Hadley’s Intro: Do the health benefits of eating dark chocolate
offset the health risks of eating toxic heavy metals in each bite?
Get the story in a guest post courtesy of NYTimes,
Written By Alice Callahan
Feb. 9, 2023
Q: There were a number of news articles about
cadmium and lead in dark chocolate recently, and
it made me incredibly anxious as someone who eats
very dark chocolate every day — including during
my pregnancy and breastfeeding! What would experts
say about how much I should worry?
The bad news came in mid-December: Consumer
Reports published an investigation showing that 23
of the 28 dark chocolate bars it had tested from
various brands contained concerning levels of
lead, cadmium or both. Research has previously
shown that consuming dark chocolate may have
several health benefits, including lowered blood
pressure, better cholesterol and a reduced risk of
heart disease. So the news that it could also
contain toxic heavy metals has worried many
Melissa Melough, an assistant professor of
behavioral health and nutrition at the University
of Delaware, said she was curious to see the
actual data as soon as she read the headlines:
“These types of reports always get
sensationalized.” When she took a closer look,
though, she agreed that the results were
“If you’re a regular consumer of these dark
chocolates, I would be concerned,” she said,
especially if you’re pregnant or breastfeeding
or have a child who enjoys dark chocolate, as the
health effects of these metals are most concerning
during early brain development.
How much lead and cadmium are we talking about?
The Consumer Reports investigation was not
peer-reviewed, but the levels of cadmium and lead
found in the dark chocolate were similar to those
reported in a more comprehensive study of cocoa
and chocolate products published by researchers at
the Food and Drug Administration in 2018. The
F.D.A. study found that dark chocolate had, on
average, 7.6 micrograms of cadmium and 0.8
micrograms of lead per one-ounce serving, and some
products had three or four times as much. (Milk
chocolate, which contains less cocoa, had much
Compared with more than 300 other foods tested by
the F.D.A. in a separate study, dark chocolate had
the third-highest concentrations of both cadmium
and lead, exceeded only by baking powder and cocoa
powder for lead, and cocoa powder and sunflower
seeds for cadmium.
Researchers and chocolate companies have been
aware of the high levels of lead and cadmium in
cocoa products for decades, said Jerome Nriagu, a
professor emeritus of environmental health
sciences at the University of Michigan School of
Public Health. In a 2005 study, he and his
colleagues also found that the lead concentrations
in cocoa powder and chocolate products were among
the highest of any foods. As You Sow, a social
responsibility nonprofit, has since put pressure
on chocolate companies to address the issue,
outlining strategies that can reduce the amount of
cadmium and lead in chocolate.
How do these metals end up in chocolate in the
first place, and are the levels high enough to be
Lead and cadmium are both natural elements in the
Earth’s crust, but human activities like mining,
manufacturing, transportation and agriculture have
increased their levels in the air, soil and water.
Because of their presence in the environment,
these metals are ubiquitous in the food supply,
said Kantha Shelke, a senior lecturer on food
safety at Johns Hopkins University and a
consultant to food manufacturers, including cocoa
processors. “Total avoidance of lead and cadmium
is impossible,” she said in an email.
But it’s clear that cadmium and lead can cause
harm to the body, especially during pregnancy and
childhood. Long-term exposure to cadmium can lead
to bone fragility as well as kidney and lung
damage. Lead can affect nearly every organ system
in the body, especially the nervous system.Editors’ Picks
Since potential toxins can’t be tested directly
on humans, it’s difficult to estimate how much
of a substance is enough to be harmful. What’s
more, different agencies have different food
safety standards. European safety standards, for
example, state that a 130-pound person should
consume no more than 21 micrograms of cadmium per
day to avoid health risks; therefore, an ounce of
dark chocolate that contains seven or eight
micrograms is unlikely to be harmful, Dr. Shelke
said. (People who weigh more or less would have
On the other hand, the “minimal risk level”
for daily cadmium intake set by the U.S. Agency
for Toxic Substances and Disease Registry is about
six micrograms for a 130-pound person. A single
one-ounce serving of dark chocolate could exceed
that amount, and people in the United States
consume an average of five micrograms of cadmium
per day via other food sources, according to a
2019 study by Dr. Melough and her colleagues.
There is no established safe intake level for lead
in the United States, because even the lowest
blood lead levels are associated with adverse
neurodevelopmental effects in children. However,
the F.D.A. does have a recommended maximum for
lead in candy, above which the agency may take
action to limit a product’s sales. The amount of
lead typically found in dark chocolate is lower
than this maximum.
Despite the variability in safety standards,
it’s clear that dark chocolate is relatively
high in both metals and can significantly increase
a person’s overall daily intake.
What’s a chocolate lover to do?
The upside is that you don’t have to give up
dark chocolate entirely. Just enjoy it in
moderation, and as part of a varied diet, Dr.
If you eat chocolate often, it may be worth
choosing products with lower heavy metal
concentrations, she said. As You Sow’s website
keeps track of cadmium and lead levels in products
from several chocolate brands.
A general rule of thumb is to consume no more than
an ounce per day, Dr. Melough said. Eating more
than that raises concerns not only about heavy
metals, but also about high levels of saturated
fat, she added. And research has shown that you
can reap the health benefits of dark chocolate by
eating as little as one-third of an ounce per day.
Because of the greater risk of harm from heavy
metals during early stages of human development,
she said, those who are pregnant or breastfeeding
should consider eating dark chocolate only once or
twice a week. The same goes for children.
But in the longer term, Dr. Melough said,
consumers shouldn’t have to carry the burden of
worrying about heavy metals in their chocolate.
“I do think this has to fall on industry and
producers to change their methods” to reduce
cadmium and lead in their products, she said.
Find out the levels of lead and cadmium in chocolate brands
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