Effect of cooking brassica vegetables on the subsequent hydrolysis and metabolic fate of glucosinolates.
Level 5 - mechanism / opinion, no new human data
Narrative review of human feeding trials and biochemical mechanisms with no new primary data or systematic meta-analysis.
PubMed 17343774 · doi:10.1017/S0029665107005319
What was done
This narrative review synthesized evidence from human feeding trials and biochemical studies examining how cooking brassica vegetables modifies the glucosinolate-myrosinase system, the site of breakdown, and subsequent absorption of isothiocyanates.
What was found
The abstract reports no numerical values. Cooking denatures plant myrosinase, alters enzymic cofactors, and can cause leaching, volatilization, or thermal breakdown of glucosinolates. Ingestion of raw brassica with active myrosinase results in hydrolysis primarily in the upper gastrointestinal tract, whereas cooked brassica is hydrolysed by colonic microflora. Human feeding trials show that glucosinolate hydrolysis and isothiocyanate absorption are greater after eating raw versus cooked brassica.
Why it matters
Culinary preparation dramatically alters the metabolic fate and bioavailability of potential cancer-preventive compounds in brassica vegetables, helping explain weak or inconsistent associations in dietary epidemiological studies.
Limits
The abstract provides no quantitative data, effect sizes, sample sizes, or details on literature search methods. Uncontrolled modifiers such as meal composition, extent of mastication, transit time, host genotype, and colonic microflora variability were noted as major confounders.
Cited by
- supports Cooking broccoli or broccoli sprouts destroys the plant enzyme myrosinase.