Your Kidneys Healthy As You Age
By Dr. Ben
it's been close to 15 years since I dissected my first cadaver in
anatomy class, I still remember being surprised when I got my first
glance at a pair of kidneys - they were much smaller than I had
expected. Up until that point, I had imagined the kidneys to be
quite large, given the amount of work that they are responsible
of your kidneys is about 4 to 5 inches long and about 1 inch thick,
weighing in at about 4.5 to 5 ounces. To put it into easy-to-visualize
terms, each of your kidneys is a bit larger than a deck of cards.
your kidneys make up less than 0.5 percent of your total body weight,
they receive close to 25 percent of the total amount of blood that
your heart pumps while you're resting. Also, your kidneys use up
about 20 to 25 percent of your bodys supply of oxygen.
Please note: To listen to an audio (mp3) recording of this
article, please download and play the following file: How
to Keep Your Kidneys Healthy as You Age - Audio File
do your kidneys such small organs receive so much
of your blood and oxygen? Because they are responsible for five
kidneys keep your blood clean by filtering it of waste products
and eliminating these waste products from your body as urine.
Your kidneys help maintain your bodys fluid composition.
Your kidneys secrete a hormone called erythropoietin, which is
responsible for stimulating the production of red blood cells
in your bone marrow.
Your kidneys produce an enzyme called renin, which is needed to
help maintain your blood pressure.
Your kidneys convert vitamin D to its most active form.
the position of your liver causes your right kidney to be slightly
lower in your abdominal cavity than your left kidney, both kidneys
are partially protected by the lower part of your ribcage.
every beat of your heart, large amounts of blood are delivered to
your kidneys via your renal arteries. Inside your kidneys, your
renal arteries split up into a number of smaller branches that distribute
blood to your nephrons, which are the microscopic processing units
of your kidneys; you have about a million nephrons per kidney.
each nephron, there are specialized beds of capillaries (even smaller
blood vessels) called glomeruli. The glomeruli filter your blood,
and pass the filtrate on to a series of specialized tubules that
are collectively known as the renal tubule its in the
renal tubule where urine is created.
process of creating urine is complex, but in essence, what happens
is this: about a fifth of the blood that passes through each of
your kidneys gets filtered by your glomeruli to enter your the renal
tubules; the stuff that passes through is referred to as filtrate,
which includes waste materials, water, chloride ions, sodium ions,
bicarbonate ions, glucose, potassium ions, urea, uric acid, and
the filtrate travels through the renal tubule, about 99 percent
of it is reabsorbed into your blood circulation. This number alone
gives you a good idea of how hard your kidneys work to produce urine;
of the approximately 40 gallons (150 litres) of filtrate that enters
your kidneys on a daily basis, only about 1 to 2 quarts (1 to 2
litres) turns into urine. The 99 percent that is reabsorbed into
your circulation is how your kidneys help to maintain your bodys
fluid composition and pH level.
you want to understand exactly how your nephrons create urine, I
recommend that you read the chapter on Kidneys and Body Fluids
in Guyton's classic textbook on human physiology this is
the go-to book when you want a detailed look at how your body works
on a microscopic level.
urine is created in your renal tubules, it is shuttled through a
series of collecting ducts until it reaches the inner, middle section
of your kidney, where urine is collected by your ureter, the tube
that allows urine to travel from your kidney to your bladder. From
your bladder, urine exits your body through your urethra.
understanding the work that your kidneys are forced to undertake
to filter your blood and produce urine, I hope its clear that
drinking large amounts of water when youre not thirsty is
a good recipe for prematurely wearing down your kidneys as you age.
body is not like a plumbing tube that gets cleaner by flushing large
amounts of water through it. A number of your organs, including
your kidneys, are designed to keep your body clean by continuously
eliminating waste materials. If you want to prevent illness as you
age, a top priority should be to prevent unnecessary burden to your
kidneys and other waste-eliminating organs.
using your sense of thirst to dictate how much water and water-rich
foods you ingest, here are two important ways to protect your kidneys
from prematurely breaking down:
Dont eat too much protein.
more protein than you need leads to greater workload on your kidneys,
which must filter a by-product of protein metabolism called blood
urea nitrogen (BUN) out of your blood. This increased workload can
contribute to premature breakdown of the glomeruli in your kidneys.
you have healthy kidneys, you can safely eat up to half of your
body weight (in pounds) in grams per day. For example, if you weigh
150 pounds and are in good health, you can safely eat up to 75 grams
of protein from minimally processed foods per day. If you have problems
with your kidneys, you should decrease this amount to a level that
results in a healthy blood urea nitrogen level.
your current health status is such that you need an objective way
to monitor how well your body is responding to the amount of protein
that you are eating, ask your doctor about monitoring your BUN level.
Whenever you eat protein, your body breaks it down into amino acids
that contain nitrogen. Nitrogen separates from amino acids and combines
with other molecules to form urea. Urea is eliminated from your
body when your kidneys filter it out of your blood and into your
healthy range for BUN is between 4 to 17 mg/dL. Anywhere between
18 to 21 mg/dL is a sign that you may be eating too much protein,
and possibly that your kidneys are under excessive strain. More
than 21 mg/dL is a strong sign that you need to significantly reduce
your protein intake.
link between eating too much protein and developing kidney disease
is one that is not often talked about by supporters of a high-protein
diet. While it is important to keep your blood sugar and insulin
at healthy levels by avoiding sugar and other simple carbohydrates,
please know that a high-protein diet poses many dangers to your
health, especially if most of your protein is cooked. Your health
is best served by replacing simple carbohydrates with lots of high
quality fat, and moderate amounts of healthy protein and non-starchy
2. Dont take over-the-counter pain pills on a regular basis.
anti-inflammatory drugs like ibuprofen (Advil, Motrin), naproxen
(Aleve), and aspirin are known to cause kidney damage and disease
if taken regularly. Acetaminophen (Tylenol and Excedrin) can also
cause kidney damage and failure if used regularly. All of these
over-the-counter pain medications probably dont pose significant
danger if your kidneys are relatively healthy and you use them for
many professional athletes have discovered during the past several
years, regular use of prescription anti-inflammatory pain medication
like Vioxx, Indocin, and Naprosyn poses even greater danger to kidney
health than over-the-counter pain killers.
that this article has helped you understand the complex design of
your kidneys and the key steps that you can take to prevent premature
breakdown of your kidneys as you age. Please remember that the best
"medicine" for all of your organs, your kidneys included,
is eating a plant-based, minimally processed diet, getting enough
physical and emotional rest, getting regular exposure to fresh air
and sunlight (without getting burned), and being physically active.
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