Why are your kidneys important for circulation?

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S.A.C. Dip (Diet, Exercise & Fitness), Advanced Human Anatomy & Physiology Level 3
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07 February 2019

What do your kidneys do?

The kidneys are important for maintaining fluid balance in the body by filtering blood and releasing toxins to be excreted through urine. As we know, blood is constantly circulating around the body and it passes through your kidneys multiple times every day. Each of your kidneys is composed of hundreds of thousands of nephrons, where the filtration of blood takes place. When blood enters the kidney, the following processes take place:

  1. Blood enters the kidney through the renal artery. 
  2. Blood is dispersed through blood vessels which get progressively smaller, until it reaches the nephrons.
  3. Within each nephron, blood flows through a cluster of tiny blood vessels (the glomerulus).
  4. The thin walls of the glomerulus filter toxins and excess water from the blood.
  5. The filtered blood remains in the blood vessel and travels past the tubule.
  6. The waste and excess water flow from the glomerulus into the tubule.
  7. As the filtered blood passes the tubule, the water and nutrients are reabsorbed into the blood vessel. 
  8. The waste products leave the kidneys via the ureter, then travel to the bladder and leave the body through the urethra, as urine.
  9. The filtered blood leaves the kidney via the renal vein and returns to the heart.

As well as filtering waste from the blood and reabsorbing necessary nutrients, the kidneys also play a role in other important processes. Other functions of the kidneys include:

  • Producing the hormone renin, which helps to regulate blood pressure
  • Filtering uric acid from the blood, too much of which can cause gout
  • Conserving water and electrolytes as required, hydrating your body
  • Helping in the activation of vitamin D, so it can circulate in the blood and assist with calcium absorption
  • Producing the hormone erythropoietin; this controls the production of red blood cells, which carry oxygen around your body in haemoglobin.  



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Why are your kidneys important for circulation?

1. They filter toxins from the blood

As I’ve mentioned, the kidneys are responsible for maintaining fluid and electrolyte balance. They do this by filtering the blood, removing toxins and reabsorbing water and minerals. Toxins can build up in the blood from various bodily processes. For instance, when food is digested, your body absorbs the necessary nutrients from your food and sends the leftover waste to the blood.

Without the filtration process which takes place within the kidneys, these toxins would build up in the blood and circulate through your body, causing damage. The kidneys allow the blood to be ‘cleaned’ before it returns to the heart and lungs to pick up oxygen, and helps to make sure that all the right nutrients are being sent round the body.

2. They regulate blood pressure

The kidneys are also involved in regulating blood pressure. If blood pressure drops, the kidneys produce renin. This hormone triggers vasoconstriction, which narrows blood vessels and restricts urination, helping to raise blood pressure. In this way the kidneys contribute to the maintenance of healthy blood pressure, by raising the pressure when it becomes too low. 

On the other hand, when blood pressure becomes high, the kidneys block this pathway which allows for vasodilation – or the widening of blood vessels – and promote more frequent urination. These mechanisms allow the blood pressure to lower.

Research has even found that transplanting a kidney from a normotensive donor – that is, a person with normal blood pressure – into a recipient with high blood pressure leads to normalised blood pressure, and reduces the damage that high blood pressure had done to their heart.1

3. They trigger the production of red blood cells

The production of red blood cells is triggered by erythropoietin, a hormone which is produced by the kidneys. Of course, red blood cells are vital to the circulation of oxygen around the body. Red blood cells contain the protein haemoglobin, which has an affinity for binding to oxygen. This allows blood to absorb oxygen when it enters the lungs and circulates it throughout the body, delivering it to all of your tissues and organs.

4. They reabsorb water

During the filtration process, your kidneys reabsorb water into the blood. When blood is sufficiently diluted, it will flow easier around the body. Therefore, if you are dehydrated then the blood will contain a lower volume of water, and your circulation will be sluggish. 

Consuming too much salt in your diet can affect how much water is conserved by the kidneys. This happens because, when salt enters the cells, water follows in order to dilute the sodium. As a result, your kidneys have to work harder to maintain the balance between water and electrolytes and will hold on to as much water as they can. Although it may seem counterintuitive, drinking more water will help to flush out this built-up fluid and reduce bloating!

How can you support your kidneys?

One of the minerals that the kidneys work so hard to balance is potassium, especially nowadays when so many packaged food products are full of excess salt. When the balance of these two minerals is altered, the kidneys are forced to work harder to maintain harmony.

You should try to consume as many fresh, unrefined and unprocessed foods as you can to increase your potassium levels and support your kidneys – bananas, apricots, avocados and sweet potatoes are just some of the tasty fruit and veg where you can find lots of potassium! If you need an extra boost on top of this, try Balance Mineral Drink. Just add it to water for a refreshing strawberry drink or add to your favourite fruit smoothie for a healthy dose of potassium, magnesium, zinc and vitamin D!

Another way to support your kidneys is to drink plenty of water. As I’ve said already, drinking more water will help to relieve fluid retention. This happens because, when an important substance is in short supply (in this case water), the body will stockpile it and conserve as much as possible. So, if you experience excess bloating and water retention, it could be that your body is dehydrated.

Rehydrating your body will release this surplus water and reduce swelling caused by water retention. However, it is important that you talk to your doctor about any concerns relating to fluid retention as it could be a sign of something more serious.

Along with drinking more water, you can incorporate Solidago Complex into your diet which can help to ease signs and symptoms of dehydration, such as puffy eyes in the morning, fatigue and lower back ache. Solidago is traditionally used for helping to support the function of the kidneys, and taking it alongside plenty of water will help to keep your kidneys ticking over. You’ll also find extract of Solidago in our Golden Rod Tea.





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