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June 12, 2020
Updated on June 13, 2020 at 23h49
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Can we “feed” her skin ?
The Detector rumors
Agence Science-Presse
DETECTOR RUMORS / moisturizers that promise to “feed” your skin to ensure it does not wrinkle and dries out. Myth or reality ?
The origin of the rumor
The initial idea was simple : it would be necessary to nourish and moisturize the skin, in the same way as it is done to his body, by providing it with water, oils, and vitamins.
The physicians of the american website specializing in health Healthline argue that in order to moisturize your skin, it should moisturize his body. They recommend drinking a lot of water and eat foods rich in water like watermelon, strawberries and cucumber to keep skin smooth and supple, as in our childhood.
A small review of the literature published in 2018 to a point in the same direction. It indicates that drinking more water can increase the hydration of the horny layer — the part of our skin is composed mainly of dead cells. The authors stress that the biological mechanism that explains this relationship remains mysterious, and that additional research is needed to determine if an increase in fluid intake reduces the signs of dry skin.
But to determine if your skin has actually need to using a cream to nourish and hydrate, it is necessary to first understand four things about how the skin works.
1) natural Hydration
The skin is composed of three layers : the epidermis, the dermis and the hypodermis. The outer layer, the epidermis, serves as a barrier against the external aggressions (sun, cold, dust, etc). The deepest layer, the hypodermis, contains mostly fat cells. In the middle is the dermis, which contains glands that produce sweat and sebum, a fat that rises to the surface to be evacuated through the pores. It is the sebum which maintains hydration of the epidermis, by limiting the evaporation of water.
To several dermatologists and other experts, the sebum is enough to ensure hydration of the skin. A priori, creams and lotions are not necessary, unless you feel the pangs due to the drought. The Detector of rumors has not found studies to support or refute their remarks.
2) How to rehydrate a dry skin
It is certain that drinking more water can counter the dehydration of the body and, by the very fact of the skin. Dehydrated skin is recognized in particular in the presence of a skin fold, that is to say that the skin takes a few seconds to regain its shape when the forceps gently between the thumb and index finger. To ensure that the skin retains its flexibility, the horny layer must be composed of at least 10 % of water and, ideally, from 20% to 30 %. It is necessary to ingest about 1.5 litres of fluid per day to avoid dehydration.
The application of fat supposed to “moisturize” the skin would be of limited utility to treat the dehydration. It would be better on skin that is parched by the sun, the dust, the cold, or by a medical treatment such as chemotherapy or hormone therapy.
A publication of the School of medicine of Harvard University notes that not all moisturizers help with dry skin by providing it with a little water and a greasy substance that holds it back. The creams are not a substitute, however, not the oil lost. Proof is that the children have a smooth skin, even if they do not produce sebum. Dry skin is therefore more a problem of lack of water than from lack of oil, the authors say.
3) Restore the elasticity to the skin
A review of eleven small studies involving 805 patients showed that taking supplements of collagen oral will increase the skin’s elasticity, hydration and density of dermal collagen. Another study of 50 women, half of whom have received a treatment and the other half formed the control group, suggests that the consumption of a nutraceutical multicomponent (non-specified) for 60 days would improve the hydration and elasticity of the skin 15 to 22 %, depending on the areas of the face. It would therefore be possible, in theory, of ingesting collagen, rather than to look for in a moisturizing cream.
4) The role of fats and vitamins
Almost all the moisturizers on the market contain, in addition to water, an oily substance, humectants (glycerin, lactic acid, urea, etc) that suck in the water in the skin both from the air and deeper layers of the skin, as well as oily substances, also referred to as moisturizers (vaseline, dimethicone, lanolin, lecithin, etc), that block the evaporation of water.
However, well-controlled studies of the ingredients are few and often conducted with small groups. An analysis of the literature published in 2018 has revealed that the formulations based on hyaluronic acid have a promising efficacy in the tightness and elasticity of the skin, as well as the rejuvenation of the face, but other studies should be conducted to validate these effects.
In addition, the School of medicine of Harvard University points out that the presence of the vitamin is supposed to make us think that moisturizers can nourish skin or the power supply of antioxidants. However, in most cases, these vitamins are likely to be little difference, either because the quantities used are too small to have an effect, either because the vitamins degrade with exposure to light and oxygen.
Verdict
The skin needs water and a certain amount of fat to maintain its elasticity. The evidence, however, are too meager to determine if the moisturizing creams are the solution. It seems that drinking a lot of water might be sufficient for you to avoid daily applications… and expense.
