The delivery method of nutrients also plays a role in how nutrients are absorbed and regulated. While skin nutrition is received both topically and internally, the vitamins people gather can actually cause or resolve problems. Traditionally, topical applications of products are widely used to address skin issues. Internal supplementation, however, has also become an effective measure in promoting skin health. The combination of both methods may prove to compliment the efficacy of each. In understanding the role of both delivery methods, it becomes clearer that perhaps a thoughtful, integrated approach may be more effective for both the body and skin over time.

As the epidermis is the first, outer layer of the skin, it serves as the protector of the body and blocks damage that would otherwise affect the dermis. The dermis contains blood vessels, hair follicles, and sebum and mainly provides strength and flexibility to the epidermis. Together, the epidermis and dermis make up the overall structure of the skin. The keratinization process involves the secretion of lipids by cells, which then form a protective layer assembled with extracellular proteins.6 This protective system is what keeps harmful matter from entering and good material, such vitamins and water, from leaving. Melanocytes in the epidermis are also very important. These cells not only produce melanin, but also absorb energy from ultraviolet rays to protect the skin. This process, in turn, minimizes issues, such as photodamage, commonly seen in the form of a sunburn. Notably, nearly 75 percent of the weight of the dermis is a matrix of collagen.1 Collagen is a protein that provides structural support and elasticity of the skin. Maintaining healthy collagen levels has been a main goal for both formulators of topical products, as well as the internal supplements industry.

Topical application for skin nutrients can be effective, depending on the type and method of application. Topicals for the skin must be formulated correctly in order to be absorbed. For example, many sunscreens, even though they claim to protect the skin, do not work because of the formulation. If the filters are poorly bonded, the sunscreen is easily degraded by skin enzymes.2 Certain vitamins, like vitamin C, are absorbed better through topical application rather than internally. The level of vitamin C attained in the skin with an oral vitamin is 20 to 40 times lower than a topical application.2 When topically applied, vitamin C can provide additional UVB protection in a sunscreen formulation. Additionally, topical application of vitamin E oil works well to unclog pores that results in fewer breakouts.2 Groundbreaking new ideas are always in the works for topicals. One idea is to incorporate probiotics into topically applied products. Probiotics can not only relieve skin conditions such as acne, but can also reduce inflammatory conditions like eczema and rosacea. Topicals are also crucial in wound-healing. When the skin starts to repair itself, topicals that contain vitamins help smooth out the healing areas and relieve any associated pain.1 Receiving nutrients internally is vital for life and the healthiness of skin. Lack of certain nutrients can cause skin problems while ingesting certain nutrients can improve skin conditions. Macro- and micronutrients work together to maintain the barrier functions of skin in the face of everyday challenges.3

Consuming vitamins, minerals, fatty acids, and natural phyto-extracts can protect the skin from pollutants.1 The lack of specific vitamins can cause issues like eczema and acne. For example, lack of vitamin A can cause or worsen conditions like acne, wound-healing and photoaging. Many who cannot heal quickly are deficient in vitamin A. Lack of vitamin B12 can result in hyperpigmentation or vitiligo. Vitiligo and hyperpigmentation are both issues pertaining to the pigment of skin. However, vitiligo is also caused as a result of damaged melanocytes.1 Nonetheless, excess of these vitamins can also cause issues. For example, an excess of vitamin A can cause shedding of skin or an excess of beta carotene can cause yellowing of the skin. This is why a balanced nutrition is important; skin issues can be caused by both a lack and excess of vitamins.

A balanced nutrition is crucial when it comes to skin health. Many attribute eating poorly to acne. Although, acne is mainly caused by testosterone in both men and women, there is a link between high glycemic load carbohydrate intake and acne.4 A study found that having a high fat diet can aggravate and even cause more acne to form. This research demonstrates that there is a relationship between nutrition and skin conditions, whether caused by specific vitamins as discussed before, or overall diet. This point is evident in the case of psoriasis. Psoriasis is an inflammatory condition that appears to be aggravated by an inflammatory diet.3 An inflammatory diet may contain foods that one is allergic to or foods that are unbalanced with omega-3 and omega-6 fatty acids.3 This is why certain diets, like a low protein diet, may be recommended for someone with psoriasis. However, when consuming too much of a certain food type, side effects may worsen, as opposed to not consuming it at all. An example of this is illustrated by a study done to see if there was a correlation between skin color and fruit/vegetable consumption.5 Thirty-five people in this study consumed different amounts of vegetables and fruits for six weeks to see if there would be a difference in skin tone. After consuming three portions of fruits and vegetables for six weeks, there was a difference. The results showed an increase in both the yellowness and redness of the skin. There was also a decrease in the lightness of skin.5 This research demonstrates how the increase or decrease of certain food groups can affect the skin in ways one may not have thought.

Supplements can also affect the skin. Popular supplements for the skin, like biotin or hyaluronan are used to strengthen or improve the skin and how it looks overall. Hyaluronic acid, like sebum, is already present in the skin. It is essential to maintain moistness in the skin tissues.6 It is a great supplement for those with dry skin and the issues dry skin presents. Hyaluronic acid is common in cosmetics as well for this very reason. Several studies have shown that ingested hyaluronic acid positively affects knee joints and the skin. In one of the studies, subjects with rough and dry skin received 240 milligrams a day of hyaluronan for six weeks.6 This intake resulted in a significant increase of skin moisture and improved dry skin on the whole body and face. They also conducted this study with varying amounts of hyaluronan. With the consumption of as little as 40 milligrams a day of hyaluronic acid for four weeks, skin was significantly more moisturized. It has even shown to help with aging in the skin as aging skin is related to a decrease of hyaluronan.

As discussed, skin nutrition is received via topical application and oral ingestion. In certain cases, both methods can be used concurrently to increase efficacy. A study of 75 people tested topical treatments, ingested treatments, and a combination of both. Researchers studied the moisture of the skin, thickness of the epidermis, and elasticity. After eight weeks of treatment, they found that the combination of tablet and cream resulted in thicker skin, higher skin moisture, increased elasticity, and even a reduction in wrinkles. However, they did state that if the topical cream is not applied on a consistent basis, the effects are not as strong. It is widely known that topical creams made with vitamins and antioxidants can improve skin conditions and issues. However, they must be formulated correctly with appropriate ingredients for optimal absorption. Likewise, ingested vitamins affect skin health in many ways. Vitamins can improve skin conditions, slow down the aging process, and even cause a change in skin color.

While neither delivery method is solely capable of addressing all skin conditions, it is wise to adopt a holistic, integrated approach to improving and maintaining skin health and vigor. This approach includes following a healthy, balanced diet and skin care routine using carefully formulated products that are free of harmful chemicals and contain essential vitamins and nutrients. Together, oral ingestion and topical applications can work in unison to facilitate a more concordant environment for the body to perform at its optimum.

References
1 Divya, S. A., et al. "Role of Diet in Dermatological Conditions | Open Access Journals." OMICS International | Open Access Journals. Journal of Nutrition & Food Sciences, 13 Aug 2015. Web. 7 Jun 2017. <http://www.omicsonline.org/open-access/role-of-diet-in-dermatological-conditions-2155-9600-1000400.php?aid=60091>.
2 Victor, Preedy. Handbook of Diet, Nutrition and the Skin.Wageningen: Wageningen Academic Publishers, 2012. Ebook. <https://books.google.com/books?id=c-pcb26nHV8C&pg=PA487&lpg=PA487&dq>.
3 Kawada, C., et al. "Ingested hyaluronan moisturizes dry skin | Nutrition Journal." Nutrition Journal | Home page. BioMed Central Ltd, 11 Jul 2014. Web. 7 Jun 2017.
<http://nutritionj.biomedcentral.com/articles/10.1186/1475-2891-13-70>.
4 Zouboulis. C., et al. "Nutritional Clinical Studies in Dermatology: Scientific, Peer-Reviewed Dermatology Article Indexed with MEDLINE/PubMed." JDD: Scientific, Peer-Reviewed Dermatology Journal Indexed with MEDLINE/PubMed. Journal of Drugs in Dermatology, Oct 2013. Web. 7 Jun 2017. <http://jddonline.com/articles/dermatology/S1545961613P1104X>.
5 Whitehead, R., et al. "You Are What You Eat: Within-Subject Increases in Fruit and Vegetable Consumption Confer Beneficial Skin-Color Changes." PLOS | Public Library Of Science. PLOS, 7 Mar 2012. Web. 7 Jun 2017. <http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0032988>.
6 Michels, A. "Skin Health | Linus Pauling Institute | Oregon State University." Linus Pauling Institute | Discovering How to Live Longer and Feel Better | Oregon State University.Oregon State University, Sep 2011. Web. 7 Jun 2017. <http://lpi.oregonstate.edu/mic/health-disease/skin-health>.
7 Lademann, J., et al. "Influence of Topical, Systemic and Combined Application of Antioxidants on the Barrier Properties of the Human Skin." Skin Pharmacol Physiol. Karger - Skin Pharmacol Physiol, Feb 2016. Web. 7 Jun 2017. <http://www.karger.com/Article/FullText/441953>.