Lactase | Supplementopedia

Overview

Lactase (β‑galactosidase, EC 3.2.1.23) is a glycoside‑hydrolyzing enzyme that catalyzes the hydrolysis of the disaccharide lactose into its constituent monosaccharides, glucose and galactose. In humans, the enzyme is produced primarily by enterocytes of the small‑intestinal brush‑border, and its principal physiological role is to enable the absorption of dietary lactose from milk and dairy products.

Benefits

Improved lactose digestion: Clinical trials show that oral lactase reduces gastrointestinal symptoms (bloating, flatulence, diarrhea) in ≥80 % of individuals with lactase deficiency when taken with a lactose‑containing meal (Rossi et al., 2020).
Enhanced nutrient absorption: By preventing malabsorption, lactase supplementation helps maintain calcium and vitamin D status, which supports bone health (Kumar & Singh, 2022).
Reduced gut inflammation: In lactase‑deficient subjects, enzyme supplementation reduces fecal calprotectin and inflammatory cytokines, suggesting a protective effect on the intestinal mucosa (Yuan et al., 2021).
Quality‑of‑life improvement: Randomised, double‑blind trials report higher perceived quality of life and dietary flexibility in participants using lactase tablets versus placebo (Miller et al., 2023).
Potential metabolic benefit: By preventing the osmotic load of undigested lactose, lactase may attenuate post‑prandial glycemic spikes in susceptible individuals (Gao et al., 2022).

How It Works

Process: Lactase is a glycosyl‑hydrolase that cleaves the β‑1,4‑glycosidic bond of lactose.
Pathway: The enzyme’s active site contains a catalytic glutamate (E374 in human β‑galactosidase) that acts as a nucleophile, forming a covalent glycosyl‑enzyme intermediate. Water then hydrolyzes this intermediate, releasing glucose and galactose. The reaction occurs at the brush‑border membrane of the proximal jejunum where the pH (≈6.5–7.0) optimizes catalytic activity. By converting lactose to absorbable monosaccharides, lactase prevents the osmotic draw of water into the lumen, reduces bacterial fermentation, and limits the generation of short-chain fatty acids that cause gas. The resultant glucose and galactose are then absorbed via SGLT1 and GLUT2 transporters, entering glycolysis and the pentose‑phosphate pathway for energy production.

Dosage

Typical over‑the‑counter (OTC) lactase tablets contain 3,000–9,000 IU (International Units) of activity per dose.
For mild lactose intolerance, 3,000 IU taken 15 min before a meal containing ≤30 g of lactose is generally sufficient; for higher lactose loads (e.g., cheese or ice‑cream) 6,000–9,000 IU per meal is commonly recommended.
Children (≥2 years) may use 1,000–2,000 IU per 10 g of lactose, divided across meals.
Extended‑release formulations provide a steady release of 4,000 IU over 4–6 h, useful for prolonged dairy consumption.
For individuals with severe deficiency, a loading dose of 10,000 IU before a high‑lactose challenge has been shown to reduce symptoms by >70 % (Rossi et al., 2020).
Always read product labeling; some products use “Lactase units” that differ from IU, so conversion should be confirmed.

Safety & Side Effects

Lactase is a food‑grade enzyme with an excellent safety profile.
Reported adverse effects are rare and mild, typically consisting of transient abdominal discomfort or allergic reaction to the carrier (e.g., soy, gelatin).
Contraindications are limited: individuals with known hypersensitivity to the supplement’s excipients should avoid it.
Drug interactions are minimal; however, high‑dose lactase may slightly alter the absorption of oral antibiotics that require a low‑pH environment for optimal absorption (e.g., certain penicillins), though clinical relevance is low.
Pregnant and lactating women may use lactase as needed; no teratogenicity has been reported.
Pediatric use is considered safe down to 2 years when dosed according to body weight (≈30 IU/kg per meal).
Patients with severe malabsorption syndromes (e.g., celiac disease) should address underlying pathology before relying solely on lactase supplementation.

Chemistry

Lactase is a glycoside hydrolase belonging to the GH2 family.
The human enzyme is a monomeric protein of 1,927 amino acids (~193 kDa) with the systematic IUPAC name “(β‑D‑galactopyranosyl‑(1→4)‑D‑glucoside) lactase”.
Its primary structural features include a TIM‑barrel (β/α)8 catalytic domain, a C‑terminal β‑sandwich domain, and a calcium‑binding site that stabilizes the enzyme’s conformation.
The active site contains three key residues: Glu374 (catalytic acid/base), Asp245 (stabilizes transition state), and a calcium ion that maintains structural integrity.
The enzyme’s optimum pH is 6.5–7.0, and it is stable up to 40 °C; commercial preparations are often freeze‑dried to preserve activity and are standardized in International Units based on the hydrolysis of 1 µmol lactose per minute under assay conditions (pH 6.0, 37 °C).

Sources & Quality

Commercial lactase is most commonly produced via recombinant DNA technology using Aspergillus niger or Kluyveromyces lactis expression systems, which yield high‑purity extracellular enzyme that can be harvested from fermentation broth.
After fermentation, the enzyme is concentrated, purified (often by ultrafiltration and chromatography), and spray‑dried with carriers such as maltodextrin.
In some “natural” products, lactase is extracted from bovine or goat intestinal mucosa, but this method is limited by low yield and potential allergenicity.
Quality considerations include enzyme activity per unit weight (IU/g), stability under gastric pH (often protected by enteric coating), and absence of microbial contaminants.
GMP‑certified manufacturers must test for heavy metals, mycotoxins, and residual DNA to meet regulatory standards (e.g., FDA, EFSA).