The research is published in the Journal of Toxicology and Environmental Health and considers the DNA damage of sucralose, the sweetener, and its metabolite, sucralose-6-acetate. Many of the mainstream articles led with sucralose and only much later wrote about sucralose-6-acetate, the focus of the study, and its concerns.
To unwind the sucralose study, we must understand the validity of the tests they used, and to make sure we are all beginning at the same place, let’s start with some definitions.
- Carcinogenicity - any substance, combination, or mixture of substances that cause an increased incidence of benign and/or malignant neoplasms or a substantial decrease in the latency period between exposure and onset of neoplasms in humans.
- Genotoxicity – is the destructive effect affecting the integrity of the genetic material of the cells (DNA, RNA).
- Clastogenicity is a form of genotoxicity and refers to the ability of a substance or agent to induce chromosomal damage, such as breaks or rearrangements, in cells. These changes may disrupt the normal structure and function of genetic material, potentially leading to genetic instability and the development of cancer.
- Aneugenicity is another form of genotoxicity and refers to the ability of a substance or agent to disrupt the normal process of cell division (mitosis or meiosis), leading to an abnormal number of chromosomes in the daughter cells. This abnormal number of chromosomes can lead to genetic instability and cancer development.
Not all clastogens are directly linked to cancer. As with all biological systems, the relationship of clastogens to cancer is complex. The development of cancer is multifactorial, and clastogens can be one of many contributing factors, but they are not the sole cause. For susceptible individuals, clastogens impact is based on dose and duration of exposure – the dose makes the poison.
The current study uses several tests to identify the clastogenic and aneugenic effects of sucralose and sucralose-6-acetate. Before looking at the results, we must, again, have some context.
The purpose of these tests is to protect the public from exposure to harmful chemicals. Generally speaking, the ideal test would identify those dangerous chemicals with few false negatives – the test's “sensitivity” and false positives, a test’s “specificity.” The false positives mandate other tests, usually testing for carcinogenicity in our rodent friends. These testing protocols are costly and time-consuming, so newer tests, like multi-flow cytometry, could supplant tests developed 30 to 40 years ago.
The sucralose study used three tests searching for clastogenic and aneugenic properties.
- The Ames test – the classic mutagenicity test identifies mutations in Salmonella typhimurium and Escherichia coli. You can find a much longer explanation of the test here. It has a sensitivity of 57% and a specificity of 64%.
- An in vitro mammalian cell micronucleus (MN) – “Micronuclei are small extra-nuclear structures that are produced by DNA breakage (clastogens) or are induced by numerical chromosomal aberrations (aneugens).” It has a sensitivity of about 75% and a specificity of 31%. It is considered a well-validated test.
- Multi-flow cytometry (MFC) – a “screening tool” predicts whether a compound may be a clastogen or aneugen based on the presence of biomarkers after cells are exposed to the chemical of concern. It has a sensitivity of about 91% and a specificity of 97%. It is considered a well-validated test, although not as validated as the MN test.
The more recently developed tests, MN and MFC, are possibly more accurate than the classic Ames test; they are also faster and less costly. Their enhanced identification of possible genotoxins makes them contenders to replace our current testing protocols and might eliminate the need for animal testing, but that has yet to occur.
Study Data Points
- Ames Test – “…sucralose-6-acetate and sucralose were both negative (non-mutagenic)….”
- Micronucleus(MN) – sucralose-6-acetate was genotoxic at a dose of 1000 μg/ml over 27 hours in the absence of metabolic activators [1]. It was not genotoxic in the presence of those activators. Sucralose itself was not tested. (These doses and “dwell times” are not real-world values.)
- Multi-flow cytometry (MFC) – sucralose-6-acetate was found to be clastogenic in the presence or absence of those metabolic activators; the lowest concentration for which clastogenicity was noted was 353 μg/ml. Clastogenicity was not identified for sucralose.
The researchers performed additional testing looking at the metabolic and physiologic impacts of sucralose and sucralose-6-acetate. Both increase intestinal wall permeability that could allow for the development of leaky gut syndrome; enhance or reduce the expression of a range of genes associated with inflammation, oxidative stress, and cancer; and impact the liver’s enzymes, which detoxify chemicals or drugs.
Those are the scientific findings, the facts of the matter. But the devil lies in connecting them.
The Study’s Narrative – How the dots were connected
Their testing concluded that sucralose-6-acetate is genotoxic, but the “potential adverse health effects” have not yet been identified in the scientific literature. In other words, a connection between sucralose-6-acetate’s genotoxic actions and cancer has not been found. That is primarily due to no one looking, but if there were a strong, robust relationship, surely some individual would have investigated.
“…. a single serving of sucralose-containing drinks may contain levels of sucralose-6-acetate that exceed a TTCgenotox of 0.15 µg/person/day by 4 orders of magnitude or more. … Repeated daily dosing enhances exposure to sucralose-6-acetate because this impurity was reported to persist in the body for at least 11 days after cessation of intake of sucralose.”
The TTCgenotox is the Threshold of Toxicological Concern (TTC) based on a predicted tumor risk of 1 in a million, derived through an analysis of genotoxic chemicals in general. [2] It is a practical means to prioritize further evaluation,
“when exposures are very low and when little or no toxicity data exists.” …[It is] not intended to be applied to chemicals which are regulated and for which specific requirements exist regarding their hazard assessment.”
Sucralose is not subject to TTC evaluation as it has regulatory approval in the US, Canada, Asia, and in the strictest of all, Europe.
There are always concerns that a genotoxic chemical may accumulate over time, the half-life of sucralose-6-acetate of roughly 38 minutes. [3] Concerning the "persistence of this impurity in the body," we need to note that the body was that of 10 rats force-fed an average dosage of 80.4 mg/kg/day for 40 days. Given the EU-regulated maximum dose of 300mg/liter of sucralose, a typical 70 kg human must ingest over 18 liters of sucralose-sweetened beverages daily to achieve comparable levels.
What to conclude?
“These findings raise health and safety concerns regarding the continued presence of sucralose in the food supply and indicate that a regulatory status review needs to be undertaken.”
The research findings do raise concerns. Perhaps the tests we rely upon to uncover genotoxicity, now 30 years old, need to be replaced by more sophisticated techniques. But that will require validation studies which we should pursue. The concerns about sucralose and its metabolite sucralose-6-acetate demonstrate that if we look hard and long enough, we will uncover unsettling physiologic changes.
But those concerns must be tempered with a degree of common sense. The US-approved daily intake of sucralose is 5mg/kg/day. A typical cake made with Splenda contains 10 milligrams of sucralose - no one will eat 35 sucralose-sweetened cakes a day or drink 18 liters of sucralose-sweetened beverages.
The media that reported on this study often mixed the effect of sucralose with that of sucralose-6-acetate and mixed genotoxicity with carcinogenicity, two related but very separate concepts. They wrote their articles to gather attention and shed light on themselves, not on their subject or the needs of their readership.
[1] These metabolic activators are a standard preparation, S9, derived from homogenized liver cells processed in a specific manner. They are used in the Ames test, a bacterial test, to more closely mimic genotoxicity in humans, where these metabolic activators are present in the body
[2] TTC is based on a frequency distribution of No Observed Adverse Effects Level (NOAELs) at the 5th percentile.
[3] The general rule of thumb is that 97% or more of the chemical will be gone after 4 to 5 half-lives; in the case of sucralose-6-acetate, that would be a little over 3 hours.
Sources: Toxicological and pharmacokinetic properties of sucralose-6-acetate and its parent sucralose: in vitro screening assays Journal of Toxicology and Environmental Health DOI: 10.1080/10937404.2023.2213903
Search for the optimal genotoxicity assay for routine testing of chemicals: Sensitivity and specificity of conventional and new test systems. Mutation Research: Genetic Toxicology and Environmental Mutagenesis DOI: 10.1016/j.mrgentox.2022.503524
Threshold of Toxicological Concern Approach in Regulatory Decision Making: The Past, Present, and Future EPA Presentation
Chuck Dinerstein, MD, MBA
Director of Medicine
Dr. Charles Dinerstein, M.D., MBA, FACS is Director of Medicine at the American Council on Science and Health. He has over 25 years of experience as a vascular surgeon.
