The purpose of this section and later sections is not to present comprehensive coverage on various aspects of lifestyle/habits and factors, but to summarize the recent progress reported in the scientific literature and how this applies to skin health and anti-aging.
4.2. Nutrition and Types of Lifestyle Diets
While diet has become a focus to enhance human health, the attention on what types of diets yield the best outcomes is paramount from the perspective of consumers. The “Mediterranean or Eastern” diets versus a “Western diet” have gained popularity to increase the general health status and well-being and address many diseases and disorders [
8,
30,
61,
62,
63,
64,
65]. For example, the Mediterranean diet is one of the most widely described and evaluated dietary patterns in the scientific literature with validated health benefits [
8,
61,
62,
64,
65]. It is characterized by high intakes of vegetables, legumes, fruits, nuts, whole grains, fish, some olive oil, moderate intake of red wine, where most proteins and fats are derived from vegetable sources with low intake of red meat, potatoes, processed meat, refined carbohydrates, and sweets [
62,
64,
65]. Additionally, the Eastern (Asian) diet has high intake of plant-based foods (source of protein from vegetables like bean sprouts, spinach, eggplant, bok choy, cabbage, kale, snow peas, leeks, and mushrooms). Fruits and legumes, grapes, melons, cherries, dates, mangoes, etc.; steamed or stir-fried produce along with nuts, seeds, beans (soy, mung), lentils, tofu, or tempeh, plus rice and whole grains. Moderate intake of fish (dependent upon country’s coastline), dairy, eggs, and poultry. Very low intake of meat, processed meat, refined carbohydrates, and sweets [
8,
61,
62]. Conversely, the Western diet, prevalent in high-income countries, contains refined carbohydrates, red meat, processed meats, fats/lipids/cholesterol, which increase sympathetic nervous system, oxidative stress, and inflammation and low intake of fruits and vegetables [
60,
61,
62] (
Figure 5). Additionally, a traditional Eastern European diet (in Russia, Poland, and the Czech Republic) may contribute to poor health status, particularly for the high cardiovascular disease rates reported by Stefler et al in 2021 [
66]. Notably, Europe and Central Asian (from the Caspian Sea in the west to Western China and Mongolia) are regions, where cardiovascular disease is responsible for more than half of all deaths across this area due to poor diets and daily habits (smoking) [
67].
4.3. Nutrition, Diet and Skin Health
A reasonable balanced diet provides the nutritional components to delay aging, prolong life and enhance the QOL [
4,
8,
43]. This narrative overview for this section demonstrates that a healthy diet is one of the most important factors to achieving healthy skin [
8,
43,
61,
68]. Certain nutrients, vitamins, minerals and other compounds/molecules and factors will be described herein, previous journal reports have presented more detailed information elsewhere as cited.
Various nutritional elements such as water, protein, trace elements (iron, iodine, zinc, copper, selenium, etc.), vitamins (A, B complex, C, D, and E) other dietary, daily habits and lifestyle heath choices are known to impact skin health.
For example, does dietary fluid intake affect skin hydration? The answer is basic and complex due to the nature and importance of water in the human body for normal physiological function, maintaining body volume (intracellular and extracellular), thermoregulation, and acting as a lubricant and shock absorbent [
69,
70]. It is also important in the character/composition of the avascular epidermis [
2,
31].
Drinking enough water is important to your overall health and to your skin (most individuals do not drink 8 to 10 glasses of water per day); however, it's not clear whether drinking extra water affects skin hydration in healthy people [
71]
. Your skin is also affected by your diet, lifestyle, environment, and skin care routine [
69]
. However, in the case of the elderly or in obesity, dry skin is a common complaint [
69]
. Higher water intake in a regular dietary routine might positively impact skin physiology especially for its hydration and biomechanical properties, particularly in individuals with lower daily water consumption [
69]
.
What about dietary protein intake? Protein is a critical nutrient for human growth, development, maintenance, and repair of body tissues/cells, which perform a large array of functions (as enzymes, structural components, transport/signaling, hormones, proper fluid, and acid-base balance, immune, and DNA replication) [
72]. It is no surprise that protein intake is essential for healthy skin, particularly the two amino acids, i.e., lysine and proline that support collagen composition [
73,
74]. Notably, collagen is the most abundant protein in the body [
73]. Protein deficiency in developed countries is rare, however, low-protein diets are associated with poor wound-healing and other skin problems, especially with aging [
43]. Finally, oral intake of collagen supplements has been reported to enhance skin, nail, and hair health [
73,
75,
76,
77].
Vitamins in both topical and oral forms, play a key role in many dermatological conditions [
74,
78]. Vitamin deficiencies can occur. Deficiencies of water-soluble vitamins, such as most B vitamins and vitamin C, may develop after weeks to months of under-nutrition, while deficiencies of fat-soluble vitamins, such as vitamins A, D, E and B12, can take up to a year to develop due to the body storage capacity for these nutrients [
74,
78]. Numerous reports suggest that oral supplementation of various vitamins can enhance general skin health and treat dermatological disorders [
74,
78,
79,
80]. In general, vitamins can have anti-aging effects such as [
73,
74,
78,
79,
80], antioxidant, anti-inflammatory, hydration, skin barrier, turgor/tone/radiant, and repair/wound healing properties that are beneficial for skin health.
In fact, feeding the skin is a new trend in food and cosmetic treatments, where beauty is no longer dissociated from well-being, and where consumers consider nutrition as an important pillar in skin health. This is especially the case when ingredients/products contain food extracts or natural plant sources having nutricosmetic and/or nutraceutical benefits. [
44,
58,
79,
80].
Lifestyle health routines of dietary intake of plant-derived compounds such as carotenoids (astaxanthin, lutein, zeaxanthin, lycopene), chlorophyll, and polyphenols (resveratrol, flavonoids, isoflavonoids, green tea, etc.) have been shown to benefit skin health in a variety of ways [
8,
58,
73,
79,
80] such as decreasing fine lines/wrinkles, dullness and roughness while enhancing healing, hydration, pigmentation, and radiance [
45,
58,
73,
79,
80,
81,
82,
83,
84,
85,
86]. The mechanisms by which plant-derived compounds enhance skin health include: anti-aging (sirtuin activation), protection against UV damage, direct antioxidant actions and/or stimulation of nuclear factor erythroid 2-related factor (Nrf2) that is the master regulator for antioxidant responses, anti-inflammatory [by blocking nuclear factor-kB (NFkappB) and activator protein 1 (AP1), interleukins and oxidative stress], stimulation of collagen, elastin, tissue-inhibitor of matrix metalloproteinase(s) (TIMPs) and superoxide dismutase (SOD), blocking androgen hormone action and enhancing skin parameters (hydration, smoothness, radiance, pore size, firmness, and frown lines/wrinkles) [
2,
8,
32,
44,
45,
47,
51,
55,
57,
61,
64,
68,
80,
81,
82,
83,
84,
85,
86,
87,
88].
Interestingly, chlorophyll, the most abundant plant pigment responsible for giving plants their green color, also blocks assaults to DNA from carcinogens, and chlorophyllin is a water-soluble derivative of chlorophyll [
87]. Finally, chlorophyll also plays a role in regenerating Co-enzyme Q 10 (CoQ10) [
87], where CoQ10 as an oxidant has been shown to: a) reduce the production of free radicals, b) be involved in the regeneration of vitamin E, c) reduce keratinocyte DNA damage, d) reduce UVA-induced MMP production from fibroblasts, e) enhance collagen and elastin expression, inhibit IL-1alpha, IL-6 production, and melanin synthesis, and f) inhibit MMPs and regulate the sulfide oxidation pathway [
73].
Probiotics are active microorganisms that have beneficial effects on the host by altering the microbiota composition of a specific portion of the host’s flora [
89]. Numerous studies have found a close relationship between the skin microbiome and skin health benefits along with the gut-skin axis, where the gut microbiome can influence the skin via various chemical messengers including hormone and immune signaling [
32,
89,
90]. Several skin-related topics (acne, antioxidant activity, atopic dermatitis, barrier function, enzymatic regulation of the extracellular matrix, moisturization, photo-aging, pigmentation, rosacea, TEWL, suppression of pathogens, and UV protection, etc.) have been covered in diverse reviews on topical and oral probiotics in skin health [
89,
90,
91,
92,
93,
94]. Therefore, it is beyond the scope of this narrative overall to describe this topic further.
Diet lifestyle factors such as the role of whole-food, plant-based (WFPB) diet on skin health parameters was reported by Solway et al in 2020 [
87]. This WFPB diet was defined as “eating plant foods in their whole, unprocessed form, such as vegetables, fruits, beans, lentils, nuts, seeds, whole grains, and small amounts of healthy fats. It did not include animal products, such as red meat, poultry, fish, dairy, eggs or processed foods or sweets” [
87]. Their findings showed that a WFPB diet maximized the antioxidant potential by providing the essential vitamins (A, C, and E) to help combat oxidative stress, advanced glycation end products (AGEs) and methylglyoxal [
95,
96,
97], which resulted in lengthening telomeres that contributed to healthier, younger-looking skin [
87]. The findings by Solway et al are supported by numerous other scientific reports that have examined different aspects of diet/lifestyle health and skin parameters [
3,
43,
50,
68,
80,
93,
99,
100,
101,
102].
From a clinical perspective, there are some reports that investigated the role of lifestyle and nutrition (especially vitamins, minerals, and dietary supplementation) on dermatological conditions such as photo-aging, psoriasis, acne vulgaris, atopic dermatitis, rosacea, and hidradenitis suppurativa, etc. [
103,
104,
105,
106].
4.4. Lifestyle/Daily Habits- Negative Impact on Skin Health [AGEs, Alcohol, Smoking,
High Fat, Body Mass Index (BMI)]
Advanced glycation end products (AGEs) are well studied toxins, where glycation is a non-enzymatic chemical process that involves the formation of a covalent bond between a sugar molecule (e.g., glucose or fructose) and a protein or lipid [
95,
96,
97]. This differs from physiologic glycation that is under enzymatic control [
87]. AGEs can accumulate within tissues/organs to disrupt structures and function, but in the skin, it causes alterations in collagen, elastin, vitronectin and laminin structures, delayed wound healing and declination of skin strength and flexibility [
99,
100]. Remarkably, external factors such UV irradiation, cigarette smoking, poor dietary choices (Western diets), alcohol, obesity, and cooking methods can increase the rate or abundance of AGEs, whereas whole-food plant-based (WFPD), Mediterranean or Eastern diets contain the least number of AGEs [
87,
107,
108,
109].
Alcohol consumption (two drinks per day) and smoking have damaging influences on skin health [
100,
101,
110]. Alcohol’s two major effects on skin: a) dehydration (diuretic water loss along with decline in vitamins and minerals) and b) inflammation (increased oxidative stress along with peripheral vasodilation), which can impair quality of sleep, skin cell turnover and alter carotenoid concentrations to lessen antioxidant defense [
100,
101,
110].
The are zero health benefits associated with smoking [
110,
111]. Smoking’s detrimental influence on skin is dependent upon history and level of use, which causes severe signs of aging (loss of skin tone/turgor and appearance of lines/wrinkles) [
110]. Even in individuals with the shortest smoking history, facial and perceived age was advanced compared to their chronological age, especially in the facial region around the mouth and eyes [
110]. Unfortunately, smoking and vaping have similar harmful influences on skin health [
111], and a growing body of research has found that e-cigarettes (vaping), like regular cigarettes, results in serious respiratory disorders especially in youth and young adults [
112].
Astonishingly, Gunn et al, in 2016, conducted a twin study entitled “Mortality is Written on the Face,” where nurses rated the perceived age of each twin from photographs and selected which twin had survived the other twin. The conclusions of study suggested that facial cues are the most important in linking perceived age and survival [
113]. Notably, for women there is a strong link between estrogen levels with aging, attractiveness, facial appearance, and coloration, which are negatively influenced by alcohol and smoking [
48,
114,
115].
High fat dietary intake and obesity (body mass index; BMI
> 30) have been linked in reference to lifestyle health, an extensive range of chronic diseases, including dermal disorders [
68,
116,
117,
118,
119]. In brief, obesity is now considered to be a global epidemic and is increasing in prevalence (by 2035 more than 50 % of the world’s population will be obese) [
117,
118]. In general, the effect of a high-fat diet results in aging of the skin by inflammatory damage [
68]. Almost 60-70 percent of obese patients present with a variety of skin disorders, such as eczema, psoriasis, atopic dermatitis, infections, poor wound healing, and other skin malignancies like melanoma [
119,
120]. Specifically, obesity is one of the important casual factors of many inflammatory diseases [
121,
122]. In the skin, functional changes in adipocytes, lymphatic vessels and epidermal keratinocytes are involved in obesity-induced exacerbation of skin inflammation [
120,
121]. Particularly, skin barrier health is directly related to the changes that occur in the composition and function of dermal immune cells that decline with aging [
123,
124]. Therefore, the profound impact of increased fat deposition and obesity on cutaneous immunology and its role in the pathophysiology of various chronic inflammatory dermatological conditions is without question [
119,
120,
121,
122,
123,
124]. However, semaglutide, a glucagon-like peptide 1 (GLP-1) receptor agonist, approved for the treatment of type 2 diabetes mellitus (T2DM) and more recently utilized for weight loss in overweight/obese individuals, has been shown to be highly effective against severe psoriasis in T2DM patients [
125,
126]. Thus, the importance of lifestyle health factors that may ameliorate the harmful influences of obesity and overweight conditions warrants further research and development of aids and treatments not only for the range of chronic diseases but to improve skin health [
119].
Finally, all nutrients, dietary supplement ingredients or daily habits covered in the section above are summarized in
Table 2 that display the various influences on the skin along with the cited reference(s).