Sources and Composition
Sources
Aloe is a genera of over 420 plants (of the family Liliaceae[1]) of which vera (sometimes referred to as Barbadensis) is the specific herb used in many supplements. Other members of this family include Aloe Ferox and Aloe Arborescens.[2] The Aloe vera plant itself is a perennial plant with turgid green leaves joined at the stem in a rosette pattern, and is most well known as a topical ointment for pain relief from burns.[3]
These plants have historically been used topically to heal wounds, and internally (consumption) as a cathartic agent[1] and have been used in Ayurveda,[4] Southern African medicine.[5]
Composition
The Aloe vera plant specifically contains:
The anthraquinone Aloin (aka. Barbalion; divided into Aloin A and Aloin B) and Isoaloin/Isobarbalion[6][7][8] and 7-hydroxyaloin A (7-OHA) and 5-hydroxyaloin A (in Aloe Ferox)[6]
Anthraquinones Aloresin A and B[6]
With some bioactive polysaccharides
Aloe vera is known to have a sensitive processing need, and can be damaged during processing.[10]
Interactions with fat metabolism
In fat cells, it also suppresses scavenger receptor A and CD36 on macrophages in white adipose tissue.[11] These are receptors for oxidized LDL particles, and inhibiting their actions may prevent inflammatory responses. This works in concert with Aloe's ability to inhibit nuclear translocation of NF-kB in vivo.[11]
Interactions with Oxidation
Mechanisms
The anti-inflammatory effects of aloe vera seem to be via aloesin derivatives and inhibiting both thromboxanes and COX2.[12] It has also been implicated in suppressing Nf-kB and downstream inflammatory cytokines.[11]
Interactions with Hormones
Thyroid
In a study assessing herbal effects on the thyroid, ingestion of 125mg/kg Aloe vera for 15 days in rats was associated with a decrease in serum T4 (-12.88%) and T3 (-25.13%).[13]
Interactions with Organ Systems
Oral Cavity
One human trial using a topical patch of 0.5% Acemannan (a polysaccharide from Aloe Vera) noted that this patch was more effective than control in reducing the size of oral aphthous ulceration (Canker Sores) when applied thrice a day for a week, but failed to outperform the active control of 0.1% triamcinolone acetonide (a topical corticosterone).[14] This has been noted elsewhere in recurrent canker sores, where thrice daily application of a gel (1.6% dry leaf remnant) was able to reduce the diameter of inflammation and pain and reduced healing time of the lesions.[15]
Liver
Aloe vera leaf gel given at 1mg/kg for a week prior to administration of alcohol (3g/kg fasted state) did not influence serum alcohol levels nor the increase in serum liver enzymes (GOP, GPT) following alcohol administration, but was able to attenuate the alcohol-induced increase in liver triglycerides via suppressing alcohol's induction of lipogenic gene mRNA expression (DGAT2, FASN, and SREBP-1; lipolytic genes not affected).[16]
1mg/kg Aloe vera can increase hepatic PPARα content by 1.3-fold relative to control without significantly influencing the target genes of CPT-1 and MCAD.[16]
Nutrient-Nutrient Interactions
Vitamin C and Vitamin E
Coingestion of vitamin C (500mg) or vitamin E (420mg as acetate) with Aloe vera gel results in a near tripling of the Area-Under-Curve and bioavailability for both compounds[1] coupled with a delayed Tmax when consumed in a fasted state. Vitamin C went from 339+/-124 1031+/-513 and Vitamin E from 19.3+/-23.2 to 71.3+/-22.5uM/h with the addition of Aloe gel, with Aloe leaf not being statistically different from control.[1] The dose of Aloe Gel was not specified.
However, this study did not note any vitamin C or E content of the Aloe itself, and was funded by the International Aloe Science Council.[1]
Safety and Toxicology
Aloe has been associated with acute hepatitis (liver inflammation) either in isolation[17][18] or when consumed as a multinutrient supplement.[19] These effects appear to be reversible and occur in the dosage range of 250-500mg a day, with the exact mechanism of the toxicity is not understood.
Aloe seems to cause wide-ranging side-effects at a doses 100mg/kg or greater bodyweight in animals. These side effects are observed in all subjects.[2]
