A. Case study
B. More information
C. Editors' comments
E. CPD questions (South Africa, Australia)
A. Case study
A 24-year-old man
visited his general practitioner after he observed what he thought was
blood in his urine that persisted for 2 days. The doctor examined him
for possible urinary tract infection, renal disease and trauma. He did
not have an increased temperature, painful micturition or other pain,
malaise of discomfort, or recent significant weight loss. The patient
assured his doctor that he felt quite healthy and had not experience
any type of trauma recently.
The doctor asked
the patient for a urine sample and tested for the presence of blood
with a dipstick. The result was negative.
What could be the
possible reasons for the test to be negative?
There is no blood present in the urine;
It is not blood that is coloring the urine but red coloring
The incorrect technique was used to do the dipstick test.
The dipstick that was used was old stock or was stored incorrectly
and thus did not provide an accurate result.
The doctor questioned
the patient about consumption of red colorings in, for example, red
soft drinks, sweets, etc. The patient denied eating any of these products.
The doctor then decided to redo the dipstick test with newer stock and
made sure that he used the correct technique. But the result was negative
once again. He decided to send a urine sample to a laboratory that would
examine it for of red blood cells, but none were detected.
the case with a colleague, the doctor was asked if he had queried the
patient about beetroot, also know as beets. He explained that the ingestion
of beetroot could result in the passing of red urine. The doctor said
that he ate beetroot regularly and had never experienced this. But the
colleague explained that this phenomenon, known as beeturia, occurs
only in about 10-14% of people. The doctor questioned his patient and
found that he had in fact eaten beetroot on both days in question. The
color of the patient's urine returned to normal when he did not eat
beetroot. He was advised that beeturia is a harmless occurrence and
that, even though beetroot colored his urine, he did not need to exclude
the vegetable from his diet.
|TIP for Allergy Advisor users:
When entering "beetroot" in the search function of Allergy Advisor,
the following information on beetroot can be obtained: background information
on the vegetable (where it is grown, what it is used for including the uses
of its red pigment in the food industry); the allergens that have been identified
in beetroot; what allergy reactions have been previously reported, how common
the allergy reactions are; what non-allergic reactions may occur; and that beetroot
can contain the following constituents: betanin, nitrates, oxalate, phenolic
acids and succinic acid to which adverse reactions can be experienced.
B. More information
The production of
pink or red urine following beetroot ingestion is known as beeturia.
This phenomenon is often misinterpreted as hematuria (blood in the urine)
by the unsuspecting. However, it is in fact the red beetroot pigment
that colors the urine. In some individuals the pigment passes intact
along the gastrointestinal tract. A proportion is absorbed and excreted
in the urine, and the remainder passes out in the stool.1,2,3,4,5
Beeturia occurs in about 10-14% of the human population. There
is a variable frequency in the occurrence of beeturia in some
individuals, while others consistently experience it after eating
It has also
(incorrectly) been suggested that beeturia is linked with food
allergies and malabsorption syndromes.1
most common in individuals with enhanced iron absorption: in 66-80%
of patients with untreated iron-deficiency anemia, 45% of patients
receiving treatment for pernicious anemia (augmented iron absoption
occurs in this disease during Vitamin B12 treatment), and 33%
in non-anemic patients with both malabsorption and biopsy-proven
jejunal atrophy (the jejenum plays an important role in iron absorption).3,4,6,7
that beeturia is more likely to occur at a time of "iron
hunger" perhaps via the pathway for iron absorption. Because
beeturia can appear and disappear in individuals, at least some
of the 14% incidence may be due to the fluctuating nature of iron
absorption in normal individuals. 6,7
mechanism has not been identified and the methods used in these
studies have received critisism. In any case, a history of or
the observation of beeturia in an infant or child should alert
the physician to the presence of an associated iron deficiency
Why might this
It has been suggested that beeturia is controlled by a single autosomal
gene, with 43% of the population being heterozygous for the gene.4
But this viewpoint has received criticism. It has been found that beeturia
will always be present in any population study that is done, and during
repeat investigations the results for any particular individual within
a group may change. This is to be not expected for an event under genetic
control.1,7(There is room, however, for disagreement with
this conclusion, as genetically determined enzyme deficiency is not
necessarily absolute, but can occur in many degrees of severity.)
It is also suggested
that beeturia is dose-related, but studies have contested this.4
Beetroot's red pigment,
widely used in the food industry as a colorant, is betalain (also known
as betalaine) consisting of betacyanines and betaxanthines. About 0.5-1%
of extracted beet juice solids are betalains. In addition to the pigments,
the root contains about 700-800mg oxalic acid and 5-6mg ascorbic acid
per 100g beetroot.4
The pigment is a
pH and redox indicator. It is structurally unstable at the extremes
of pH, loosing its color in alkaline conditions and undergoing irreversible
decomposition (to red or yellow) in acid solution. Studies have shown
that betalain is decolorized by hydrochloric acid, ferric ions and colonic
bacteria preparations, but not by pancreatic or mucosal enzymes. It
has been suggested that the red color is stabilized by reducing agents,
including oxalic acid and ascorbic acid, until it can reach the colon
and be absorbed.1,4
individuals the pigment is decolorized by non-enzymic processes in the
stomach and colon. The acid conditions of the stomach might also be
expected to decolorize the red pigment, but it has been postulated that
the oxalic acid and ascorbic acid stabilize the pigment throughout the
passage through the stomach. Beeturia results from colonic absorption
of betalain. Although it has been suggested that oxalic acid and ascorbic
acid preserves the red color to the colon, it has now been shown that
an intake of 1g ascorbic acid together with beetroot does not induce
beeturia. The reason suggested for this was that ascorbic acid is absorbed
from the jejenum and does not pass to the colon. (But it might still
help in preserving the red color up to that point.) It is thus oxalic
acid that preserves the red color all the way to the colon.4
It seems that the
difference between a non-beeturic individual and a beeturic individual
rests with oxalic acid in the colon. The more oxalic acid present in
the colon, the more pigment available for absorption, which then determines
if the urine will be colored. The concentration of oxalic acid will
depend on the residue of the enteric oxalic acid not absorbed from the
small intestine (which can vary between individuals). Another variable
is the colonic bacterial metabolism. It has been hypothesizeded that
beeturia can be influenced by the presence or absence of a bacterial
decolorizing system. This theory was based on in vitro experiments and
is difficult to prove or disprove. There are around 500 species of bacteria
in the colon whose enzymes can be induced and have an influence on the
pigments that are present in the colon. Urinary oxalic acid content
probably has no influence on beeturic status, and little relationship
with the colonic concentration.1,4
Also, one could
expect an association with beeturia and certain conditions, e.g., calcium
oxalate kidney stones and short bowel syndrome where the level of oxalate
intake is generally restricted.
Beeturia is thus
affected by the quantity of pigment entering the systemic circulation,
and this in turn is influenced by:
factors controlling the amount of pigment present in the gut.
factors controlling the pigment's absorption.1
Beeturia is thus
a function of an individual's physiological constitution and not a phenomenon
under direct polymorphic genetic control as originally implied.1
can influence beeturia?
The type of beetroot. Individuals who produce an intense coloration
with one variety can produce urine with a virtually normal coloration
with another. The pigment concentration of the "Detroit Rubidus"
variety is twice than that of the "Firechief" variety,
The times of planting and harvesting. Additionally, concentrated
beetroot extract is added to certain brands to enhance coloration.
These factors, amongst others, can help in explaining the variation
in results in the literature.1,7
Preparation. Boiled beetroot does not predictably lead to beeturia,
whereas pickled beetroot does. The acid vinegar may alter the
state of the oxalic acid.4
Intestinal function. Where there is reduced absorption from
the small intestine, as in malabsorption, more oxalic acid would
pass to the colon to protect the pigment and induce beeturia.1,4
on other food idiosyncracies will follow in the next 6 months.
||compiled by Karen du Plessis
Food & Allergy Consulting & Testing Services (FACTS)
PO Box 565
Comments by our editors
Sabine Spiesser B.Sc. Dip. Ther. Diet.
Urine colour and odour is frequently altered due to the food recently
ingested. Changes in urine colour, especially if it is red can cause
distress in patients due to the possible presence of haematuria.
It is important for the medical practitioner or nurse to test for
the presence of blood and obtain laboratory analysis to determine
the cause of the abnormal discoloration.
Colour changes may occur due to ingestion of drugs, vitamin supplements,
food dyes, bilirubin, beetroot and berries, bacterial growth, pH
and metabolic abnormalities. In alkaptonuria urine turns black on
standing. Blue diaper syndrome renders diapers blue due to a defect
in transport of the amino acid tryptophan in the small intestine,
the infant's urine turns blue on bacterial fermentation when it
hits the air.
Odour can be due to asparagus, trimethylaminuria, MSUD (Maple syrup
urine disease), fenugreek and colonic fermentation volatiles.
For more information
on this subject and other allergy and intolerance related topics, visit:
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go to http://groups.yahoo.com/group/AllergyDietitian
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1. Mitchell SC. Food
idiosyncrasies: beetroot and asparagus. Drug Metab Dispos 2001;29:539-43.
2. Tunnessen WW, Smith C, Oski FA. Beeturia. A sign of iron deficiency.
Am J Dis Child 1969 Apr;117(4):424-6.
3. Sotos JG. Beeturia and iron absorption. Lancet 1999 Sep 18;354(9183):1032.
4. Eastwood MA, Nyhlin H. Beeturia and colonic oxalic acid. QJM 1995
5. Watts AR, Lennard MS, Mason SL, Tucker GT, Woods HF. Beeturia and
the biological fate of beetroot pigments. Pharmacogenetics 1993 Dec;3(6):302-11.
6. Watson WC, Luke RG, Inall JA. Beeturia: its incidence and a clue
to its mechanism. Br Med J 1963;2:971-2.
7. Charlton RW, Bothwell TH. Iron absorption. Ann Rev Med 1983;34:55-68.
8. Pearcy RM, Mitchell SC, Smith RL. Beetroot and red urine. Biochem
Soc Trans 1992 Feb;20(1):22S.
Questions (South Africa, Australia)
ALL THE QUESTIONS
1. What percentage
of the human population is affected by beeturia?
2. True or false:
There is a variable frequency in the occurrence of beeturia in some
individuals, while others consistently experience it after eating beetroot.
3. Which of the
following has beeturia not been associated with?
(a.) Food allergies
(b.) Malabsorption syndromes
(c.) Iron-deficiency anemia
4. For which of
the following statements are there sufficient scientific evidence?
(a.) Beeturia is controlled by a single autosomal gene
(b.) Beeturia is dose dependant
(c.) Beeturia is determined by the concentration of ascorbic acid present
in the colon
(d.) Beeturia is determined by the concentration of oxalic acid present
in the colon
5. Which of the
following is betalain decolorized by in the human body?
(a.) Hydrochloric acid and ferric ions
(b.) Pancreatic enzymes and mucosal enzymes
(c.) Oxalic acid and ascorbic acid
(d.) Oxalic acid alone
6. Which of the
following does not influence the concentration of oxalic acid in the
(a.) The residue of oxalic acid not absorbed from the small intestine
(b.) The colonic bacterial metabolism
(c.) Urinary oxalic acid content
(d.) Amount of oxalic acid absorbed from the gut
7. True or false:
Individuals who present with beeturia after ingestion of one variety
can have no beeturia with another.
8. True or false:
Boiled beetroot leads to beeturia, whereas pickled beetroot does not.
|1. a [ ] b [X] c [ ] d
||2. a [X] b [ ]
||3. a [ ] b [ ] c [ ] d
|4. a [ ] b [ ] c [ ] d
||5. a [X] b [ ] c [ ] d
||6. a [ ] b [ ] c [X] d
|7. a [X] b [ ]
||8. a [ ] b [X]
1. b. 10-14%
2. a. True
3. d. Hematuria
4. d. Beeturia is determined by the concentration of oxalic acid present
in the colon
5. a. Hydrochloric acid and ferric ions
6. c. Urinary oxalic acid content
7. a. True
8. b. False