Getting moving is one of the best things we can do for our bodies. The benefits are almost endless: improved insulin resistance and cardiovascular health, good for our muscles and bones (especially as we age), improved cognition, mood and coordination (1). The list goes on. But exercise also has a profound, yet much less appreciated effect on our immunity. You may think that exercise associated immunological changes aren’t a big deal. Surely it is fat loss and muscle gain that are the desired outcomes of moving our bodies? I’d argue otherwise. Let’s take a look at why…
Our immune system
Our immune system is a complex, highly organised constellation of cells and molecules spread throughout every inch of our body. Not just for fighting infections, the immune system has an important role in the incidence of lifestyle-related diseases (so-called non-communicable diseases – or NCDs for short – health conditions that are not infectious), it’s responsible for healing and damage repair AND is actually our main cancer surveillance system. It speaks a common biochemical language with all our body’s systems, including the nervous system and endocrine system, communicating via shared neurotransmitters, hormones and chemical mediators in the body. In fact, the immune system is an integral part of all physiological processes – even reproduction. Exercise has a profound impact on the ability of the immune system to carry out its many tasks. And this foundation for health and wellbeing starts with the lymphatic system.
The lymphatics – grand avenues of the immune system
One of the most important immune strengthening benefits of movement is probably the most neglected and least understood part of our body – the lymphatic system.
For our immune system to function properly, our lymphatics – the grand avenues of our immunity need to be in constant flow (2). The lymphatics are a network of vessels and nodes that are the circulatory system of our immunity and spans the entire body. Except for cartilage, nails and hair, our entire body is bathed in lymph fluid, called chyle. This clear fluid, that we have around 15 litres of (compared to around 5 litres of blood), permeates every nook and cranny of our body carrying many of our immune cells, hormones and proteins – even mixing with the brain and spinal fluid. The lymphatics have been historically the ugly stepchild of our body, somewhat neglected in favour of it’s fraternal twin – the blood circulatory system. Both blood vessels and lymphatic vessels share many functional, structural and anatomical similarities, but lymphatics are unique. Unlike the blood system, which is a closed loop with the heart actively pumping blood to oxygenate our tissues, lymphatics are open-ended. Movement through the network is instead governed by our rhythmic daily muscle movements propelling chyle. In this way physical activity contracts our muscles, forcing the lymph fluid through the body.
This magnificent network’s purpose has long been misunderstood by the medical community, and its activities misinterpreted by most. In fact, if you look for information about the lymphatic system online, you’ll find mostly references to “swollen lymph nodes” and “cancer” with relatively little in-depth information about the lymphatics system’s function in healing and preventing illness. Let’s start with a closer look at some of the core functions of lymphatics to our immune health.
Functions of the lymphatics
So we know from research that exercising makes the muscles contract and pushes the lymph fluid through the body. This assists in the lymphatic vessels, that plays multifaceted roles in the body, which can be grouped into 4 main areas:
Circulatory super highways of the immune system:
Movement of lymph fluid through the lymphatic vessels acts as a transport system for immune cells to patrol all the remote corners of our body. This transport system fulfils probably one of the most important roles for the immune system – surveillance, keeping a lookout for anything untoward. Surveillance of our body for infection and potentially cancerous cells is a critical daily immune cell task (3). This surveillance role allows the immune cells to keep an eye out for infections or potentially cancerous cells (4). The lymphatics bring immune cells together in hubs of immune activity called lymph nodes – operational centres for activating our body’s defences. If the flow of lymph stops or becomes impaired, this vital immune surveillance and defence function can also become compromised. When the lymphatic system is congested as a result of genetic issues, acute stress, sedentary lifestyle or poor digestion, the lymphatic system’s ability to circulate can be adversely affected (3).
Lymphatics are the entry point for fats and fat-soluble vitamins from your diet. Responsible for transporting them from the intestine to every corner of the body: When the lymphatics are not flowing, we may feel our energy levels drop and fat-soluble vitamins like A, D, E and K are poorly transported from the digestive tract around our body.
Detox-channel for cellular metabolites and inflammation:
If your body is analogous to a car then your lymphatic system are like oil filters. Like the drains in your house, the lymphatics are fundamental to filtering away the daily waste products from the day-to-day running of the cells in our body, toxic by-products from pesticides and environmental pollutants that are too big to enter the bloodstream. It picks up waste products from the day-to-day running of the cells in our body, toxic by-products from pesticides and environmental pollutants that are too big to enter the bloodstream all end up being collected into the larger lymphatic vessels that line the intestinal tract, and are sent off to the liver for processing (7).
Maintaining whole body fluid balance:
As blood carries nutrients and oxygen around the body, fluid diffuses out into our tissues (8). One of the principal functions of the lymphatic system is to gather this fluid and return it to the blood system to maintain overall fluid balance. Swelling, known as lymphedema*, occurs when this fluid accumulates in a certain area of our body such as a limb. Over time, persistent lymphedema can lead to complications that affect the function of that body part such as inflammation, fibrosis (a kind of scarring) and deposition of fatty tissue.
*Lymphoedema can be due to a specific genetic condition (known as primary lymphedema) or due to surgery, certain infections and various lifestyle factors including lack of physical activity.
When lymph goes wrong
Despite the many fundamental benefits of our lymphatic system, this wonderous can be exploited. Lymphatics are one of the main ways toxins are absorbed and removed from the body but it may enhance their toxicity, since they are distributed to other organ systems in the body without being metabolized by the liver. On the same vein, cancer cells can go into the small lymph vessels close to a tumour and travel into nearby lymph nodes. Here cancer cells can be destroyed but some may survive and grow to form tumours in one or more lymph nodes. This lymphatic metastasis is a sneaky method employed by tumours to spread.
Problems can also occur when the daily flow of the lymphatics are disrupted. For example, inflammation – a normal and vital component of our immune defence against infection – is also a damaging chemical storm. Inflammation causes expansion of the lymphatic network and weakening of its ability to do its job, leaving us vulnerable to infection (3). These efforts damage our own tissues and as a repair response our immune system builds new lymphatics to bring in immune cells to repair. This also encourages the lymphatics to deposit fat tissue at the site of inflammation. This is useful if we have an infection or a graze but if we have low grade inflammation that is on-going or non-resolving our lymphatics never return to their normal state. Expanded and leaky lymphatics don’t drain so well leaving us vulnerable to ill-health and infection. Accumulation of fat tissue and inflammatory immune cell infiltration are associated with the progression of long-term inflammation that is implicated in several chronic health conditions.
We know that being sedentary is a shortcut to low immune function, leaving you open to infections (9). Being sedentary can increase the risk of being at an unhealthy weight and studies have shown that obesity markedly decreases lymphatic function (10). The relationship between obesity and the lymphatic system are bidirectional, as defects in the lymphatics contribute to the development of obesity and vice versa. It seems that there is a low-grade inflammation associated with progressive weight gain that leads to lymphatic dysfunction in obesity and this in turn can further worsen the complications of being overweight. Leptin, a hunger and satiety hormone which is produced by fat cells and deregulated by obesity also causes dysfunction and disorganisation of the lymphatics. This dysfunction can also contribute to high blood pressure and stimulates growth of fat cells, altering your body composition from its healthy set point (12). There are even genes (Forkhead box protein C2 – FOXC2 and PROX1 CC variant) that play a role in formation of lymphatics which are associated with obesity. One study in humans showed subjects with particular lymphatic genes had higher accumulation of belly fat, but surprisingly lower daily food consumption (13) suggesting that there is a percentage of individuals whose accumulation of abdominal fat is not due to an excess of caloric intake.
The lymphatic system is uniquely susceptible to stress. Stress causes a remodelling of lymphatic vessels and impairs the proper drainage of tissues, which can have negative consequences for our health. Chronic exposure to large surges of cortisol, the stress hormone, can literally cause the lymphoid tissue to die-off. Persistently high levels of the stress hormone cortisol have been linked to suppressed immune system function and reduced circulation of the antibodies that the body desperately needs to fight off foreign invaders (14). Diet can also have an impact on our lymphatics: salt imbalance (15), poor digestion and an out-of-whack gut microbiome (16) all affect the lymphatics, compromising their key functions. We now know that in individuals with type 2 diabetes, the walls of the lymphatic system become leaky, impairing their ability to do their job properly, opening up to infection (11).
For body and for mind: the lymphatics and the self-cleaning brain
The recent discovery of the brain lymphatics overturns decades of what we once thought we knew about the lymphatic system – it showed that the brain is actually directly connected to the immune system via vessels previously thought not to exist (17). This paradigm-shifting discovery alters how we perceive brain-immune interactions. Scientists have now shown that the lymphatics act as an irrigation system for the brain, with the immune system eliminating toxins from the cerebrospinal fluid bathing our brain through lymphatic vessels (18). This activity clears out metabolic waste products that have been linked to cognition, memory and cognitive decline. It appears to be highly influenced by physical activity (19) and is particularly active during deep restorative phases of the natural sleep cycle (20).
How to move your lymph
Getting your body moving, independent of weight loss, improves lymphatic function and reverses some of the unhealthy changes accumulated through sedentary behaviour (10). Forces from the movement of our muscles helps maintain a healthy lymphatic flow. As knowledge of our lymphatic system has grown, so has interest in combining therapeutic techniques with body movement—though, for many years, researchers made no connection between body movement and the lymphatic system? At the beginning of the 19th century, a system of therapeutic gymnastics was popularised, designed to maintain physical condition and health. Followed by a German gymnastics system called turnen, which can be roughly translated as “movement.” One critical regulator of lymphatic flow is nitric oxide (NO), a molecule that also mitigates the damaging effects of inflammation and regulates our blood pressure (21). Exercise is the most potent activator of nitric oxide production. It has been shown that as little as 20 to 30 minutes of aerobic exercise is enough to increase nitric oxide levels and to have a positive effect on lymphatic flow, particularly if you breathe through your nose. And here is the kicker: slow or fast, young or old, overweight or otherwise – walking is what we are built to do and adding a brisk walk to your day is enough! Water adds more beneficial pressure to those lymphatic vessels so go swimming if you can (and even better if its in cold water).
Vegetables—notably leafy green vegetables and beets—contain nitrate, which can be converted in the body to nitric oxide which regulates lymphatic flow (22). Many plant foods, including fruits, chocolate, and red wine, also provide polyphenols and other compounds that can increase nitric oxide production. High-protein foods such as nuts, beans, seeds, turkey, seafood, and dairy products supply arginine, which is an amino acid (one of the building blocks of protein), used by cells to make nitric oxide (23).
Just as the heart is the pump for the circulatory system, the diaphragm can assist in pumping the lymphatic system (24). Deep diaphragmatic breathing is the most important facilitator of lymphatic function. Combined with gentle stretching this can also be a nice way to self-manage stress and relieve tension at the end of the day.
Lymph fluid responds very well to G-forces, which is why it can be useful to use mini-trampolines, often called rebounders (25). Gentle up and down bouncing activates lymph flow. The gravitational pull caused by the bouncing causes the one-way lymphatic valves to open and close, moving the lymph and your immune cells all around the body.
Effleurage e.g lymphatic massage
While lymphatic massage techniques may vary, it generally involves the practitioner manipulating the body, much like an extra mechanical pump, to physically drain the lymphatic fluid, and it does produce tangible evidence-based results. Often referred to as lymphatic drainage, this was developed for the treatment of lymphedema (lymphatic blockage leading to painful swelling). A recent study showed that a combination of lymphatic drainage massage and exercise were beneficial in the treatment of conditions that involve blocked lymphatics following surgery (26). Massage also attenuates chronic inflammation and helps aid recovery from injury (27).
Dehydration is a common cause of lymph congestion. Lymph becomes thicker and less mobile when you are dehydrated so make sure you drink whenever you’re thirsty (27).
Cryo- or thermo-therapy
Lymphatic vessels contract when exposed to cold and dilate when exposed to heat. This decreases the lymph-flow significantly during cooling, followed by a rebound effect where flow is improved afterwards (28). If you don’t fancy running into the sea in winter or have access to a sauna, then a hot bath or a cold shower at home is a handy. And if you are brave enough, try combining them.
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