(Poly)phenol toxicity in vivo following oral administration: A targeted narrative review of (poly)phenols from green tea, grape, and anthocyanin‐rich extracts

Abstract

Fruit‐ and vegetable‐derived (poly)phenols are secondary plant metabolites that may have beneficial effects on human health when consumed regularly. Recent years have seen rapid growth in both consumer demand for and research interest in (poly)phenol‐rich dietary supplements, natural colorants, and functional foods. As these products continue to enter the marketplace and (poly)phenol intake patterns change from traditional food products to these sources, attention must be paid to the potential for toxicity from consuming elevated doses of (poly)phenols. To date, much remains unknown regarding the safety of high doses of (poly)phenols, especially in vivo. In this targeted narrative review, we summarize evidence from in vivo investigations of (poly)phenol toxicity after oral administration of green tea extracts, grape‐derived phenolics, and anthocyanin‐rich extracts. There is limited evidence of overt toxicity from oral ingestion of these (poly)phenol‐rich sources, though more research on the safety of high doses—as well as defining what constitutes a “high” dose of both individual and complex mixtures of (poly)phenols—is needed before these observations can be used to create dietary guidance for consumers.

Efficacy and safety of dietary polyphenol supplementation in the treatment of non-alcoholic fatty liver disease: A systematic review and meta-analysis

“…They have great application potential in food, cosmetics, and medicine (130). In terms of safety, anthocyanins as food additives have been proven to have a wide range of safety (131). Evidence shows that anthocyanins in ingested foods are complex flavonoid mixtures, not only non-toxic and non-mutagenic but also these bioflavonoids have various effects on human health maintenance (132,133).…”

The adverse and beneficial effects of polyphenols in green and black teas in vitro and in vivo

“…For example, if the polyphenol content in G7 or R3 (10g/100ml) is 0.14% or 0.07% respectively, the ideal consumption for a 50 kg person would be 500 ml of hot water (containing 0.7 g G7 or 1.6 g R3) to achieve a protective prophylactic concentration of polyphenols (0.2 mg/kg) 47 . These emphasize the importance of determining the polyphenol content in black and green teas to establish the most beneficial consumption amounts 48 .…”

Natural Functional Beverages as an Approach to Manage Diabetes

“…Currently, there is little evidence to suggest toxicity from polyphenols at higher dosages, since most of the polyphenol research has been focused on determining the lowest amount required to show a positive health impact. Although the dose of individual polyphenols can be investigated using traditional toxicological or pharmacological models, alternative methods are needed to study the complex mixes that consumers are exposed to [156]. ↓ TAG, body weight, insulin resistance ↑ glucose tolerance, HDL-C, GCK activity [113] Fresh pomegranate juice 1.5 mL/kg, once, in T2D patients ↑ β-cell function ↓ FPG, insulin resistance [145] Bitter gourd fermented beverage 45 mL, daily, for 1 and 6 months in diabetic patients ↓ FBG and PPBS (1 month) ↓ FBG and PPBS, = blood lipid profile, ↑ HbA1c (6 months) [148] Grapefruit sweetened juices 2-3 mL, daily, for 2 weeks in HFD-OR ↓ body weight, FBG, FSI, liver TAG [114] Vaccinium corymbosum infusion Cup of juice, daily, for 2 years, in a pre-diabetic ↓ serum glucose, HbA1c, insulin resistance [151] Palm An interesting aspect of this research is the positive effects observed in certain fermented beverages that were studied.…”