The Ins and Outs of Aging: Intrinsic/Extrinsic Factors and Nutricosmetic Fixes

Read the full article in the October 2021 digital edition. . .

As the global population is growing older, the consequences of aging have gained significant attention. Science continues to uncover effective approaches to support healthy aging and maintain quality of life. Skin aging, in particular, has gained interest not only because it is the most obvious manifestation of the aging process, but also because it represents a picture of overall human health. For instance, dryness is the most common cause of itching skin but itching can also reflect an internal condition; it could be an early symptom of cirrhosis or hepatitis.

As is well-known, skin aging is a natural process and the many influences that affect this process vary throughout life. These include extrinsic factors such as environmental and lifestyle, and intrinsic factors such as genetics and body composition.

It is generally agreed that external and internal factors, as well as the body’s response to these factors, comprise what is referred to as the exposome. In 2005, American epidemiologist Christopher Wild coined this term to describe the totality of exposures to which an individual is subjected from conception to death.¹ More recently, Krutmann et al. reviewed the impact of the exposome in skin aging, proposing that the key extrinsic variables are UV radiation, air pollution, tobacco smoke, nutrition and cosmetic products;² intrinsic factors include genetics, age, gender, origin and life stages.

The combined effects of aging over the human lifespan can impact the structural integrity and physiological function of skin. Older skin, for instance, is more susceptible to dryness, wrinkling, loss of elasticity and hyperpigmentation. The present article reviews these influences and present nutricosmetic solutions to support skin health and well aging.

Intrinsic Aging

Intrinsic aging is generally considered the normal decline of skin associated with chronological age and the natural processes that occur over time. These inherent qualities are individual characteristics not determined by a person’s environment; for example, through the natural aging process, the skin becomes thinner, wrinkles form and skin becomes rougher and abnormally dry. Clinical traits characterizing intrinsic skin aging thus include fine lines, dryness and laxity.³

Intrinsic factors also include those associated with gender, ethnicity and anatomical variations. Studies indicate that aging male and female skin differs in type, consistency and sensitivity to external factors. The same has also been documented for aging between individuals of different origins. Indeed, one study by Makrantonaki, et al., postulated it is important to examine the aging processes taking place in both genders and diverse ethnic groups separately, to consider different approaches to support healthy skin aging for each population.⁴

Genetics and origin: As noted, physical and biological phenotypes of skin aging processes manifest differently between ethnic populations.^5, 6 The most apparent ethnic skin difference relates to color, which is a consequence of the presence of melanin. The photoprotection conferred by melanin influences differences in the rate at which skin changes between various racial groups. For example, Caucasians have an earlier and greater onset of skin wrinkling and sagging than other ethnic groups. Asians, in contrast, are more prone to uneven skin tone, with wrinkles appearing later.⁷

Other less evident differences also have been described. One study demonstrated that Chinese skin tends to exhibit notably lower pore size and density across all age groups, compared with other ethnicities.⁸ Another study showed Caucasian skin had strong barrier properties, followed by African, Chinese and Indian.⁹

Gender and life stages: Hormones and gender-specific factors may also play an important role in skin health and aging. For example, sebum content, skin pigmentation and thickness are all significantly higher, facial wrinkles are deeper, and facial sagging is more prominent in the lower eyelids of men.¹⁰ Makrantonaki, et al., in a whole genome screening of sun-protected skin areas, showed an overlap of just 39 genes, highlighting how the process of aging may differ between males and females.¹¹

From around the age of 25, the first signs of aging begin to become apparent. In fact, from this age, there is a 1% annual decrease in collagen production. There is also a steady depletion of collagen content and reduced skin thickness following menopause, with yearly reductions of 2.1% and 1.1%, respectively.¹² This observation suggests estrogen may have beneficial effects against skin aging; indeed, estrogen deficiency following menopause results in atrophic skin changes and an acceleration of skin aging. Estrogen insufficiency also decreases skin’s defenses against oxidative stress, and skin becomes thinner with less collagen and demonstrates decreased elasticity, increased wrinkling, increased dryness and reduced vascularity.^{13, 14}

Extrinsic Factors in Skin Aging

Up to 85% of the visible signs of aging can be directly attributed to extrinsic causes, so skin aging also depends heavily on environmental exposures, lifestyle and habits. Sun and pollution exposure, tobacco use, diet, exercise, excessive stress and lack of sleep have been identified¹⁵ as exacerbating factors of skin aging. In fact, studies^16-18 performed in identical twins have illustrated how smoking, sun exposure, high stress and weight gain can influence aging. Noticeable evidence of extrinsically aged skin includes uneven and irregular pigmentation, liver spots and coarse wrinkles.

Photoaging: Sunlight is composed of different wavelengths ranging from short, high energy ultraviolet radiation (UVR) and visible light (VL), to long wavelength, low energy infrared radiation (IRA). These penetrate the skin at different levels. UVR, including UVA and UVB, is the primary extrinsic factor affecting skin physiology and it effects are well-known;¹⁵ long wavelength UVA1 rays are especially relevant because they deeply penetrate skin and exert direct effects at the dermal fibroblasts level.¹⁹

Chronic exposure to sunlight affects skin aging and mainly results from daily exposure to non-extreme, low doses that do not cause visible changes at the time of exposure but do lead to biological changes. UVR causes both acute stress responses, such as the upregulation of extracellular matrix-degrading enzymes, pro-inflammatory mediators, ROS, etc., and chronic damage responses, which are caused by the accumulation of macromolecular damage in non-proliferating skin cells. Examples include DNA damage, oxidized proteins and membrane lipids, etc., all of which drive the skin aging process.¹⁹

Beyond the UV spectrum, other wavelengths present in natural sunlight have been implicated in skin aging.²⁰ Near-infrared radiation (IRA) deeply penetrates human skin and reaches beyond the dermis to the subcutis, potentially causing wrinkle formation by collagen degradation.^{21, 22} The blue light portion of natural sunlight and artificial light from digital screens, light-emitting diodes (LEDs) and fluorescent lighting also may affect skin aging. Extended exposure to high energy blue light has been shown to increase ROS formation, DNA damage, cell and tissue death, skin barrier damage, skin pigmentation and photoaging.^23, 24 Consumer concerns about blue light and its potentially damaging effects in skin have grown as research on this topic expands; interest also has expanded during the last year with increased exposure to smartphones and digital devices during the COVID-19 pandemic.

Pollution: Air pollution is a major problem in recent decades, with a serious toxicological impact on human health. Experts have found that aside from UVR, ongoing daily exposure to contaminants such as polycyclic aromatic hydrocarbons (PAHs), volatile organic compounds (VOCs), oxides, particulate matter (PM) and ozone (O3) accelerate extrinsic aging and aggravate inflammatory skin disorders such as atopic dermatitis, eczema, psoriasis, acne, etc.^25, 26 Furthermore, recent studies suggest the effects of UVR and air pollution are not independent of each other, and that facial lentigines are the consequence of an interplay of UVR and air-related traffic exhaust pollutants.²⁷

Epidemiological studies also reveal air pollution plays a key role in accelerating extrinsic aging. Vierkotter, et al., for example, found that air pollution positively correlated with the presence of coarse wrinkles and with a 20% increase in pigmented spots on the forehead and cheeks.²⁸ Hüls, et al., demonstrated the association between the presence of NO2 with a higher number of pigmented spots on cheeks.²⁹

Furthermore, two German cohort studies observed that accumulated ozone exposure was positively associated with coarse wrinkles on the face.³⁰ Research also found that those living in highly polluted areas have significantly worse skin hydration and more compromised skin barrier functioning than subjects living in cleaner suburbs, despite urban subjects making better lifestyle choices.^{31, 32}

Several mechanisms through which air pollutants cause skin damage and aging have been proposed. The current evidence specifies four in particular: increased oxidative stress, promotion of a pro-inflammatory environment in skin and disruption of the barrier, activation of the aryl hydrocarbon receptor (AhR) and alteration of the skin microbiome.³³

Air pollution is an unavoidable consequence of an urban lifestyle and makes it difficult to minimize skin exposure to pollutants. As such, consumers seek strategies to protect skin. While topical products are eligible candidates, they are not always sufficient because they only protect the outermost layers of skin—and it is known that internal structures of skin can also be affected. More specifically, ultrafine particles (UFP) and PAHs may accumulate in the hypodermis, dermis and bottom of the hair follicle, which are highly vascularized, and can even reach the deep epidermis.³⁴ Moreover, certain pollutants can penetrate the skin via indirect systemic distribution of inhaled or ingested pollution through the blood.^{35, 36}

The damage exerted is therefore not only superficial, but also affects all the layers of the skin. It is for these reasons that the shielding efficacy of skin care products might better be complemented with a dietary approach for a more holistic strategy.

Climate: Seasonal variations also have a major impact on skin appearance and texture. One study, for example, showed that pigmentation and wrinkles were reduced in winter vs. summer; other features, such as skin barrier and moisture, declined.³⁷ Another study showed that seasons induce changes in skin hydration, sebum content, scaliness, brightness and elasticity.³⁸ For instance, dry environmental conditions have been shown to increase the permeability of the epidermis, resulting in abnormal barrier function and decreasing skin hydration, which can also adversely influence the incidence and/or severity of skin disorders such as contact and atopic dermatitis.³⁹ Also, both cold temperatures and dry conditions have been linked to a higher rate of skin irritation,⁴⁰ with lower water content in the stratum corneum accentuating wrinkles related to skin dryness.⁴¹

Lifestyle Habits and Skin Aging

Cigarette smoking: The relationship between cigarette smoking and skin aging is supported by epidemiological studies and in vitro and in vivo mechanistic evidence. Smoker’s skin is characterized by prominent facial wrinkling particularly around the mouth and upper lip and eyes.⁴² In several studies, smoking has been associated with increased wrinkles, tissue laxity, up to 40% thinner skin and pigmentary changes;⁴³ one of these studies estimated that 10 years of smoking corresponded to appearing roughly three years older than one's chronological age.⁴⁴

. . .Read more in the October 2021 digital edition. . .

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