Sunscreen, Vitamin D and photostable filters

Riccardo Matera

Our characteristic complexion depends on the quantity and quality of the melanin present in our skin and this contributes to defining our skin type [1] that is, personal sensitivity to sun exposure. The habit of choosing sunscreen from the sun protection factor (SPF – sun protection factor) appropriate to our skin type for optimal sun protection is now widespread. The beneficial effects of the sun on mood are well known but also the stimulation of Vitamin D, an essential factor for the well-being of our bones and the immune system.

Do sun creams prevent the production of vitamin D?

The conversion of Vitamin D in the skin from an inactive form to an active form is a reaction that requires much less time than tanning, therefore even short exposures are beneficial for the body. Sometimes, little authoritative sources claim that sunscreen evades these beneficial effects but it is now recognized that people who regularly use sunscreens are the same ones who like to spend more time in the sun who ultimately tend to have high levels of vitamin D, in fact Recent studies have confirmed that regular use of sunscreens does not cause vitamin D depletion [2].

While in the sun, apply the sunscreen indicated for your skin type taking care to use a higher protection at the beginning of the summer season. Apply the sunscreen 20 minutes before sun exposure and reapply it again every 2 or 3 hours especially after immersion in water or excessive sweating.

It is known that the intensity of radiation depends on several factors such as latitude, altitude, time of day, the presence of clouds, the reflective power of the environment. Generally very fair skin needs high sun protection, generally 30 or 50+.

But what does the SPF number actually mean?

The SPF number indicates the amount of UVB radiation that potentially reaches the skin if sunscreen is applied following the appropriate indications. An SPF30 sunscreen allows approximately 1/30 (3.3%) of the UV radiation to be absorbed by the skin, therefore filtering 96.7% of it. Instead, an SPF50 protection is estimated to filter 98% of UV radiation letting only 1/50 (2%) reach the skin. SPF30 or SPF50 both provide excellent protection if applied correctly. We keep sunscreen away from heat and use a large quantity of product. Generally an adult needs about 5 g (one teaspoon) for the face and décolleté, one for the arm or leg and one for the front and back of the body. Generally about 35 mL of sunscreen for each application on the whole body.

Which sunscreens to choose?

A broad-spectrum sunscreen manages to filter both UVA and UVB radiation. UVA radiation penetrates deeply into the skin, interacting with the cells of the dermis causing long-term effects such as wrinkles, loss of skin tone and elasticity, photo-aging, dyschromia and hyper-pigmentation contributing to the development of skin tumors. UVB rays stop at the surface layers of the skin acting at the level of the epidermis and are mainly responsible for tanning, but also for sunburn, sun rashes and allergic reactions. It is therefore important to protect the skin from both UVA and UVB rays. An important aspect for our safety in the sun is the photostability of solar filters to radiation. Little photostable filters, once absorbed the radiation, are quickly damaged by not fulfilling their function anymore. As described in our previous study, we choose high photostability sun filters as in the BeC formulations with high quality photostable filters.

After taking all the common sense precautions such as: protecting the head, wearing opaque clothes and being in the habit of using sunglasses, remember to use adequate sun protection: your last defense against sunburn!

[1] Kawada A. Risk and preventive factors for skin phototype. J Dermatol Sci. 2000;23 Suppl 1:S27‐S29. doi:10.1016/s0923-1811(99)00074-2

[2] Passeron T, Bouillon R, Callender V, et al. Sunscreen photoprotection and vitamin D status. Br J Dermatol. 2019;181(5):916‐931. doi:10.1111/bjd.17992

Cyclooxygenase, lipoxygenase and the inflammatory process

Cyclooxygenase and lipooxygenase are the two families of enzymes that are commonly involved in the inflammatory process, through a complex of reactions which is called arachidonic acid cascade. This complex of reactions develops as follows: a first enzyme, a phospholipase cleaves the phospholipids of biological membranes, releasing arachidonic acid, a polyunsaturated fatty acid with 20 carbon atoms (eicosa-5Z,8Z,11Z,14Z-tetraenoic acid ; C20:4; ω-6). The arachidonic acid is then transformed by two parallel enzymatic pathways, that is, by two families of enzymes: the cyclooxygenase which transforms it into prostaglandins and thromboxanes and the lipooxygenase which transforms it into hydroperoxides which in turn transform into leukotrienes .
There are two cyclooxygenase isoforms indicated with type 1 and type 2, briefly COX-1 and COX-2. COX-1 is the enzyme present in most cells (except red blood cells), and is constitutive, that is, it is always present. COX-2 is an inducible cyclooxygenase isoform: it is constitutively present in some organs such as brain, liver, kidney, stomach, heart and vascular system, while it can be induced (i.e. developed if necessary) following inflammatory stimuli on the skin, white blood cells and muscles.
There are various types of lipooxygenase that lead to different products, the most important in the inflammatory process is 5-lipooxygenase, 5-LOX.

Prostaglandins, Thromboxanes, and Leukotrienes

Prostaglandins, Thromboxanes, and Leukotrienes are chemical messengers or mediators, that is, molecules that bring a message to specific cells and activate or deactivate metabolic responses in these cells. They, therefore, have a function similar to hormones, only that, unlike what hormones do, the chemical message is carried only at a short distance, that is, only to the cells that are in the vicinity of the place where the mediators were produced. There are different prostaglandins, different thromboxanes and different leukotrienes that carry specific messages. In many cases these act as mediators of the inflammatory process , therefore they trigger all the events that are involved in inflammation:
– vasodilation with consequent blood supply (redness),
– increased capillary permeability with consequent fluid exudation (swelling or edema),
– stimulation of nociceptive nerve signals (pain),
– on-site recall of immune system cells that attack a possible invader (chemotactic action)
– activation of the biosynthesis of fibrous tissue to strengthen or repair the affected part (even if there is no need)
– generations of free radicals that can chemically destroy an invader (but also damage our tissues, i.e. they just “shoot in the middle”).
Prostaglandins and thromboxanes, however, also play important physiological roles in normal conditions, i.e. in the absence of inflammation. For example, they regulate the secretion of mucus that protects the walls of the stomach, they regulate the biosynthesis of cartilages and synovial fluid in the joints, they regulate vasodilation, hence the correct flow of blood in the various local districts, and more.


Triglycerides are the main components of most oils and fats. These are heavy, non-volatile and little polar molecules, insoluble in water, made up of glycerol (or glycerin) esterified with three molecules of fatty acids: therefore, it is a tri-ester of glycerin, from which the name derives. Each fatty acid contains 8 to 22 carbon atoms (commonly 16 to 18) and can be saturated, mono-unsaturated or poly-unsaturated. The size of the fatty acids and their saturation determines the physical and sensorial properties of the triglycerides, which can appear as oils (liquids at room temperature) or fats (solid or semi-solid) and can have greater or less greasiness and smoothness on the skin. Unsaturated triglycerides or with shorter fatty acids are more fluid and have greater flowability.

Fatty acids (saturated, mono-unsaturated and poly-unsaturated)

The name fatty acids is commonly used to indicate those organic acids that are found in the composition of lipids, that is, in animal and vegetable oils and fats, both in the free form and in the form of esters with glycerol (e.g. in triglycerides), or they are esterified with “fatty” alcohols, that is, long chain alcohols, to form waxes. Fatty acids are carboxylic acids (formula R-COOH) which have a long carbon chain (R), unlike common organic acids such as acetic acid and propionic acid, which have 2 or 3 carbon atoms in total, respectively. Fatty acids are defined as saturatedif they do not have double carbon-carbon bonds, (called “unsaturations”), they are defined mono-unsaturated if they have only one, they are defined mono-unsaturatedpoly-unsaturated if they have two or more double bonds (see figure). The term omega-3 (ω-3) or omega-6 (ω-3), refers to the position of the first double bond starting from the bottom of the chain of carbon atoms: if the first double bond is encountered after 3 carbon atoms the fatty acid is classified as omega-3 , if after six carbon atoms omega-6 , as shown in the figure. The most common saturated fatty acids are palmitic acid (16 carbon atoms and no double bond, C16: 0) and stearic acid (18 carbon atoms, 18: 0), the most common mono-unsaturated is the oleic acid, typical of olive oil (18 carbon atoms and 1 double bond in position 9, C18: 1; ω-9), while the most common poly-unsaturated are linoleic acid and linolenic acid, progenitors respectively omega-6 and omega-3 (see figure).

Terpenes and terpenoids

Terpenes or terpenoids are a large family of natural molecules, typically containing 10 to 30 carbon atoms, which are biosynthesized from a common “brick”, isopentenyl pyrophosphate (IPP), containing 5 carbon atoms (see figure). The discovery that the repetitive brick consists of 5 carbon atoms is relatively recent, while it was once assumed that the entire family was created by repeating a brick of 10 carbon atoms, which was called “terpene”. Therefore, the molecules with 10 carbon atoms (such as limonene, see figure) were called mono-terpenes, i.e. composed of a single brick, diterpenes those with 20 carbon atoms (e.g. the cafestol that gives the aroma to the coffee), triterpenes those with 30 carbon atoms (e.g. beta-carotene). Since molecules made from 15 carbon atoms were also found (such as bisabolol), it was thought they contained a terpene and a half, and were called sesquiterpenes (from the Latin semis = half + atque = and). Today it is known that the repetitive unit is composed of 5 carbon atoms, therefore it is easy to understand how mono-terpenes contain two (see figure), sesquiterpenes three, diterpenes four, triterpenes six.