Understanding CollagenAging, as we all know, is a natural process. In our youth, skin cells die and regenerate every 28 days, but with time, this turnover slows down and by middle age, the life cycle of skin cells is 35 days (1). The production of water-retaining and texture-enhancing compounds such as hyaluronic acid and polysaccharides as well as skin-firming collagen and elastin also deplete with age, creating a need to fill in that gap. Many people rely on topicals to moisturize and support aging of skin, but topicals can only do so much. To truly enhance the body’s ability, on a physiological level, to maintain or even improve the structure of our skin, nutricosmetics are an important tool. That is not to say that topicals don’t have a use. In fact, topicals can be great for soothing and even blocking environmental factors of aging such as pollution and UV rays. Utilizing both topicals and nutricosmetics provides a well-rounded defense against signs of aging, but for now, let’s discuss the nutricosmetics, starting with perhaps the most well recognized and popular ingredient in the space, collagen.
Collagen has an important place in two dietary supplement categories, nutricosmetic and sports nutrition/recovery. That does not mean products in both can be used interchangeably. This is because they rely on different types of collagen. “Type I and III are primarily found in the skin as well as hair, skin, nails, teeth, eyes, bones,” explains Tracy Kreider, national product educator for Country Life Vitamins, based in Hauppauge, NY. “There are actually 16 different types of collagen, so while you have tendons and ligaments covered in Type I and III, cartilage is supported with Type II.”
Because joint support products are designed to target cartilage, which gets the brunt of wear and tear related to heavy physical activity, Type II collagen is the main ingredient while those seeking to support skin need predominantly Type I and III. “Collagen Type I makes up over 90% of the collagen in the human body since it is abundant in bone, skin, tendon, ligament, and organs,” explains Douglas Jones, sales and marketing manager for BioCell Technology, LLC, Irvine, CA. “Collagen Type I is primarily used for the manufacture of gelatin and generic collagen products due to high production yields and lower cost.” Indeed, in line with collagen’s popularity, many enjoy bone broth from beef or poultry not only for its taste, but because of its collagen content in gelatin.
However, there is a big difference between a hearty broth, generic collagen and a specially formulated and studied collagen ingredient. “The key to collagen effectiveness lies in whether the specific collagen product in question has been subjected to scientific research and proven in human clinical studies,” continues Jones. “Given the complexity of collagen and the various types, sources, molecular size, composition, and manufacturing methods, it is important to avoid drawing comparisons or conclusions on their mechanisms of action based on simplistic variables.”
Kreider agrees, also citing the importance of clinically formulated and studied ingredients and being able to see the difference in the real world. For example, brands such as Country Life, NeoCell and BioCell, to name a few, utilize patented ingredients made from hydrolyzed collagen that are supported by research. Other brands such as Vital Proteins refer to hydrolyzed collagen as collagen peptides. However, without education, consumers may not be aware of the difference. “Most people would think numbers equate better, so when one is in the store comparing labels, one product will say 5,000 mg of collagen while Country Life’s will say 2,500 mg,” Kreider explains. “You might think more is better, but what we explain is that collagen is a very complex structure, called the triple helical structure and it’s very difficult for the body to digest and break down.”
This is where hydrolyzed collagen comes in. Simply put, “The process of hydrolyzing turns naturally occurring collagen into a bioavailable substance,” says Timothy Mount, CN, CCMH, director of education, NeoCell, Irvine, CA, which manufactures collagen products with clinically tested and trademarked BioActive NeoCell Collagen. Therefore, while they may be taking less in milligrams, consumers are in fact getting more out of the collagen than more affordable, generic products. How does this work? The Health Home Economist explains that like gelatin, hydrolized collagen is derived from cattle, pigs or fish and has an amino acid profile consisting mainly of glycine, glutamic acid, proline and alanine (2). It’s these amino acids, particularly glycine and proline, that help the body form new collagen, says Corey Friese, VP of compliance and product strategy, Vital Protein, based in Elk Grove Village, IL. However, hydrolyzing collagen breaks down the amino acid chains into smaller units than that of gelatin, giving it a much less complex structure that makes for superior bioavailability (2).
“Not only does collagen provide the building blocks for skin, it can help stimulate the fibroblasts in our skin to produce collagen,” says Friese. “With these new techniques, it makes the same dose of collagen more effective, with only its amino acid structure being the difference.”
Hydrolyzed collagens also vary between brands, with differing manufacturing processes. Branded ingredients have the benefit of clinical research that verifies their efficacy and allows the ingredient and therefore the finished product to make certain claims others cannot. For example, Country Life’s MaxiSkin is made with Verisol, a branded hydrolyzed collagen manufactured by Gelita USA Inc., based in Sergeant Bluff, IA. This allows Country Life to put claims such as “increases collagen by 60%” and “enhances elasticity.”
These claims are backed by research on the ingredient. One double-blind, placebo-controlled trial measuring wrinkle reduction on 69 women 35-55 years of age found that those in the Verisol group showed a statistically significant improvement in skin elasticity compared to placebo in just four weeks, with some women experiencing an increase of skin elasticity up to 30% after eight weeks (3).The key to collagen effectiveness lies in whether the specific collagen product in question has been subjected to scientific research and proven in human clinical studies.
Another double-blind, placebo-controlled trial of 114 women aged 45-65 years randomized to receive 2.5 g of the hydrolyzed collagen or placebo once daily for eight weeks found that after four weeks of treatment, the supplement group showed a statistically significantly reduced eye wrinkle volume of more than 7.0% on average, with a more pronounced positive effect after eight weeks of intake (4). This study also demonstrated a 65% higher content of procollagen Type I and 18% higher content of elastin in subjects taking the hydrolyzed collagen.
While most nutricosmetic collagen products will be composed of type I and III collagen, patented BioCell Collagen provides a matrix of 60% hydrolyzed type II collagen, 20% chondroitin sulfate and 10% hyaluronic acid that has some clinical evidence it may boost collagen production. One human study made up of 26 subjects with visible signs of aging who took one gram of BioCell Collagen for 12 weeks, resulted in a significant 13% reduction in facial lines and wrinkles, a 76% reduction in dryness and skin scaling as well as a 3.5% increase in the content of type I and III collagen in the dermis (5).
Plant-based BeautyCollagen is certainly trending in the nutricosmetic space, but its one big downside is that all collagen products are derived from animals, alienating a large portion of the natural products consumer-base. However, there are a good deal of other efficacious nutricosmetic ingredients that consumers can turn to if they are avoiding animal products or simply want a complementary ingredient in their nutricosmetic regimen.
When it comes to skin health, protecting ourselves from oxidation as a result of environmental factors makes antioxidant ingredients an important tool in one’s nutricosmetic arsenal. Natural antioxidants such as carotenoids and polyphenols can help support skin health. “The collagen in our skin (natural or supplemented) is affected by the microenvironment in the skin and is constantly being degraded due to oxidative stress and inflammatory challenges,” explains Dr. Karin Hermoni, Ph.D., head of science and nutrition at Lycored, based in Orange, NJ. “Natural phytonutrients such as carotenoids can help protect the collagen network by balancing these processes, therefore, reducing the degradation of the collagen.”
Lycopene, phytoene, phytofluene and astaxanthin, in particular, are natural carotenoids proven to support skin health, states Golan Raz, Ph.D., head of the global health division at Lycored. Indeed, research has shown that consuming carotenoids does have a photoprotective effect on our skin. One 2008 study published in the British Society of Investigative Dermatology, studied 20 individuals who either received 55 g of tomato paste with 10 g of olive oil or just olive oil for 12 weeks. Nutra-Ingredients reported that those taking tomato paste experienced 33% more protection against sunburn than the control group, a level of protection equivalent to 1.3 SPF sunscreen (6). It is believed that the lycopene content neutralized the production of excess reactive oxygen species, otherwise known as free radicals, as a result of UV exposure.
A 2005 study of lycopene in supplement form published in The International Journal for Vitamin and Nutrition Research compared synthetic lycopene to a tomato extract (Lyc-o-Mato) and a drink containing a solubilized version of the same extract mixed into a beverage. All groups consumed about 10 mg per day for 12 weeks and all experienced a significant increase in lycopene serum levels, total skin carotenoids, while only the Lyc-o-Mator groups experienced increased serum levels of phytofluene and phytoene (7). Subjects also had erythema induced at 0, 4 and 12 weeks with a solar light simulator. Photoprotective effects, determined by evaluating reddening before and 24 hours after irradiation, were the most pronounced in the tomato extract at 35% and the drink at 48% compared to the synthetic lycopene extract (25%).
The comparison between the synthetic lycopene and tomato extracts is important because different carotenoids work synergistically with one another. “Lycopene, the vibrant red carotenoid from the tomato, has been found to have many skin benefits, however, research shows that the colorless carotenoids phytoene and phytofluene also found in the tomato are key to many synergistic activations to skin wellness,” says Hermoni. “The benefits of this tomato-derived carotenoid mix are greater than the lycopene on its own.”
Polyphenols, another natural antioxidant, says Hermoni, can optimize carotenoids further. “The polyphenol carnosic acid derived from rosemary extract has been found to synergize with the tomato carotenoids and amplify their impact,” she explains. “When combined, these phytonutrients have been found to optimize the skin’s natural protection mechanisms and help the skin cells better cope with different challenges.”
Flavonoids are also important free radical scavengers, says Richard Passwater, Jr., product education director for Bio Minerals, the maker of BioSil, a specialty line from Monroe, WA-based Natural Factors. “Flavonoids such as those in green tea extract, citrus fruits, rose hips, pine bark, grape seed, bilberry, blueberry, and turmeric actually stick to collagen to protect it,” he states.
Astaxanthin, harvested from algae and found in salmon that feed on algae, is an exceptionally powerful antioxidant, says Karen A. Hecht, Ph.D., scientific affairs manager for AstaReal, based in Burlington, NJ. “Astaxanthin, unlike most antioxidants, has a unique structure that allows it to span skin cell membranes, providing more antioxidant coverage and protection,” she explains. “Astaxanthin is also a stronger antioxidant and a pure antioxidant. AstaReal Astaxanthin is 6,000 times, 800 times, 560 times and 75 times stronger than vitamin C, coenzyme Q10, catechin and alpha-lipoic acid, respectively.”
Collagen is produced by skin cells called fibroblasts, explains Hecht, and fibroblasts are vulnerable to free radicals, therefore reducing collagen production. “AstaReal Astaxanthin neutralizes free radicals in the skin, helping to preserve collagen production by protecting fibroblasts,” she says. “While other ingredients may boost collagen production in healthy fibroblasts, they cannot effectively protect fibroblasts from free radical damage.”
For example, she cites a study which showed that vitamin C increased collagen production by 32% in healthy cells but in cells subjected to free radicals, vitamin C was not able to protect cells from damage and collagen production was completely abolished. “In contrast, AstaReal Astaxanthin was able to protect cells from free radical damage, allowing restoration of 80% of the collagen production even in the presence of free radicals,” Hecht explains.
Astaxanthin’s use as a nutricosmetic has been shown in research to support our skin at all levels with optimal results from combining topical and nutricosmetic applications. One open label non-controlled study of 30 healthy female subjects taking 6 mg oral and 2 ml topical astaxanthin per day found that subjects saw improvement in crow’s feet after eight weeks, age spots after eight weeks, elasticity after eight weeks, skin texture after four weeks and moisture content after eight weeks. “It may suggest that astaxanthin derived from H. pluvialis can improve skin condition in all layers such as corneocyte layer [stratum corneum], epidermis, basal layer and dermis by combining oral supplementation and topical treatment,” writes Kumi Tomigana, et al. in The Journal of the Polish Biochemical Society (8).
In a different study, this time a double-blind, placebo-controlled study, 36 healthy men were given 6 mg of astaxanthin daily for six weeks. Improvement was seen in crow’s feet wrinkles, elasticity and transepidermal water loss as well as a tendency for improvement in moisture content and sebum oil levels at the cheek zone. Looking at both studies together, Tomigana et al. write, “It seems that a double administration by combining oral supplementation and topical treatment should be recommended for wrinkle reduction and oral supplementation might be more potent than topical treatment. The mechanism of action of wrinkle reduction by astaxanthin could be explained as a dermis condition improvement through collagen fiber recovery. Astaxanthin promotes collagen fiber recovery by protecting the dermal layer from singlet oxygen damage which has been substantiated by an in vitro study using human dermal fibroblasts. Elasticity was also improved as a result of collagen fiber recovery [in] both [studies].”
Supporting the skin on all levels is important because every layer of the skin serves a purpose. As Hecht explains, the stratum corneum (SC) is the skin’s outermost layer which protects the skin’s underlying layers from external chemical and UV damage, and helps hold in moisture. The epidermis is where basal cells mature and replenish old SC cells as they are shed every 28 days in a cycle of skin renewal as well as contain the cells that produce melanin, which is stimulated by UV exposure leading to formation of age spots and persistent pigment darkening as we age. The dermis is largely made up of water, and structural proteins such as elastin and collagen fibers and provides resilience to the skin secreting essential connective tissue factors important for the skin. “UV destabilizes dermal cells called fibroblasts, which make collagen,” says Hecht. “Damage to collagen or collagen production can cause fine lines or even dermal scars.”
The innermost and thickest layer of skin is the hypodermis, which contains a capillary bed that brings nutrients to the skin. “Clinical studies have shown that AstaReal Astaxanthin helps improve antioxidant capacity, blood flow, and nutrient supply to this deepest skin layer, resulting in improved maintenance and overall health of the skin,” explains Hecht. According to Passwater, the branded ingredient BioSil (choline-stabilized orthosilicic acid) “generates new collagen, elastin and keratin by activating and supporting enzymes critical to making these ‘three beauty proteins.’ BioSil also helps protect collagen and elastin by neutralizing homocysteine, an ‘anti-collagen’ amino acid that destroys collagen and elastin throughout the body while also suppressing new collagen and elastin production.”These collagen powders are unflavored and most people can’t tell it’s even in their food when eaten, making it an ideal supplement to increase the nutritional content of recipes for the whole family.”
It’s able to generate collagen because the orthosilicic acid in BioSil serves as a cofactor in the functioning of at least two key enzymes meant for collagen production and the choline in the product protects the the functioning of a third, says Passwater.
The results of one 20-week study on women 40 to 65 years old with photo-damaged skin, showed the women taking two BioSil capsules had a significant increase in skin elasticity and a reduction in the depth of their fine lines and wrinkles (9). “Skin elasticity measurements improved 89% when comparing the improvements in the BioSil group to the continued deterioration in the placebo group,” explains Passwater. “Fine lines and wrinkles of the women in the BioSil group decreased 19% in depth, a 30% improvement compared to the continued deepening of the fine lines and wrinkles of the women in the placebo group.” In this same study, nail brittleness was also significantly reduced. The ingredient can also support hair health, with research focusing on hair cross-sectional diameter and the strength and elasticity of each hair fiber. “In a 9-month study, women taking two BioSil capsules per day increased their hair strength about 13.1% and their hair thickness about 12.8% compared to women taking placebo pills,” says Passwater (10).
Hair is believed to improve from the ingredient in four different ways. As Passwater explains, the derma papilla is the hair formation site that gets smaller with age. “BioSil stimulates collagen production in the dermal papilla and increases its size,” he says. “The bigger the dermal papilla, the thicker and stronger the hair fiber.”
Second, because BioSil increases the collagen production in the skin, this in turn improves microcirculation. “This results in better blood flow, and better nutrient delivery, to the dermal papilla,” he explains. “Generally better circulation results in healthier, faster growing hair.” Thirdly, BioSil’s activation of keratin and supporting enzymes that make keratin, a protein that makes up 97% of hair, may play a big role. The last way, says Passwater is that some orthosilicic acid from BioSil may be incorporated into the hair structure improving the strength of the keratin.
One of the most popular supplements to support hair and nail health is biotin. “Our Biotin and Maxi-Hair, this is a 20-year product for us, it’s a million dollar SKU and has a cult following on YouTube,” says Kreider. Biotin is a very powerful B-vitamin that supports hair’s elasticity and strengthens its keratin structure, ideally in the presence of other complementary components. “You also have to have those other components, MSM and methianin and cystine, those are all lending sulfur units and that’s really important for hair, skin and nail structure,” Kreider explains. “So it’s a compilation of all the minerals we are desperately deficient in, you have a mineral complex, then you have a complex helping with a high amount of biotin.”
Raz agrees. “When it comes to healthy hair strategy, the basics are the B vitamins,” he says. “Fortifying our daily diet with a solid dosage of B-vitamins is a good place to start. On top of that it is recommended to monitor the consumption of vitamins A, E, C as well as iron and zinc. Also, making sure that the diet includes quality protein is beneficial when working to slow down hair loss.”
A major innovation in hair health supplements is keratin, the main protein in hair, which only recently became possible to take as a supplement. “Solubilized keratin, known as Cynatine, has been shown in clinical studies to stimulate cells within the body that produce new hair,” explains Mount. “Results begin after just 15 days to increase hair thickness, shine and volume, while also reducing hair loss from washing.”
SynergyAs mentioned above, many products do well in the presence of other nutrients that provide a spectrum of activity, whether that be a family of carotenoids or a combination of B-vitamins and minerals. Here are some other important synergistic combinations.
Those familiar with collagen, will certainly be aware of hyaluronic acid (HA). Derived from rooster combs or produced with bacterial fermentation, vegans and vegetarians should be cautious about what products they buy. HA can also come in a variety of delivery forms such as flavored liquid and capsule. That being said, HA is highly beneficial to health and appearance of one’s skin.
“Hyaluronic acid is nature’s ‘moisture magnet’ and is found in high concentrations in the skin,” explains Mount. “Each HA molecule attracts 1,000 water molecules, leading to a soft, youthful appearance. HA tends to act quickly with hydration benefits appearing in days or weeks.”
This is because HA is a glycosaminoglycan, says Friese, which are highly polar, attracting water. “As people age, the body synthesizes less HA, and because of its short half-life, HA is depleted quickly in the epidermis,” says Steve Holtby, president & CEO, Soft Gel Technologies, Inc., Commerce, CA. “Depletion of HA in the extracellular matrix of the skin causes elastin to dry up and become brittle, which leads to fine lines and rough, dry, brittle skin.”
Soft Gel’s branded HA, Injuv, offers a 9% lower molecular weight hyaluronic acid complex that “is able to be absorbed by the intestinal tract, enter the bloodstream and move to its target sites,” says Holtby. He cites a study that measured the moisture content and pH of the skin’s surface to assess the barrier function of the skin. Results showed that 52 subjects taking Injuv for 30 days, demonstrated significant improvement in skin moisture without any adverse effects. “Supplementation with Injuv can increase the hyaluronic acid (HA) content throughout the body—including the dermis,” Holtby explains. “HA exists in both the dermis and epidermis, therefore Injuv moisturizes from the dermis to the epidermis (from deeper layer to upper layer).”
Those taking collagen would be wise to also take HA in conjunction. “Collagen and hyaluronic acid work synergistically by way of the dermal collagen network and how it is needed to support moisture retention,” explains Friese. “ When the collagen network in the skin breaks down as we age, it also loses the ability to hold water and hydration. By taking collagen and hyaluronic acid at the same time, you are providing your body with ingredients to not only help build the collagen matrix in the skin, but also the moisture content.”
Vitamins can play an important role in the health of our skin, hair and nails. “For a triple layer effect, on top of the trademarked ingredient we did add in vitamin A and vitamin C (with the exception of MaxiSkin) and although it’s a very small amount, it’s added as a supporting element because vitamin A is essential for skin cell renewal and vitamin C as well will help strengthen the elastin,” says Kreider. Passwater agrees, explaining that there are at least 7 of the 10 enzymes involved with the production of collagen that require vitamin C.
Mentioned previously, different antioxidants can also support one another and improve the effectiveness of a finished product when included in other popular ingredients such as collagen. “Astaxanthin mixes well with protein, micronutrients, other carotenoids and antioxidants, as well as popular skin nutrients such as collagen and HA,” says Hecht. “In fact, astaxanthin can protect other nutrients, like evening primrose oil and grapeseed oil from oxidation, giving astaxanthin a dual purpose as a functional nutrient for skin and protecting the quality of the finished product.”
Besides taking multiple supplements or a supplement that blends a variety of ingredients to enhance its effect, Mount also suggests approaching synergy to not just improve one factor, but to support skin, hair and nail health together because these factors all contribute to healthy aging. “A complete ‘beauty from within’ routine would ideally address all of these areas with multiple ingredients,” says Mount. “Collagen is best for skin structure, HA and Ceramides for hydration, and biotin and Cynatine for hair/nail support. These nutrients can all be combined into nutricosmetic supplements or taken individually.”
Versatility and Novel Delivery FormatsDietary supplements have seen substantial growth as the industry continues to broaden its reach. In part, this has been the result of ingredient innovation, allowing supplements to be safely, easily and with positive results, incorporated into food and beverages either by manufacturers into finished products or by consumers at home. Nutricosmetics has been the latest category to do this with versatile and easy to use products that consumers can easily incorporate into their lives.
“We noticed as a company, over the last three years, that people have pill fatigue and they want an alternative,” explains Kreider. While beauty is a great motivator, most dietary supplement consumers take a variety of other products that come in capsules and tablets to support heart health or healthy inflammation, for example. This creates a hierarchy that very likely places the nutricosmetic at the bottom. By providing an alternative delivery method such as powder or liquid form to be mixed in food or drink, that nutricosmetic can become a component of their meals, something most consumers don’t skip or forget about.
Collagen in particular has enormous versatility. “In their natural form, they do not react with other ingredients; therefore, they can enhance and optimize the most diverse applications — from liquids to solids,” explains Heather Arment, marketing coordinator, North America, Gelita, describing Verisol. “They can be used for different beverage applications — carbonated or near-water drinks, drinkable yogurt or whey beverages; for cereal, fruit or high protein bars — with a wide range of possibilities to produce bars with different and special textures; in fermented products like alcoholic beverages or yogurt; and, in combination with ingredients like polyphenols which are commonly used in healthy food — mainly in juices.” NeoCell, has been actively marketing its products to home cooks to incorporate into everyday meals.
“Collagen powders, such as NeoCell’s Super Collagen or Derma Matrix, have been shown in research to be unaffected by normal cooking temperatures,” says Mount. “These collagen powders are unflavored and most people can’t tell it’s even in their food when eaten, making it an ideal supplement to increase the nutritional content of recipes for the whole family. Most people add one scoop of collagen powder per person eating the meal. Collagen can easily be mixed into coffee or tea, or included in soups, salad dressings or sauces.”
Besides flavorless powders, finished product manufacturers are getting even more creative with their collagen powders. For example, Country Life recently released a spa-inspired extension to its Maxi-Skin line in Berry flavor with vitamin B12 to energize and Mandarin Orange & Chamomile flavor with L-Theanine for relaxation. Vital Protein has an immense amount of SKUs that provide consumers with thoughtful ways to incorporate collagen into their diets such as Collagen Creamer and Matcha Collagen. While unflavored powders are more versatile for mixing into food or drinks, products that provide fun and interesting flavors, particularly trending ones such as matcha, are certain to increase in the category.
Astaxanthin is another functional ingredient that has value incorporated into food and beverages. “AstaReal Astaxanthin comes in various powdered forms that are at least as bioavailable as oil, and in some cases more bioavailable,” explains Hecht. “The astaxanthin oil incorporates well into chocolates (such as Esthechoc using AstaReal Astaxanthin), gummies, and baked goods. AstaReal Cold Water-Soluble Astaxanthin is one of our newest offerings with uniquely excellent dispersion properties and stability for instant drinks, both cold and hot. Because of the unique properties of AstaReal’s cold water-soluble product we can assure stability, even in hot instant teas.”
A major factor that contributes to these ingredients being incorporated into liquids is water solubility. This is a good fit for some, a poor fit for other. “When it comes to the B-vitamins that are ‘water-soluble,’ a water based beverage can be a natural fit,” says Raz. “However, when it comes to vitamins like A, E and especially when we speak of natural carotenoids, mixing with water isn’t as easy as it may look. These important nutricosmetics, are all ‘oil-soluble,’ this is simply saying that without an oily mix these products will suffer from minimal bio-availability and therefore absorption will be at risk. When it comes to lycopene and its carotenoid siblings, a soft-gel capsule is still the favorable bet.”
This is where the importance of capsule technology comes in. While a more conventional application, not all products are capable of being mixed in water or cooked with, but their ability to be absorbed by the body as a capsule is still crucial. “A good example is a technology called ‘micro-encapsulation,’” says Raz. “This technology allows us to cover each molecule with its standalone protecting layer that improves stability and to control absorption. Some ingredients (for example B vitamins that are important for healthy hair strategy) are sensitive to the digestion acids. With micro-encapsulation technologies, you can potentially protect the essential vitamins all the way to the point in which they can be better absorbed.”WF
References
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- “The Lowdown on Hydrolyzed Collagen,” https://www.thehealthyhomeeconomist.com/hydrolyzed-collagen-uses-and-benefits/, Accessed January 3, 2018.
- E. Proksch, et al. “Oral supplementation of specific collagen peptides has beneficial effects on human skin physiology: a double-blind, placebo-controlled study.” Skin Pharmacol Physiol. 27(1):47-55. 2014.
- E. Proksch, et al. “Oral intake of specific bioactive collagen peptides reduces skin wrinkles and increases dermal matrix synthesis.” Skin Pharmacol Physiol. 27(3):113-9. 2014.
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- K. Tominaga et al. “Cosmetic benefits of astaxanthin on humans subjects .” The Journal of the Polish Biochemical Society and of the Committee of Biochemistry and Biophysics Polish Academy of Sciences. 59(1): 43-47. 2012.
- Barel A, Calomme M, Timchenko A, De Paepe K, Demeester N, Rogiers V, Clarys P, Vanden Berghe D (2005). Effect of oral intake of choline stabilized orthosilicic acid on skin, nails and hair in women with photodamaged skin. Arch Dermatol Res 297: 147-153.
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