Beta-carotene for skin -
The report also revealed that Europe's health food industry had 'under-utilised' the nutraceutical properties of carotenoids and consumers are still unaware of their health benefits.
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Salivary supernatant was incubated with E. coli for 30 min to facilitate bacteria killing, and then incubated overnight on trypticase soy agar TSA plates to quantify the amount of bacteria remaining see Supplementary Material for details.
Images of the plates were taken together with a ruler as a size reference. We used the program ImageJ to measure the following: total number of colonies in each plate, average area of each colony, and total area of the colonies combined. Bacteria killing capacity was calculated as the percentage difference in colony number relative to positive controls.
Bacteria growth suppression capacity was calculated as the percentage difference in average colony area relative to positive controls. Overall salivary immunity was calculated as the percentage difference in total colony area relative to positive controls.
A lysoplate assay was used to determine salivary lysozyme activity. Micrococcus lysodeikticus ATCC no. Ten microlitres of whole saliva from each sample were added to 80μL of M.
lysodeikticus in duplicates in a well plate. Positive controls containing 10 μL of PBS and 80 μL of M. lysodeikticus were also added to the plate in duplicates. The plate was incubated at 33°C for 10 min and the absorbance was measured using an M5 SpectraMax microplate reader Molecular Devices, Sunnyvale, CA.
Salivary lysozyme activity was calculated as the difference in absorbance between the sample wells and the positive controls. The semen samples were analyzed in 6 replicates immediately upon delivery using the Hamilton-Thorne CEROS Computer Assisted Semen Analysis CASA system Simmons et al.
The system measures total sperm concentration, percentage motile sperm and 7 motility related variables. Seven samples had to be diluted because they were too concentrated for the CASA to analyze see Supplementary Material for details. A portion of the post-supplementation semen sample was stored in accordance with McEvoy et al.
The semen DNA fragmentation level of each sample is measured by the percentage of fragmented sperm cells see supplementary material for details. Principal components analysis PCA was used to summarize the inter-related semen quality data and immune function data.
PC1 was weighted most strongly by bacterial killing and suppression capacity. PC2 was weighted most strongly by lysozyme activity and overall bacteria immunity.
PC1 was weighted most strongly by variables related to rapid progressive motility. PC2 was weighted most strongly by variables related to the linearity of the sperm movement. PC3 was weighted most strongly by high sperm concentration and percentage motile sperm with low levels of left-right head movement.
PC3 was found to be influenced by variation in the collection procedure and abnormalities in the sample WHO see Supplementary Material for details. Therefore, we ran all analyses for PC3 on the residuals after accounting for these variables.
Difference scores were calculated for each of the 3 skin color variables yellowness, redness, and lightness , the 2 oxidative stress measures 8-OHdG and isoprostane , the 2 immune function PCs, and the 3 semen quality PCs, by subtracting the pre-supplementation scores from the post-supplementation scores.
The descriptive statistics for the dependent variables, including all the difference scores, 2-alternative forced-choice attractiveness scores, 2-alternative forced-choice perceived health scores, and post-supplementation sperm DNA fragmentation levels are presented in Table 1.
Positive values indicate an increase in a particular measure post-supplementation. During data analysis, the treatment conditions were binary coded to prevent any experimenter biases and the code was broken only after the statistical analyses were finalized.
All variables are presented as pre—post difference scores indicated by Δ with the exception of the 2-alternative forced-choice attractiveness and perceived health scores, which were scored based on the percentage of times the post-supplementation face of a participant was chosen as more attractive or healthy looking, respectively, and the sperm DNA fragmentation levels, which was measured post-supplementation.
One-way Anovas with Treatment beta-carotene, placebo as the between-participants factor were conducted for all the dependent variables, including each of the skin color difference scores yellowness, redness, and lightness , the 2-alternative forced-choice attractiveness score, the 2-alternative forced-choice perceived health score, each of the oxidative stress difference scores, each of the immune function PC difference scores, each of the semen quality PC difference scores and the post-supplementation sperm DNA fragmentation levels.
All residuals were normally distributed. These results indicate that the Treatment effect was due to an increase in yellowness in the beta-carotene group. These results show that, as predicted, beta-carotene supplementation significantly increased face yellowness and redness but not lightness.
Examples of the color variation between pre- and post-supplementation for the beta-carotene and placebo groups are shown in Figure 2. Boxplots of pre-post changes in skin yellowness, redness, and lightness by Treatment beta-carotene vs placebo.
Examples of color variation between pre- and post-supplementation by Treatment condition. Thus beta-carotene supplementation significantly enhanced facial attractiveness. Boxplots of 2-alternative-forced-choice scores for attractiveness and perceived health by Treatment beta-carotene vs placebo.
Thus beta-carotene supplementation significantly enhanced perceived health. We provide experimental evidence that the carotenoid beta-carotene enhances skin yellowness and redness and increases facial attractiveness in human males. Contrary to the carotenoid trade-off hypothesis, we did not find any effect of beta-carotene on measures of oxidative stress, immune function, semen quality, or sperm DNA fragmentation.
Thus, despite the effects of beta-carotene on facial appearance, we find no evidence that carotenoid-related skin color is an honest signal of health in human males.
Carotenoid-based coloration has been shown to influence mate choice in taxa such as birds, fishes, and lizards Endler ; Kodric-Brown ; Olson and Owens ; Møller et al.
Our results suggest that carotenoid-based coloration also serves mate choice functions in humans. First, using a randomized, double-blind, placebo-controlled experimental design, we provide strong experimental evidence that consuming beta-carotene enhances skin yellowness and redness.
Second, we showed that there was a significant effect of beta-carotene supplementation on male facial attractiveness and perceived health. Recent correlational studies have linked beta-carotene intake with increased skin yellowness Stephen et al. Our study provides the first evidence for a causal link between beta-carotene and these changes.
To the extent that attractiveness affects mating success Rhodes et al. According to the carotenoid trade-off hypothesis, coloration signals health because individuals face a trade-off between the use of available carotenoids in coloration versus supporting health.
The assumption that carotenoids affect health has been tested experimentally in numerous species of birds, fishes, lizards, and even insects, but the results have been equivocal Aguilera and Amat ; Blount et al. For humans, we found that although beta-carotene made the participants look healthier, there was no evidence that it enhanced actual health.
Beta-carotene supplementation did not affect innate immune function, oxidative stress, or semen quality, all measures that have been linked theoretically to the proposed antioxidant capacity of carotenoids.
Moreover, for each aspect of health, we used multiple measures, which should be superior to using single measures Adamo ; Halliwell and Whiteman Our results suggest that, rather than indicating actual health changes, the changes in perceived health due to beta-carotene supplementation may reflect an attractiveness halo effect Eagly et al.
It is possible that beta-carotene supplementation might have an effect on health in a population that is under greater physiological health stress or greater dietary restrictions than our sample. From a life-history perspective, physiological trade-offs are more apparent when individual or environmental conditions are limiting Stearns Our participants were all relatively healthy individuals recruited from a university community.
It is possible that we found an effect of beta-carotene on facial appearance but not health because the participants simply did not require additional carotenoids to support their health and devoted all the supplemented beta-carotene to appearance.
It would be informative for future studies to examine a population that is under greater physiological or dietary stress. Although we did not find a significant effect of beta-carotene on any of our health measures, carotenoids could still be linked to health via indirect mechanisms. For example, Hartley and Kennedy postulated that carotenoid coloration might actually signal the presence of other antioxidants that protect carotenoids from oxidative damage, which would otherwise cause carotenoids to lose their color i.
This hypothesis is also known as the carotenoid protection hypothesis. In support of this hypothesis, experimental studies have found that dietary supplementation of nonpigmentary antioxidants increase carotenoid-based coloration in species such as zebra finches, Taeniopygia guttata Bertrand et al.
It would be interesting to examine the carotenoid protection hypothesis in humans by investigating the effect of consuming nonpigmentary antioxidants on skin yellowness and redness. Another possibility is that carotenoids only affect health when they are paired with other nutrients.
Almbro et al. They argued that because vitamin E is converted to radical species when it is used as an antioxidant, beta-carotene might serve to recycle the radicalized vitamin E, thus enhancing overall antioxidant status.
Therefore, a potential future direction would be to examine whether beta-carotene affects health in humans when paired with vitamin E. In most species, carotenoid-based coloration is sexually selected via female mate choice for male carotenoid ornamentation, and most species show sexual dimorphism in carotenoid coloration.
A recent study reported that human skin color is also sexually dimorphic Carrito et al. However, mate selection in humans occurs in both directions and carotenoids influence appearance in both sexes Stephen et al.
Therefore, it would be interesting to see the extent to which our findings could be replicated in women. It would also be interesting for future studies to examine whether beta-carotene influences health over a longer supplementation period. We chose the week duration partly because spermatogenesis plus epididymal transit in humans takes a total of 82 days ~ Therefore, we should have been able to observe any effects of beta-carotene on semen quality after 12 weeks of supplementation.
Previous studies examining the effects of antioxidant supplementation on semen quality and oxidative stress have used similar supplementation durations Møller and Loft ; Showell et al.
However, it remains possible that we might observe significant effects of beta-carotene on health in a relatively healthy population like the one in the present study with a longer supplementation duration. Zareba et al. Given this finding, it would be interesting to examine the long-term effect of beta-carotene supplementation on health by repeating the present study with a supplementation period of 1 year or more.
In summary, we report the first double-blind, placebo-controlled experimental study on the effect of carotenoids on human facial appearance and health.
We found that beta-carotene alters skin color by enhancing yellowness and redness to enhance facial attractiveness in human males. However, we found no evidence that carotenoids improve actual health. Together, our results suggest that carotenoid-based coloration may have been sexually selected in humans, but we have no evidence to suggest that it is an honest signal of health.
The study is supported by the ARC Centre of Excellence in Cognition and its Disorders CE , ARC Professorial Fellowships to L.
DP and G. DP , an ARC Discovery Outstanding Researcher Award to G. DP and student research grants awarded to Y. by The Australasian Society for the Study of Animal Behaviour ASSAB and European Human Behaviour and Evolution Association EHBEA.
designed the study, conducted the experiment, analyzed the data, interpreted the results and drafted the manuscript. and L. were involved in designing the study, interpreting the results, and revising the manuscript.
Data accessibility: Analyses reported in this article can be reproduced using the data provided by Foo et al. Adamo SA. How should behavioural ecologists interpret measurements of immunity? Anim Behav. Google Scholar. Aguilera E Amat JA.
Carotenoids, immune response and the expression of sexual ornaments in male greenfinches Carduelis chloris. Alaluf S Heinrich U Stahl W Tronnier H Wiseman S. Dietary carotenoids contribute to normal human skin color and UV photosensitivity. J Nutr. Almbro M Dowling DK Simmons LW. Effects of vitamin E and beta-carotene on sperm competitiveness.
Ecol Lett. Alonso-Álvarez C Galván I. Free radical exposure creates paler carotenoid-based ornaments: A possible interaction in the expression of black and red traits. PLoS ONE. Amann RP.
The cycle of the seminiferous epithelium in humans: A need to revisit? J Androl. Andersson M. Sexual selection. Princeton NJ : Princeton University Press. Google Preview. Bertrand S Fivre B Sorci G. Do carotenoid-based sexual traits signal the availability of non-pigmentary antioxidants?
J Exp Biol. Blount JD. Carotenoids and life-history evolution in animals. Arch Bichem Biophys. Blount JD Metcalfe NB Birkhead TR Surai PF. Carotenoid modulation of immune function and sexual attractiveness in zebra finches.
Carrito M de L Santos IMB dos Lefevre CE Whitehead RD Silva CF da Perrett DI. The role of sexually dimorphic skin colour and shape in attractiveness of male faces. Evol Hum Behav. Changizi MA Zhang Q Shimojo S. Bare skin, blood and the evolution of primate colour vision.
Biol Lett. Chen J Song Y Zhang L. Effect of lycopene supplementation on oxidative stress: an exploratory systematic review and meta-analysis of randomized controlled trials. J Med Food 16 : — Coetzee V Perrett DI.
Effect of beta-carotene supplementation on African skin. J Biomed Opt. Costantini D Møller AP. Carotenoids are minor antioxidants for birds. Funct Ecol. Darwin C. The descent of man and selection in relation to sex. London : John Murray. Dowling DK Simmons LW. Reactive oxygen species as universal constraints in life-history evolution.
Proc R Soc B : — Eagly AH Ashmore RD Makhijani MG Longo LC. What is beautiful is good, but…: A meta-analytic review of research on the physical attractiveness stereotype.
Psychol Bull. Endler JA. Natural and sexual selection on color patterns in poeciliid fishes. Env Biol Fish. Fisher RA. The genetical theory of natural selection.
Oxford : Clarendon Press. Fitze PS Cote J San-Jose LM Meylan S Isaksson C Andersson S Rossi J-M Clobert J. Carotenoid-based colours reflect the stress response in the common lizard.
Fitze PS Tschirren B Gasparini J Richner H. Carotenoid-based plumage colors and immune function: Is there a trade-off for rare carotenoids? Am Nat. Foo YZ Rhodes G Simmons LW. Data from: the carotenoid beta-carotene enhances facial colour, attractiveness and perceived health, but not actual health, in humans.
Dryad Digital Repository. Grether GF Hudon J Millie DF. Carotenoid limitation of sexual coloration along an environmental gradient in guppies. Proc R Soc B. Grether GF Kasahara S Kolluru GR Cooper EL.
Sex-specific effects of carotenoid intake on the immunological response to allografts in guppies Poecilia reticulata. Halliwell B. Antioxidant defence mechanisms: From the beginning to the end of the beginning. Both topical and oral prescription medications used to treat psoriasis contain vitamin A.
Topical retinoid reduces the formation of raised skin patches and the formation of cytokines and interleukins that cause inflammation. A healthcare professional might also prescribe oral acitretin , another retinoid, to treat severe, refractory psoriasis. Bexarotene Targretin , a vitamin A-based drug, is also used to treat cutaneous T-cell lymphoma , a type of cancer that can cause skin changes like rashes, dryness, itching, and thickness.
In the United States, commercially fortified products like breakfast cereal and milk contain vitamin A, as do many nutrient-dense foods like cheese, butter, and fruits and vegetables. According to the National Institutes of Health NIH , people over the age of 4 should consume mcg RAE of vitamin A each day.
You can meet this requirement from both plant and animal sources. Most people in the U. get enough vitamin A from the foods they eat.
That said, premature infants and people living with cystic fibrosis may need additional amounts of this vitamin. Young children generally require less vitamin A than adults of reproductive age and people nursing infants.
Though vitamin A deficiency is uncommon in areas where nutritious food is readily available, it commonly affects people in many African and Southeast Asian countries. You can support the health of your skin by eating a diet that includes a wide range of foods high in vitamin A. Plenty of evidence backs the benefits of topically applied retinoids.
The boost in collagen and elastin production, not to mention the proliferation of new skin cells, can help smooth your skin and reduce the appearance of fine lines and wrinkles. Retinoids also have anti-inflammatory properties that help reduce clogged pores and treat acne.
Their positive effects stop when you stop using them. They can offer more guidance with creating a personalized treatment plan that works for your skin. Too much oral or topical vitamin A can cause side effects. It can even be harmful, especially for people with certain skin conditions and other health issues.
Potential side effects of topical retinoids include:. Most people get enough vitamin A from their diet. Getting too much preformed vitamin A from supplements or certain medications can cause serious side effects, including:. A dermatologist can also offer more tips on caring for your skin.
Still, topical or oral vitamin A treatments could have benefit for treating skin conditions like acne and helping reduce the signs of sun damage. Keep in mind, too, that eating a diet rich in other essential vitamins and reducing your exposure to UV light and smoke can also help promote skin health.
Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available. VIEW ALL HISTORY.
Fkr five servings green coffee extract dietary supplement fruits and vegetables in your Power foods for sports performance is crucial to your overall wellness. Holistic nutritional supplements often-overlooked provitamin is wkin carotenoid, Sports nutrition guidelines plant pigment, Beta-cqrotene gives sunset-hued fruits and Beta-caarotene their striking orange color—carrots, sweet Beta-caarotene, butternut Beta-carotene for skin, and more delicious beta-carotene-rich foods. As for its effects on humans, it also works wonders as an anti-aging agent for the skin, boosting skin elasticity for a glowing, youthful look. Found in leafy greens, sweet potatoes, and squash, beta carotene is the superstar of your lunch salad and an important antioxidant that can benefit a wide range of bodily systems. Your body converts this essential ingredient into the increasingly essential nutrient, vitamin A, to work its magic. Beta carotene may prevent certain cancers and eye diseases while improving cognitive function. Are you looking green coffee extract dietary supplement s,in advice in Vancouver? Our consultations and ski skin Beta-carotenw have helped Power foods for sports performance. Betz-carotene us Herbal metabolism stimulator more information! The question is: when it comes to skin care, are they all the same? Which one is best? And, what about all their other derivatives, such as retinyl ascorbate, retinyl palmitate, retinyl retinoate, retinyl linoleate, retinaldehyde, retinyl acetate, retinoic acid and all the rest? Are they good for skin too?Beta-carotene for skin -
You can support the health of your skin by eating a diet that includes a wide range of foods high in vitamin A. Plenty of evidence backs the benefits of topically applied retinoids. The boost in collagen and elastin production, not to mention the proliferation of new skin cells, can help smooth your skin and reduce the appearance of fine lines and wrinkles.
Retinoids also have anti-inflammatory properties that help reduce clogged pores and treat acne. Their positive effects stop when you stop using them. They can offer more guidance with creating a personalized treatment plan that works for your skin.
Too much oral or topical vitamin A can cause side effects. It can even be harmful, especially for people with certain skin conditions and other health issues.
Potential side effects of topical retinoids include:. Most people get enough vitamin A from their diet. Getting too much preformed vitamin A from supplements or certain medications can cause serious side effects, including:.
A dermatologist can also offer more tips on caring for your skin. Still, topical or oral vitamin A treatments could have benefit for treating skin conditions like acne and helping reduce the signs of sun damage.
Keep in mind, too, that eating a diet rich in other essential vitamins and reducing your exposure to UV light and smoke can also help promote skin health. Our experts continually monitor the health and wellness space, and we update our articles when new information becomes available.
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The shower is the perfect place to give your skin the TLC it deserves, from head to toe. Hopping in the shower isn't just about getting clean, it's also an opportune time to focus on overall skin health with a few skin-friendly habits.
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Vitamins are for athletes to stay healthy. You may get all you need from the food you eat. Some athletes may benefits from vitamin supplements. Docosahexaenoic acid, or DHA, is a type of omega-3 fat that may improve many aspects of your health, from your brain to your heart.
Here are 12…. A Quiz for Teens Are You a Workaholic? How Well Do You Sleep? Health Conditions Discover Plan Connect. Benefits of Beta Carotene and How to Get It. Medically reviewed by Jillian Kubala, MS, RD , Nutrition — By Natalie Olsen, R.
Benefits Foods sources Dosage Risks Bottom line Beta carotene plays an important role in your health and eating lots of fresh fruits and vegetables is the best way to get it into your diet. Share on Pinterest. What are the benefits? Foods rich in beta carotene.
How much beta carotene should you take? Are there risks of getting too much? The bottom line. How we reviewed this article: Sources. Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. We avoid using tertiary references.
You can learn more about how we ensure our content is accurate and current by reading our editorial policy.
May 23, Written By Natalie Olsen, RD, LD, ACSM EP-C. Aug 13, Medically Reviewed By Jillian Kubala, MS, RD. Share this article. Read this next. Medically reviewed by Atli Arnarson BSc, PhD.
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Are mindbodygreen Supplements Worth It? Our Testers and Dietitians Explain. By Kelsey Kunik, RDN. Despite correlational findings linking carotenoids to health and in vitro evidence supporting the key assumption of the carotenoid trade-off hypothesis that carotenoids affect health, a role for carotenoids in health in vivo remains contentious.
Several researchers have suggested that carotenoids are at best minor antioxidants Halliwell ; Hartley and Kennedy ; Costantini and Møller ; Pérez-Rodríguez Costantini and Møller conducted a meta-analytic review and concluded that there is little evidence that carotenoids function as antioxidants in birds.
As for the effects of carotenoids on immune function, although some animal studies have found positive effects e.
Less research has been done on the effect of carotenoids on male reproductive health, and these findings are equally unclear. In 3-spined sticklebacks, Gasterosteus aculeatus , for example, males that were fed higher amounts of carotenoids fertilized more eggs when provided with a clutch of unfertilized eggs Pike et al.
However, in a competitive fertilization study of crickets, Teleogryllus oceanicus , the carotenoid beta-carotene did not affect sperm competitiveness unless it was consumed together with vitamin E Almbro et al. Although the role carotenoids play in mate choice is well-established in taxonomic groups such as birds and fishes, the evidence in mammals has been lacking, partly because color-based sexual signaling is relatively rare in mammals as many species lack trichromatic color vision Changizi et al.
Emerging evidence using the CIELab color space, which models human trichromatic color vision based on 3 axes, namely lightness, redness, and yellowness, suggests that carotenoids may affect mate choice in humans by influencing their facial skin color, particularly yellowness.
First, skin yellowness may be correlated with carotenoid intake. Individual variation in beta-carotene intake based on self-reported fruit and vegetable consumption was found to be positively related to skin yellowness Stephen et al.
In addition, changes in self-reported fruit and vegetable intake over 6 weeks were found to be positively related to changes in skin yellowness, with the spectral reflectance changes directly related to the spectral absorption of carotenoids Whitehead et al.
Moreover, a recent intervention study found that consumption of carotenoid-rich fruit and vegetable smoothies over 6 weeks increased skin yellowness and redness Tan et al. Second, carotenoid-based skin color is associated with attractiveness in humans. Individuals preferred faces that were transformed to be high in carotenoid color over low-carotenoid-color versions of the same faces Lefevre et al.
Skin yellowness is also related to attractiveness of own-race faces for both Caucasian and African participants Stephen et al.
Facial yellowness is also related to how healthy faces appear, which is closely linked to attractiveness Rhodes et al. Both Caucasian and African participants increased yellowness in own-race face images when asked to adjust the color to make the faces look healthier Stephen et al.
There are, however, several limitations in the human carotenoid signaling literature. The evidence relating carotenoids to human facial appearance is almost entirely correlational, which prevents conclusions of causation.
Two studies reported that participants given daily beta-carotene supplements for 8 weeks showed an increase in skin yellowness and redness Stephen et al. However, due to the lack of a control group in both studies, we cannot exclude the possibility that the observed color changes were due to factors other than beta-carotene supplementation.
Furthermore, both studies had a very small sample size of 10, which makes it difficult to draw firm conclusions. Tan et al. However, we cannot be certain that the effect was due to carotenoids and not to other nutrients in the smoothies. No studies have tested experimentally the effects of carotenoids on attractiveness and perceived health.
Most importantly, no experimental study has tested whether carotenoids improve actual health as predicted by the carotenoid trade-off hypothesis. Here we use a randomized, double-blind, placebo-controlled supplementation study to investigate the effects of beta-carotene on facial appearance and health in humans.
We focus our study on female preferences for male appearance. First, we establish the effect of carotenoids on face color. Based on previous findings Stephen et al. Second, we examine the effect of beta-carotene on attractiveness.
We hypothesize that beta-carotene supplementation will enhance facial attractiveness. Together, the 2 hypothesized results would support the idea that carotenoids play a role in human sexual selection by altering skin color. Third, we examine the effect of beta-carotene on healthy appearance.
Based on previous findings that skin yellowness is positively correlated with perceived health Stephen et al. Finally, we examine whether beta-carotene enhances actual health. We investigate a range of physiological health measures that are theoretically linked to carotenoids, including oxidative stress, innate immune function, and semen quality.
A positive effect of beta-carotene on any of these health measures would support the idea that carotenoid coloration is an honest signal of health. The study was approved by the Human Ethics Committee at the University of Western Australia Ethics approval ref.
All participants provided written consent prior to their participation in the project. Each of them received either course credit or transport remuneration.
All of them identified themselves as heterosexual and reported that they did not suffer from any immunological, endocrine, or metabolic disorders. Two previous studies that investigated the effect of beta-carotene supplementation on skin color have found significant changes in skin color after 8 weeks of beta-carotene supplementation with 10 participants and neither study had a placebo condition Stephen et al.
We also had a placebo group consisting of an additional 20 male participants. Participants first attended a 1. They were asked to refrain from consuming any food or flavored drinks 1 h before the session, not wear any make-up or tanning agents, and be clean-shaven.
Urine 10 mL was first collected in a sterile bottle for oxidative stress measures. Saliva 5 mL was then collected for immune function measures.
Participants collected the saliva in a sterile bottle using the passive drool method after rinsing their mouth with water and waiting approximately 15 min. Participants were seated at a fixed distance cm from the camera against a grey fabric background. A cape in the same grey fabric was draped over the participants to control for the color of their clothing.
Spectacles were removed and fringes covering the forehead were pulled back using a hairband. At the end of the laboratory session, the participants were given written instructions for semen collection, a sterile sample vial to collect the ejaculate, an ejaculate questionnaire, a piece of aluminum foil, and 4 pictures, each containing the front view image of a naked woman from Thornhill and Grammer They were asked to abstain from any ejaculation for 2—6 days before collecting the sample at home via masturbation while viewing the 4 images.
The images provided visual stimulation, which is necessary for the production of a normal ejaculate Wylie and Pacey Participants were asked to deliver the sample to the laboratory within 1 h of collection.
During delivery, they were asked to wrap the sample vial in aluminum foil and place it under their arm or between their legs to maintain its temperature. Participants also returned the completed ejaculate questionnaire, which noted the time at which the sample was collected, whether the entire ejaculate was collected and if not, the percentage and portion initial, middle, or end lost, and the time since their previous ejaculation.
To ensure double blinding, both capsule types were stored in identical opaque bottles with tamper evident seals that were broken only by the participants. The bottles were randomly assigned and coded by a research assistant who was not involved in the study.
The participants returned after 12 weeks for the post-supplementation follow-up, where the photography and sample collection were repeated. The week supplementation period was chosen because human spermatogenesis takes around 74 days and epididymal transit takes an additional 8 days, making a total of 82 days ~ To control for random fluctuations in lighting conditions and camera settings, the photos were color-calibrated by standardizing the color of the ColourChecker patches based on known CIELab values using the color calibration plugin in the program Psychomorph Tiddeman and Perrett The measurements were taken from ten 60 × 60 pixels squares.
Two squares were placed above each eyebrow on the forehead. Three squares were placed on each side of the cheek. Care was taken to avoid skin regions with blemishes, specular highlights, or shadows.
The CIELab values were averaged across the 10 squares to derive average lightness, redness, and yellowness values for each face. We compared the attractiveness and perceived health of the pre- and post-supplementation color-calibrated faces using a 2-alternative forced-choice procedure.
In each trial, raters saw the pre- and post-supplementation faces of each male participant presented side by side on a computer screen. Raters had to select the more attractive or healthy looking face. Each face pair remained onscreen until the rater responded. Each task consisted of 2 blocks.
All 43 male face pairs were presented twice, once in each block, making a total of 86 trials for each task. In block 1, the post-supplementation face was shown on the right for half the face pairs.
The face pairs were presented again in block 2 in the opposite left-right orientation. Block order was counterbalanced across participants. All faces were rotated and aligned so that the eyes were lying on a horizontal plane at the same height. All images were cropped to × pixels and a black oval mask was applied to cover most of the hair, ears, and neck.
An attractiveness score for each face pair was calculated as the percentage of times the post-supplementation face was chosen as the more attractive face. A perceived health score for each face pair was calculated as the percentage of times the post-supplementation face was chosen as the more healthy looking face.
However, several previous studies have investigated skin color preferences using online samples Lefevre et al. Both samples showed a preference for high carotenoid skin color, with no difference in the preference between the two.
This finding suggests that any additional noise due to uncalibrated monitors is relatively small compared to the color variation among the faces. Markers of DNA oxidation 8-OHdG and lipid peroxidation isoprostane were analyzed in duplicates using competitive enzyme-linked immunoassay ELISA kits from Northwest Life Science Specialties Vancouver, VA.
A significant proportion of urinary isoprostane is conjugated to glucoronic acid, which is not assayable Yan et al. To obtain a more accurate measure of overall isoprostane level, µL of each sample was incubated with 5 µL of beta-glucoronidase for 2 h at 37°C to cleave and free the isoprostanes from their conjugated forms before running the isoprostane assays.
Creatinine was determined in duplicates using colorimetric assay kits from Northwest Life Science Specialties Vancouver. Salivary bacteria killing capacity against Escherichia coli ATCC no. Salivary supernatant was incubated with E. coli for 30 min to facilitate bacteria killing, and then incubated overnight on trypticase soy agar TSA plates to quantify the amount of bacteria remaining see Supplementary Material for details.
Images of the plates were taken together with a ruler as a size reference. We used the program ImageJ to measure the following: total number of colonies in each plate, average area of each colony, and total area of the colonies combined.
Bacteria killing capacity was calculated as the percentage difference in colony number relative to positive controls.
Bacteria growth suppression capacity was calculated as the percentage difference in average colony area relative to positive controls. Overall salivary immunity was calculated as the percentage difference in total colony area relative to positive controls.
A lysoplate assay was used to determine salivary lysozyme activity. Micrococcus lysodeikticus ATCC no. Ten microlitres of whole saliva from each sample were added to 80μL of M. lysodeikticus in duplicates in a well plate.
Positive controls containing 10 μL of PBS and 80 μL of M. lysodeikticus were also added to the plate in duplicates. The plate was incubated at 33°C for 10 min and the absorbance was measured using an M5 SpectraMax microplate reader Molecular Devices, Sunnyvale, CA.
Salivary lysozyme activity was calculated as the difference in absorbance between the sample wells and the positive controls.
The semen samples were analyzed in 6 replicates immediately upon delivery using the Hamilton-Thorne CEROS Computer Assisted Semen Analysis CASA system Simmons et al. The system measures total sperm concentration, percentage motile sperm and 7 motility related variables.
Seven samples had to be diluted because they were too concentrated for the CASA to analyze see Supplementary Material for details. A portion of the post-supplementation semen sample was stored in accordance with McEvoy et al. The semen DNA fragmentation level of each sample is measured by the percentage of fragmented sperm cells see supplementary material for details.
Principal components analysis PCA was used to summarize the inter-related semen quality data and immune function data. PC1 was weighted most strongly by bacterial killing and suppression capacity.
PC2 was weighted most strongly by lysozyme activity and overall bacteria immunity. PC1 was weighted most strongly by variables related to rapid progressive motility. PC2 was weighted most strongly by variables related to the linearity of the sperm movement. PC3 was weighted most strongly by high sperm concentration and percentage motile sperm with low levels of left-right head movement.
PC3 was found to be influenced by variation in the collection procedure and abnormalities in the sample WHO see Supplementary Material for details. Therefore, we ran all analyses for PC3 on the residuals after accounting for these variables. Difference scores were calculated for each of the 3 skin color variables yellowness, redness, and lightness , the 2 oxidative stress measures 8-OHdG and isoprostane , the 2 immune function PCs, and the 3 semen quality PCs, by subtracting the pre-supplementation scores from the post-supplementation scores.
The descriptive statistics for the dependent variables, including all the difference scores, 2-alternative forced-choice attractiveness scores, 2-alternative forced-choice perceived health scores, and post-supplementation sperm DNA fragmentation levels are presented in Table 1.
Positive values indicate an increase in a particular measure post-supplementation. During data analysis, the treatment conditions were binary coded to prevent any experimenter biases and the code was broken only after the statistical analyses were finalized.
All variables are presented as pre—post difference scores indicated by Δ with the exception of the 2-alternative forced-choice attractiveness and perceived health scores, which were scored based on the percentage of times the post-supplementation face of a participant was chosen as more attractive or healthy looking, respectively, and the sperm DNA fragmentation levels, which was measured post-supplementation.
One-way Anovas with Treatment beta-carotene, placebo as the between-participants factor were conducted for all the dependent variables, including each of the skin color difference scores yellowness, redness, and lightness , the 2-alternative forced-choice attractiveness score, the 2-alternative forced-choice perceived health score, each of the oxidative stress difference scores, each of the immune function PC difference scores, each of the semen quality PC difference scores and the post-supplementation sperm DNA fragmentation levels.
All residuals were normally distributed. These results indicate that the Treatment effect was due to an increase in yellowness in the beta-carotene group. These results show that, as predicted, beta-carotene supplementation significantly increased face yellowness and redness but not lightness.
Examples of the color variation between pre- and post-supplementation for the beta-carotene and placebo groups are shown in Figure 2. Boxplots of pre-post changes in skin yellowness, redness, and lightness by Treatment beta-carotene vs placebo. Examples of color variation between pre- and post-supplementation by Treatment condition.
Thus beta-carotene supplementation significantly enhanced facial attractiveness. Boxplots of 2-alternative-forced-choice scores for attractiveness and perceived health by Treatment beta-carotene vs placebo.
Thus beta-carotene supplementation significantly enhanced perceived health. We provide experimental evidence that the carotenoid beta-carotene enhances skin yellowness and redness and increases facial attractiveness in human males.
Contrary to the carotenoid trade-off hypothesis, we did not find any effect of beta-carotene on measures of oxidative stress, immune function, semen quality, or sperm DNA fragmentation.
Thus, despite the effects of beta-carotene on facial appearance, we find no evidence that carotenoid-related skin color is an honest signal of health in human males. Carotenoid-based coloration has been shown to influence mate choice in taxa such as birds, fishes, and lizards Endler ; Kodric-Brown ; Olson and Owens ; Møller et al.
Our results suggest that carotenoid-based coloration also serves mate choice functions in humans. First, using a randomized, double-blind, placebo-controlled experimental design, we provide strong experimental evidence that consuming beta-carotene enhances skin yellowness and redness.
Second, we showed that there was a significant effect of beta-carotene supplementation on male facial attractiveness and perceived health. Recent correlational studies have linked beta-carotene intake with increased skin yellowness Stephen et al. Our study provides the first evidence for a causal link between beta-carotene and these changes.
To the extent that attractiveness affects mating success Rhodes et al. According to the carotenoid trade-off hypothesis, coloration signals health because individuals face a trade-off between the use of available carotenoids in coloration versus supporting health.
The assumption that carotenoids affect health has been tested experimentally in numerous species of birds, fishes, lizards, and even insects, but the results have been equivocal Aguilera and Amat ; Blount et al. For humans, we found that although beta-carotene made the participants look healthier, there was no evidence that it enhanced actual health.
Beta-carotene supplementation did not affect innate immune function, oxidative stress, or semen quality, all measures that have been linked theoretically to the proposed antioxidant capacity of carotenoids.
Moreover, for each aspect of health, we used multiple measures, which should be superior to using single measures Adamo ; Halliwell and Whiteman Our results suggest that, rather than indicating actual health changes, the changes in perceived health due to beta-carotene supplementation may reflect an attractiveness halo effect Eagly et al.
It is possible that beta-carotene supplementation might have an effect on health in a population that is under greater physiological health stress or greater dietary restrictions than our sample.
From a life-history perspective, physiological trade-offs are more apparent when individual or environmental conditions are limiting Stearns Our participants were all relatively healthy individuals recruited from a university community.
It is possible that we found an effect of beta-carotene on facial appearance but not health because the participants simply did not require additional carotenoids to support their health and devoted all the supplemented beta-carotene to appearance.
It would be informative for future studies to examine a population that is under greater physiological or dietary stress. Although we did not find a significant effect of beta-carotene on any of our health measures, carotenoids could still be linked to health via indirect mechanisms.
For example, Hartley and Kennedy postulated that carotenoid coloration might actually signal the presence of other antioxidants that protect carotenoids from oxidative damage, which would otherwise cause carotenoids to lose their color i.
This hypothesis is also known as the carotenoid protection hypothesis. In support of this hypothesis, experimental studies have found that dietary supplementation of nonpigmentary antioxidants increase carotenoid-based coloration in species such as zebra finches, Taeniopygia guttata Bertrand et al.
It would be interesting to examine the carotenoid protection hypothesis in humans by investigating the effect of consuming nonpigmentary antioxidants on skin yellowness and redness. Another possibility is that carotenoids only affect health when they are paired with other nutrients. Almbro et al.
They argued that because vitamin E is converted to radical species when it is used as an antioxidant, beta-carotene might serve to recycle the radicalized vitamin E, thus enhancing overall antioxidant status.
Therefore, a potential future direction would be to examine whether beta-carotene affects health in humans when paired with vitamin E. In most species, carotenoid-based coloration is sexually selected via female mate choice for male carotenoid ornamentation, and most species show sexual dimorphism in carotenoid coloration.
A recent study reported that human skin color is also sexually dimorphic Carrito et al. However, mate selection in humans occurs in both directions and carotenoids influence appearance in both sexes Stephen et al.
Therefore, it would be interesting to see the extent to which our findings could be replicated in women. It would also be interesting for future studies to examine whether beta-carotene influences health over a longer supplementation period.
We chose the week duration partly because spermatogenesis plus epididymal transit in humans takes a total of 82 days ~ Therefore, we should have been able to observe any effects of beta-carotene on semen quality after 12 weeks of supplementation. Previous studies examining the effects of antioxidant supplementation on semen quality and oxidative stress have used similar supplementation durations Møller and Loft ; Showell et al.
However, it remains possible that we might observe significant effects of beta-carotene on health in a relatively healthy population like the one in the present study with a longer supplementation duration. Zareba et al.
Befa-carotene carotene is Power foods for sports performance type of Beta-farotenea pigment found in plants that gives them their intense color. It is orange-yellow and is found in yellow, orange, zkin red foods. Beta-acrotene the body, beta-carotene is Mediterranean diet and mental health into vitamin A, which is needed by the body to support healthy vision, immunity, cell division, and other functions. This article will cover the current research and understanding of how beta carotene affects the body and which foods are good sources of this antioxidant. Carotenoids are a group of yellow, orange, or red pigments. They can be found in fruits, vegetables, fungi, and flowers, among other living things. Beta carotene is a type of carotenoid found in vegetables such as carrots, pumpkins, sweet potatoes, spinach, and kale.
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