Ageing is defined as the process of becoming older. As humans we all know the feeling of getting older, but what is the biological process? Well, we’ve not fully got to grips with it yet, but we’ve got some pretty good ideas and the same concepts apply to our trusty companions.
Cells are thought to have a finite number of times they can replicate and divide. Like a chicken is born with the number of eggs they will ultimately lay, the Hayflick limit suggests that a normal cell has a limit and when it has reached that limit, it cannot divide anymore and will break down by programmed cell death. It is this limited capability that we see as ageing.
This programmed cell death usually occurs when 'telomeres' (protective structures found at both ends of chromosomes) reach a critical length. It is therefore considered that telomere length serves as a biological clock.
What is particularly interesting is that certain lifestyle factors can influence telomere length – for example better dietary choices have been seen to prevent excessive shortening (older before your time concept). Telomere shortening occurs at every DNA replication – so if there is an increased need for cell replication, they will become shorter. In areas of the body that have a high turnover of cells like the liver, gastric cells or skin, it’s easy to see why these are the first places that “age!”
This is also why smoking in humans is the biggest contributor of ageing – the damage caused increases the need for new healthy cells, and so the limit is reached sooner.
Shorter telomeres can also induce genomic instability and as we know, this is the leading factor in cancer. Cells have planned programmes to divide, replicate and ultimately die (apoptosis) – they get these messages from the genes. When genes are unstable, their messages get a little muddled and so the cells go rogue – dividing and replicating, but not dying – this aberrant growth is implicated in cancer.
What can cause shortened telomeres?
Telomere shortening is a natural part of life, but as we’ve noted there are things can expedite this process.
In humans exposed to air pollutionon a regular basis, their telomeres were found to be significantly shorter. https://pubmed.ncbi.nlm.nih.gov/19772576/ This again is largely due to the genotoxic capacity of air pollution, leading to DNA instability.
Stress is also associated with increased telomere shortening and subsequent ageing. Stress involves the release of glucocorticoid hormones from the adrenal glands – these hormones are known to reduce levels of antioxidant proteins, which are in fact protective of oxidative damage. Oxidative damage also contributes to DNA instability, and so accelerates telomere shortening. In one human study, women who were exposed to daily stress exhibited shorter telomeres than those who were not. The change in telomere length was the equivalent to 10 years of ageing - https://pubmed.ncbi.nlm.nih.gov/19089916/
Not surprisingly, diet can also affect telomeres.
- A diet contain omega-3 fatty acids is associated with a reduced rate of telomere shortening
- Consumption of a diet including Vitamin E, Vitamin C and beta-carotene is also associated with longer telomeres – the inclusion of antioxidant compounds protects against oxidative damage
- Dietary restriction also reduces oxidative burden, reducing damage to DNA – it is regularly associated with improved lifespans. In a study in Labrador retrievers, results indicated that 25 % restriction in food intake increased median life span and delayed the onset of signs of chronic disease. https://pubmed.ncbi.nlm.nih.gov/18062831/
That being said, it is still important to ensure sufficient nutrients, particularly to maintain lean body mass. Muscle loss is common in ageing pets, therefore a moderate protein content (unless undergoing a treatment plan with a qualified professional) is warranted.
Proteins are the building blocks of the body. The word comes from the Greek word proteios which means of prime importance simply because they have numerous functions. They are the major structural components of hair, skin, nails, tendons, ligaments, and cartilage. They are also involved in a number of physiological and chemical processes in the body including:
- Cell signalling
- Muscle contraction
- Oxygen and nutrient transport in the blood
- Reactions including enzymes, and energy production
Amino acids are the basic units of proteins and are held together by peptide linkages to form long protein chains. Dietary amino acids are absorbed in the gastrointestinal tract, following disruption of the peptide bonds. The liver then changes amino acids so they can be used by the rest of the body.
Although hundreds of amino acids exist in nature, there are some which are commonly found as protein components. They are classified as either essential or non-essential.
Essential amino acids cannot be synthesised by the body so must be supplied by the diet. Non-essential amino acids, whilst still critical to bodily processes, can be synthesised within the body (when it is healthy).
The source of protein you offer your ageing pet is therefore crucial – it should be of high quality and available. Fresh food is generally more bioavailable – meaning that your dog can digest it and utilise what he needs. Red meat, poultry, fish, and eggs are great sources!
For the ageing pet, the inclusion of fat is still important. Cognitive function often declines with age, but this is even more apparent when deficits in polyunsaturated fats occur.
Essential fatty acid Omega-3 is critical contributor to cell structure and function in the nervous system. Deficits are regularly linked to cognitive decline during ageing and neurodegenerative disease. It is considered that Omega-3 contributes to membrane integrity in the brain, represses inflammatory mediators that can contribute to neurodegeneration and is also seen to modulate oxidative damage.
On the subject of brain health, it is relevant to mention the glymphatic system. As we know, the body possesses its own sewerage system – the lymphatic system – but the brain has its own independent waste disposal system known as the glymphatic system. This system is gaining traction and being implicated in neurodegenerative disease. Researchers suggest that the glymphatic system may also function to help distribute non-waste compounds like glucose, lipids, amino acids and neurotransmitters.
This system functions mainly during sleep, being largely disengaged during times of wakefulness – this suggests that amongst its many functions, sleep provides a state of activity that enables the elimination of potentially neurotoxic waste products. But, it does flow into the lymphatic system, and as this system doesn’t have its own circulatory system, but relies on the cardiovascular system, movement and exercise is important to eliminate these waste products.
The bottom line, both sleep and exercise (within reason) are crucial for your ageing dog.
That said, whilst exercise is necessary for lymphatic clearance and maintaining muscle and structural function, degenerative musculoskeletal issues are common in the ageing dog. The inclusion of fatty acids in the diet, is known to be beneficial in many degenerative joint conditions due to their modulation of the inflammatory response.
In small breeds, a higher lifespan is to be expected than with larger dogs, especially the giant breeds. Therefore, no exact time setting for the onset of ageing is possible, as there are individual differences and for this reason, the biological age may differ from chronological age. In large dogs, old age starts earlier compared to smaller breed dogs of the same chronological age. Commonly, large breed dogs are classified as senior from the age of 5-8 years, small breed dogs from the age 8-10 years.
That said, it’s never too early to be including functional nutrients in their diet.
- Feed a fresh food diet – with protein and fat
- Include antioxidant compounds – nuts, seeds, berries, leafy greens, herbs etc
- Ensure Omega-3 Fatty acids
- Reduce oxidative burden through exposure to toxins
- Ensure adequate rest and recovery
- Maintain appropriate exercise – follow your dog’s lead
Supporting your ageing dog;
A liver cleanse can support detoxification and waste clearance.
Pre & Probiotics can support gut health.
Use a skin & coat supplement that contains functional ingredients to support skin health which is particularly important in areas of high cell turnover.
Use a bone & joint supplement to support structural degeneration, especially one that has been specifically designed for the older companions in our lives.