This is the first clinical research to determine the effects of dietary aloe supplementation on facial wrinkles/elasticity and the type I procollagen and MMP-1 gene levels in aged human skin. In this study, we found that aloe vera gel supplementation clinically improved facial wrinkles and elasticity, while it increased type I procollagen and it decreased the MMP-1 gene expressions in the photoprotected skin.
In this study, the degree of clinical wrinkles was objectively measured by using a device (the Visiometer) that converts the skin surface roughness to numerical values. The facial wrinkles decreased in both the lower-dose and higher-dose groups; however, no dose-response relationship was seen in this study. This may be partially attributed to the small number of subjects in this study and a relatively short time period of aloe gel supplementation. The decrease in facial wrinkles as measured by the Visiometer reflects increased type I procollagen in both dosing groups. At the gene level, lower-dose aloe was shown to increase type I procollagen mRNA in the photo-protected buttock skin, albeit without statistical significance, whereas no change was seen in the MMP-1 mRNA levels. In the higher-dose group, while aloe gel had little effect on the type I procollagen mRNA levels, it caused a significant decrease in the MMP-1 mRNA levels. As a result, both dosing groups would have a net gain of procollagen that would correlate clinically with the improvement of wrinkles, as measured by the Visiometer. Type I procollagen immunostaining also demonstrated an upregulated protein expression in both groups.
The mechanism by which aloe exerts its anti-aging effects is unknown. The therapeutic action of aloe has been studied mostly for wound healing. When wounded diabetic rats were treated orally and topically with aloe gel, increased collagen formation was later demonstrated17
, and the collagen formed had a higher degree of crosslinking, indicating enhanced levels of type III collagen18
. According to the literature on the therapeutic effect of aloe, immunostimulation frequently appears as a contributory factor. Aloe gel extracts, when applied after UV exposure, were found to prevent suppression of local and systemic immunity to haptens and delayed type hypersensitivity responses to Candida albicans
. This was attributed to the presence of polysaccharides in the aloe vera gel. They have no significant anti-oxidant activity; the immune-protective action of aloe polysaccharides takes place at a step downstream from DNA damage and repair, possibly by modulating the DNA-damage-activated signal transduction pathways20
. These compounds may act by novel mechanisms to block the signal transduction pathways and the production of immunosuppressive cytokines. An acetylated glucomannan in aloe was found to be the biologically active, dominant polysaccharide, so much so that it was named acemannan5
. Acemannan from aloe was shown to increase collagen biosynthesis, and perhaps this occurred through macrophage stimulation21
. In addition, active glycoproteins have been demonstrated in aloe gel and they may well play some part in aloe's therapeutic activity, either immunologically as lectins or as proteases such as anti-bradykinins. Superoxide dismutase activities have also been reported from Aloe vera
There are 3 cases of oral aloe vera-induced hepatitis in the medical literature23-25
. In this study, no toxicity was observed in association with oral aloe intake. The doses used in the study were determined arbitrarily based on the daily recommended dosage of aloe by the manufacturer of the study material. From the two doses used in this study, no dose-response relationship could be demonstrated clinically (wrinkles and the elasticity measures), biochemically (procollagen and the MMP-1 gene levels) or microscopically (procollagen staining). Our results indicate no added advantage of high-dose aloe vera gel ingestion for cutaneous anti-aging purposes. The limitations of the study include the lack of a control group. In addition, daily sunblock use may have added to the protective effects of aloe; however, sunblock alone does not actively increase procollagen production or reduce the MMP-1 gene expression. It only renders skin less susceptible to further photodamage that would occur with the passage of time. Therefore, the role of sunblock as an active anti-aging substance could be excluded. For determining the optimal effective daily dosage of aloe, a placebo-controlled study with a larger number of subjects and a longer study period is warranted.
Since aloe significantly decreased wrinkles and it increased elasticity in photoaged human skin in vivo with an increase of the net procollagen, oral aloe gel supplementation may be a novel anti-aging strategy that prevents and repairs cutaneous photoaging. A future challenge will be to determine the mechanism of action of aloe gel in preventing cutaneous aging.