Use of silicon for skin and hair care: an approach of chemical forms available and efficacy (2024)

Abstract

Silicon is the second most abundant element on Earth, and the third most abundanttrace element in human body. It is present in water, plant and animal sources.On the skin, it is suggested that silicon is important for optimal collagensynthesis and activation of hydroxylating enzymes, improving skin strength andelasticity. Regarding hair benefits, it was suggested that a higher siliconcontent in the hair results in a lower rate of hair loss and increasedbrightness. For these beneficial effects, there is growing interest inscientific studies evaluating the efficacy and safety of using dietarysupplements containing silicon. Its use aims at increasing blood levels of thiselement and improving the skin and its annexes appearance. There are differentforms of silicon supplements available and the most important consideration tobe made in order to select the best option is related to safety andbioavailability. Silicon supplements are widely used, though there is widevariation in silicon bioavailability, ranging from values below 1% up to valuesclose to 50%, depending on the chemical form. Therefore, the aim of this studywas to evaluate the scientific literature related to the different chemicalforms of silicon supplements available and the limitations and recent progressin this field. According to reported studies, among the different chemical formsavailable, the orthosilicic acid (OSA) presents the higher bioavailability,whereas the others forms have absorption inversely proportional to the degree ofpolymerization. However, clinical studies evaluating safety and efficacy arestill lacking.

Keywords: Biological availability, Collagen, Dietary supplements, Hair, Silicon, Silicon compounds, Skin aging

INTRODUCTION

Silicon is the second most abundant element on earth, exceeded only by oxygen. Also,it is the third most abundant trace element in the human body.^1,2 It is present in the water and in plant and animal sources. Onthe skin, it is suggested that silicon is important for optimal synthesis ofcollagen and for activating the hydroxylation enzymes, improving skin strength andelasticity. It was shown that physiological concentrations of orthosilicic acid(OSA) stimulate fibroblasts to secrete collagen type I.^3-5 In the caseof hair, it is suggested that higher silicon content in the hair fiber results in alower rate of hair loss and increased brightness. Nails are also affected by thepresence of silicon, since this is the predominant mineral in theircomposition.^4,5 For these beneficial effects, thereis growing interest in scientific studies to examine the efficacy and safety of theuse of dietary supplements containing silicon, which aims to increase serum levelsof this element and hence lead to improvements in the skin and its annexes. Thereare different forms of silicon supplements available and to select the most suitableoption, the most important considerations to be made are regarding safety andbioavailability. In some countries, these supplements are already widely used,although there is great variation in silicon bioavailability, ranging from less than1% up to values close to 50%, depending on the chemical form.^6,7

However, it is observed that there is still no consensus among researchers about thestatement that silicon is an essential element for man or about the real benefitsobtained from the use of supplements containing silicon. Thus, it is extremelyimportant to critically evaluate the information published so far regardingefficacy, safety and bioavailability of silicon used in complementary supplements tothe diet. That was the aim of this study.

SKIN AGING PROCESS

The aging process occurs by two main mechanisms: intrinsic and extrinsic. Theintrinsic aging is unavoidable and results in atrophy, fibroblasts reduction andthinning of blood vessels. The collagen fibers are particularly affected in thisprocess, which results from the accumulation of irreversible degenerativechanges associated with aging.^4,8,9 The extrinsic aging primarily results from damage causedby ultraviolet radiation. Other factors related to this type of aging includesmoking, pollution and inadequate nutrition. These types of injury lead toincreased degradation of collagen and elastin. Also, a reduction in the numberof extracellular matrix proteins and a decrease in fibroblasts aredescribed,^8,9 in addition to a reduction ofsilicon levels and hyaluronic acid in the connective tissues.¹⁰

Collagen and fibers formed by it are responsible for the biomechanical propertiesof the skin, allowing it to act as an organ of protection from external trauma.They present as essential components of structural integrity of the connectivetissue and are present in large quantities in the skin, bones andjoints.^9,11 A reduction in the amount ofcollagen in the skin of about 1% per year after 21 years of age is described,resulting in thickness reduction and elasticity loss, which is directly relatedto the wrinkles depth.^11,12

Changes occurring after menopause are even more striking, including loss of about30% of skin collagen in the first 5 years and annual loss of 0.55% ofelastin.^13,14 The biosynthesis process ofcollagen after the third or fourth decade of life remains at a low level,insufficient to allow mature skin to repair or replace the collagen that hasbeen lost as part of the degradation processes associated with age.⁹ The decrease of collagen thatoccurs after menopause especially correlates with decreased bone mineral densityassociated with age.¹⁴

By the study of skin aging process, it's possible to observe that the degradationof collagen fibers has a remarkable role in this context. Based on this, the useof mechanisms that influence the biosynthesis of this protein is as a potentialtool for improving and preventing skin aging.

SILICON: A UBIQUITOUS ELEMENT

Considering the abundance of silicon in the human body, it seems unlikely thatits deficiency occurs in men and women.¹⁵

In 1972, two studies by two different research groups showed that silicon was anessential element in chickens and mice.^16,17 Theseexperiments demonstrated that nutritional deficiencies of silicon led toskeletal deformities such as abnormal skull and long bone structures, as well asmalformed joints with cartilage poor content. Thus, an important role of siliconin bone mineralization was demonstrated.

After that, several studies showed silicon participation in different mechanisms,with positive results associated with higher concentrations of this element inthe blood in patients with osteoporosis, atherosclerosis, skin aging and fragilehair and nails.^10,15 However, there are noconclusive data to determine whether or not silicon is an essential nutrient forhumans and superior animals, since its deficiency has not led to cell cycleinterruption in mammals, and its functional role remains to be clearlydefined.^15,18-20 Most of the silicon present in the blood is filtered bythe kidneys, suggesting that this mechanism represent the major route ofexcretion and that levels of silicon in blood correlate with the levels presentin urine.²¹ For this reason,various studies evaluate the serum concentration as well as the one present inurine in order to study the bioavailability of silicon and its derivatives.

FOOD SUPPLEMENTS CONTAINING SILICON

Different consumptions patterns of supplements containing silicon are observedaround the world. As an example, the organic silicon - commonly the monomethylsilanetriol (MMST) - is more consumed in France, while in Germany the colloidalsilicon are more present and, in Belgium, choline-stabilized OSA (ch-OSA) ismore frequent.^6,7

The MMST is not only organic, but also monomeric while other silicates showdifferent degrees of polymerization, which should explain the different siliconabsorption values in experiments with rats and in some preliminary studies inhumans.^25,27 Some studies have shown thatit is readily absorbed after digestion and observed no adverse events with itsuse. Nevertheless, it is noteworthy that, until the completion of these works,specific studies to evaluate its safety were not conducted.²⁸

Jugdaohsingh et al, in 2013, conducted a study to assess thesafety of using this supplement. A group of 22 healthy women, who were notmenopausal, received MMST oral supplementation for 4 weeks, with the maximumrecommended dose of 10.5 mg/Si/day. The authors concluded that MMST intake issafe and that it was absorbed. They also presented data to prove that, afteringestion, there is conversion of MMSR in OSA, which would justify itsabsorption.²⁸

However, in response to the published article, Vanden Berghe questioned somepoints of the study, claiming that studies of longer duration in humans andtoxicological tests in vitro and in animals are needed in order to prove thesafety of using the supplement containing MMST. According to Vanden Berghe,these studies were not presented in the article in question and they are alsoscarce in the available literature on the subject. The statement on MMSTconversion in OSA was also questioned.²⁹

The authors of the original study published a response that kept emphasizing thestudy's findings. They argued that they used rigorous methodology and that, inthe adopted conditions, they could conclude it was safe to use the supplementcontaining MMST. The authors, however, agreed that studies with larger numbersof volunteers and greater length of time would be needed for the continuation ofresearch involving this supplement.³⁰

MMST has been used as a silicon source for a long time around the world,especially in Europe.²⁸ Thissupplement, unlike others available, does not contain nano-silica particles, onwhich concerns regarding the safety have been reported.^31,32 However, the European Food Safety Authority (EFSA)considers that there is not enough data to justify the use of MMST as siliconsupplement.¹⁹

The greatest number of studies in the literature evaluates ch-OSA. The ch-OSA hasbeen approved for human consumption and is known to be non-toxic, in addition torepresenting the most bioavailable form of silicon.^15,22

In chemical terms, ch-OSA is a mixture of OSA and choline chloride. Given thelack of data about adverse reactions to silicon, a recommended dose has not beenestablished. Nevertheless, according to the American regulatory agency, choline,silicon oxides and various silicates are classified as substances "generallyrecognized as safe".^18,19

The stabilization with choline is considered the most advanced technology for OSAstabilization. Choline has important characteristics that place it in theposition of an ideal stabilizer for OSA, in addition to promoting benefits dueto its own characteristics.³³In high concentrations, choline avoids extensive polymerization and aggregationof silicon particles, to keep it in an aqueous suspension.³³

Furthermore, as previously mentioned, choline present in the compound may have asynergistic effect with OSA, since it is well known its participation in manybasic biological processes.³³Choline is a precursor of phospholipids, which are essential for the formationof cell membranes, as well as being involved in processes such as cellsignaling, lipid metabolism and protection against the collagen breakdownmediated by homocysteine.^34,35

In 2009, EFSA requested a scientific opinion to the Panel on Food Additives andNutrient Sources Added to Food concerning ch-OSA safety. The only objective wasto evaluate ch-OSA as a silicon source and also its bioavailability. Thus,silicon safety itself, in terms of daily amounts that can be consumed and itsclassification as a nutrient, was outside the scope of scientific opinionpublished by the Panel.¹⁹

Based on different studies conducted in animals and in humans, the Panelconcluded that the silicon present in ch-OSA is bioavailable and that its use insupplements, in the proposed doses, does not present risks for safety, providingthat the choline maximum level is not exceeded (3.5 g/day).

Studies were analyzed both in animals and in humans so the conclusion onbioavailability and safety were published by EFSA. A study of calves thatreceived supplement containing ch-OSA or placebo for 23 weeks evaluated theevolution of serum silicon concentration. There was a 4.9% increase at thisconcentration in the group of animals receiving silicon.³⁶ In another study, VandenBerghe assessed the bioavailability of silicon in offspring of 21 pigs, whichreceived or not (control) supplement containing ch-OSA during the gestation (16weeks) and lactation (four weeks) period. In the offspring of pigs that receivedsupplement containing silicon, significantly higher silicon concentrations werefound (150% increase) than in the offspring of the control group. The authorsattributed this result to the bioavailability of silicon in the supplementcontaining ch-OSA and also to the maternal transfer capability of absorbedsilicon.³⁷ The siliconabsorption from supplement containing ch-OSA was assessed in a study of 14healthy volunteers aged 22-34 years. Each volunteer received successive oraldoses of silicon from different sources. A significant increase in serumconcentration of silica compared to baseline was observed for ch-OSA.^6,19 This study demonstrated that the bioavailability ofsilicon is to a great extent dependent on the chemical form of the compound.

In another study, conducted in order to examine in vivo absorption of silicon byevaluating its serum dosage and its urinary excretion, different patterns ofabsorption for the different sources used were found. This study obtaineddifferent results, depending on the source, although it has evaluated absorptionin just a healthy volunteer. It was observed that a diet rich in silicon doesnot result in sufficient bioavailable amounts of this element that would lead toa statistically significant increase in its urinary excretion and serum levels,when compared with the period in which the volunteer was subjected to a normaldiet. A significant increase in silicon urinary excretion was observed when theevaluated supplementation consisted of tablets containing dry extract ofhorsetail. However, the silicon serum levels remainedconstant. Only the biologically active silicon present in solution at 2% siliconin a matrix of choline and glycerol was absorbed, which reflected in thesignificant increase of silicon in both serum levels and in urine excretion.Based on this study, the authors concluded that silicon absorption is stronglyinfluenced by its chemical form and matrix.

Sripanyakorn et al measured silicon uptake from 8 differentsources. In healthy volunteers, blood and urine samples were analyzed toquantify the concentration of silicon. The results confirmed that the degree ofsilicon polymerization is inversely proportional to intestinalabsorption.⁷

SILICON AND ITS RELATION WITH SKIN, HAIR AND NAILS

Regarding the skin, it is suggested that silicon is important for optimalsynthesis of collagen and for activating the hydroxylation enzymes, important inthe formation of collagen network, improving skin strength and elasticity.Silicon is also associated with the synthesis of glycosaminoglycans. Concerningthe hair, it is suggested that strands with higher silicon content tend to havelower falling rate and higher brightness. Nails are also affected by thepresence of silicon, since this element is one of the predominant mineral intheir composition. The presence of soft and brittle nails can indicate systemicdeficiency of silicon. By improving the quality of nails, there is an increasedprotection against nail infections.^4,5

In a study with 50 healthy volunteers, aged between 40 and 65 years and withclear clinical signs of facial photoaging, the effect of the intake ofsupplements containing ch-OSA to the skin, hair and nails were analyzed. Thesupplement was held for a period of 20 weeks, with 2 capsules containing 10 mgof ch-OSA taken daily. Also, serum concentrations of various components in theblood were evaluated in order to verify safety of oral treatment. The siliconintake under these experimental conditions was considered safe, since there wereno reported adverse events with this treatment. This study, according to theauthors, was the first randomized, double-blind, placebo-controlled trial thatshowed positive results in the skin microtopography and anisotropy after theintake of supplement containing ch-OSA. At the end of the period of usesupplement containing silicon, there was a significant improvement in the skinsurface characteristics and in its mechanical properties.

Also in this study, it was observed a significant improvement in the fragility ofnails and hair in the group using the ch-OSA. The placebo did not lead tosignificant differences in rating assigned by the volunteers by theself-assessment questionnaires completed before the start and after the end ofthe study.

Another randomized study with 48 volunteers investigated the effect of ch-OSA onhair. The volunteers had thin hairs and were divided into 2 groups: ch-OSA andplacebo. The first group received daily doses of 10 mg of silicon, for a periodof 9 months.⁴ Morphology andmechanical properties of hair were evaluated at the beginning and at the end ofthe study. In general, positive results were obtained in the evaluated hairproperties, such as strand resistance to breaking, for example. Furthermore, thearea of the strand front section increased significantly after 9 months ofsupplementation containing ch-OSA, whereas the placebo group exhibited nosignificant difference.⁴

The fact that ch-OSA have partially prevented the loss of hair tensile strengthsuggests that it has a structural effect on hair fibers. According to theauthors, an interaction with keratin is possible, considering that OSA is thechemical form of silicon prevalent in physiological fluids and that silanolgroup, present on OSA, is known to form complexes with amino acids andpeptides.^4,38,39

CONCLUSION

The analysis of the scientific literature on the use of supplements containingsilicon shows great therapeutic potential of this element, as it operates indifferent conditions of human health and presents aesthetic properties. Among thevarious chemical forms available, the analysis of studies shows that OSA is the formthat presents greater bioavailability; other forms have absorption inverselyproportional to the degree of polymerization. We also observed that ch-OSA is themost referenced form in the literature, suggesting a greater scientific supportregarding its use. However, there are few studies evaluating the safety, efficacyand bioavailability of the different existing chemical forms of silicon that useproper design, large number of volunteers and long follow-up period.

Footnotes

Study performed at Faculdade de Ciências Farmacêuticas de Ribeirão Preto, ofUniversidade de São Paulo (USP) - Ribeirão Preto (SP), Brazil.

Financial Support: None.

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