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Summer is here! And with it the plethora of activities that come with this beautiful and sunny season. Many of us are just wishing for more sunlight, which we welcome as the best source of Vitamin D. Others are looking forward to more time outdoors, going for hikes and walks, which is great, since you get to move your body, have more contact with nature and its healing effects, get more sun and, if you go barefooted, even get the added the benefits of grounding or earthing! Healing energy from planet Earth.

Spending more time outside, even in your backyard, is a must do during this season. But with all these wonderful outdoor activities, some health concerns are also raised. A big one we are often asked about is the use of sunscreen to provide some protection from the sun’s ultraviolet radiation. But what is this ultraviolet (UV) radiation?

UV Radiation

UV is a form of electromagnetic radiation, with a broad-spectrum of wavelength, ranging from 10 to 400nm. UV radiation has a shorter wavelength than that of visible light, but higher energy. UV radiation is present in sunlight, constituting about 10% of the total electromagnetic radiation output from the Sun. UV radiation can affect human health, both in a positive and negative way1. There are three primary types of UV radiation: UVC, UVB, and UVA.

  • UVC (220–290nm)
  • UVB (290–320)
  • UVA (320–400nm)

As sunlight passes through the atmosphere, 100% UVC and approximately 90% of UVB radiation are absorbed by ozone, water vapor, oxygen and carbon dioxide. The amount of UVA radiation being absorbed by the atmosphere is minimal, and this radiation accounts for approximately 95% of the UV radiation reaching the Earth’s surface2,3.

Effects on human health3,4 

UVCShort-wavelength radiation

Would be the most damaging.  However, since it is 100% absorbed by the atmosphere and does not reach the earth’s surface, it is not a concern for human health.

UVB – Medium-wavelength radiation

Penetrates only the superficial layers of the skin and is, at biological level, very active. UVB is the radiation that triggers vitamin D production in the skin; also responsible for delayed tanning and burning. However, excessive exposure to UVB may cause sunburn and DNA strand breaks. Excessive UVB exposure is associated with nonmelanoma skin cancers and skin aging. 

UVA – Long-wavelength radiation

Penetrates deep into the skin layers. This deeper penetration leads to the production of free radical oxygen species, which may indirectly cause DNA damage. The immediate tanning effect is due to UVA, but this radiation also contributes to skin aging, pigmentation, and wrinkling. Other effects of UVA are the increased number of inflammatory cells in the dermis and the decrease in the number of antigen-presenting cells. Recent studies also suggest that UVA may increase the development of certain skin cancers.

The health concerns and possible negative effects associated with excessive exposure to UV radiation, led to the development of many forms of protection from the sun, one of the main and most broadly used, sunscreen. 

What is sunscreen?

Sunscreen is a type of photoprotection used for the reduction of UV radiation reaching the skin. There are many factors that influence the transmissions of UV light to the human skin, called photoprotective agents. Photoprotective agents protect the skin by preventing and minimizing the damaging effects of UV rays of natural sunlight, and include1,5,6:

  • environmental agents, such as ozone, pollutants, clouds, and fog
  • naturally occurring biologic agents, namely the epidermal chromophores. (A chromophore is the part of a molecule responsible for its color. There are several molecules in our skin that contain chromophores and therefore contribute to solar radiation absorption.) 
  • physical photoprotective agents, including clothing, hats, make-ups, sunglasses, and window glass
  • ultraviolet light filters, which includes sunscreen ingredients and sunless tanning agents
  • agents that regulate the effects of UV radiation on the skin, like antioxidants, plant extracts, osmolytes, and DNA repair enzymes, which help to limit skin damage by disturbing the photochemical cascade that occurs with UV sunlight4 

As mentioned previously, the main damaging effects of UV radiation are1

  • photoaging – manifested as sagging, pigmentation and wrinkling of the skin
  • photocarcinogenesis – caused by damage to cells and deoxyribonucleic acid (DNA)

The use of sunscreen is aimed at reducing these damaging effects, associated with excessive exposure to UV radiation. 

Types of sunscreens

There are many types of sunscreens, usually made up of a mix of different chemicals. Sunscreens can use inorganic chemicals, organic chemicals, or a mix of both. Their effect on sunlight is very different4:

  • Organic (carbon-based) chemicals absorb high-energy UV rays through their chemical bonds. As the bonds absorb UV radiation, the components of the sunscreen slowly break down and release heat
  • Inorganic chemicals can reflect or scatter UV light (also called physical sunscreen as it acts much the same way as a physical barrier, like clothing)


The specific range of wavelength a sunscreen absorbs will vary, but organic chemical sunscreens consist of UVA and UVB blockers. UVB blockers include aminobenzoates, cinnamates, salicylates, octocrylene, ensulizole, and camphor derivatives. UVA blockers are benzophenones, anthranilates, avobenzones, and ecamsule.

Yes, there are some very difficult names here, but these are chemicals you can often find in your bottle of sunscreen. Broad-spectrum sunscreens absorb UV radiation from both the UVA and UVB portions.


Since the mechanism of action has its basis on the reflection and scattering of UV light, the reflective properties determine the effectiveness of the sunscreens. These properties include the reflective index (the higher the reflective index, the better the UV filter), the size of the particles, the film thickness, and the dispersion of the base. Inorganic chemicals deflect both UVA and UVB rays.

  • zinc oxide
  • titanium dioxide 

Sunscreens that use a combination of organic and inorganic filters act by absorbing, scattering, and reflecting UV radiation.

Another agent of photoprotection mentioned above are antioxidants, which help reduce skin damage induced by free radicals. Sunscreens are often developed including some type of antioxidant, such as vitamin C, vitamin E, green tea polyphenols and silymarin4.

What is SPF?

Do Sunscreens Contribute to Vitamin D Deficiency?

SPF – Sun Protection Factor, refers to sunscreen protection against UVB radiation. Although there are broad-spectrum sunscreens that block both UVA and UVB, there is currently no standard for listing UVA blocking power. 

According to the Federal Food and Drug Administration (FDA), “SPF is a measure of how much solar energy (UV radiation) is required to produce sunburn on protected skin (i.e., in the presence of sunscreen) relative to the amount of solar energy required to produce sunburn on unprotected skin. As the SPF value increases, sunburn protection increases8.” 

As highlighted by the same agency, the SPF is not directly related to the time that you are exposed to the sun, but to the amount of solar exposure1. Protection Factor is related to other variants besides time of exposure, such as intensity of solar energy, type of skin, quantity of sunscreen applied, etc8. We are all aware that being in the sun at 8am or 1pm is completely different in terms of intensity of solar energy and that people with fair skin are more sensitive than people with darker skin. 

The amount of UVB radiation blocked by sunscreen8:

  • SPF 15 about 93% of UVB rays
  • SPF 30 about 97% of UVB rays
  • SPF 50 about 98% of UVB rays
  • SPF 100 about 99% of UVB rays

This is amazing, right? Maybe not…

Concerns with Sunscreens

Some of the chemicals present in sunscreens may actually be… carcinogenic. Researchers have found at least two different sunscreen components that are carcinogens — benzene and benzophenone. The bigger issue is that these compounds don’t even appear on the product label! Just last year, in 2021, an independent testing lab found the carcinogen Benzene in 78 popular sunscreens! Benzene has been associated with blood cancer and other illnesses. 

Another huge concern about sunscreens is the potential endocrine-disrupting effects of some organic compounds, namely the ingredients homosalate, avobenzone and oxybenzone9. The European Commission has also published preliminary opinions on the safety of three organic UV filters, oxybenzone, homosalate and octocrylene, limiting the percentage of oxybenzone and homosalate because previous concentrations were not considered safe9

The truth is there are not enough studies evaluating the safety of almost any of the chemicals used on sunscreens, especially considering the skin is a highly absorbent organ. Even after just one use, the ingredients oxybenzone, octinoxate, octisalate, octocrylene, homosalate and avobenzone are all systemically absorbed into the body9. Furthermore, studies found that some sunscreen ingredients could be detected on the skin and in the blood weeks after no longer being used, and some have even been detected in breast milk and urine samples9!

An interesting fact is that in 2019 the FDA, which governs sunscreen safety, reporting on sunscreen regulation, found that only TWO ingredients on sunscreens could be classified as safe and effective. Those were zinc oxide and titanium dioxide. Although particles of zinc or titanium hardly penetrate the skin and reach any tissue, there are some inhalation concerns associated with these two components9.

Another factor of uttermost importance is vitamin D production. Sunlight exposure, and in this case UVB radiation, is essential for Vitamin D production and should not be something we avoid or run away from. The use of sunscreens, even with low protective factors, substantially reduces Vitamin D production. The numbers are astonishing:

  • sunscreen with SPF 8 reduces the skin’s previtamin D3 production by more than 95%
  • sunscreen with SPF 15 absorbs 93% of UVB light and reduces vitamin D3 production by 99%

This basically means that the use of sunscreen, even with a low protective factor, blocks most of UVB light and concomitantly, vitamin D production!

These are some of the reasons why the use of sunscreen often brings about contradictory opinions and as with many health-related subjects, it’s hard to come to an agreement. 

One problematic issue is the strong association that the general population (and most doctors) still make between sun exposure and skin disorders, especially nonmelanoma skin cancer. This leads most people to the use and overuse of sunscreens! While chronic excessive exposure to sunlight does increase the risk of nonmelanoma skin cancer, avoiding all direct sun exposure or always using sunscreen increases exponentially the risk of vitamin D deficiency, and may pose a threat due to chemicals present in most commercial sunscreens. 

So, what is the best approach? 

Suggested protocol for sunlight exposure

We recommend exposure to the sunlight to be gradual and sensible to protect the skin from excessive, harmful radiation and avoid its potential negative effects. 

What is gradual and sensible?

Gradual means starting with small durations and slowly increasing the duration of exposure, especially if you haven’t been out in the sun for a while or live in geographical areas where winters are more rigorous and sun exposure during the winter is very reduced or almost nonexistent.   

Sensible exposure means10,11:

  • Never to be exposed to an amount of sunlight that would cause a sunburn since this is the major cause for both melanoma and non-melanoma skin cancer
  • The amount of time in the sun should be around 10-15 minutes
  • Try to have your body as exposed as possible, at least the arms and legs or the hands, arms, and face exposed to the sun
  • Aim at doing this two to four days a week
  • The sun should be at his peak during exposure, to maximize vitamin D production

This sensible exposure is aimed not just at minimizing the risk of sunburn and sun related skin disorders, but also at maximizing Vitamin D production. Even when exposed to sunlight, the duration of sunbathing and the area of the skin exposed are of utmost importance to achieve optimal skin synthesis of vitamin D. Try to expose as much area of your skin as possible when sunbathing. The duration will vary with the level of skin pigmentation (melanin present in the skin) and age, being inversely proportional. This means older people and those with darker skin will need longer periods of sun exposure. 

Another important factor, mentioned above, is the location of the sun in the sky, which ideally should be at its peak. When the sun is at its highest point, it is said to be on the zenith: the ideal position of the sun to trigger vitamin D production. When the angle of the sun from the zenith increases (when the sun rays are more oblique) the ability of the body to produce vitamin D decreases substantially. This explains why the synthesis of vitamin D in the skin almost stops during winter (November– March), particularly in people who live in regions above 40° northern latitude (which happens in most of the USA, except for the southern states). This is a major cause of concern for those living in those regions, especially during the winter, and the reason why people living in the Northern Hemisphere, and especially older and darker skinned people, are at very high risk of Vitamin D deficiency and should consider supplementation.

In sum, we do need sun exposure for skin production of vitamin D, a vitamin that is ESSENTIAL for our health. Even when it relates to cancer, as Dr. Thomas Lodi wrote in his article Why the Sun Does Not Cause Cancer in 2010, more than a decade ago, “the sun actually decreases cancer rates” and “the less sun exposure, the greater the chances of dying from cancer12.”  What is important is to make sure that exposure to sun is sensible and done without the use of sunscreen, because sunscreens block most of vitamin D production and “many sunscreen products are toxic and should be avoided by most people12.” Sun is also crucial for your overall health and happiness!

However, chronic excessive exposure to sunlight does increase the risk of nonmelanoma skin cancer, and if you are not able to follow this gradual and sensible exposure to the sun, or if something unexpected or an extraordinary event is happening (a big walk in the sun or going to a water park for the whole day), then the use of sunscreen would be advisable. When needing to use sunscreen, we strongly recommend that you consult with your holistic physician to determine which sunscreens are safer and best suited for you. 

Another useful recommendation is to increase the intake of foods rich in antioxidants, that help to protect the skin from the inside. Antioxidant rich foods include berries, cruciferous vegetables, leafy greens and nuts. Also consider increasing vitamin C and E, whether through foods or in supplement form (always consult your physician before starting any supplementation). 

Good sources of Vitamin C are:

  • Guava
  • Kiwi
  • Bell peppers
  • Strawberries
  • Papaya
  • Broccoli
  • Tomato
  • Kale
  • Chili pepper
  • Cauliflower
  • Brussel sprouts
  • Parsley
  • Acerola
  • Black currant

Good plant sources of Vitamin E:

  • Sunflower seeds
  • Almonds
  • Hazelnuts
  • Pinenuts
  • Olives and olive oil
  • Turnip greens
  • Swiss chard
  • Mustard greens
  • Avocados
  • Spinach

Enjoy the sun happily and safely 😊


  1. Latha MS, Martis J, Shobha V, Sham Shinde R, Bangera S, Krishnankutty B, Bellary S, Varughese S, Rao P, Naveen Kumar BR. Sunscreening agents: a review. J Clin Aesthet Dermatol. 2013 Jan;6(1):16-26. PMID: 23320122; PMCID: PMC3543289.
  2. World Health Organization. Ultraviolet Radiation. https://www.who.int/health-topics/ultraviolet-radiation#tab=tab_1, accessed May 5, 2022.
  3. Gabros S, Nessel TA, Zito PM. Sunscreens And Photoprotection. [Updated 2021 Nov 15]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537164/
  4. World Health Organization. Radiation: Ultraviolet (UV) radiation. Q&A. 9 March 2016. https://www.who.int/news-room/questions-and-answers/item/radiation-ultraviolet-(uv), accessed May 5, 2022. 
  5. Rai R, Srinivas CR. Photoprotection. Indian J Dermatol Venereol Leprol. 2007 Mar-Apr;73(2):73-9. doi: 10.4103/0378-6323.31889. PMID: 17456910.
  6. Kullavanijaya P, Lim HW. Photoprotection. J Am Acad Dermatol. 2005 Jun;52(6):937-58; quiz 959-62. doi: 10.1016/j.jaad.2004.07.063. PMID: 15928611.
  7. Young AR. Chromophores in human skin. Phys Med Biol. 1997 May;42(5):789-802. doi: 10.1088/0031-9155/42/5/004. PMID: 9172259.
  8. U.S. Food and Drug Administration. Sun Protection Factor (SPF). https://www.fda.gov/about-fda/center-drug-evaluation-and-research-cder/sun-protection-factor-spf, accessed May 9, 2022.
  9. Environmental Working Group. The trouble with ingredients in sunscreens. https://www.ewg.org/sunscreen/report/the-trouble-with-sunscreen-chemicals/, accessed May 9, 2022.
  10. Holick MF. Sunlight, ultraviolet radiation, vitamin D and skin cancer: how much sunlight do we need? Adv Exp Med Biol. 2014;810:1-16. PMID: 25207357.
  11. Wacker M, Holick MF. Sunlight and Vitamin D: A global perspective for health. Dermatoendocrinol. 2013 Jan 1;5(1):51-108. doi: 10.4161/derm.24494. PMID: 24494042; PMCID: PMC3897598. 
  12. Lodi T. An Oasis of Healing. Health Articles. Why The Sun Does Not Cause Cancer. Published Apr 5, 2010. https://www.anoasisofhealing.com/why-the-sun-does-not-cause-cancer/, accessed May 10, 2022.