research, with much of the evidence so far coming from experimental studies.

And it supports a healthy gut barrierOpens in a new tab, which prevents metals from “leaking” into circulation. 

While fish is often flagged for containing high levels of mercury, headlines don’t mention that many speciesOpens in a new tab also contain seleniumOpens in a new tab. When selenium levels exceed mercury levels (the case in nearly all commonly eaten fishOpens in a new tab), selenium may help reduce mercury toxicity by forming stable complexes. 

Bottom line: For most people, eating two to three 4-ounce servingsOpens in a new tab of salmon, sardines, or trout each week keeps mercury exposure within safe limits while providing omega-3 fats, protein, and other essential vitamins and minerals.

Calcium, iron, and zinc: Block heavy metal absorption

Heavy metals and essential minerals compete for the same nutrient transport proteins in your gut. When you eat nutrient-dense meals, more minerals occupy these transporters, leaving fewer available for heavy metals, effectively blocking their absorption. 

• Zinc decreases cadmiumOpens in a new tab absorption
• Iron decreases both leadOpens in a new tab and cadmiumOpens in a new tab absorption 
• Calcium decreases leadOpens in a new tab absorption

Fiber and phytochemicals: Bind and block heavy metals

Compounds in plant foods, including dietary fiberOpens in a new tab, polyphenols and other phytochemical compounds reduce absorption of heavy metals. This may be because they bind to heavy metals in the gut, forming complexes that are too large to cross the intestinal wall and unable to use metal transporters. 

The result: Heavy metals like mercury, Opens in a new tabcadmiumOpens in a new tab, leadOpens in a new tab, and arsenicOpens in a new tab are excreted instead of absorbed. Phytochemical compounds with heavy metal-reducing properties include:

• CatechinsOpens in a new tab in green tea
• QuercetinOpens in a new tab in apples and onions
• ProanthocyanidinsOpens in a new tab in berries
• CarotenoidsOpens in a new tab in carrots and spinach
• CurcuminOpens in a new tab in turmeric

FiberOpens in a new tab and phytochemicalsOpens in a new tab also support a diverse, resilient gut microbiome and strengthen the intestinal barrier, both of which may further reduce heavy metal absorptionOpens in a new tab. 

Probiotics: Support a healthy gut barrier 

ResearchOpens in a new tab suggests consuming certain probiotics strains (via yogurt or supplements) may reduce blood levels of heavy metals in people with known exposure. The likely reason: reduced absorptionOpens in a new tab in the gut. 

Here’s what might be causing that: 

• Probiotic bacteria, including Lactobacillus strains, may improve gut barrier integrityOpens in a new tab. In one animal study, Lactobacillus plantarum helped block cadmium absorptionOpens in a new tab by reversing damage to tight junction proteins — structures in the gut’s lining that prevent compounds from “leaking” into circulation.
• Probiotic bacteria may also help trap and eliminateOpens in a new tab heavy metals or convert them to less bioavailable formsOpens in a new tab the body can’t absorb as well, according to lab studies. 

Although early findings are promising, much of this evidence comes from animal and lab studies, with only limited human research so far — more is needed to confirm these effects. 

The bottom line here: Foods often flagged for containing heavy metals also contain nutrients that prevent their absorption. Testing reports measure total content but don’t reflect these protective interactions, missing the complete biological picture.

Why Do Some People Absorb More Heavy Metals Than Others? 

Two people can eat the same meal and absorb very different amounts of heavy metals. That variability comes down to individual factors like nutrient status, life stage, and gut health.

Nutrient deficiencies

Low mineral status opens the door to higher metal absorption. Iron, zinc, and calciumOpens in a new tab deficiencies are linked to higher absorption of heavy metals like leadOpens in a new tab and cadmiumOpens in a new tab. Animal studiesOpens in a new tab have found that mice on a calcium-deficient diet eliminated 40% less lead than mice who got enough calcium. 

Here’s why: When you’re low on these nutrients, it makes it easier for heavy metals to attach to the nutrient transporters in the gut and enter your circulation. Mineral deficiencies often trigger the body to create more of these transportersOpens in a new tab, giving heavy metals more “doors” to slip through and less competition to get through them. 

Life stage 

Children can absorb 40-50%Opens in a new tab of the lead they ingest. That’s about 4–5 times as much as adults, and they're more likely to be on the high end if they have iron and calciumOpens in a new tab deficiencies. 

Although research is lacking, pregnant women may also absorb more heavy metalsOpens in a new tab. That’s because as nutrient demands rise, many pregnant women experience nutrient deficienciesOpens in a new tab that can increase heavy metal absorptionOpens in a new tab. 

ResearchOpens in a new tab in rats suggests that pregnancy may also increase the numbers of nutrient transporters, which can let more heavy metals into the body. 

Gut microbiome and barrier function

Your intestinal lining is meant to be selectively permeable, allowing for the regulated uptake of vitamins, minerals, and other nutrients into circulation, while keeping harmful compounds out — or at least reducing their absorption. 

AlcoholOpens in a new tab, low fiber intakeOpens in a new tab and high sugar consumptionOpens in a new tab disrupt the balance of microbes, leading to changes that make the gut barrier “leaky,” or less discerning about what (or how much) gets through. When that happens, heavy metals may have an easier route into circulationOpens in a new tab. 

Gut microbiome disruption can also blunt demethylationOpens in a new tab of a highly toxic form of mercury, a reaction that makes mercury less bioavailable and less toxic.

What Bioavailability Means for Your Daily Food Choices 

Most foods contain trace heavy metals, but most healthy adult bodies are generally well-equipped to handle those miniscule exposures, especially when you’re properly nourished. So it’s best not to fixate on whether a specific food contains metals.

Instead ask: “Am I eating in a way that minimizes their bioavailability?” Here’s what that looks like in practice:

• Focus on overall diet quality, not trace-level contamination. Build meals around whole and minimally processed vegetables, fruits, nuts, seeds, legumes, healthy fats like olive oil, and high-quality dairy, fish, and meats. These foods supply the minerals that block metal absorption and the fiber that helps remove what gets through.
• Meet your mineral needs. Regularly eat foods rich in calciumOpens in a new tab (e.g. dairy, sardines and salmon with bones, dark greens), ironOpens in a new tab (e.g. beef, beans, lentils, spinach), zincOpens in a new tab (e.g. meat, fish, oysters, pumpkin seeds), and seleniumOpens in a new tab (e.g. Brazil nuts, sardines, cottage cheese, eggs). Getting enough of these minerals ensures that transport proteins in the gut move nutrients into circulation instead of heavy metals.
• Maintain a healthy gut. A healthy microbiome supports detoxification and gut barrier integrity. Prioritize fiber, probiotic-rich fermented foods, and colorful plant foods containing phytochemicals. Limit alcohol and sugar and take steps to curb stress. 

Trace heavy metals are everywhere, but your body has systems in place to deal with them. So don’t major in the minors. Stay nourished, keep your gut healthy, and you’ll have already solved most of the problem.

This was the fifth article in our six-part "Toxicology in Context: Heavy Metals" series. Want to read the other articles? Check them out below: 

• A brief history of heavy metalsOpens in a new tab
• Toxic metals vs. toxicology: Why dose mattersOpens in a new tab
• Understanding heavy metal regulations like Prop 65Opens in a new tab
• How to read a toxicology report: What does parts per billion mean?Opens in a new tab
• Mechanisms of detoxification: How the body clears heavy metalsOpens in a new tab

FAQ 

Q: Does your body absorb all the heavy metals you eat?

A: No. Bioavailability varies widely depending on the metal, your nutrient status, gut health, and the overall food matrix (the physical and chemical structure of a food). A significant portion of heavy metals pass through the digestive tract unabsorbed, while another portion are processed by organs like the liver and eliminated. 

Q: How does selenium protect against mercury?

A: Selenium (especially when present in greater quantitiesOpens in a new tab) binds tightly to mercury, forming stable, less-toxic complexes that reduce its reactivity and absorption. Selenium also supports demethylation, a process that converts methylmercury into less bioavailable inorganic mercury. Most fish contain more selenium than mercuryOpens in a new tab, providing natural protection.

Q: Why do some people absorb more heavy metals than others?

A: Absorption depends on factors like nutrient status, gut integrity, and life stage. Deficiencies in minerals such as calcium, iron, and zinc increase metal uptake because these elements share nutrient transport pathways. In fact, pregnant women may absorb more lead as they’re at greater risk for iron deficiency, while growing children may absorb moreOpens in a new tab due to greater nutrient demands.

Q: Are heavy metals in vegetables dangerous if they're not absorbed?

A: No. Only a portion of the trace metals present in vegetables is absorbed, and many plant components may reduce absorption further. Fiber, polyphenols, and minerals in vegetables bind metals in the gut and support elimination. The nutrients that make vegetables healthy are the same ones that help keep heavy metals in check.

Originally published May 2026; updated July 2026