Writing in Foods, researchers from Deakin University said the findings reflected substantial gaps in product transparency, which could limit product comparability and lead to poor consumer decision-making.
A total of 121 supplements containing only anthocyanin and in capsule, tablet and soft gel formats were purchased online from iHerb and Amazon Australia between July and August 2024 for this study.
Common sources of anthocyanins include fruits such as bilberry and elderberry.
While all products declared the amount of fruit extract, only about one in five (18%) or 22 products declared the amount of anthocyanin, which is the bioactive content.
For example, two products can disclose 500mg of bilberry extract each, but one might contain 5mg of anthocyanins, while the other might contain 150mg of anthocyanins, reflecting different effectiveness.
Out of the 22 products that declared anthocyanin content, more than half were bilberry-based supplements, with concentrations of anthocyanins ranging from 3% to 36%.
There is currently no effective standardised dosage for anthocyanin content in supplements, although researchers have suggested more than 80mg/day, based on a 2020 study.
Main fruit source and country of origin
Bilberry (17%) was the most common source of anthocyanin, based on the analysis of these 121 anthocyanin supplements.
This was followed by elderberry (16%), tart cherry (14 %), and cranberry (11%). These four sources accounted for more than half of the supplements analysed.
Less common sources include hawthorn berry, blueberry, acai berry, camu camu and goji berry.
The majority of supplements originated from companies based in the United States (87%), followed by Australia (7%), the United Kingdom, New Zealand, Canada and China. In this study, the origin of the product was taken as the country in which the company is headquartered, rather than the location of product manufacture.
The most dominant delivery format appeared to be capsules, accounting for 85% products, followed by tablets and softgels.
Extract ratio
Researchers also drew data on extract concentration, measured as plant-to-extract ratio, which indicates how concentrated the extract is compared to the actual fresh fruit.
A 4:1 extract in a 500 mg serving, for example, corresponds to 2000 mg fresh fruit equivalent.
However, the plant-to-extract ratio does not indicate the bioactive content. It also does not fully determine the quality or potency of botanical extracts, the researchers pointed out.
“Importantly, label-declared extract ratios should not be interpreted as direct indicators of anthocyanin content or bioactivity without independent verification, as formulation and processing factors may contribute to substantial variability in the final extract composition,” the researchers wrote.
Of the 121 products, 70 products (58%) did not report a plant-to-extract ratio. For those that declared, the most common extract ratios were 4:1 and 10:1, primarily found in bilberry, elderberry, tart cherry, acai berry, cranberry, and hawthorn berry.
In addition, there were inconsistencies in disclosing extract concentrations across brands.
For example, some Australian labelled products reported extract strength as equivalent to the amount of fresh fruit. An example is “each film-coated tablet contains bilberry extract 166.67 mg, equivalent to 15 g fresh fruit”.
Many USA-origin products, on the other hand, typically reported an extract ratio, such as 10:1 or 12:1.
Future work
The researchers have urged for future work to incorporate third-party testing and chromatographic quantification.
Doing so could determine how declared extract ratios relate to actual measured anthocyanin content and product-to-product variability.
“Overall, these findings highlight the need for improved consistency in labelling and stronger alignment between health claims and scientific evidence to ensure that anthocyanins are represented and utilised as bioactive pigments in a transparent, evidence-based manner within the Australian nutraceutical market,” they concluded.
Source: Foods, 15(6), 992. doi: 10.3390/foods15060992. " Anthocyanin-Rich Pigment Supplements in the Australian Online Market: Sources, Labelling Practices, and Bioactivity Claims." Authors: Kumkum, R et al.
