Tier 2 — strong

Japanese intake of flavonoids and isoflavonoids from foods

Kimira M, Arai Y, Shimoi K, Watanabe S

Journal of Epidemiology 1998 8(3):168-75

Bibliography

DOI: 10.2188/jea.8.168
PubMed: PMID 9782673
Funding: Not stated; conducted at Tokyo University of Agriculture, Japan.
Competing interests: Not stated in the reviewed sections.

Study snapshot

Design	Observational dietary survey. Fifty adult women recorded all food intake by weight for 3 days in September 1996, alongside a health check-up; flavonoid and isoflavonoid intake estimated from a 40-food-item database and analysed against health markers.
Model	Human observational cohort; general population dietary survey, not a disease model.
Sample	50 adult women.
Intervention	None; observational dietary intake study.
Duration	3-day weighed dietary record period, September 1996.
Endpoints	Average daily intake of flavonoids: kaempferol, quercetin, rutin, myricetin, luteolin, myricitrin, fisetin, eriodictyol; Average daily intake of isoflavonoids: daidzein, genistein; Association of intake with HDL cholesterol, triglycerides, creatinine, uric acid, bone density, BMI and blood pressure

What the study showed, in plain terms

Before claiming fisetin is safe at dietary levels, someone has to establish how much fisetin people actually eat. This 1998 survey did that for a Japanese population.

Fifty women recorded everything they ate for three days, and researchers calculated intake of eight flavonoids and isoflavonoids, including fisetin.

Average daily fisetin intake was about 0.4 mg per person, a figure widely cited as the baseline dietary exposure, far below doses used in preclinical fisetin studies.

Bottom line: not a fisetin pharmacology study; it is the source of the typical dietary fisetin intake benchmark used to contextualise supplement doses.

Key findings

In a 3-day survey of 50 Japanese women, average daily intake was 0.4 mg fisetin, 4.9 mg kaempferol, 8.3 mg quercetin, 1.5 mg rutin, 0.6 mg myricetin, 0.3 mg luteolin, 0.01 mg myricitrin, 0.3 mg eriodictyol, and roughly 39.5 mg total isoflavones; flavonoid intake correlated positively with age and HDL cholesterol and negatively with triglycerides.

What this study can and cannot tell us

Small, narrow sample (50 women, one Japanese city, 1996); 3-day recall may not reflect habitual intake. Food database covered only 40 items. Late-1990s Japanese dietary data may not generalise to other populations or current patterns.