Cadmium In Cacao: Where It Comes From And What Gets Tested
Cadmium in cacao comes out of the ground, not out of the factory. The cacao tree draws it up from soil that already contains it, concentrates it in the bean, and no amount of careful roasting afterwards takes it back out. That is why the question is a sourcing question, and why the only honest answer a chocolate maker can give is a test result.
Most of the category answers it differently. It says "we care about quality" and publishes nothing. The limits are public and the science on how cadmium reaches a bean is public, so the silence is a choice rather than a difficulty.
Where the cadmium in cacao actually comes from
It comes from the soil, and the soil varies enormously by region. A 2022 quantitative synthesis in PLoS ONE by Wade and colleagues at the University of Illinois pulled together 31 usable studies covering 489 site-years and 2,127 observations from ten countries across the cacao belt, and modelled what predicts cadmium in the bean.
Two findings matter for anyone reading a label. First, cacao is an unusually efficient accumulator: 77.0% of observations had a bioconcentration factor above 1, meaning the bean held more cadmium than the soil it grew in, with a mean of 2.5 and a range of 0.1 to 30. Second, soil pH was among the strongest predictors, cadmium being far more available in acidic soils. The authors estimate that increasing acidic soil pH from 5 to 7 together with increasing a low soil carbon content (SOC) from 2% to above 3.5% would cut the bioconcentration factor in half.
Total soil cadmium mattered less than you would guess, its effect plateauing at around 1.5 mg per kg of soil. The limitation worth stating: this is a synthesis of other people's field data, with a model error of 0.636 mg/kg bean dry mass, large relative to the legal limits below. It explains patterns. It does not predict a given farm.
The cadmium limits that apply to chocolate in Great Britain
There are legal maxima, they are specific to cocoa content, and they have been in force since the start of 2019. They were introduced by Commission Regulation (EU) No 488/2014, which amended the contaminants regulation and now sits in the GB statute book as assimilated law.
| Product category | Maximum cadmium level |
|---|---|
| Milk chocolate with less than 30% total dry cocoa solids | 0.10 mg/kg |
| Chocolate with less than 50% total dry cocoa solids; milk chocolate with 30% or more | 0.30 mg/kg |
| Chocolate with 50% or more total dry cocoa solids | 0.80 mg/kg |
| Cocoa powder sold to the final consumer, including drinking chocolate | 0.60 mg/kg |
Read the table in order and the logic is obvious. The more cocoa in the bar, the higher the permitted figure, because the ceiling is set on what a normal portion delivers rather than on the raw material. A 77% dark chocolate sits in the last of the chocolate rows, at 0.80 mg/kg. Article 2(2) set the application date at 1 January 2019.
The underlying benchmark is a tolerable weekly intake of 2.5 micrograms per kilogram of body weight, which the regulation's recitals cite from the European Food Safety Authority, noting that some population subgroups may exceed it around twofold across the whole diet. Cacao is one dietary contributor among several.
What fermentation moves, and what it does not
Here is the part that almost never makes it into a guide. Fermentation changes where the cadmium sits inside the bean, and only slightly changes how much is there.
Vanderschueren and colleagues, in Food Research International in 2020, fermented four cacao batches from Ecuadorian fields in duplicate boxes and tracked cadmium between the testa, the thin husk, and the nib, the part that becomes chocolate. Before fermentation about 9% of the bean's cadmium sat in the testa and 91% in the nib. After five to seven days in two of the batches, roughly 20% had moved into the testa, an outward migration the authors describe as running against the concentration gradient. Nib cadmium fell by a factor of about 1.3.
The catch is the condition. That migration appeared only where fermentation drove the pH inside the nib below 5.0; the two batches that stayed above 5 showed no such shift, and the authors note the balance involved, since a very low nib pH brings an acidic taste with it. Total cadmium in the bean fell by about 15% across three batches, which the authors suggest may be related to mucilage lost in the fermentation sweatings, and not at all in the batch that was pre-dried first. Four batches is a small study on one country's beans. Treat it as a mechanism, not a yield figure.
So the processing levers are real but modest. The large lever is which farm the beans came from, the same conclusion the Illinois synthesis reaches from the soil end. For lead, which arrives by a different route, see our note on lead and cadmium in chocolate, and for what alkalisation does, how Dutch processing changes cacao.
What "batch tested" should mean on a label
The phrase is unregulated, so ask three questions of anyone using it. Which metals and which pesticides does the panel cover? Is it every batch or a periodic spot check? And will they send you the certificate of analysis for the batch code on the pack in front of you?
A brand that tests once on a new origin and then coasts for two years is technically telling the truth and practically telling you little. Soil cadmium is a field-by-field property, so a new lot from a new field is a new unknown. Per-batch testing is the only version of the phrase that tracks the actual variable.
What is in a Chaski tube
Chaski Cacao is a 600 g tube of 77% dark chocolate buttons, with a daily dose on the pack of four buttons. The cacao is single-origin Peruvian and Ecuadorian, from a farm our founder has visited and whose farmers he has met, and it is ground at low temperature. The sweetener is coconut sugar. There are no emulsifiers, no seed oils and no palm oil in it, and no added cane sugar. It also contains Lion's Mane as a fruiting body extract and Cordyceps sinensis mycelium.
Every batch is tested for lead, cadmium and pesticides. The composition and the format are set out on the Chaski Cacao product page, and the rest of the library sits in our guides, including the background on what the phrase "ceremonial grade" covers.
If you are comparing bars, ask the maker for a batch certificate. The ones who have it will send it.
Frequently Asked Questions
Is there a legal limit for cadmium in dark chocolate in the UK?
Yes. Commission Regulation (EU) No 488/2014, now assimilated law in Great Britain, sets maximum cadmium levels by cocoa content: 0.10 mg/kg for milk chocolate under 30% total dry cocoa solids, 0.30 mg/kg for chocolate under 50% and milk chocolate at 30% or more, and 0.80 mg/kg for chocolate with 50% or more total dry cocoa solids. Cocoa powder sold to the final consumer is capped at 0.60 mg/kg. Article 2(2) applied those levels from 1 January 2019.
Why does cacao contain more cadmium than other crops?
Because the tree concentrates it. A 2022 synthesis in PLoS ONE covering 31 studies and 2,127 observations from ten countries found that 77.0% of observations had a bioconcentration factor above 1, meaning more cadmium in the bean than in the soil, with a mean of 2.5 and a range of 0.1 to 30. Soil pH was a leading predictor, with uptake much greater in acidic soils. The model carried an error of 0.636 mg/kg bean dry mass, so it describes patterns rather than predicting any one farm.
Does roasting or fermentation remove cadmium from cacao?
Not to any large degree. A 2020 study in Food Research International fermented four Ecuadorian cacao batches and found total bean cadmium fell by about 15%, attributed mainly to mucilage lost in the fermentation sweatings, with no loss at all in a batch that was pre-dried first. Fermentation did move cadmium outward from the nib into the testa, but only where nib pH fell below 5.0. Four batches from one country is a small dataset, so treat it as a mechanism rather than a yield.
What does "every batch tested" actually cover?
The phrase is not regulated, so it is worth asking what sits behind it. Three questions settle it: which metals and pesticides the panel includes, whether testing happens on every batch or as a periodic spot check, and whether the maker will send the certificate of analysis matching the batch code printed on the pack. Soil cadmium varies field by field, so a new lot from a new field is a new unknown. Per-batch testing is the version of the phrase that tracks that variable.
Sources
- Wade J, Ac-Pangan M, Favoretto VR, Taylor AJ, Engeseth N, Margenot AJ, PLoS ONE, 2022;17(2):e0261989
- Commission Regulation (EU) No 488/2014, legislation.gov.uk, 2014
- Vanderschueren R, De Mesmaeker V, Mounicou S, Isaure M-P, Doelsch E, Montalvo D, Delcour JA, Chavez E, Smolders E, Food Research International, 2020;127:108743
See what is in the tube
Chaski Cacao — 600 g tube, 77% dark, every batch tested for lead, cadmium and pesticides