ALDOB Gene Test (Aldolase B)

• Identify whether you carry ALDOB variants that cause or increase risk for hereditary fructose intolerance, a condition where the body cannot safely metabolise fructose, sucrose, or sorbitol.
• Help explain otherwise unexplained nausea, vomiting, abdominal pain, or low blood sugar after eating fructose-containing foods and drinks, especially in infants and young children.
• Inform personalised nutrition strategies, including whether strict fructose and sucrose restriction is required, or whether more moderate fructose-aware patterns are most appropriate.
• Provide context for liver, kidney, and metabolic monitoring, particularly in people with raised liver enzymes, fatty liver concerns, or a family history of hereditary fructose intolerance.
• Clarify your baseline fructose-handling capacity alongside blood biomarkers and lifestyle data, so long-term nutrition and liver protection plans can be built around your biology.

ALDOB encodes aldolase B, one of three aldolase isoenzymes (A, B, and C) that catalyse key reactions in glycolysis and gluconeogenesis. While aldolase A is predominant in muscle and aldolase C in brain, aldolase B is the main isoform in adult liver, kidney, and small intestine.

Aldolase B cleaves fructose 1,6-bisphosphate in glycolysis and gluconeogenesis and, crucially, also cleaves fructose 1-phosphate in fructose metabolism. Variants that severely reduce aldolase B activity cause hereditary fructose intolerance, where fructose 1-phosphate accumulates in hepatocytes and other tissues, leading to cellular toxicity and metabolic disturbances.

ALDOB sits at a central junction between fructose metabolism and core glucose pathways. In glycolysis and gluconeogenesis, aldolase B catalyses the reversible cleavage of fructose 1,6-bisphosphate into glyceraldehyde 3-phosphate and dihydroxyacetone phosphate, allowing glucose to be broken down for energy or built up from precursors when needed.

In fructolysis, ALDOB acts on fructose 1-phosphate generated by ketohexokinase from dietary fructose. It splits fructose 1-phosphate into glyceraldehyde and dihydroxyacetone phosphate, which can then enter glycolysis, gluconeogenesis, glycogen synthesis, or lipid synthesis pathways. When ALDOB activity is impaired, fructose 1-phosphate builds up, trapping phosphate, impairing ATP production, and triggering downstream metabolic and organ damage.

ALDOB contributes to three interconnected systems: fructose tolerance and carbohydrate metabolism, liver and kidney health, and broader metabolic and growth outcomes in infants and adults. With normal aldolase B function, dietary fructose is efficiently converted into usable energy and building blocks with minimal stress on the liver.

In hereditary fructose intolerance, usually due to biallelic pathogenic ALDOB variants, even modest amounts of fructose, sucrose, or sorbitol can cause hypoglycaemia, lactic acidaemia, abdominal symptoms, and progressive liver and kidney damage if not recognised. Milder or heterozygous variants may shape how well individuals tolerate high-fructose loads over time, which, together with overall diet and lifestyle, influences risk for fatty liver and metabolic disturbances.

It is easy to assume that ALDOB testing, fructose breath tests, and standard liver blood tests provide similar information, but they answer different questions. ALDOB genotyping shows whether you carry inherited variants that disrupt aldolase B structure or function and therefore alter the fundamental ability of your liver and intestine to metabolise fructose 1-phosphate.

By contrast, hydrogen or methane breath tests assess carbohydrate malabsorption and fermentation in the gut, not enzyme activity inside liver cells. Liver enzymes, bilirubin, clotting factors, and imaging show current organ health and injury but cannot distinguish hereditary fructose intolerance from other causes of liver disease without additional context. Together, ALDOB status, clinical history, and functional tests provide a much clearer picture than any single test alone.

The influence of ALDOB variants is shaped by diet, age at exposure, overall liver health, and co-existing metabolic and genetic factors. Several modifiable elements can either buffer genetic effects or amplify them.

• Fructose, sucrose, and sorbitol intake: In hereditary fructose intolerance, strict avoidance of fructose, sucrose, and sorbitol is essential to prevent acute symptoms and long-term liver and kidney damage. In milder contexts, high-fructose diets can exacerbate fatty liver and metabolic strain.
• Age and developmental stage: Infants typically present with hereditary fructose intolerance when fructose or sucrose containing solids, formula, or medications are introduced. Early recognition and dietary management dramatically improve outcomes and growth.
• Overall liver health: Alcohol intake, obesity, viral hepatitis, and other causes of liver stress can compound the consequences of impaired fructose metabolism. Protecting liver health is especially important in carriers of pathogenic ALDOB variants.
• Total sugar and energy load: Even with normal ALDOB, very high sugar intake, especially from sugary drinks and processed foods, contributes to fatty liver, uric acid elevation, and metabolic disturbances. In people with ALDOB-related vulnerability, this burden is magnified.
• Co-existing metabolic genes and pathways: Variants in other carbohydrate and lipid metabolism genes, and in uric acid handling pathways, can interact with ALDOB status to shape real-world risk. A whole-system view is more informative than ALDOB alone.
• Nutrient density and overall diet pattern: Diets rich in whole foods, fibre, and balanced macronutrients support liver resilience, whereas patterns dominated by processed foods and sweetened drinks increase strain on fructose metabolism and liver function.

Yes. Many people carry single or even mild ALDOB variants without evident symptoms, especially if overall fructose exposure is modest and liver health is otherwise good. Heterozygous carriers of hereditary fructose intolerance variants usually do not develop the condition.

Even some individuals with hereditary fructose intolerance may appear well between exposures if their diet unintentionally avoids fructose and sucrose. However, repeated or heavy exposure in the presence of pathogenic variants can lead to serious consequences, particularly in early life, including poor growth, recurrent vomiting, and progressive liver damage if not addressed.

Common ALDOB genotypes primarily differ in whether aldolase B function is normal, partially reduced, or severely impaired. Understanding your pattern can help guide decisions about fructose intake and clinical monitoring rather than framing sugar tolerance in simplistic terms.

• Normal or reference pattern: Individuals without known pathogenic variants typically have full aldolase B activity, though overall fructose tolerance still depends on diet, liver health, and broader metabolic status.
• Heterozygous carriers of pathogenic variants: Carrying one pathogenic ALDOB variant generally maintains sufficient aldolase B activity to prevent hereditary fructose intolerance, but can still be important for family planning and may modestly shape tolerance to very high fructose loads in some contexts.
• Biallelic pathogenic variants (hereditary fructose intolerance): Two disease-causing variants, either identical or compound heterozygous, result in markedly reduced aldolase B function. This causes toxic accumulation of fructose 1-phosphate when fructose, sucrose, or sorbitol are ingested, and defines hereditary fructose intolerance.
• Other missense and regulatory variants: Some variants may subtly influence enzyme stability, substrate handling, or expression, with potential small effects on fructose metabolism. Their clinical significance is usually interpreted in the context of symptoms, biochemical findings, and other genetic data.

For DNA-based ALDOB testing, preparation is straightforward because your genotype does not change with diet, illness, or medications. The key step is understanding with your clinician why testing is being done, for example to investigate suspected hereditary fructose intolerance, clarify family risk, or support precision nutrition.

Cheek swab, saliva, or blood-based ALDOB testing does not require fasting. If ALDOB testing is bundled with liver function tests, metabolic markers, or imaging, your clinician may request specific preparation, such as fasting or avoiding alcohol for a short period, to improve interpretability of those additional investigations.

An ALDOB test is most valuable when the result will influence diagnosis, dietary advice, and monitoring, rather than as a curiosity in isolation. It becomes particularly informative when combined with clinical history, biochemistry, and imaging.

• Infants or children with symptoms after fructose or sucrose: Recurrent vomiting, lethargy, hypoglycaemia, abdominal pain, or growth issues after exposure to fruit, sweetened foods, or sucrose-containing formulas or medications are key triggers for ALDOB testing.
• Unexplained liver disease or metabolic disturbances: Raised liver enzymes, unexplained hypoglycaemia, or lactic acidaemia, especially in younger individuals, can prompt evaluation for hereditary fructose intolerance as part of a broader workup.
• Family history of hereditary fructose intolerance: If a first-degree relative is diagnosed, ALDOB testing can clarify carrier status and inform early-life dietary and diagnostic strategies in children and family planning decisions in adults.
• Personalised nutrition and liver protection planning: In people actively structuring long-term diet and liver health strategies, knowing ALDOB status can help define how firm fructose and sucrose limits need to be and where monitoring should focus.