What is Acid-base balance



Acid-base balance is defined by the
concentration of hydrogen ions.



In order to achieve homeostasis, there
must be a balance between the intake or
production of hydrogen ions and the net
removal of hydrogen ions from the body.

An Acid



Molecules containing
hydrogen atoms that
can release
hydrogen ions in
solutions are referred
to as an acid.



An example of an
acid is hydrochloric
acid (HCL)

A Base



A base is an ion that
can accept a
hydrogen ion.



An example of a base
is is the bicarbonate
ion.( HCO3

How is Acid-Base balance

measured



Hydrogen ion concentration is expressed
on a logarithm scale using pH units
(part/percentage hydrogen).



7.0 being neutral



Body systems carefully control pH of the
body within the range of 7.35-7.45

pH



A low pH corresponds
to a high hydrogen
ion concentration



The term “Acidosis”
refers to the
addition of excess
hydrogen ions and
the body has a pH
that falls below 7.35



A high pH corresponds
to a low hydrogen
concentration



The term “Alkalosis”
refers to excess
removal of hydrogen
ions from the body
and has a pH that
rises above 7.45

How the Body defends

against fluctuations in pH



Three Systems in the body:

1.

Buffers in the blood

2.

Respiration through the lungs

3.

Excretion by the kidneys

Buffers in the Blood



Buffers are substances that neutralize
acids or bases



Bicarbonate which is a base and carbonic
acid in the body fluids protect the body
against changes in acidity



These buffer systems serve as a first line
of defense against changes in the acid-
base balance

Respiration through the lungs



Carbon Dioxide which is formed during
cellular metabolism forms carbonic acid
in the blood decreasing the pH



When the pH drops respiration rate
increases this hyperventilation increases
the amount of CO2 exhaled thereby
lowering the carbonic acid concentration
and restoring homeostasis

Excretion by the Kidneys



The kidneys play the primary role in
maintaining long term control of Acid-
Base balance



The kidney does this by selecting which
ions to retain and which to excrete



The kidneys adjust the body’s Acid-Base
balance

The Importance of the Body’s

Buffering Systems



Can be quickly realized if one considers the

low concentration of hydrogen ions in the body

fluids and the relatively large amounts of acids

produced by the body each day



Example: 80 milliequvilalants of hydrogen is

either ingested or produced each day by

metabolism.



Whereas the hydrogen ion concentration of

the body fluids normally is only about .

0004meq/L

There are 4 Types of Acid-

base Imbalances



Respiratory Alkalosis



Respiratory Acidosis



Metabolic Alkalosis



Metabolic Acidosis

Respiratory Alkalosis



Is a decrease in CO2, decrease in H+
(Hydrogen ions) and in increase in pH



This condition can be caused by severe
exercise, or anxiety reaction



The body compensates by the lungs
slowing the respiration rate and kidneys
excreting more bicarbonate

Respiratory Acidosis



Is an increase in CO2, an increase in H+ and
a decrease in pH



This condition can be caused by emphysema,
restrictive or obstructive lung diseases



The body compensates by the lungs
increasing respiration rate and the kidneys
by conserving bicarbonate ions and
increasing renal net acid excretions

Metabolic Alkalosis



Is a decrease in CO2, a decrease in H+
and an increase in pH



This condition can be caused by
vomiting, diarrhea, increased ingestion of
alkali



The body compensates by the lungs
creating a slow respiration rate and the
kidneys excreting more bicarbonate

Metabolic Acidosis



Is an increase in CO2, and increase in H+
and a decrease in pH



This condition can be caused by diabetes,
diarrhea, alkaline loss,excess acid
production or ingestion



The body compensates by the lungs
increasing respiration rate and the kidneys
increasing renal net acid excretion

How does the diet effect Acid-

base balance



After nutrients from

food are metabolized in

the cell they may yield

an excess of mineral

elements that are

potentially acid or base



This consideration is

based on whether the

food ingested contains

more cations or anions

Food Components



Cations



Have a positive
charge



Na+



K+



Ca+



Mg+



Anions



Have a negative
charge



Cl-



HCO

3

-



S-



P-



Organic Acids



Proteins

What happens when we put

our bodies into acid overload



Frassetto (1998) stated
“Normal adults eating
an average American
diet (as reported in the
National Health and
Nutrition Examination
Survey)
characteristically have
chronic, low grade
metabolic acidosis”.

“Metabolic Acidosis”



This persisting upsetting of the body’s Acid-Base
balance occurs because metabolism of the diet
releases noncarbonic acids into the systems
circulation (e.g. sulfuric acid from the metabolism
of proteins) in amounts that exceeds the base
released (e.g. bicarbonate from the metabolism of
potassium in vegetables foods



The size of the difference between acid and base
production determines the net acid load of the diet

Metabolic Acidosis



This condition
overloads the bodies
buffering systems
and they cannot keep
up with the necessary
excretions of acids in
the body.

Four ways in which to

measure Acid-base balance in

the body

1.

Blood pH

2.

Urine pH

3.

Renal net acid
excretion

4.

Net acid load

Studies conducted on Diets

and Acid-base balance

Subjects and Methods



141 subjects ranging in ages from 17-73



20 different whole food diets for a period
of one week(previously shown to be
sufficient for establishing a steady state
of acid-base balance)



Diets: Values for protein, potassium were
taken for the 20 diets ingested

Diets &

Results



Protein content
ranged from 39-
193g/d



Potassium content
ranged from 40-
133mEq/d



Renal net acid
excretion then ranged
from 12-136 mEq/d



Protein content and
potassium content
were independent
predictors of renal net
acid excretion



Renal Net Acid
Excretion

1.

For protein= 0.94

2.

For potassium = -0.61

Results



This suggests that increasing protein content

increases renal net acid excretion and

increasing potassium content decreases it.



The results here indicate that in normal subjects

steady state renal net acid excretion is highly

correlated with the ratio of the dietary content

of total protein to potassium.



The information for the 2 components, protein

and potassium used in this diet is widely

available in standard food composition tables

Results



Given that steady state Renal net acid
excretion in normal subjects corresponds
closely with the diet-dependent rate of
acid-production. These results provide a
relatively simple and reliable method for
determining and controlling the net acid
load of the diet.

Subjects and Methods



6 Adults



3 Diets were given that consisted of Low
protein 49(g/d), Moderate Protein 95(g/d)
and High Protein 120(g/d)



Diets consisted of foods for which
nutrient composition was taken and
analyzed

Diets



The study was carried out in 4
consecutive diet periods, was a repeated
measure design in which all subjects
received the above diets in the same
chronological order.



Each diet period lasted 5 days



During each 5 day period the respective
food diet was kept constant

Results



During the last 2 days of each diet period
timed 24 hour urine samples were
collected



Acid-base status was determined



The mean urinary pH for the low protein
diet was 6.7, for the moderate protein
diet it was a pH of 5.4 and the high
protein diet was a urinary pH of 5.5

Conclusion



This study then concluded that urine pH
values confirmed that diet composition
can significantly influence acid-base
balance

What happens in the body

during Acid-Base imbalances



Researchers Barzel and Massey (1998)
stated that “The average American diet
which is high in protein and low in fruits
and vegetables generates a large amount
of acid and this type of diet can
adversely effect bone.”



The key in this statement is “large
amount of acid”



The kidney’s can compensate for only so
much but when there is too much acid in the
body the kidney can’t keep up so then other
body systems move in to help neutralize the
acid



One of these systems is a release of calcium
(Ca+) from our bones.This helps to act as a
buffer to neutralize the excess amount of
acid in the body



Calcium in the urine is directly related to
net acid excretion



A diet high in acid foods causes excessive
calcium loss



Overtime it is the balance of dietary acid
and base that determines calcium
balance

Calcium



“Bone and Mineral investigators should
look at acid-base effects of the diet and
use appropriate methods to measure
these affects. The 24-hour urine
collection as a part of total calcium
balance measurement is the gold
standard of acid-base research”

Study



Todd (2000) stated in her research that hip
fractures is a major health problem in the
elderly and is directly related to animal
protein intake.



They analyzed reported hip fracture
incidences among different countries in
women aged 50 years and older in relation to
their consumption of vegetables and animal
foods.

Study cont.



Hip fracture incidences correlated directly
with the ratio of vegetable and animal protein
intake and accounted for 70% of the total
variation in hip fracture incidences



Conclusion was stated as the finding suggest
that the critical determinate of hip fracture
risk in relation to the acid-base effects of diet
is the net acid load of the diet

Study



Kerstetter, Brien and Insogna (2003) stated in
their research that “Almost 30 million Americans
are affected by Osteoporosis and women are 4x
more likely to suffer from this disease than men.



The health problem is reaching near epidemic
proportions in the United States and world wide.
Less than 30-50% of U.S. adults consume
dietary protein that could be considered
moderate

Study cont.



Given the increasing prevalence of
osteoporosis and the clear impact dietary
protein has on calcium metabolism it is
imperative that we gain a better
understanding of the complex interplay
between dietary protein and skeletal
health”

Systemic effects of metabolic

acidosis



Cardiovascular

1.

Heart: Bradycardia; arrhythmias;
reduced contractility

2.

Vascular: Arteriolar dilation; increased
venous tone

Systemic effects of metabolic

acidosis



Gastrointestinal: Gastric distention;
Intestinal effects



Renal: Sodium/potassium wasting; Uric
acid retention; Hypercalciuria



Electrolytes:
Potassium,calcium,magnesium,phosphor
us

Systemic effects of Metabolic

acidosis



Metabolic/Hormonal

1.

Protein wasting

2.

Organic acid synthesis;

3.

Aldosterone secretion may be increased;

4.

Parathyroid hormone;

5.

Action on bone enhanced;

6.

Vitamin D activation may be impaired

Standard of Care



Respiratory Alkalosis- slowing down the
respiration rate and increasing the CO2
production



Respiratory Acidosis- increasing minute
ventilation and decreasing CO2
production

Standard of Care



Metabolic Alkalosis- replacing potassium
losses, and trying to restore electrolyte
imbalances



Metabolic Acidosis- ventilation must be
increased, less acid production or
ingestion, and try to increase the
systemic pH

Recommended Treatment



Consultation with Patient



Diet History



Lab Values



pH testing to see if there are in acid-base
balance



Create an individualized nutritional plan
for your patient

Recommended Treatments



Putting patient on a diet that help to maintain
the acid-base balance in their bodies



We have sources available to us as Dietitians
one of these is from the USDA Nutrient Data
Laboratory which has Lists of Food Composition
Tables



This lists 1000’s of foods and the nutrient
contents of them



Webpage is www.nal.usda.gov/fnic/foodcomp/