Hyaluronic acid (HA)
Hyaluronic acid is a key glycosaminoglycan for skin hydration. Several human clinical trials show that oral HA improves skin hydration and elasticity and reduces the appearance of wrinkles.pubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.gov. For example :
- Hsu et al. (2021)– Double-blind RCT, 40 subjects (35-64 years) ingesting 120 mg/day of HA for 12 weeks. Compared to placebo, the HA group showed a significant increase in stratum corneum water content and skin elasticity, as well as a reduction in wrinkles (assessed by imaging)pubmed.ncbi.nlm.nih.gov.
-Oe et al. (2017)– RCT, 60 subjects (22-59 years) with wrinkles around the eyes, 120 mg/day of HA (two molecular weights) vs. placebo for 12 weeks. Both forms of HA resulted in a significant reduction in wrinkle volume and area (replica measurements), particularly with 300 kDa HA (significant reduction from 8 weeks vs. placebo)pubmed.ncbi.nlm.nih.gov. Furthermore, skin radiance and suppleness improved in all participants vs. baseline.
- Liu et al. (2023)– RCT, 129 women (young and elderly groups) receiving 100–200 mg/day of HA (oral formula) for 12 weeks. Results showed a significant increase in skin hydration after 2–8 weeks in all age groups, as well as an improvement in skin tone (ITA°) after 4–8 weeks and an increase in epidermal thickness at 12 weekspmc.ncbi.nlm.nih.gov.
These studies indicate that moderate oral HA supplementation (100–200 mg/d) can increase skin hydration and reduce wrinklespubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.gov.
The results on elasticity are also positive, although some effects are observed in the long term (8–12 weeks).
Vitamin C
Vitamin C is an essential cofactor in collagen synthesis and a major skin antioxidantpmc.ncbi.nlm.nih.govIt participates in the defense against oxidative stress induced by UV rays.pmc.ncbi.nlm.nih.gov.
Clinical studies examining oral vitamin C alone are rare, but many nutritional interventions or antioxidant supplements (including vitamin C) have shown overall skin benefitspmc.ncbi.nlm.nih.gov.
For example, one review notes that nutritional interventions rich in antioxidants generally improve skin elasticity, wrinkles, texture, and evennesspmc.ncbi.nlm.nih.gov.
-Reilly et al. (2024)– RCT, supplement containing 2.5 g of hydrolyzed collagen + 54 mg of vitamin C (vs placebo) over 12 weeks. Daily intake increased skin hydration by +13.8% (p<0.01) and R2 elasticity by +22.7% (p<0.01) compared to placebopubmed.ncbi.nlm.nih.govWrinkles (Rz profilometry) decreased by –19.6% (p<0.01)pubmed.ncbi.nlm.nih.gov.
This result suggests that vitamin C (even at moderate doses) enhances the effect of collagen on the skin.
Overall, taking vitamin C orally in addition to collagen or other antioxidants shows positive effects on skin hydration and firmness.pmc.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govNo single study can conclude on the 100% effect of vitamin C alone, but its benefits for collagen synthesis and skin antioxidant protection are well established.pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov.
Vitamin E
Vitamin E (α-tocopherol) is a lipid antioxidant that protects cell membranes from UV-induced oxidative stresspmc.ncbi.nlm.nih.govFew clinical trials have studied its oral effect alone on the skin. In dermatological practice, vitamin E is often combined with vitamin C.
In a Bangladeshi study, 121 subjects exposed to arsenic received 400 IU/d of vitamin E and 100 µg of selenium, alone or in combination, for 6 months. Skin lesion (hyperkeratosis) score improved slightly in the active vs. placebo groups, but the difference was not statistically significant.pubmed.ncbi.nlm.nih.gov.
In summary, oral intake of vitamin E, alone or with selenium, showed at best a minor, non-significant effect on chronic skin lesionspubmed.ncbi.nlm.nih.gov.
On the other hand, in theory vitamin E reinforces the antioxidant role of vitamin C and selenium in the skinpmc.ncbi.nlm.nih.gov.
Available data suggest that Vitamin E and C taken together (antioxidant supplement) may improve skin resistance to photooxidative stress, but direct clinical evidence remains limited.
Vitamin A (retinol/β-carotene)
Vitamin A (retinol) is a regulator of epidermal cell renewal and collagen synthesis.
Topically, retinol (and its topical derivatives) is well known to reduce wrinkles and improve skin firmness.
Oral vitamin A in the form of the precursor β-carotene has mainly an antioxidant and photoprotective role.
Clinical trials show that daily supplementation with carotenoids (including β-carotene) increases skin tolerance to UV rays. For example:
-Baswan et al. (2020)– RCT, 60 subjects (phototypes II–IV) took a multi-carotenoid supplement (Nutrilite Multi Carotene, including β-carotene) or placebo for 12 weeks.
The supplementation group showed a significant increase in the minimal UVB erythema threshold (MED) and the minimal UVA pigment dose (MPPD) compared to placebopubmed.ncbi.nlm.nih.gov.
In other words, the skin of the supplemented subjects was better protected against UVB sunburn and UVA-induced pigmentation.pubmed.ncbi.nlm.nih.gov.
Thus, β-carotene taken orally acts as a photoprotector and skin antioxidant.
Its direct impact on skin radiance or texture beyond photoprotection is not clearly established in current literature.
Selenium
Selenium is an essential trace element, a cofactor of glutathione peroxidase, which participates in the neutralization of lipid peroxides in the skinpmc.ncbi.nlm.nih.gov.
In practice, it is often associated with vitamins E and C to strengthen skin antioxidants.pmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov.
Clinically, as mentioned, a trial (Bangladesh) with 100 µg/d of selenomethionine + vitamin E showed only a slight improvement in chronic skin lesions, not significantpubmed.ncbi.nlm.nih.gov.
No significant improvement in skin dryness or redness has been reported specifically with oral selenium supplementation alone.
Selenium, however, remains considered beneficial for the overall antioxidant protection of the skin.pmc.ncbi.nlm.nih.gov.
Summary of the complete formula
A formula combining all of these elements (often combined with collagen) has been clinically tested.
After 3 months, women taking this supplement experienced:
- Significant decrease in the overall wrinkle score (from 5.9 to 5.0 on average, p<0.0001)pmc.ncbi.nlm.nih.gov.
- Significant increase in skin elasticity (measured R2: from 0.65 to 0.74, p<0.0001)pmc.ncbi.nlm.nih.gov.
- Improvement in skin texture, evenness of tone and radiance (100% of participants observed benefits)pmc.ncbi.nlm.nih.gov
These results suggest a synergistic effect of the complete formula on skin aging.
In summary, clinical literature on individual ingredients and combined formulas indicates positive benefits on hydration, wrinkle reduction and elasticity, as well as on skin radiance and photoprotection.pubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.govThe effects described are generally positive, with few neutral or contradictory studies for these dosages of HA (100–300 mg/d) and vitamins/minerals.
Minor contradictions may exist (e.g. the Bangladeshi study on selenium/Vit E showed only a non-significant improvement in lesions), but overall the formula studied improves several clinical parameters of skin health.
Main references:human studies summarized with population, dose and resultspubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govpubmed.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.govpmc.ncbi.nlm.nih.gov.
