There was a time when, for most people, “health” meant simply not smoking or avoiding sugar. But these days, in part as a reaction to big corporations having such a major impact on our food and environments, many of us have taken our holistic health into our own hands. Today, non-healthcare professionals are researching how to safeguard their health to a greater degree than ever before. We’re checking ingredients and manufacturing processes on the food we buy, and we’re careful with what we use to cook and store our food, too.

The fact that we care so deeply about our health today is an incredible phenomenon, which shows that we’re recognising the power we have to influence our wellbeing, and that we’re the leading experts on our own bodies. But this growing interest in our health comes with a slight pitfall for those of us who aren’t particularly scientifically inclined: It means that, now more than ever, we’re having to grasp complex scientific terms and processes that we come across in the course of our research.

“We’re recognising the power we have to influence our wellbeing, and that we’re the leading experts on our own bodies.”

One such confusing process is biomagnification, which designates the accumulation of a specific toxic substance as it moves up the food chain — meaning that, for example, by the time we’re eating seared mahi mahi, we’re ingesting a higher concentration of mercury than would have been present in the smaller fish the mahi mahi ate, and a much higher concentration than would have been present in the plankton that smaller fish ate. Here, we break down exactly what biomagnification is — and how it affects our food sources and, in turn, our health.

So, why is everyone talking about biomagnification?

For such an opaque biological process, biomagnification sure has been in the mainstream news and parlance a lot recently. This may be slightly unusual, but it’s not particularly surprising in context.

“More and more people are feeling unwell and they are trying to figure out why.”

– Dayan Goodenowe, Ph.D

“Our psychological environment, physical exposure environment, and food exposure environment have become increasingly pro-inflammatory,” says Dayan Goodenowe, Ph.D., a neuroscientist and clinical research expert. “More and more people are feeling unwell and they are trying to figure out why. Once you start looking, there is a lot to see. People are just trying to make sense of it all.”

Even if someone isn’t suffering from particular symptoms, prevention is key for many of us now. “I think we are seeing a broader shift toward preventative health and environmental awareness,” says Dr. Olalekan Otulana, a general practitioner and addiction physician at Cassiobury Court in the UK.

“People are more engaged with what they’re putting into their bodies and rightly so. There is also a growing interest in the intersection between climate change, food production, and health, and biomagnification is a part of that.”

What is biomagnification?

Biomagnification is, in simple terms, “when certain harmful substances become more concentrated as they move up the food chain,” says Dr. Otulana. “Essentially, a small amount of a toxin in plants or smaller animals accumulates over time in the bodies of the animals that eat them. So, by the time you get to top predators, including humans, the levels can be significantly higher.”

“Essentially, a small amount of a toxin in plants or smaller animals accumulates over time in the bodies of the animals that eat them.”

– Dr. Olalekan Otulana, Ph.D

Meanwhile, any research you might have done about biomagnification will often bring up the term “bioaccumulation” as well — but these two processes aren’t synonymous. “Bioaccumulation refers to accumulation within a single organism, and biomagnification refers to accumulation up a chain of organisms (typically apex predators),” says Dr. Goodenowe. Essentially, bioaccumulation means that a toxin is accumulating in an organism (say, a piece of fruit) over time, if that organism eliminates that particular compound more slowly than it’s ingesting it.

What substances actually biomagnify?

Biomagnification doesn’t apply to just any substance; it only applies to those that are eliminated from an organism (say, a person or a shark) more slowly than they are consumed.

“Any substance that is not easily metabolized or excreted can accumulate,” says Dr. Goodenowe. “Trace metals like mercury and petrochemical-based compounds like PCBs (polychlorinated biphenyls) are the most common types of substances subject to biomagnification.” Dr. Otulana also cites lead and certain pesticides as toxic substances that biomagnify and can pose a danger to human health.

How does biomagnification affect our food sources?

Many of the foods humans eat can become contaminated with harmful toxins, in particular as a result of pollution in the environment. “Humans are omnivores,” says Dr. Goodenowe. “We are exposed to a large variety of food so we are subject to both bioaccumulation (eating contaminated fruits or nuts for example) and biomagnification (eating shark steak).”

When it comes to biomagnification and humans, the problem is that we’re quite high up in the food chain, especially for those who eat meat and fish. “These animals have had time to accumulate high levels of toxins, and that’s what we then ingest,” says Dr. Otulana. “Over time, even a low-level exposure can contribute to long-term health problems.”

What does biomagnification mean for our health as consumers?

Unfortunately, biomagnification of harmful toxins from food sources can lead to various symptoms and health concerns in humans.

“Biomagnification substances are small biochemicals, not large biomolecules like proteins,” explains Dr. Goodenowe. “Therefore, they disrupt biochemical pathways necessary for healthy human function.” The expert says that, when consumed in large amounts over time, these substances can negatively affect mitochondrial function (or cellular health, which is linked to diagnoses such as type 2 diabetes, cardiovascular disease, and Alzheimer’s disease, according to a 2023 review). Biomagnification of certain toxins can also cause endocrine (hormone) disruption.

“When consumed in large amounts over time, these substances can negatively affect mitochondrial function.”

“From these core effects, many diverse health consequences can be observed and mistaken for flu-like symptoms or other nonspecific symptoms — fatigue, confusion, muscle aches and pains, cosmetic changes to hair and skin, cancer,” says Dr. Goodenowe.

Of course, different toxins have different effects on our health. “Mercury, for example, can affect brain function and is particularly harmful during pregnancy as it can impact the development of the child,” says Dr. Otulana. “PCBs have been linked to immune system issues, hormonal disruption, and potentially cancer. Because these substances persist in the body, even small [and/or] regular exposures can become a concern.”

What you can do about biomagnification:

It would be close to impossible to completely avoid exposure to, or ingestion of, foods that are subject to biomagnification — but there are ways to reduce it. For example, the conversation around biomagnification typically concerns fish, which are particularly prone to accumulating harmful heavy metals.

“Try to limit intake of large predatory fish such as shark, marlin, swordfish, and even tuna, especially if you’re pregnant or feeding young children,” says Dr. Otulana. “Opt instead for smaller, oily fish like sardines, mackerel or anchovies, as they’re lower on the food chain and still offer good omega-3 content with less risk of toxin buildup.”

“Eating a large variety of carefully sourced foods is another great way to protect yourself against the accumulation of a particular toxin — think of eating the rainbow.”

Eating a large variety of carefully sourced foods is another great way to protect yourself against the accumulation of a particular toxin — think of eating the rainbow.

“Our bodies are designed to metabolize and excrete virtually every toxin; it is a matter of exposure and time,” says Dr. Goodenowe. “Even the most toxic chemicals will dissipate with enough time. Small exposures of a large variety of toxins is better than a large exposure to a small number of toxins. Remember, everything is toxic if over-consumed.”

Where possible, you should also try to buy organic meat and dairy products, while prioritizing a plant-based diet can also help reduce your exposure to certain toxins — though plants can also contain toxic substances.

“Small exposures of a large variety of toxins is better than a large exposure to a small number of toxins.”

– Dr. Goodenowe

Essentially, while there are some things you can do to reduce the negative effects of biomagnification, you should try not to worry about it too much — both because there’s only so much you can do about it, and because causing yourself excessive stress over it is counterproductive. “The most important thing for everyone to remember is that the human body is amazing. It is capable of incredible feats of healing and resilience,” says Dr. Goodenowe. 

“Eliminate as many negatives as can reasonably be achieved but focus most of your energy on mental and physical health. A mentally and physically healthy body is your best defense against biomagnification.”

Iris Goldsztajn (she/her) is a freelance writer and editor based in London, UK. Her work has been featured in British Vogue, Marie Claire, Refinery29, SELF, Bustle and many more. Iris can typically be found on her way to a fitness class or with her nose in a good book.