10.5826/dpc.1304a256
Functional foods, or whole foods that provide health benefits beyond their nutritional value, may provide multiple dermatological benefits. Research studies have documented benefits ranging from enhanced skin barrier function to improved wound healing, radiance, photoprotection, and hormonal regulation. Although the majority of research to date has involved small-scale human interventions or animal models, promising findings have been noted. In this review, we discuss the potential dermatological role of functional foods in hopes of advocating for larger-scale, evidence-based, human studies to expand this promising field.
text/xml
2160-9381
3122
en
Rajani Katta
https://creativecommons.org/licenses/by-nc/4.0
Dermatology Practical & Conceptual
dermatology
Functional Foods in Dermatology
Text.Serial.Journal
https://dpcj.org/index.php/dpc
Review
2023-10-31
2022-12-28
2023-10-31
2024-01-16
e2023256
Dermatol Pract Concept
Functional foods, or whole foods that provide health benefits beyond their nutritional value, may provide multiple dermatological benefits. Research studies have documented benefits ranging from enhanced skin barrier function to improved wound healing, radiance, photoprotection, and hormonal regulation. Although the majority of research to date has involved small-scale human interventions or animal models, promising findings have been noted. In this review, we discuss the potential dermatological role of functional foods in hopes of advocating for larger-scale, evidence-based, human studies to expand this promising field.
Rajani Katta
2023/10/31
10.5826/dpc.1304a256
e2023256
Clinical Professor of Dermatology, McGovern Medical School at UTHealth Houston
2160-9381
dermatology
en
e2023256
Armanini D, Mattarello MJ, Fiore C, et al. Licorice reduces serum testosterone in healthy women. Steroids. 2004;69(11-12):763-766. doi:10.1016/j.steroids.2004.09.005
Functional Foods in Dermatology
https://dpcj.org/index.php/dpc/article/download/3122/2335
                          Functional Foods in Dermatology
Emily Strouphauer1, Milbrey Parke2, Ariadna Perez-Sanchez3, Evelyne Tantry4, Rajani Katta5


1   Medical Student, Baylor College of Medicine, Houston, TX, USA
2   Department of Internal Medicine Resident, Tulane University School of Medicine, New Orleans, LA, USA
3   Department of Internal Medicine, University of Texas Health San Antonio, San Antonio, TX, USA
4   Graduate, Rice University, Houston, TX, USA
5   Clinical Professor of Dermatology, McGovern Medical School at UTHealth Houston, Houston, TX, USA



Key words: functional foods, diet, dermatology, photoprotection
Citation: Strouphauer ER, Parke MA, Perez-Sanchez A, Tantry E, Katta R. Functional Foods in Dermatology. Dermatol Pract Concept.
2023;13(4):e2023256. DOI: https://doi.org/10.5826/dpc.1304a256
Accepted: June 23, 2023; Published: October 2023
Copyright: ©2023 Strouphauer et al. This is an open-access article distributed under the terms of the Creative Commons Attribution-
NonCommercial License (BY-NC-4.0), https://creativecommons.org/licenses/by-nc/4.0/, which permits unrestricted noncommercial use,
distribution, and reproduction in any medium, provided the original authors and source are credited.
Funding: None.
Competing Interests: None.
Authorship: All authors have contributed significantly to this publication.
Corresponding Author: Rajani Katta, MD, 6750 West Loop South Suite 695, Bellaire, TX, 77401 Phone: 281-501-3150
Fax: 832-810-0072 Email: info@kattamd.com




    ABSTRACT            Functional foods, defined as whole foods that provide health benefits beyond their nutritional value,
                        may provide multiple dermatologic benefits. Research studies have documented multiple benefits,
                        including enhanced skin barrier function, improved wound healing, radiance, photoprotection, and
                        hormonal regulation. Although the majority of research to date has involved small-scale human in-
                        terventions or animal models, promising findings have been noted. A number of potential molecular
                        mechanisms have been described, such as the ability of some foods to combat oxidative stress and
                        thus reduce visible and histologic skin changes in response to UV radiation. Additional mechanisms
                        have been described for wound healing, photo-carcinogenesis, and other outcomes. In this review,
                        we discuss the potential dermatologic role of functional foods in order to advocate for larger-scale,
                        evidence-based, human studies to expand this promising field.




Introduction                                                             dietary supplements in that functional foods are whole
                                                                         foods consumed as part of the usual diet, while dietary
A growing body of research has explored the benefits of                  supplements are manufactured, individual biological com-
specific dietary approaches to improving skin health [1,2].              pounds taken in addition to the diet [4]. There has been
One approach centers on a diet rich in functional foods,                 some overlap in terminology with the term “nutraceutical,”
which can be defined as foods that provide health bene-                  though nutraceutical has traditionally been used to describe
fits beyond their nutritional value [3]. These differ from               supplements [4,5].



Review | Dermatol Pract Concept. 2023;13(4):e2023256                                                                                  1
    A variety of different foods have been shown to serve          compared the consumption of argan and olive oils in a group
as functional foods, including herbs, fruits, vegetables, and      of 60 postmenopausal women and reported that argan oil,
plant oils, among others. Many different studies, including        but not olive oil, significantly decreased TEWL and increased
human trials, population studies, and animal and laboratory        epidermal water content [13].
studies have elucidated the benefits of specific foods for skin       Dietary hempseed oil, which contains omega-6 and
health. While the term “functional foods” has been used in         omega-3 fatty acids in a ratio of 2:1, has been studied in
different contexts to describe supplements and foods, here it      patients with atopic dermatitis (AD). One crossover RCT,
is being used solely to describe foods.                            using a 4-week washout period, compared outcomes in 16
    The main advantage of functional foods over the tradi-         individuals with AD who consumed either 2 tablespoons of
tional topical application of dermatologic products is their       hempseed oil daily or a control (olive oil) [14]. Despite no
oral ingestion, which facilitates metabolism into active forms     pronounced reduction in TEWL, participants consuming
and absorption from the intestines to the bloodstream. This        hempseed oil reported significant decreases in skin dryness
allows deposition of metabolically active compounds into           and itchiness along with decreased usage of topical medica-
multiple areas of the skin, including the subcutaneous tissue,     tions as compared to controls.
                                6
dermis, epidermis, and sebum. Another benefit is that func-           Fermented dairy products are another promising area
tional foods may provide additive benefits to topical prod-        of research. These are rich in probiotics, prebiotics, and
ucts, as with photoprotection [7].                                 ­bioactive compounds that interact with the gut microbiota to
    Due to these factors, there has been an increasing inter-      reduce oxidative stress and enhance epidermal differentiation
est in the role of functional foods in skin health. Research       [15-17]. Two separate studies observed skin barrier changes
into specific foods has demonstrated antioxidant and signal        among healthy Japanese volunteers after 4 weeks of daily
modulation properties as well as effects on barrier function.      consumption of fermented milk containing ­Bifidobacterium
These properties allow functional foods to impact the skin         breve strain Yakult (BbrY) and galactooliogosaccharides
barrier, wound repair, radiance, photoaging, photoprotec-          (GOS) [17,18]. Both studies reported significant increases in
tion, and photocarcinogenesis, among other effects.                keratinocyte differentiation compared to control cohorts, as
                                                                   well as improved skin hydration. There was also evidence
                                                                   of wrinkle reduction and improved skin clarity compared
Skin Barrier Function
                                                                   to controls, determined using a visual analog scale [17]. Ad-
Several human studies have documented the role of func-            ditional small-scale human studies have found similar im-
tional foods in improving the skin barrier. The skin barrier,      provements in TEWL after consumption of milk fermented
composed of the stratum corneum, microbiome, immune                with Lactococcus lactis strain H61, conventional yogurt, and
system components, and chemical components, is the body            yogurt fermented with LB81 lactic acid bacteria [16,19].
defense against external insults and water loss [8,9]. Skin bar-      Several other functional foods have been linked to en-
rier function is commonly measured through transepidermal          hanced skin barrier function, though research is limited. In
water loss (TEWL) and stratum corneum hydration. TEWL              a study of 33 healthy participants, the TEWL effects of oral
is considered a good indicator of skin barrier integrity, with     turmeric, a turmeric-containing supplement, and a ­placebo
higher values indicating impairments in barrier function [10].     were compared. The turmeric group showed a trend toward
                                                                   decreasing TEWL among participants with higher sebum
Human Studies                                                      concentrations, while the supplement group showed a sta-
Healthy oils with various lipid profiles, particularly flaxseed,   tistically significant decrease in TEWL. Foods that contain
hempseed, and argan oil, have resulted in TEWL improve-            polyphenols are another area of interest, such as green tea,
ments in several small-scale human studies. Consumption            coffee, and cocoa beans [20-23]. Extracted food polyphenols
of flaxseed oil, rich in alpha-linolenic acid (ALA), resulted      have shown promise in improving dry skin via impacts on
in significant improvements in TEWL and decreased skin             skin barrier water homeostasis, but whole food studies are
sensitivity in response to nicotinate irritation in 2 separate     lacking. Table 1 summarizes human studies of selected func-
studies. In one, healthy participants were randomly assigned       tional foods and their associated dermatologic benefits.
to consume placebo- or flaxseed oil-filled capsules daily
[11]. After 12 weeks of treatment, TEWL was decreased
                                                                   Wound Healing
by about 25% within the flaxseed oil cohort (with no im-
provement in the placebo cohort), along with significantly         Wound healing occurs in a series of stages orchestrated by
decreased inflammatory skin response. A later study echoed         signaling molecules and chemical mediators. Damaged tis-
these ­results, with significantly decreased TEWL and skin         sue leads to inflammatory changes involving catecholamines,
sensitivity, along with improvements in skin roughness and         ­reactive oxygen species (ROS), nitric oxide (NO), and tu-
scaling, in those consuming flaxseed oil [12]. Another study       mor necrosis factor (TNF)-alpha, followed by fibroblast

2                                                                             Review | Dermatol Pract Concept. 2023;13(4):e2023256
              Table 1. Human Studies of Functional foods in Dermatology (selected examples).
      Function                                Associated foods with evidence from human studies
 Skin barrier          Flaxseed oil: improvements in TEWL [12,61]
 function
                       Argan oil: Improvements in TEWL [13]

                       Hempseed oil: decreases in skin dryness and itching in those with atopic dermatitis [14]

                       Fermented dairy products: improved skin hydration [17,18]

                       Fermented dairy products: improvements in TEWL [16,19]
 Wound healing         Olive oil: decrease in duration of wound healing and hospitalization [25]
 Radiance              Increased fruit and vegetable consumption over six weeks: documented increases in skin redness and
                       yellowness and perceptions of increased health and attractiveness [32]
 Anti-photoaging       Almonds consumed daily for four months: decreased wrinkle severity and width [33]

                       Avocado, daily consumption for eight weeks: increases in forehead skin firmness and elasticity [34]

                       A diet reported to be higher intake of monounsaturated fatty acids from olive oil: lower risk of
                       severe photoaging [36]

                       Reported consumption of higher intake of total dietary polyphenols from all sources: decreases in
                       pigmented spots scores [35]
 Photoprotection       Tomato paste: improvement in MED [42,43]

                       High flavanol cocoa powder or chocolate: Improvements in MED [23,44,45]
 Reduction of          Cruciferous vegetables (broccoli, Brussels sprouts, watercress): potential benefit in reducing DNA
 DNA damage            damage [49-51]

                       Tomato purée: protected DNA against oxidative damage [52]

                       Kiwi fruit: increased efficiency of base excision repair activity [53]

                       Tart cherry juice: increase in DNA repair activity [54]
 Hormonal              Spearmint tea derived from the plant Mentha spicata: decreased free and total testosterone levels [56]
 regulation
                       Green tea for 12 weeks in women with PCOS: decrease in free testosterone levels [59]

MED = minimal erythema dose; PCOS = polycystic ovarian syndrome; TWEL = transepidermal water loss.


proliferation, angiogenesis, and re-epithelialization [24].        environment [26]. An excisional lesion was created, followed
Several rodent and human studies have investigated the role        by 14 days of olive oil consumption in a stress-induced
of olive oil and certain mushroom species in modulating the        environment. This intervention significantly accelerated
                                                                   ­
wound healing process.                                             wound contraction and improved collagen deposition and
                                                                   angiogenesis, likely due to a decrease in ROS damage and
Human Studies                                                      catecholamine synthesis. A similar mouse study echoed these
The effects of olive oil ingestion were investigated in 100        results, reporting that olive oil administration accelerated
hospitalized patients who had experienced second degree
­                                                                  NO synthesis, reduced oxidative damage, and decreased
or higher burn wounds over 10-20% of their total body              expression of TNF-alpha, thereby improving the wound
surface area [25]. Admitted patients were prepared salads          ­healing process in pressure ulcers [27].
with either olive oil or sunflower oil (control) dressing. Re-         Mushrooms have also exhibited wound-healing proper-
sults showed a ­significant decrease in the duration of wound      ties in diabetic rats. Administration of the mushroom ­Sparassis
healing (7.2 days versus 8.7 days) and duration of hospital-       crispa for four weeks significantly accelerated wound closure
ization (7.4 days versus 8.9 days) in the olive oil group as       by increasing macrophage and fibroblast ­migration, type I
compared to the control group.                                     collagen deposition, and re-epithelialization in diabetic rats
                                                                   as compared to a control cohort [28]. Similarly, consumption
Animal Studies                                                     of the polysaccharide of another mushroom, Ganoderma
Rodent studies shed some light on potential mechanisms of          ­lucidum, (Gl-PS, 250 mg/kg) significantly accelerated wound
action. In one mouse study, dietary supplementation with           closure by as much as 2 days in diabetic mice as compared
olive oil improved cutaneous wound healing in a stressful          to control mice.

Review | Dermatol Pract Concept. 2023;13(4):e2023256                                                                             3
    Finally, while a number of traditional herbs have been       Photoprotection
shown to promote wound healing, and thus warrant further
investigation into benefits and mechanisms of action, a full     The cutaneous effects of ultraviolet (UV) radiation range
review of these is outside the scope of this review.             from acute erythema to the clinical features of photoaging, to
                                                                 the molecular changes of photocarcinogenesis that increase
                                                                 the risk of skin cancer. Mechanistically, UV radiation induces
Radiance                                                         oxidative stress and subsequent free radical production, pri-
Human Studies                                                    marily in the form of ROS. These unstable compounds cause
                                                                 damage to multiple skin components, including proteins,
Functional foods rich in phytochemicals, specifically
                                                                 lipids, and DNA. In addition, ROS activate several inflam-
carotenoids, promote the appearance of health and skin
­
                                                                 matory pathways, causing further damage to the epidermis
radiance by influencing skin coloration, luminance, and
                                                                 and dermis [37].
vascularization. Carotenoids cannot be synthesized de
­
                                                                    Given the constant threat of free radicals, the body
novo in the body and are primarily obtained through the
                                                                 defense systems have evolved to provide multiple layers
                                                                 ­
consumption of fruits and vegetables [29]. The correlation
                                                                 of protection. One of the key methods by which the body
between high dietary intake of fruits and vegetables and
                                                                 combats oxidative stress is through antioxidants, which
increased yellow and red facial pigmentation is well docu-
                                                                 may directly neutralize ROS or upregulate genes that encode
mented in the literature [29-31]. Carotenoids are thought to
                                                                 ­neutralizing enzymes [38]. Antioxidants, found within the
generate these observable changes due to their deposition in
                                                                 epidermis and dermis, include vitamin C, vitamin E, sele-
every skin layer, particularly the epidermis [31].
                                                                 nium, and ­carotenoids, as well as endogenous protective en-
    Individuals with greater yellow and red skin coloration
                                                                 zyme systems such as glutathione peroxidase [39,40]. These
are often perceived as being healthier, as presented in one
                                                                 are depleted throughout the day and require constant replen-
study exploring cross-cultural consistency in preferences for
                                                                 ishment from dietary sources. This has directed attention to
skin yellowness [29]. In another study, increased fruit and
                                                                 functional foods and their role in enhancing photoprotection.
vegetable consumption over 6 weeks resulted in percep-
                                                                    A number of human interventional studies have identi-
tions of increased health and attractiveness, likely due to
                                                                 fied beneficial foods, while animal and laboratory studies
­documented increases in skin redness and yellowness [32].
                                                                 have identified many other promising photoprotective foods
                                                                 and food components. Interventions studied have included
Anti-Photoaging                                                  tomato paste, high flavanol cocoa, grapes, and multiple indi-
                                                                 vidual food components.
Human Studies
Although limited, a few human studies have investigated the
role of functional foods in modifying photoaging. In one         Protection Against UV-Induced Erythema
small randomized control trial (RCT) of 28 post-menopausal       Human Studies
women, the group consuming 2 ounces of almonds daily for         Multiple studies have evaluated the effect of functional foods
4 months had decreased wrinkle severity and width as com-        on the minimal erythema dose (MED), used to m
                                                                                                             ­ easure
pared with controls [33]. In another small trial of 39 healthy   ­sensitivity to sunlight and which represents the lowest UV
overweight women, daily consumption of 1 avocado for             dose necessary to produce sunburn or redness. This visible
8 weeks significantly increased forehead skin firmness and       erythema represents multiple biochemical and histologic
elasticity [34].                                                 skin changes [41].
    Small cross-sectional survey studies have also identified       In one RCT, researchers investigated a dietary source
some promising correlations.                                     naturally rich in carotenoids. Over 10 weeks, volunteers in-
In a survey of Japanese women in which food consumption          gested 40 grams of tomato paste in olive oil daily. At the
was reported by patients, a correlation was noted between        end of the study, subjects demonstrated 40% lower erythema
consumption of coffee (as well as total polyphenols from all     formation following UV exposure [42]. In another RCT, vol-
sources) with a decrease in pigmented spot scores [35]. In       unteers ingested 55 grams of tomato paste in olive oil daily
a large-scale, cross-sectional study including 1264 women        for 12 weeks, resulting in significant improvement in the
and 1655 men, reported diet was compared to severity of          MED [43]. Biopsies taken following UV radiation at the end
facial photoaging. After controlling for possible confound-      of the study demonstrated a significant reduction in matrix
ing variables, a lower risk of severe photoaging in both men     metalloproteinase-1 enzyme in the tomato paste group as
and women was associated with higher intakes of monoun-          compared to control participants. This enzyme, induced by
saturated fatty acids from olive oil (but not with intake via    oxidative stress from UV radiation, leads to the degradation
animal sources) [36].                                            of dermal proteins and plays a major role in the pathogenesis


4                                                                           Review | Dermatol Pract Concept. 2023;13(4):e2023256
of photodamage [43]. It has been noted that the bioavailabil-    Reduction of DNA Damage-Human Studies
ity of carotenoids from tomato paste is higher than that from    DNA damage caused by oxidative stress is a major factor
tomato juice or fresh tomatoes, suggesting that the source of    in photocarcinogenesis. Therefore, multiple studies have
antioxidants may also influence improvements in MED [42].        evaluated the role of fruits and vegetables that are rich in
   Cocoa beans have also been studied, as they are rich in       antioxidants and their role in reducing DNA damage. For
strongly antioxidant flavanol compounds. Researchers have        example, cruciferous vegetables, including broccoli, Brussels
specifically studied the effects of cocoa products with high     sprouts, and watercress, contain high levels of antioxidants
flavanol content (ie products in which flavanol content was      and have shown potential benefit in reducing DNA damage
retained during the cocoa bean manufacturing process).           in several small human studies [49-51]. Tomato puree, high
   In one RCT, 2 groups of women consumed either high            in the carotenoid lycopene, protected DNA against oxidative
flavanol (HF) or low flavanol (LF) cocoa powder daily            damage in a small human study, while kiwifruit increased
for 12 weeks. Those in the HF group experienced a 25%            the efficiency of base excision repair activity in another small
decrease in erythema from baseline following irradiation
­                                                                human study [52,53]. Tart cherry juice was also shown to
with a solar light simulator, with no change noted in the LF     increase DNA repair activity in an RCT of older adults [54].
group [23]. In another RCT, subjects consuming 20 grams          Further research into the effect of these functional foods on
of high flavanol chocolate for 12 weeks also demonstrated        skin processes is warranted.
significant improvement in MED [44]. Finally, another RCT           Nicotinamide, a form of vitamin B3, has shown promise
found some improvements in MED in women consuming ei-            in skin cancer prevention. Its mechanism of action is not felt
ther 30 grams daily of either HF or LF chocolate [45].           to be due to antioxidation properties but rather via promo-
   Grapes, high in polyphenols, have also shown promise.         tion of DNA repair via the provision of extra energy stores.
In one study, 19 volunteers consumed California table grape      A large, multicenter, phase III trial demonstrated the benefit
(CTG) powder (reconstituted in water) 3 times daily for          of oral nicotinamide in reducing the rates of actinic kera-
14 days, with each serving equivalent to 1 serving (0.75 cup)    toses and non-melanoma skin cancer in a high-risk patient
of fresh grapes [46]. The MED improved in 11 volunteers          group [55]. As research to date has studied the effects of the
and stayed in the same in 7. Eighteen participants under-        isolated vitamin, further research is indicated on the role of
went further biopsy for molecular biomarker studies, which       foods rich in nicotinamide.
demonstrated reduced markers of DNA damage, inflamma-
tion, and apoptosis [47].
                                                                 Hormonal Regulation
Prevention of Photocarcinogenesis                                Functional foods may serve to modulate hormone bio-
                                                                 availability in certain disease states with dermatological
Multiple RCTs of antioxidant supplements have failed to          ­manifestations. Polycystic ovarian syndrome (PCOS), char-
show benefit for the prevention of non-melanoma skin can-        acterized by hyperandrogenism, anovulation, and polycystic
cer [40]. On the other hand, although individual foods have      ovaries, increases the risk of hirsutism and acne in female pa-
rarely been studied, research on overall eating patterns has     tients [56]. A number of studies have evaluated the potential
shown promise for the role of antioxidant-rich diets in skin     role of foods in combating hyperandrogenism [57].
cancer prevention, emphasizing the importance of additive
and synergistic properties of foods [40]. This also highlights   Human Studies
the need for additional studies of eating patterns as opposed
                                                                 Spearmint tea derived from the plant Mentha spicata has
to individual nutrients.
                                                                 demonstrated anti-androgen effects in multiple human trials
                                                                 [56,58]. One RCT observed the effects of twice-a-day spear-
Animal Studies                                                   mint tea consumption in 41 women with PCOS compared to
A few foods have been evaluated for their role in prevention     placebo tea [56]. After the 30-day treatment period, free and
of photocarcinogenesis. Tea has shown promise, although          total testosterone levels were significantly decreased in the
current studies are limited to animal models. In one study,      spearmint tea cohort. Although patient perception of degree
mice consumed black or green tea daily as their sole source of   of hirsutism was reduced in the spearmint cohort, there was
drinking fluid over 31 weeks of UVB treatment [48]. Admin-       no measurable reduction in objective hirsutism ratings. One
istration of black, green, decaffeinated black, or decaffein-    shortcoming of the study, however, is its short duration, as
ated green tea inhibited the number of carcinomas per mouse      hormonal alterations would need longer time to impact fol-
by 93%, 88%, 77%, and 72%, respectively. The mean con-           licular hair growth.
centration of tea leaves used in the study, 1.25 g/100 mL wa-       Green tea and licorice have also been studied for their
ter, is comparable to that of tea brews ingested by humans.      androgen-modulating effects. One RCT evaluated the effects


Review | Dermatol Pract Concept. 2023;13(4):e2023256                                                                           5
of green tea consumption as compared to placebo in 60                        7. Parrado C, Philips N, Gilaberte Y, Juarranz A, González S.
overweight women with PCOS [59]. After 12 weeks, the                            Oral Photoprotection: Effective Agents and Potential Candi-
                                                                                dates. Front Med. 2018;5:188. DOI:10.3389/fmed.2018.00188.
group consuming green tea had significantly decreased free
                                                                                PMID: 29998107. PMCID: PMC6028556.
testosterone levels. Similarly, the effects of a commercial
                                                                             8. Kanwar A. Skin barrier function. Indian J Med Res.
preparation of licorice (3.5 g) consumed daily throughout                       2018;147(1):117. DOI:10.4103/0971-5916.232013.
2 consecutive menstrual cycles were observed in 9 healthy                    9. Strugar TL, Bs AK, Seité S, Lin M, Lio P. Connecting the Dots:
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27.8 ± 8.2 at baseline to 17.5 ± 6.4 ng/dL by the second                        the Role of Moisturizers in Repairing the Skin Barrier. J Drugs
                                                                                ­Dermatol. 2019;18(6):581.2019;18(6):6. PMID: 31251552.
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                                                                            10. Akdeniz M, Gabriel S, Lichterfeld-Kottner A, Blume-Peytavi
warrant additional study to evaluate clinical effects.
                                                                                 U, Kottner J. Transepidermal water loss in healthy adults: a
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Conclusions                                                                      2018;179(5):1049-1055.
                                                                                 30022486.
                                                                                                               DOI:10.1111/bjd.17025.      PMID:


                                                                            11. Spirt SD, Stahl W, Tronnier H, et al. Intervention with flax-
The past few decades have seen an increased focus on the
                                                                                 seed and borage oil supplements modulates skin condition
effects of food on skin health. Numerous studies have iden-
                                                                                 in women. Br J Nutr. 2008;101(3):440-445. DOI:10.1017
tified promising functional foods, although the majority of                      /S0007114508020321. PMID: 18761778.
research to date has involved small-scale human interven-                   12. Neukam K, De Spirt S, Stahl W, et al. Supplementation of flaxseed
tions or animal models. Larger human trials are warranted,                       oil diminishes skin sensitivity and improves skin barrier func-
especially to help elucidate populations that may benefit. In                    tion and condition. Skin Pharmacol Physiol. 2011;24(2):67-74.
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                                                                            13. Boucetta KQ, Charrouf Z, Derouiche A, Rahali Y, Bensouda Y.
beneficial compounds in foods exhibit many additive and
                                                                                 Skin hydration in postmenopausal women: argan oil benefit with
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and laboratory studies to elucidate the biochemical pathways                     2014;13(5):280-288. DOI:10.5114/pm.2014.46470. PMID:
and molecular mechanisms by which these observed clin-                           26327867; PMCID: PMC4520377.
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                                                                                  16019622.
anti-photoaging, photoprotection, and hormonal regulation.                  15.   García-Burgos M, Moreno-Fernández J, Alférez MJM,
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                                                                                  ing milk fermented by Lactococcus lactis H61 on skin health in
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