Metabolic waste: What it is and how your body gets rid of it

Hearing the word metabolism can often conjure thoughts of speed over substance. Who has a fast one, who has a slow one, and what that means for how easily we might lose weight and how quickly we might put it back on, but the truth of the matter is that the human metabolism is about a lot more than just the numbers you might see on the scales.

In fact, our metabolism is dictated by a series of specific and nonspecific systems and metabolic pathways that are vital for keeping our bodies functioning, and it's all triggered by basic human behaviours like eating and breathing.

Understanding how these life processes work isn't always easy, though, and it's one thing to know that your body uses what it consumes, and another to know how it uses what it consumes, what indigestible materials it makes as a part of using plant and animal material, and what it does with what it can't use.

Metabolic waste, such as nitrogenous waste products and carbon dioxide, is a significant part of these processes, marking not only an essential step in the energy production process but also playing a role as an indicator of the health of the body's specific elimination mechanisms.

If that's all going over your head, we get it! It can be confusing, so here, we'll break it down for you, looking at what metabolic waste is, how it interacts with metabolic processes, and what it can tell you about your overall health.

What is metabolic waste?

The human body is constantly undergoing a range of metabolic processes in order to both live and to function. These life-sustaining chemical reactions are varied and complex, but put simply, they are the processes by which our bodies break down nutrients from the food we eat in order to make cellular energy, as well as how the body builds and repairs itself. These organic materials produced are vital in organ function as they are what help us to breathe, circulate blood, adjust hormone levels and even keep the heart beating [1].

Metabolic waste is basically what’s left over after those metabolic reactions occur that your body can’t use and doesn’t need, making it something that needs to be excreted.

What causes metabolic waste?

Our metabolism ultimately operates in two parts, which need to remain in balance in order for us to be healthy.

The first is known as catabolism and is basically what happens after we eat. It’s the breakdown of food (a process also known as cellular respiration) from the snack or meal we put in our mouths, perhaps an apple or a slice of pizza, into its individual complex organic chemicals, such as carbohydrates, glucose, proteins (amino acids) and dietary fats. These individual components are then sorted in order for them to be used by the body as energy, either immediately or stored for later. In the latter case, when the body needs that energy, it'll pull it from storage in a process known as ATP hydrolysis.

The second part is anabolism, which is when and how that energy gets used for building and repairing cells, supporting cell growth, and helping to regulate your body temperature for homeostasis. In this, the body creates new nucleic acids (DNA or RNA) and complex molecules through chemical processes and metabolic activity, keeping your body running [6].

These processes all create waste as they work, which is then transported from cells by the bloodstream in order to be excreted from the body in a process known as metabolic waste removal [2]. This happens through both the respiratory system and the digestive tract.

Examples of metabolic waste in the body

Metabolic waste can come in the form of liquid, gas or solid waste (including organic pigments that present differently in animals and plants), meaning there are not only a lot of different types of metabolic waste products, but several ways that they travel throughout the body.

The most common types of metabolic waste products are:

• Excess water
• Carbon dioxide
• Phosphates
• Sulfur
• Nitrogen; and
• Inorganic salts and other crystalline solids, such as ammonia and urea.

All of these metabolic waste products can become toxic if they accumulate, especially as your liver and kidneys have the capacity to absorb large quantities of them. As a result, they can make you sick if your body is unable to get rid of them, making metabolic waste removal of the utmost importance.

What are the symptoms of metabolic waste buildup?

Metabolic waste accumulation can represent disposal mechanisms failures and cause a range of conditions, such as hyperammonemia (excess nitrogen) and metabolic acidosis (the buildup of uric acid), which may severely impact your health and lead to liver and kidney damage. Symptoms of metabolic waste build-up include:

• Lethargy and feelings of weakness
• Nausea and vomiting
• A loss of appetite
• Confusion
• Rapid heartbeat; and
• Changes in breathing [4]

In extreme cases of hyperammonemia, it can also cause brain damage and coma [2], demonstrating how important it is that metabolic wastes are removed. If you have any of the above symptoms, you should speak to your doctor immediately.

How is metabolic waste removed from the body?

How the body removes metabolic waste products depends on whether or not the waste is solid, liquid or gas, and ultimately what sort of waste it is, i.e. whether it contains nitrogen compounds, carbon dioxide or other waste matter.

In this sense, gaseous wastes (namely carbon dioxide) is exhaled through the respiratory system, while some solid waste products are removed by the digestive system, particularly the large intestine in the form of faeces, and the sole liquid waste (excess water) is excreted as urine, with some solid waste products such as urea and ammonia dissolved within it [2].

The role of the liver and kidneys

The liver and kidneys play vital roles in metabolic waste disposal because they ultimately control the filtering, conversion and elimination of nitrogenous wastes such as ammonia, one of the most significant metabolic waste products. How it does this is that the liver absorbs excess ammonia and its nitrogenous compounds, converting them into urea, which is then filtered by the kidneys and dissolved into excess water in order for you to excrete that unusable waste as urine [3]. Conditions that impact your liver or kidneys as a result can seriously impact your body’s capacity to remove metabolic waste, and need to be closely monitored.

Other ways your body eliminates waste

The other major metabolic waste product is carbon dioxide (CO2), which is an odourless, colourless gas your body makes during metabolic processes. Your body requires molecular oxygen for protein breakdown in order to generate metabolic energy in a process known as oxidative metabolism. Excess quantities of carbon dioxide are produced during these biochemical processes, which the body's cells do not require. As a result, carbon dioxide needs to be excreted.

When it’s ready to eliminate this particular waste product, your blood will carry the carbon dioxide to your lungs to breathe it out. Having an excess of carbon dioxide in your blood as a result can be an indication that your body’s metabolic processes aren’t working as they should, and your doctor may assess this via a CO2 blood test [5].

How to support your body’s natural detox processes

When we talk about metabolism, it’s often in the context of weight loss, but the reality is that supporting your metabolic processes is vital to so much more than that. It’s a major player in your overall health, and can have a significant impact on the way you feel in your body. As we get older, our metabolism can naturally slow down, too, so finding ways to increase our activity and get our metabolic pathways back up to speed can have us looking and feeling our best in no time.

The best ways you can support your body’s natural detox process as a result is eating a healthy, balanced diet and making sure you get regular exercise.

Eat healthy

Eating healthy means eating a wide variety of food from across the five major food groups:

• Vegetables and legumes such as leafy greens, nightshades and marrows
• Fruit such as apples, bananas, berries and citrus fruits
• Protein such as lean meats and poultry, fish, eggs, tofu, and nuts and seeds
• Grain foods such as high fibre cereal, wholegrain bread and brown rice
• Dairy such as low-fat milk, yoghurt, and cheese

Some drinks, such as green tea, have also been found to have a positive effect on your metabolism and detoxification, being chock full of antioxidants that support your liver function [7].

Not sure where to start?

The Juniper Programme offers guidance and innovative ideas from professional dieticians to help you reinvent your eating habits. From recipes to meal planning to bespoke dietary advice, this program is designed to help you achieve your weight goals in a way that's both healthy and sustainable.

Regular exercise

While high-intensity interval training (HIIT) has been found to have a particularly positive impact on your metabolism, any exercise that you can make a habit of and do regularly is going to be great for both your metabolic processes and your overall health.

If HIIT isn’t for you, try another cardio-focused exercise to get the blood pumping, such as running, swimming or dancing, interspersed with some strength training such as Pilates or yoga to round out your week.

‍

Image credit: Pexels