Strong Genetic

Hereditary Fructose Intolerance (HFI)

Name: Hereditary Fructose Intolerance (HFI)
Creator: Realised
Published: 2026-03-01

GeneALDOBrsIDrs1800546, rs76917243, rs78340951, rs1800545InheritanceAutosomal recessiveCarrier frequency~1 in 60-80 EuropeansSystemCarrier Screening

Summary

Hereditary fructose intolerance is a metabolic condition where the body cannot process fructose — a sugar found in fruit, table sugar (sucrose), honey, and many processed foods. The ALDOB gene encodes aldolase B, the liver enzyme responsible for breaking down fructose-1-phosphate. When this enzyme is absent or non-functional, fructose-1-phosphate accumulates in liver, kidney, and intestinal cells, causing direct toxicity.

Practical takeaway

This matters when planning children. With a European carrier frequency of roughly 1 in 60-80, the chance of your partner also being a carrier is not negligible. A carrier test through a GP or genetic counselling service can determine your partner's status. If you are both carriers, a genetic counsellor can discuss what HFI management looks like in practice — primarily dietary management from the point of weaning. The key practical point: if both parents are carriers, newborns should be tested before introduction of fructose-containing foods or formulas. Breastmilk and standard lactose-based formulas are safe (they contain no fructose). Realised does not calculate reproductive risk or advise on reproductive decisions.

Evidence detail

What Carrier Status Means For You

You are not affected. One working copy of ALDOB produces enough aldolase B enzyme for completely normal fructose metabolism — you can eat fruit, sugar, and sorbitol-containing foods without any issue. Your carrier status becomes relevant if your partner also carries an ALDOB variant. In that scenario, each child has a 25% chance of having HFI, a 50% chance of being an unaffected carrier, and a 25% chance of inheriting neither variant.

Population Context

HFI carrier rates are highest in people of European descent, particularly Central and Northern European populations. The A149P variant accounts for approximately 65% of European HFI alleles and is the most commonly tested variant on consumer platforms. The condition occurs across all ethnic groups but at lower frequencies outside Europe. HFI is sometimes called a "hidden" condition because many affected individuals self-diagnose through food aversion — they learn to avoid sweet foods and may never receive a formal genetic diagnosis. The true prevalence may therefore be higher than estimates suggest.

Limitations

23andMe tests 4 of over 40 known pathogenic ALDOB variants. The tested panel covers the most common European variants (A149P alone captures ~65% of European alleles), but may miss rarer variants or those more prevalent in non-European populations. A "not detected" result reduces but does not eliminate carrier risk. Comprehensive carrier screening through a clinical laboratory covers substantially more variants and is recommended if your partner is a known carrier or if there is a family history of fructose intolerance.

Sources (5)

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