Because of its association with heart disease, most of us are worried about our cholesterol. We try to avoid too much cholesterol in our diet, and if our blood cholesterol is elevated, we may take medications, such as a ‘statin’, to reduce it.
These associations can lead to the notion that cholesterol is simply bad. But in fact, cholesterol is an essential ingredient in all of our cells.
Cholesterol is a major component of the membranes that surround each and every living cell in our body. It is also one of the three key lipids (or fats) that form the waterproofing membranes in the outer layer of our skin – the stratum corneum. These lipids in skin are what form the permeability barrier – that ability of the skin to keep the outside out and the inside in.
Our cells can manufacture their own cholesterol – or they can use the cholesterol in our blood that we get from our diet. That is – most of our cells can use the cholesterol in blood – but some cannot. Brain cells can’t use it, because the ‘blood brain barrier’ keeps out its delivery vehicle, called LDL (for low density lipoproteins).
The epidermal cells (epidermis is the outer layer of skin) that generate lipids for the permeability barrier also can’t use blood cholesterol. This is because they lack LDL-receptors – which are the molecules on the cell membrane that bind the LDL particles and allow the cell to take up the cholesterol carried on these lipoprotein particles.
Bottom line: brain and epidermal cells have to make their own cholesterol from scratch.
It is possible that they share this common feature because they both arise from the same embryonic structure – the neuroectoderm. But it is also possible that the production of cholesterol in skin remains autonomous from the blood supply because cholesterol is so critical to skin function.
In order to make a tight skin barrier, cholesterol has to be generated in the same proportion as are the other two key lipids of the barrier – fatty acids and ceramides. Maybe cholesterol is too important to be left to the chance of an inadequate dietary source. You wouldn’t want your skin to become leaky because your diet was lacking cholesterol.
So, whether or not our diet is rich in cholesterol, skin will keep producing exactly what it needs.
Fortunately, too, most of the ‘statins’ that we take to lower our blood cholesterol don’t seem to affect our skin. Even though these drugs act to inhibit the body’s own synthesis of cholesterol, their main effect is in the liver where LDL-cholesterol (known better as the ‘bad’-cholesterol) is generated. Most of the statin’s we take are ‘cleared’ by the liver – and don’t reach the other cells in the body, including the skin. Sometimes, though, at higher doses or with some types of statins, enough drug may reach the skin to cause dry skin.
As we age, our skin barrier becomes weaker – and this is due, at least in part, to an age-related decrease in cholesterol synthesis. Our skin cells capacity to generate cholesterol declines somewhat as we age. This is why older adults are more prone to dry skin – especially in winter when our skin’s barrier is under stress because of the low humidity in our homes.
A few products to treat dry skin or other skin disorders may contain cholesterol or a cholesterol-like analog. This can be beneficial if the sterol is provided in a balanced formulation with the other two key lipid types, ceramides (or a ceramide-like analog) and fatty acids, because such balanced formulations of physiologic lipids can repair the skin barrier. EpiCeram®, is an example of such a balanced barrier repair formulation that contains cholesterol and was developed by research from the Elias laboratory.