The ketogenic (keto) diet, characterized by its low-carbohydrate and high-fat composition, has surged in popularity as an effective weight loss strategy. However, this metabolic shift can lead to unexpected consequences, notably the potential for false-positive breathalyzer results. This article explores how the keto diet affects breath alcohol testing, the science behind false positives, and the legal defenses available to individuals facing DUI charges due to ketosis-related breathalyzer interference.
How the Keto Diet Affects Breathalyzer Results
The ketogenic diet is designed to shift the body into ketosis, where fat is used as the primary energy source instead of glucose. While keto has gained popularity for its weight loss benefits, it has also been linked to false-positive breathalyzer results, leading to wrongful DUI charges. Understanding the relationship between ketosis and breath alcohol testing is critical for anyone following a keto lifestyle and facing DUI allegations.
The Science Behind False Positives on a Keto Diet
When a person follows a ketogenic diet, their body produces ketones as a natural byproduct of fat metabolism. One of these ketones, acetone, can be converted into isopropanol, a type of alcohol that is exhaled through the breath. Some older or poorly calibrated breathalyzer devices may mistake isopropanol for ethanol, the type of alcohol found in alcoholic beverages.
Research has shown that individuals in ketosis may produce enough acetone to trigger a false-positive BAC (blood alcohol concentration) reading, even if they have not consumed alcohol. This is particularly problematic for individuals pulled over under suspicion of DUI, as officers rely heavily on breathalyzer tests to determine impairment.
Ketone Bodies and the Ketogenic Diet
The ketogenic diet (KD) primarily consists of high-fats, moderate-proteins, and very-low-carbohydrate dietary macronutrients. Specifically, in a 2000 kcal per day diet, carbohydrates amount up to 20 to 50 g per day. This high-fat, low-carbohydrate diet induces ketone body production in the liver through fat metabolism. The goal is to mimic a starvation state without depriving the body of necessary calories to sustain growth and development.
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The very high-fat diet almost eliminates carbohydrates from the patient's food selection - result is the substitution of ketone bodies as a source of energy. Ketone bodies replace glucose as a primary source of energy during ketogenesis due to low blood glucose feedback, stimulus for insulin secretion is also low, which sharply reduces the stimulus for fat and glucose storage. Other hormonal changes may contribute to the increased breakdown of fats that result in fatty acids. Fatty acids are metabolized to acetoacetate which is later converted to beta-hydroxybutyrate and acetone are the basic ketone bodies that accumulate in the body as a ketogenic diet is sustained. This metabolic state is referred to as "nutritional ketosis". If the body continues to be deprived of carbohydrates, metabolism remains in the ketotic state.
Ketone bodies acetoacetate and -hydroxybutyrate then enter the bloodstream and are taken up by organs including the brain where they are further metabolized in mitochondria to generate energy for cells within the nervous system. Ketone body acetone, produced by spontaneous decarboxylation of acetoacetate, is rapidly eliminated through the lungs and urine. Nutritional ketosis state is considered quite safe, as ketone bodies are produced in small concentrations without any alterations in blood pH. This greatly differs from ketoacidosis, a life-threatening condition where ketone bodies are produced in extremely larger concentrations, altering blood ph to acidotic a state.
Variations of the Ketogenic Diet
A classic KD is typically composed of a macronutrient ratio of 4:1 (4 g of fat to every 1 g of protein plus carbohydrates combined) - so shifting the predominant caloric source from carbohydrate to fat. Lower ratios of 3:1, 2:1, or 1:1 (referred to as a modified ketogenic diet)can be used depending on age, individual tolerability, level of ketosis and protein requirements. More 'relaxed' variants have been developed, including the modified Atkins diet (MAD), the low glycemic index treatment (LGIT) and the ketogenic diet combined with medium chain triglyceride oil (MCT).
MAD typically nets a 10-20 g/day carbohydrate limit, roughly equivalent to a ratio of 1-2:1 of fat to protein plus carbohydrates. LGIT involves 40-60 g daily of carbohydrates with the selection of foods with glycemic indices <50, approximately 60% of dietary energy derived from fat and 20-30% from protein. The MCT variant KD uses medium-chain fatty acids provided in coconut and/or palm kernel oil as a diet supplement and allows for greater carbohydrate and protein intake than even a lower-ratio classic KD, which can improve compliance.
How Breathalyzers Detect Alcohol and Why Keto Matters
Breathalyzer devices function by analyzing the chemical composition of exhaled breath to estimate a person’s BAC. They are designed to detect ethanol, but some models are not advanced enough to distinguish ethanol from other substances with similar chemical properties, like acetone.
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Factors that can increase the risk of a false-positive due to ketosis include:
- Prolonged fasting or strict adherence to a very low-carb diet
- Dehydration, which can elevate ketone production
- Individual metabolic differences in how the body processes ketones
While newer breathalyzer technology has improved in distinguishing isopropanol from ethanol, many law enforcement agencies still use older devices, increasing the potential for incorrect DUI charges.
The Role of Isopropanol
Endogenous breath volatiles like acetone are not oxidized at the same electrode potential. However, the secondary alcohol isopropanol (2-propanol) is oxidized at a slightly faster rate than ethanol and these two alcohols cannot be distinguished. Since acetone may convert to a significant amount of isopropanol, this is alarming. A dieting person may be under the legal limit, but the isopropanol will be added to the amount of ethanol detected by the Datamaster DMT.
Physiological vs. Pathological Insulin Resistance
Physiological insulin resistance is a temporary, beneficial adaptation that occurs during fasting or prolonged carbohydrate restriction. It allows peripheral tissues, primarily muscle, to conserve glucose for organs that depend heavily on glucose, such as the brain, red blood cells, and renal medulla. In contrast, pathological insulin resistance seen in pre-diabetes and Type 2 diabetes results from chronic metabolic dysfunction, typically associated with prolonged high carbohydrate intake, inflammation, obesity, or sedentary lifestyle.
During ketogenic fasting, the liver’s metabolic priorities shift dramatically toward gluconeogenesis and ketogenesis. During ketogenic fasting, your liver’s glycogen reserves significantly diminish. Under normal conditions, liver glycogen helps buffer alcohol’s acute metabolic and neurological effects. Elevated ketones, particularly beta-hydroxybutyrate, alter brain metabolism and neurotransmitter function. Physiological insulin resistance is a smart, temporary adaptation that protects glucose-dependent organs during low-carb states. Pathological insulin resistance is a disease state requiring medical intervention. The subjective perception of alcohol’s effects can also markedly differ during ketogenic fasting.
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Legal Defenses for a DUI Charge Involving the Keto Diet
For individuals who follow a ketogenic diet and receive a false-positive DUI charge, there are several potential legal defenses:
- Dietary Evidence: Providing documentation or testimony that the defendant follows a keto diet can explain the presence of ketones in their breath.
- Secondary Chemical Testing: Requesting a blood test instead of a breath test can confirm whether actual ethanol was present.
- Challenging the Breathalyzer Device: Arguing that the breathalyzer used was an older model or not properly calibrated to differentiate between ethanol and isopropanol.
- Officer Misinterpretation: Demonstrating that law enforcement misread the breathalyzer results without considering the defendant’s metabolic state.
The Importance of Blood Tests
In Michigan, police officers have the ability to force a motorist to submit to a breath, blood, or urine test under Michigan's implied consent laws. A blood test will not be effected by the presence of isopropanol.
Why You Need a DUI Attorney If You Follow a Keto Diet
A false-positive DUI charge can result in serious legal consequences, including fines, license suspension, and even jail time. If you follow a ketogenic diet and believe you have been wrongly accused of DUI due to ketosis-related breathalyzer interference, consulting an experienced DUI defense attorney is essential.
An attorney can review breathalyzer accuracy, officer procedures, and the reliability of the test results, potentially leading to case dismissal or reduction of charges. Understanding how the keto diet affects breath alcohol testing can mean the difference between a conviction and a strong legal defense.
Real-World Examples
A 59-year-old man undergoing weight loss with very low calorie diets (VLCD) attempted to drive a car, which was fitted with an alcohol ignition interlock device, but the vehicle failed to start. Because the man was a teetotaller, he was surprised and upset by this result. VLCD treatment leads to ketonemia with high concentrations of acetone, acetoacetate and beta-hydroxybutyrate in the blood. The interlock device determines alcohol (ethanol) in breath by electrochemical oxidation, but acetone does not undergo oxidation with this detector. However, under certain circumstances acetone is reduced in the body to isopropanol by hepatic alcohol dehydrogenase (ADH). The ignition interlock device responds to other alcohols (e.g. methanol, n-propanol and isopropanol), which therefore explains the false-positive result. This 'side effect' of ketogenic diets needs further discussion by authorities when people engaged in safety-sensitive work.
Flight attendant Andre Riley was midair when a medical emergency struck, and he leapt into action to help a sick passenger. But Riley isn't he didn't have a drop. In this state, the body begins to produce compounds called ketones for energy. This is what causes some keto dieters to have breath that smells like nail polish remover. A 2007 studyfound that during the process of breaking down acetone, the body produces isopropanol, a form of alcohol. Other anecdotes support this finding. The US government is testing the keto diet to treat veterans' diabetes.
The Limitations of Breathalyzer Technology
Some substances are so similar to ethyl alcohol that early single-wavelength infrared EBTs had difficulty distinguishing them or were unable to distinguish them. Theoretically, these “interfering substances” could inflate breath test results. There are only a few volatile substances that can be found in the breath of a living, breathing person other than alcohol. In fact, only one potentially interfering substance has been shown to exist in measurable concentrations in the human body over time: acetone.
The body produces acetone as a byproduct of incomplete digestion in a very few individuals such as diabetics whose insulin levels are not controlled. If a person is diabetic or fasting, the officer and prosecutor should obtain as much information as possible about the person’s condition or diet. Additionally, people, most notably painters, may be exposed to acetone at work. The APRI focuses on acetone, observing that single-wavelength infrared EBTs could "theoretically" inflate breath test results. There's nothing "theoretical" about it, especially regarding single-wavelength infrared EBTs. To the contrary, it is well-known and accepted that a single-wavelength EBT cannot distinguish between ethanol and acetone, which is why most modern breath testing devices employ multiple wavelengths.
The BAC Datamaster employs an infrared wavelength of 3.37 and 3.44 um. The Datamaster DMT measures at 3.37, 3.44, and 3.50 um. (Michigan State Police opted to disable the 3.50 um filter for no apparent reason, as well as crippling the Datamaster DMT by disabling the flow, volume and BrAC slope plotting software. The Datamaster DMT is supposed to trigger a "chemical interference" if enough acetone is present in a breath sample. Although there are concerns regarding the amount of acetone necessary to trigger an error message, it is highly improbable that a Datamaster DMT would provide a reading in excess of the legal limit if only acetone were present. This is not true regarding single-wavelength infrared EBTs, and early advocates of the Atkins diet used older breath testing machines to measure a dieting subject's breath to ensure compliance with the program.
Although modern breath testing devices are designed to guard against confusing acetone for alcohol, breath testing devices cannot discriminate between different kinds of alcohol. There are several different kinds of alcohols, including ethanol, methanol, isopropanol, and ethylene glycol. But it's not like you're drinking methanol on the Atkins diet, right? An electrochemical detector, such as a PBT device, will respond to "acetaldehyde, methanol, isopropanol and n-propanol vapours besides ethanol, but it was insensitive to acetone vapour." Since these devices do not respond to acetone, a motorist who had a breath interlock testing device inside a company car was surprised when the car would not start. He never consumed alcohol and was a teetotaler, and he was not using mouthwash or any alcohol containing products.
Adverse Effects and Contraindications of the Ketogenic Diet
Short-term effects (up to 2 years) of the ketogenic diet are well reported and established - however, the long-term health implications are not well known due to limited literature. Most common and relatively minor short-term side effects of ketogenic diet include a collection of symptoms like nausea, vomiting, headache, fatigue, dizziness, insomnia, difficulty in exercise tolerance, and constipation, sometimes referred to as keto flu. Symptoms resolve in a few days to few weeks. Adequate fluid and electrolyte intake can alleviate some of these symptoms. Long-term adverse effects include: hepatic steatosis, hypoproteinemia, kidney stones, and vitamin and mineral deficiencies.
With respect to diabetic patients appropriate adjustment of insulin or oral hypoglycemic agents is required to avoid severe hypoglycaemia if the medications are not appropriately adjusted before initiating this diet. Ketogenic diet is contraindicated in patients with pancreatitis, liver failure, disorders of fat metabolism, porphyrias, primary carnitine deficiency, carnitine palmitoyltransferase deficiency, carnitine translocase deficiency, or pyruvate kinase deficiency.