Our Summary
Vitamin C is essential for collagen synthesis and skin health, yet many people consume far less than what the skin requires to function optimally. This 2025 study published in the Journal of Investigative Dermatology by New Zealand and German researchers investigated whether simply eating more vitamin C through whole food, specifically two SunGold kiwifruits per day providing approximately 250 mg of vitamin C, could meaningfully raise vitamin C levels in the skin and improve skin function. The study had two components: a cross-sectional analysis of skin tissue from surgical patients examining the relationship between blood and skin vitamin C levels, and an 8-week dietary intervention with 24 participants across two countries (Christchurch, New Zealand and Hamburg, Germany) who ate two kiwifruits daily and had their skin assessed before and after. The findings were clear and significant across both parts of the study: vitamin C levels in both the dermis (deep skin layer) and epidermis (outer skin layer) were directly and positively correlated with plasma vitamin C levels, confirming that what you eat reliably translates into how much vitamin C reaches the skin through active transport from the bloodstream. After 8 weeks of kiwifruit consumption, skin cell proliferation increased significantly, a measure of skin renewal and repair activity, and higher vitamin C concentrations in fibroblasts were observed, directly supporting greater collagen synthesis capacity. The lead researcher summarized the practical implication plainly: increasing dietary vitamin C intake raises vitamin C in all compartments of the skin and supports the collagen production machinery, with an intake of around 250 mg per day, achievable through two kiwifruits, being sufficient to produce these effects.
PMCID: PMC11521643
PMID: 39479621
Abstract
The current systematic review and meta‐analysis was conducted to evaluate the effects of kiwifruit intake on anthropometric indices and key cardiometabolic parameters. Related articles were found by searching PubMed, ISI Web of Science, and Scopus to detect relevant Randomized Clinical Trials (RCTs) and novel systematic reviews relating to kiwi consumption in adults, up to August 2023. The weighted mean difference (WMD) and 95% confidence intervals (CIs) were calculated using a random‐effects model. Heterogeneity, sensitivity analysis, and publication bias were assessed and reported using standard methods. Six RCTs were included in the meta‐analysis. Analyzing overall effect sizes demonstrated a significant reduction in low‐density lipoprotein cholesterol (LDL) levels (WMD: −9.30 mg/dL; 95% CI: −17.56 to −1.04, p = .027), whereas no significant alterations of triglycerides (TG) (WMD: −12.91 mg/dL; 95% CI: −28.17 to 2.34, p = .097), total cholesterol (TC) (WMD: −7.66 mg/dL; 95% CI: −17.85 to 2.52, p = .141), high‐density lipoprotein cholesterol (HDL) (WMD: 2.87 mg/dL; 95% CI: −0.36 to 6.11, p = .141), fasting blood glucose (FBG) (WMD: 1.06 mg/dL; 95% CI: −1.43 to 3.56, p = .404), C‐reactive protein (CRP) (WMD: 0.15 mg/dL; 95% CI: −0.40, 0.70, p = .0598), body weight (BW) (WMD: 0.85 kg; 95% CI: −1.34 to 3.04, p = .448), body mass index (BMI) (WMD: 0.04 kg/m2; 95% CI: −0.75 to 0.83, p = .920), and waist circumference (WC) (WMD: 0.18 cm; 95% CI: −1.81 to 2.19, p = .855) were found. Our findings suggest that consuming kiwifruit does not have a significant impact on anthropometric indices and cardiometabolic factors, except for LDL‐C levels.
Keywords: anthropometric indices, cardiometabolic indices, integrative medicine, kiwifruit, lipid profile, systematic review, traditional Persian medicine
