As a global fruit with an annual production of nearly 50 million tons, apples (Malus domestica) have become a hot topic of concern in both industry and academia due to the potential of polyphenols extracted from their processing by-products in regulating blood lipids. However, a core issue has always plagued the upstream and downstream of the industry chain:
Does Apple Extract have sufficient human clinical evidence to support its claim of "assisting in cholesterol reduction"?
What is the cholesterol-lowering mechanism?
Apple polyphenols are not single compounds, but a complex system composed of catechins, anthocyanins, chlorogenic acid, and root bark glycosides. According to multiple literature reviews, the molecular mechanism of cholesterol regulation mainly includes the following aspects:
1. Inhibit the activity of cholesterol ester transfer protein (CETP)
Apple polyphenols can reduce the ratio of non-high-density lipoprotein cholesterol (non-HDL-C) to low-density lipoprotein cholesterol (LDL-C) by inhibiting plasma CETP activity. This mechanism has been validated in animal models, but there is still insufficient long-term cohort research data for healthy populations.
2. Upregulation of peroxisome proliferator-activated receptor alpha (PPAR alpha) expression
In the liver cell model, apple polyphenol extract can significantly upregulate PPAR α expression, enhance fatty acid β oxidation, and indirectly reduce the supply of cholesterol synthesis substrates in the liver. This pathway provides a molecular biology basis for explaining its lipid-lowering effect.
3. Regulating the gut microbiota bile acid axis
Polyphenolic substances may inhibit endogenous cholesterol synthesis by altering the structure of gut microbiota, promoting bile acid excretion, and activating the negative feedback mechanism of hepatic intestinal circulation. This mechanism has been frequently explored in research after 2022, but a clear dose-response relationship model has not yet been formed.
Key conclusion: Although mechanism research is becoming increasingly in-depth, existing evidence mostly remains at the level of animal experiments and in vitro studies.
It is explicitly stated that the majority of mechanism research was published around 2005, and the complete literature metadata of high-impact human randomized controlled trials (RCTs) included in China National Knowledge Infrastructure (CNKI) between 2020 and 2023 has not yet been publicly retrieved, which constitutes the biggest scientific shortcoming of functional claims.
What is the current situation of market application?
1. Product form
Common foods such as "Apple Polyphenols Pressed Candy" and "Apple Vinegar Soft Capsules" dominate the market. By designing a formula with a recommended daily intake of ≥ 500mg polyphenols, consumer education is achieved with a "smooth and silent" texture. This type of product avoids the high threshold for registering health food, but cannot claim functionality.
2. Function claim blank
As of the end of 2023, no registration certificate with "apple extract" as the main raw material and approved "auxiliary lipid-lowering" function was found in the health food database of the State Administration for Market Regulation. The only associated product is Tianting ® Apple calcium pyruvate tablets have the function of "weight loss", and apple extract is only an auxiliary ingredient in the formula, with an added amount of less than 10%.
3. R&D investment gap
The R&D investment in the industry is focused on optimizing extraction processes (such as supercritical CO₂ extraction and enzyme-assisted extraction), but there is insufficient investment in RCT research for specific populations (such as mild hypercholesterolemia). The 2020 Koutsos study mentioned was an RCT, but the subjects were the whole fruit intake of "two apples per day", which was not a standardized extract and could not be directly transferred to product applications.
Conclusion
The scientific hypothesis that apple polyphenols can lower cholesterol has a reasonable molecular mechanism and sufficient raw material foundation. From 2021 to 2023, China's apple production will remain stable in the range of 46 million to 50 million tons, and the supply of raw materials will be guaranteed.
The key to the development of the industry in the next 3-5 years lies in whether any enterprise can take the lead in completing RCT research that meets the characteristics of the Chinese population and submitting new raw material registration. In this process, it is necessary to adhere to the bottom line of scientific authenticity, avoid exaggerating epidemiological associations as causal effects, and fully utilize the scale advantage of China's apple industry to promote the transition of extracts from "low-value raw materials" to "high-value functional components". For more details about apple polyphenols, connect with Serrisha from APPCHEM. (Email: cwj@appchem.cn; +86-138-0919-0407)
Reference
[1]Apples: an apple a day, still keeping the doctor away?. Torsten Bohn et al. [2020]
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[3]Y. Pathak. "Handbook of Nutraceuticals Volume II: Scale-Up, Processing and Automation." (2011). [2011-05-16]
[4]C. Bondonno, Xingbin Yang et al. "Flavonoid-rich apples and nitrate-rich spinach augment nitric oxide status and improve endothelial function in healthy men and women: a randomized controlled trial.." Free radical biology & medicine (2012). [2012]