Addition of strawberries to the usual diet increases postprandial but not fasting non-urate plasma antioxidant activity in healthy subjects

Abstract

Strawberries can augment plasma antioxidant activity, but this may be confounded by selection of methods, time of blood sampling and concomitant dietary restrictions. We examined the effect of strawberry consumption on ferric reducing ability (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity (DPPH-test) of native and non-urate plasma in healthy subjects on their usual diet. Eleven subjects consumed strawberries (500 g daily) for 9 days. Fasting and 3-h postprandial plasma and 24-h urine collection were obtained before, during and after strawberry course for FRAP, DPPH-test and polyphenols determination. Fifteen subjects served as a control in respect to plasma antioxidant activity changes and effect of 300 mg of oral ascorbate. First, 5th and 9th strawberry dose increased 3-h postprandial DPPH-test by 17.4, 17.6 and 12.6%, and FRAP by 15.5, 25.6 and 21.4% in comparison to fasting values in non-urate plasma (p<0.05). In native plasma only a trend was observed to higher postprandial values for both tests. Strawberries increased urinary urolithin A and 4-hydroxyhippuric acid whereas plasma polyphenols were stable. No changes of FRAP and DPPH-test were noted in controls and after ascorbate intake. Strawberries transiently increased non-urate plasma antioxidant activity but this cannot be attributed to direct antioxidant effect of polyphenols and ascorbate.

Physico-chemical characterization and antioxidant capacity of the colombian berry (Vaccinium meridionale Swartz) with a high-polyphenol content: potential effects in people with metabolic syndrome

“…Another acute study evaluating plasma antioxidant capacity after strawberries consumption, reported no increases in polyphenol levels. The authors stated that antioxidant activity may be confounded by selection of methods and time of blood sampling (Prymont-Przyminska et al, 2016). Volunteers in this study consumed the agraz nectar during 4 wk; thus, it was expected that with this chronic consumption the levels of polyphenols in serum and their antioxidant capacity would be higher, compared to the placebo period, regardless of time of blood sampling.…”

Hemodialysis Decreases the Concentration of Accumulated Plant Phenols in the Plasma of Patients on Maintenance Dialysis: Influence of Residual Renal Function

“…Zimmerman et al determined that clearance of hippuric acid was fivefold higher than that of creatinine (30). In our previous study, we determined that the molar ratio in the concentration of total phenols to creatinine in morning spot urine reached nearly 1 : 4 (27) and the ingestion of a single meal rich in phenols did not lead to an increase in the concentration of certain phenolic acids in plasma within 3 h after consuming them (31). Instead, the repeated ingestion of such meals led to the elevation of phenolic concentration in 24-h urine collection, which suggests high renal clearance (31).…”

“…In our previous study, we determined that the molar ratio in the concentration of total phenols to creatinine in morning spot urine reached nearly 1 : 4 (27) and the ingestion of a single meal rich in phenols did not lead to an increase in the concentration of certain phenolic acids in plasma within 3 h after consuming them (31). Instead, the repeated ingestion of such meals led to the elevation of phenolic concentration in 24-h urine collection, which suggests high renal clearance (31). This is supported by similar observations of other authors, who have reported a remarkable rise in phenolic concentration in urine several hours after a polyphenol-enriched meal (4,32).…”

Dietary Vitamin C, E and β-Carotene Intake Does Not Significantly Affect Plasma or Salivary Antioxidant Indices and Salivary C-Reactive Protein in Older Subjects

“…This observation was similar to another finding in which serum UA decreased in elderly subjects after they were supplemented with high doses of vitamin C [ 45 ]. Strawberries added to the usual diet as a source of vitamin C did not increase fasting non-urate plasma antioxidant activity [ 46 ]. Wang et al [ 7 ] reported that plasma TAC (determined by VCEAC—vitamin C equivalent antioxidant capacity) was positively associated with dietary intakes of γ-tocopherol and β-carotene, as well as with plasma α-tocopherol and UA, in overweight and apparently healthy postmenopausal women.…”