Red-Fleshed Apples for Better Health

    Apples are among the most popular fruits worldwide because they grow in many climates, taste good, and are affordable. They are also widely seen as a symbol of good health. Studies show that eating apples can lower the risk of heart disease, heart-related death, type 2 diabetes, and overall death. Apples contain healthy nutrients such as phenolic compounds, soluble fiber (pectin), plant sterols, triterpenes, vitamins, and other trace minerals. Phenolic compounds are among the most studied nutrients for their health benefits. Apples contain several types of phenolic compounds, such as hydroxycinnamic acids, flavan-3-ols, dihydrochalcones, anthocyanins, and flavonols.

    Anthocyanins, which give many fruits and plants their red to dark purple color, have gained attention for their possible benefits against cardiometabolic diseases. They help lower "bad" LDL cholesterol, raise "good" HDL cholesterol, reduce inflammation, and fight oxidative stress. Recently, red-fleshed apples have gained attention due to their high anthocyanin content. Research indicates that these apples have significantly higher phenolic content and antioxidant capacity than white-fleshed apples, suggesting they may offer additional health benefits.

    Animal studies suggest that red-fleshed apples may help reduce artery thickening and inflammation. In one study, Wistar rats on a high-fat diet were given either red-fleshed apples (HFD+R), white-fleshed apples (HFD+W), or an anthocyanin-rich infusion from Aronia fruit (HFD+A). The red-fleshed "Redlove" apple, naturally rich in anthocyanins, was compared to the white-fleshed Granny Smith apple, which has no anthocyanins. The Aronia infusion was used to test the effects of anthocyanins alone, without other apple components (1).

    Results showed that anthocyanin levels increased in the blood, urine, and feces after HFD+R and HFD+A, while flavan-3-ols increased after HFD+W. Both apple types boosted dihydrochalcone levels. All supplements helped reduce artery thickening, improved kidney function and lowered insulin levels. These findings suggest that anthocyanins alone can protect the heart. However, other apple compounds like flavan-3-ols and dihydrochalcones may also work together to improve heart health in cases of high cholesterol (1).

    In another animal study, researchers studied the effects of red-fleshed apples, white-fleshed apples, and an extract infusion from Aronia fruit equivalent to a dose of cyanidin-3-O-galactoside (main anthocyanin) as red-fleshed apples on heart and artery proteins in rats with high cholesterol. The study compared how these treatments influenced key cardiovascular tissues (2).

    Hypercholesterolemia Wistar rats were separated into six groups (n = 6/group; three males and three females):  Regular chow diet as control; High-fat diet (to induce high cholesterol); High-fat diet + freeze-dried red-fleshed apples; High-fat diet + freeze-dried white-fleshed apples;    High-fat diet with Aronia extract added to drinking water; and High-fat diet with atorvastatin, a cholesterol-lowering drug, in drinking water. Rats in the control group ate a chow diet for 9 weeks, while the other groups were on a high-fat diet for 3 weeks, followed by 6 weeks of a high-fat diet with their respective supplements. Atorvastatin dosage was adjusted based on weight and water intake. The proteome profile of the aorta and heart was analyzed using advanced protein detection methods (2).

    Red-fleshed apples lowered inflammation-related proteins C1QB and properdin (CFP) in the aorta and C-reactive protein in the heart. C1QB is a protein that is part of the complement system and a key part of the immune system. Properdin is a glycoprotein that plays a crucial role in the innate immune system, specifically in the complement cascade. White-fleshed apples also reduced C1QB and CFP in the aorta and lowered other proteins, Complement component C9, and Complement C3 (C9 and C3) in both the aorta and heart. Complement component C9 (C9) is a protein crucial for forming the membrane attack complex, a pore-forming complex that disrupts the membranes of pathogens, leading to their death. Complement C3 is a protein that plays a crucial role in the immune system. It is part of the complement cascade, a series of reactions that help to eliminate pathogens and damaged cells. Aronia fruit infusion affected proteins involved in cell signaling (2).

    The results suggest that both apples have anti-inflammatory effects by influencing the complement system, with red-fleshed apples specifically reducing C-reactive protein, a marker of inflammation. This study also highlights the role of other apple nutrients, beyond anthocyanins, in reducing inflammatory proteins (2).

    Limited research exists on the effects of red-fleshed apples on humans. One recent study found that red-fleshed apples may boost immune function and positively affect gut bacteria compared to white-fleshed apples (3).

    A study compared the effects of red-fleshed and white-fleshed apples on healthy humans in a randomized, placebo-controlled trial. Twenty-five participants consumed dried portions of red or white apples for two weeks, followed by a one-week washout and a two-week crossover period. Researchers analyzed fecal microbiota and blood samples (3).

    The red apple group showed significant changes in gut bacteria, including reduced levels of Streptococcus, Ruminococcus, Blautia, and Roseburia, and increased Sutterella, Butyricicoccus, and Lactobacillus (p<0.05). Gene expression analysis found 18 differentially expressed mRNA transcripts, with 16 related to immune function. These genes were linked to pathways involved in immunity, such as immunoglobulin production, B cell-mediated immunity, complement activation, and phagocytosis. The study suggests anthocyanin-rich red apples may influence immune function and gut microbiota differently than white apples (3).

    Red-fleshed apples are new varieties packed with vital nutrients, these apples contain high levels of phenolic compounds, especially anthocyanins. Research shows that red-fleshed apples have superior antioxidant capacity and phenolic content compared to white-fleshed varieties.  Animal studies reveal that these apples effectively combat artery thickening and inflammation, improving heart function and reducing inflammation markers like C-reactive protein. While human studies are limited, initial findings suggest that red-fleshed apples may boost immune function and positively influence gut bacteria. Overall, red-fleshed apples emerge as a powerful ally for better health.

References:

1.     Yuste S, Ludwig IA, Romero MP, Piñol-Felis C, Catalán Ú, Pedret A, Valls RM, Fernández-Castillejo S, Motilva MJ, Macià A, Rubió L. Metabolic Fate and Cardiometabolic Effects of Phenolic Compounds from Red-Fleshed Apple in Hypercholesterolemic Rats: A Comparative Study with Common White-Fleshed Apple. The AppleCOR Study. Mol Nutr Food Res. 2021 May;65(10):e2001225. doi: 10.1002/mnfr.202001225. Epub 2021 May 3. PMID: 33851768.

2.     Catalán Ú, Pedret A, Yuste S, Rubió L, Piñol C, Sandoval-Ramírez BA, Companys J, Foguet E, Herrero P, Canela N, Motilva MJ, Solà R. Red-Fleshed Apples Rich in Anthocyanins and White-Fleshed Apples Modulate the Aorta and Heart Proteome in Hypercholesterolaemic Rats: The AppleCOR Study. Nutrients. 2022 Feb 28;14(5):1047. doi: 10.3390/nu14051047. PMID: 35268023; PMCID: PMC8912372.

3.     Barnett MPG, Young W, Armstrong K, Brewster D, Cooney JM, Ellett S, Espley RV, Laing W, Maclean P, McGhie T, Pringle G, Roy NC, Ferguson LR. A Polyphenol Enriched Variety of Apple Alters Circulating Immune Cell Gene Expression and Faecal Microbiota Composition in Healthy Adults: A Randomized Controlled Trial. Nutrients. 2021 Mar 27;13(4):1092. doi: 10.3390/nu13041092. PMID: 33801641; PMCID: PMC8065949.

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