We all know that as we get older, our bodies undergo certain changes, such as getting more wrinkly skin, going grey or losing our hair, and getting more forgetful. But there’s more to ageing than just the things we see on the surface; many changes occur in different parts of our body, as they get less efficient at doing their jobs.
Such changes include DNA instability, dysfunction of the mitochondria (the powerhouses of the cell), less efficient nutrient sensing in the gut and loss of stem cells.
Some aspects of ageing are only skin deep, but that doesn’t mean we shouldn’t care about them. Skin care is researched for both health and cosmetic reasons.
Skin consists of proteins such as collagen and elastin. Healthy, supple skin requires these proteins to function properly, and the body makes an effort to maintain and repair them. However, they can be damaged in various ways, including oxidative stress and glycation.
During glycatio, molecules of glucose and fructose, sugars which make up sucrose (table sugar), are bonded to the collagen and elastin fibres in the skin. This impairs their function, and prevents the body from repairing them properly.
Glycation is responsible for the formation of advanced glycation end-products (AGEs). These are produced as a result of normal metabolism, but increased levels in the long-term can be highly damaging. AGEs are formed, not only in the skin, but all over the body, and are a key factor in cardiovascular disease.
Since 1945, it has been known that high sugar diets are associated with higher levels of sugar in the blood and skin. In addition, poorly controlled diabetes, and so high blood sugar, is associated with increased glycation and increased formation of AGEs.
Telomeres as a measure of cellular ageing
Wrinkly skin and greying hair are not the only features of ageing. As there’s no single strict definition of what ageing actually is, it is hard to measure directly. However, one of the most preferred measurements of internal ageing is telomere length.
Telomeres are protective caps on the ends of chromosomes that prevent DNA from being damaged or lost when cells replicate. Each time a cell divides, the telomeres shorten slightly. Once the telomeres are lost, the cell becomes senescent, and so cannot divide further. This means that if the telomeres are not replaced, there is a limited number of divisions a cell can undergo.
How are ageing and metabolism linked?
Leading causes of death in the modern age include cancer, cardiovascular disease (e.g. heart disease and stroke) and dementia (including Alzheimer’s). These are all considered to be diseases of old age, for the most part.
As well as being linked to age, these diseases are all known to have a metabolic component, meaning they are influenced by how well the body processes its fuels.
As most studies test for association rather than causatio, it is hard to say whether ageing causes metabolic issues, or metabolic issues cause ageing.
Type 2 diabetes is a classic example of a metabolic disease: the body is unable to regulate its blood glucose levels and this leads to a number of health issues and complications, such as kidney disease, cardiovascular disease and nerve damage.
Aside from these well-known complications though, type 2 diabetes is also linked to shorter telomere length, and by associatio, is therefore linked to ageing. However, it is not yet possible to say whether type 2 diabetes (and so metabolic dysfunction) causes ageing, or vice versa, as this relationship is currently purely associational.
Type 2 diabetes is not the only metabolic factor associated with shorter telomeres though. Physical inactivity, insulin resistance and obesity have all been shown to be associated with shorter telomere length.
What can we do about this?
We’ve all seen advertisements from health companies claiming that their supplement slows down the ageing process, and indeed, there’s a lot of foods and supplements that have been shown to be beneficial in some manner. However, good health requires more than just popping a pill every now and then. Arguably the most important thing is to eat a diet that promotes metabolic health.
A diet that is high in sugar is known to cause insulin resistance and non-alcoholic fatty liver disease. Most of this effect is attributable to fructose, which makes up 50% of table sugar (sucrose). Fructose is metabolised primarily by the liver, where it is readily converted into visceral fat. It is this process that causes insulin resistance to develop. High-sugar diets also increase blood triglycerides, another marker of poor metabolic health.
Since sugar promotes poor metabolic health, and this is associated with formation of AGEs and shorter telomere length, it stands to reason that reducing the amount of refined carbohydrates and sugars in the diet should reduce the negative impacts of ageing.
Indeed, a study published in 2014 saw increases in telomere length in people following a Mediterranean diet intervention for five years. These increases in telomere length were inversely associated with obesity measurements, meaning telomere length increased as people lost body fat on this diet. Low sugar diets have also been shown to lower levels of sugar in the skin, thus reducing the risk of glycation damage to the skin’s collagen and elastin.
Furthermore, as poor metabolic health and ageing are both factors in the quintessential diseases of the modern age (cancer, cardiovascular disease and Alzheimer’s), reducing sugar intake is likely a good strategy for reducing the risk of these developing.