Fruits Over Luxury Serums? Insights from a Study Measuring Skin Changes with "8 Weeks of Kiwi"

"Vitamin C is good for the skin"—this phrase is almost common knowledge. It's a familiar staple ingredient in serums and creams. However, a study by the University of Otago reported by ScienceDaily suggests it might slightly "turn that common knowledge on its head." The point is simple and strong: "Eating it might reach the 'inside' of the skin" better than applying it topically. ScienceDaily

"Skin is made from blood" shown with data

The research team focused on the relationship between the concentration of vitamin C in the blood (plasma) and within the skin. The results were surprisingly linear. The higher the plasma vitamin C, the higher the vitamin C in the skin, and this connection was notably stronger than in other organs, according to lead researcher Professor Margreet Vissers. ScienceDaily

The important point here is that the "pathway to reach the skin" has been clarified. The study showed that vitamin C travels through the bloodstream to reach all layers of the skin, linking to improved skin function. ScienceDaily

How was the experiment conducted: Two phases + 8 weeks of "Kiwi lifestyle"

According to the announcement (university newsroom), the study was structured in two phases.

• Phase 1: Using healthy skin tissue obtained during elective surgeries to confirm the relationship between plasma and skin vitamin C. University of Otago

• Phase 2: A dietary intervention was conducted with 24 healthy adults (12 at each site) in New Zealand (Christchurch) and Germany (Hamburg), using a before-and-after comparison. University of Otago

The intervention involved "eating two gold kiwis daily for eight weeks." The researchers tracked changes in blood vitamin C levels, skin vitamin C, and skin function through skin sample collection and various measurements. In Germany, they also evaluated skin thickness, elasticity, UV-related indicators, and epidermal cell renewal using ultrasound measurements. ScienceDaily

What happened?—Improvements in "thickness" and "renewal"

Two major outcomes were highlighted.

1. Increase in skin vitamin C (plasma increases → skin increases) ScienceDaily

2. Accompanied by an increase in skin thickness (interpreted as a reflection of collagen production) and promotion of epidermal renewal (regeneration) ScienceDaily

Particularly, "skin thickness" is often discussed in the skincare context as an indicator related to "firmness" and "density." The researchers explained the increase in thickness as being linked to increased collagen production. ScienceDaily

Why "eating" makes more sense than "applying"

This is the buzzworthy part of the topic. Vitamin C is water-soluble and does not easily penetrate the outer skin barrier. While it's included in topical applications because it "relates to collagen," it inherently has the weakness of being difficult to reach inside. This study, conversely, suggested that the skin has a high capacity to absorb vitamin C from the bloodstream, with a priority on uptake by the outer epidermis. ScienceDaily

In other words, the skin is remodeled not only by "nutrients applied externally" but also by "materials carried by the blood." The novelty of this study lies in showing this obvious fact with actual data from within the skin. ScienceDaily

Stay calm here: The "limitations" and "points to note" of the study

There are points where readers should remain calm.

1) Scale and study design

Secondary media have pointed out limitations such as "small scale" and "lack of a control group (no placebo)." Therefore, caution is needed before concluding that "kiwi caused skin rejuvenation." Health

2) Bias in participant conditions

The study targeted healthy adults, and the "initial vitamin C status" might affect the potential for improvement (those with a deficiency might see more significant increases). Additional research is needed for generalization. Health

3) Funding (risk of conflict of interest)

The study was supported by the kiwi-related company Zespri, which provided fruit and covered indirect costs. However, it is explained that there was no influence on the design, analysis, or publication. It's practical to "understand this as transparency" rather than "doubt." SciTechDaily

Tips for making "skincare from the inside" a reality

Researchers emphasize "stabilizing daily blood levels." Since the body does not store vitamin C long-term, continuous intake is key. As a guideline, for healthy individuals, about 250mg/day can easily optimize blood levels. ScienceDaily

Moreover, the study suggests that similar effects can be expected from foods high in vitamin C, such as citrus, berries, bell peppers, and broccoli, not just kiwis. ScienceDaily

To put it into practice, a realistic plan would be like this.

• Approach "5 plates of fruits and vegetables" daily, with one plate dedicated to high vitamin C (close to the researchers' suggestion) University of Otago

• Instead of immediately fixing on "two kiwis," those with weak stomachs can divide the amount (since fruits also increase dietary fiber) Health

• Since some people are allergic to kiwis, replace them with other foods if they do not suit your constitution (safety first here)

What was trending on social media? (Based on confirmed posts)

Due to platform viewing restrictions, it's challenging to comprehensively track the "content of comments" on social media. However, several public posts that sparked dissemination have been identified.

• Official university video post: Otago University's Facebook video introduces the study content with the catchy phrase "Skin loves vitamin C." Facebook

• Media/medical page Facebook post: A post introducing the study by a Drug Today-related account was found. Facebook

• Shares on X (formerly Twitter): Posts sharing the ScienceDaily article link can be found through searches. X (formerly Twitter)

• Mentions in Instagram Reels: Short videos (Reels) using the study as a topic have also been found. Facebook

From the way these posts "cut out headlines," it can be seen that social media tends to converge on three main points of interest.

1. The strength of the "eating over applying" reversal message (easy to buzz in the beauty context) ScienceDaily

2. The ease of replicating "2 kiwis × 8 weeks" (easy to turn into a challenge) ScienceDaily

3. The point of critique "sponsored by a kiwi company" (easy to spread with cautionary notes) SciTechDaily##