**Background:** Vaccinium uliginosum L. (bog bilberry) and Vaccinium myrtillus L. (bilberry) are low-growing deciduous shrubs of the Ericaceae family that produce dark purple berries rich in anthocyanins. These berries are consumed fresh, frozen, dried, or as juices, jams, and supplements. In vitro studies have shown that bilberry extracts exhibit anti-glycation, radical-scavenging, and strong antioxidant properties due to abundant bioactive substances such as anthocyanins and flavanols. Pharmacological effects include vascular regulation, anti-dysentery, antigenic activity, diabetic retinopathy protection, and potential anti-cancer effects. Despite many studies on Vaccinium species, no comprehensive comparison of V. uliginosum and V. myrtillus regarding biological activity and functional food use had been published. This review aims to present the similarities and differences between these two species.
**Methods:** This is a narrative review that synthesizes existing literature on the occurrence, chemical composition, and biological activities of V. uliginosum and V. myrtillus. The review covers polyphenols (including flavonols, flavanols, anthocyanins, proanthocyanidins, and phenolic acids), other organic acids, polyunsaturated fatty acids (PUFAs), α-tocopherol, and wax composition. It also discusses the use of these berries in dermatology, ophthalmology, gynecology, diabetology, cardiology, antimicrobial applications, and oncology. Data are drawn from in vitro studies, animal models, and clinical trials.
**Key Results:** The review reports that V. myrtillus has pH values ranging from 2.94 to 3.47, total anthocyanin content (TAC) of 232.7–475.5 mg/100 g fresh weight (FW), and total phenolic content (TPC) of 452–902 mg/100 g FW, with antioxidant capacity (DPPH) of 60.9–106.0 μmol TE/g FW. V. uliginosum has a higher pH (3.5), moderate titratable acidity (1 g citric acid/100 g), and main sugars fructose (2138 ± 149 mg/100 g FW) and glucose (1664 ± 121 mg/100 g FW). In a comparative study, V. myrtillus dry samples contained 21.8 ± 0.1 mg/g total anthocyanins and 26.6 ± 0.1 mg/g total phenolics, while V. uliginosum dry samples had 14.3 ± 0.3 mg/g and 21.1 ± 0.3 mg/g, respectively. Fresh samples showed similar trends. The review notes that V. uliginosum contains more complex anthocyanins, with malvidin-3-glucoside as the main compound (471 mg/100 g dry weight vs. 230 mg/100 g in V. myrtillus). In ophthalmology, a randomized double-blind trial (29 subjects, 4 weeks) found that V. uliginosum extract (1000 mg/day) significantly alleviated visual discomfort from screen use, with improvements in tired eyes (p = 0.001), irritated eyes (p = 0.010), eye pain (p = 0.038), watery eyes (p = 0.005), dry eyes (p = 0.003), visual discomfort (p = 0.018), and blurred vision (p = 0.035). In cardiology, a study of 36 participants consuming 150 g frozen bilberries three times weekly for 6 weeks showed decreased glucose (p = 0.005), triglycerides (p = 0.001), total cholesterol (p = 0.017), LDL-C (p = 0.0347), and increased HDL-C (p = 0.044). In oncology, a mouse model of colorectal cancer showed that 10% anthocyanin-rich extract significantly reduced colon length reduction (p < 0.004) and tumor number compared to controls. Antimicrobial studies found that V. uliginosum anthocyanins at 0.53 mg/mL exhibited significant activity against S. enteritidis, V. parahaemolyticus, L. monocytogenes, and S. aureus.
**Clinical Implications:** The review suggests that both V. uliginosum and V. myrtillus can be used interchangeably as functional foods due to their antioxidant, anti-inflammatory, and anti-cancer properties. Specific applications include dietary supplements for eye health (dry eye, asthenopia, age-related macular degeneration), skin protection (UV damage, wound healing), cardiovascular risk reduction (improving lipid profiles), glycemic control in type 2 diabetes, and as natural antimicrobials. The review notes that V. uliginosum is less studied than V. myrtillus, and more research is needed to confirm its therapeutic potential. No significant side effects were reported in clinical trials, though monitoring for bleeding disorders is advised in patients on antiplatelet therapy.