Showing posts with label skin. Show all posts
Showing posts with label skin. Show all posts



In the previous post, we discussed about the detrimental and beneficial effects of the sun's ultraviolet rays. In this post, we'll take a look into the factors that determine how much of the UV rays is absorbed by each individuals. 

Know thy skin type

Your genes is, foremost, the most important factor that you should take note of before exposing yourself to the sunlight. Experts have identified six different skin types based on the colors of the hair and eye, and the reactions caused by being under a strong sun. Refer to the diagram and the categories to know your type. [1]

Type I - Often burns, rarely tans. Tends to have freckles, red or fair hair, and blue or green eyes.
Type II - Usually burns, sometimes tans. Tends to have light hair, and blue or brown eyes.
Type III - Sometimes burns, usually tans. Tends to have brown hair and eyes.
Type IV - Rarely burns, often tans. Tends to have dark brown eyes and hair.
Type V - Naturally black-brown skin. Often has dark brown eyes and hair.
Type VI - Naturally black-brown skin. Usually has black-brown eyes and hair.


Check the UV Index

The UV Index (UVI) indicates how strong the UV rays (UVR) from the sun is at a particular place. The index is reported by various local weather forecasts worldwide. Refer to the list in the WHO website for your local weather forecasts link or go to www.uvawareness.com and type in your location.

Depending on the UVI of the day, you should take the necessary precautions according to the severity imposed given in the following table,[1] which is very much dependent on your skin type.


Terrestrial UVR

The UV Index is a general indicator. Depending on where you are specifically and various other conditions, the following rules should be factored in as well. [2,3]
* Time of the day. Peak hours for UVR are from 10am to 4pm.
* Altitude. The higher you are above the sea level, the more exposed you are to the sun's radiation. Each 1 km increase in altitude increases the ultraviolet flux by about 6%.
* Clouds. Light cloud virtually makes no difference to the UVR intensity. Heavy cloud reduces the UVR but not by much therefore do not assume that you are protected from the strong sun. Only very heavy storm clouds will shield us from the rays.
* Surface reflection. You are not completely protected even when in the shades. The snow, sand, and ground/water reflect 30%-80%, 15%-30%, and <5% of UVR respectively.
* Geographical latitude. Annual UVR flux decreases with increasing distance from the equator.


Safe level of sun exposure

A 2007 study submitted by the University of Ottawa to the Department of Health and Human Services in Washington, D.C. reports that there is not enough information to determine a safe level of sun exposure. More recently, a research to model the seasonal variation of Vitamin D due to sun exposure [4] summarised that the current advice of about 10-20 minutes of daily sun exposure during the summer months does little in boosting the Vitamin D3 level in our body. Yet, sufficient sun exposure to achieve a worthwhile benefit could adversely impact skin's health. To this effect, many independent sites and research are recommending that we stick to the advisable sun exposure level [6] and fill in the missing Vitamin D3 dosage from other safer nutritional sources [5].

The recommendation for safe level of sun exposure hence, can be summed up by the following:
* Fair skin people should spend no more than 10 minutes in the midday sun in shorts and tank top without sunscreen. This produces 10,000 international units (IU) of the vitamin. As this amount is more than the recommended level of 2,000 IUs per day - published in various health sites and by researchers such as Dr. Edward Giovannucci, Professor of Nutrition and Epidemiology of the Harvard School of Public Health [6,7,8] - soaking up the summer sun for 10 minutes should be done 3-4 times a week, not everyday.
* Dark skin people requires around 15-20 minutes under the sun.

Of course, logic applies depending on the various other conditions as highlighted in this article. If you are at the peak of Mount Everest or K2 when the sun is at its peak hour, no minimal amount of sun exposure without sunscreen, I'd say, is advised.

As it clearly shows that we are not getting enough Vitamin D3 from sun exposure, which I'd rather stay away than suffer the many health and skin issues due to excessive exposure as we discussed in Part 2 of this series,  the quest to find balanced alternatives to the sun UVR continues in Part 4. Stay in tune for Part 5 for sunscreen recommendations.

Related posts:
Part 1 - Introduction
Part 2 - The good and bad of UV rays exposure

References


Let's soak up the sun.. or not (Part 3 - Too much or too little UV rays?)

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In my quest to understanding the beneficial and detrimental effects of sunlight, I came to know that categorically, there are three main types of the sun UV rays as a function of the wavelengths. Let's examine them one by one.

Composition of the sun UV rays

UVC with wavelength between 100 to 280nm and being the most harmful to the human skin, is fortunately completely absorbed by the earth's stratospheric zone layer and does not reach the earth's surface.[1]

UVB, with wavelength in the region of 280-315nm, is responsible for between 1-10% of the whole UV rays (UVR) that reach the earth's surface.[1] There is a concern that, with the depletion of the earth's stratospheric layer, we are in the risk of being exposed to a larger percentage of UVB that passes through the ozone layer.[2] UVB penetrates as far as the outer layer of the skin's dermis.

The third type of UV rays emitted by the sun, UVA, has wavelength between 315nm and 400nm.[1] 90%-99% of UVA reaches the earth. UVA penetrates into the deep end of the dermis layer. UVA can be further categorized into UVA1 (340-400nm) and UVA2 (315-340nm).

The detrimental effects of the UVR

The skin, when exposed directly to solar UVR, will attempt to defend itself against the damaging action caused. The skin does so by triggering sunburn, thicken the epidermis' stratum corneum, and activating the pigment cells which produce pigmentation when exposed to UVB. Further damage to the skin's cellular DNA will cause skin cancer, which occurs mostly at the skin's epidermis layer.

Image taken from the research paper
Vitamins and Photoaging: Do scientific data support their use?
Basal cell carcinoma (BCC), is the most common malignant skin cancer and the biggest risk factor has been associated to the exposure of the sun UVB rays, especially for those with fair skin.[4] Like BCC, Squamous cell carcinoma (SCC) occurs in the epidermis layer, is not as common as BCC but certainly more dangerous.[5] Melanoma is the most dangerous type of skin cancer that can be caused by prolonged exposure to the sun. There are many researches that associate UVR with the development of melanoma risk.[6,7,8,9]

When exposed to UVA, the skin produces less high quality collagen and elastin fibres. This, as we know, causes premature aging. But what exactly is at work here that results in photo-aging? When UVA enters the skin layer, it is absorbed by the skin's molecules that generates harmful compounds called reactive oxygen species (ROS) and sets activator protein (AP)-1 in motion for a longer period of time.[3] This in turn increases the production of matrix metalloproteinases (MMP) ezyme that in turn increases the breakdown of collagen. UVR also decreases the transforming growth factor (TGF) that complements the AP-1 in regulating the collagen by promoting the production of collagen. In short, an increase in collagen breakdown due to increasing AP-1 and a decrease of collagen production due to decreasing TGF will lead to skin sagging and wrinkles. The synthesis is best described in the picture on the right.

The benefits of the solar UV

The human body has the ability to synthesize vitamin D3 from absorbing the solar UVB rays. The lack of Vitamin D3 have been found to be associated with many issues such as[10,11,12]:
* Type 1 diabetes mellitus
* Autoimmune disorders including multiple sclerosis and rheumatoid arthritis
* Rickets amongst children.
* Osteoporosis amongst adults
* Cardiovascular disease
* A certain level of exposure to UVB may even decrease the risk of non-melanoma skin cancer (NMSC).[11]

Now that we have an inkling of the good and bad of sun rays, what should we do to ensure we stay away from the bad stuffs yet benefit from the good parts. Stay with me for the next post.

Related posts:
Part 1 - Introduction
Part 3 - Too much or too little UV rays?

References:

1 The Real Value of Novel Particulate Carriers for Sunscreen Formulation
2 The effects on human health from stratospheric ozone depletion and its interactions with climate change.
3 Overview of skin aging and photoaging
4 The role of UV radiation in the development of basal cell carcinoma
5 Fact sheet: Preventing and detecting skin cancer
6 Sun damage in ultraviolet photographs correlates with phenotypic melanoma risk factors in 12-year-old children
7 Multiple melanoma susceptibility factors function in an ultraviolet radiation response pathway in skin
8 Landmark research links melanoma to UV radiation
9 How UV Radiation Triggers Melanoma
10 Sunlight and vitamin D for bone health and prevention of autoimmune diseases, cancers, and cardiovascular disease
11 UV Radiation, Vitamin D and Epidermal Carcinogenesis
12 Solar UV Doses of Young Americans and Vitamin D 3 Production

Let's soak up the sun ... or not? (Part 2 - The good and bad of UV rays exposure)

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A holiday in Asia is always a wonderful break from the cold wintery months in Europe. I recently had the pleasure of one; a last minute decision but a good one as I was beginning to feel a little depressed and sluggish.

I started writing this article as an overview of the sun UV ray and its effects, and the importance of sunscreen. However, there are more grounds to cover and each of the sections below warrants a comprehensive analysis and write-up from reliable medical sources, so stay tune for Part 2 to 6.

The good and bad of sun exposure

It is no secrets that too much sun causes old spots, skin and bone diseases. Too little or none at all isn't an ideal situation as well because the sun is the best natural source to obtain Vitamin D which is important to regulate the amount of calcium and phosphate in the body and increase the immunity system.

Read more of Part 2 - The good and bad of UV rays exposure

How much sun is too much, or too little?

As a general rule of thumb, it is usually recommended that around 10 minutes are spent under the sun without sunblock every day during summer and around 15-20 minutes during winter or when the sky is overcast. People with fairer skin tone should spend shorter time under the sun compared to people with darker skin tone.

Read more of Part 3 - Too much or too little UV rays?

Vitamin D supplements?

It is reported that most of us are generally deficient in Vitamin D and the recommended dose for each person is different. Seek advice from your doctor if you are worried about the level of your Vitamin D before simply choosing any Vitamin D supplement at your local health store.

Use sunscreen for protection

If you spend a lot of time under the sun, sunscreen application is a must! The consequences of excessive sun exposure such as skin cancer, far outweight the benefits of Vitamin D. Choose a good sunscreen. Needless to say, chemical sunscreen with ingredients such as Oxybenzone and Avobenzone is a huge no-no! A good sunscreen should be natural and safe. It should be physical sunscreen and contains sufficient amount of zinc oxide, between 18% and 20%. Zinc Oxide is the best ingredient because it guards off against the UVA1, UVA2 and UVB rays. In fact, it is the only ingredient that reflects off all the mentioned three types of UV rays that penetrates into our skin's epidermis and dermis layers otherwise.

Which sunscreen product?

This will be the last of the series on this topic where I will recommend and compare between a few physical sunscreen products out there in the market.

Let's soak up the sun.. or not (Part 1 - Introduction)

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