Measurement and Dietary Assessment of Vitamin A: A Detailed Analysis

This report provides a comprehensive analysis of vitamin A assessment, encompassing both measurement techniques and dietary evaluation. It begins with an introduction to vitamin A, its importance, and its various forms, including retinol, retinyl esters, and retinoic acid. The report then delves into the laboratory methods used to measure vitamin A levels, focusing on high-performance liquid chromatography (HPLC) and liquid chromatography-mass spectrometry (LC-MS), highlighting their sensitivity and efficacy. A detailed literature review explores the biochemistry of vitamin A, its role in the body, and the clinical significance of its levels in serum. Furthermore, the report outlines critical considerations in the vitamin A testing process, including patient preparation, sample collection, sensitivity to light and temperature, transportation, and storage. Dietary assessment methods, such as 24-hour dietary recall, are also discussed, emphasizing the importance of evaluating vitamin A sources and understanding potential deficiencies. The report underscores the significance of vitamin A in maintaining health and preventing related diseases, providing valuable insights for healthcare professionals and students in nutrition and related fields.

Running head: ASSESSMENT OF VITAMIN A 1
Measurement and Dietary Assessment of Vitamin A
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Measurement and Dietary Assessment of Vitamin A
Introduction
Vitamin A is an important micronutrient in the body because it regulates various
activities like vision, improvement of immunity [2]. Vitamin A is one of the fat-soluble
vitamins that are naturally obtained from plant and animal sources. Many professionals in
laboratory medicine have provided various views on the efficacy of high-performance liquid
chromatography (HPLC) in the determination and assessment of fat-soluble vitamins in the
bodies in food and human serum. The improved sensitivity of the HPLC increased the
interests of professionals in using the multi-facet approach in the assessment of the nutritional
importance of vitamin A; therefore reducing the cases of deficiencies [1]. The prevention of
vitamin A deficiencies results in reduction of the risks of chronic diseases; therefore,
improving general public health status. All fat-soluble vitamins have similar characteristics,
especially in the biological dynamics. All fat-soluble vitamins are also biochemically and
chemically distinct because they have different metabolism, absorption, distribution and
clearance in the human body despite. Vitamin A can easily be measured in blood because
they are found in higher levels in the serum as compared to other fat-soluble vitamins like
vitamins K and D [3].
The assessment of vitamin A and other fat-soluble vitamins in human serum is
important because their lower levels in the body may be compromised especially in the cases
of diseases the interfere with fat absorption like inflammatory bowel disease, tropical sprue,
coeliac disease, cystic fibrosis, and short bowel syndrome [9]. Additionally, in developing
countries, malnutrition is a common is one of the problems that affect public health status.
Malnutrition is the main cause of deficiency of fat-soluble vitamins, especially vitamin A.

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The main reason for the assessment of vitamin A in serum is to avoid the consequences
related to its deficiencies and also to confirm the type of the disease experienced by a patient.
Literature Review
Liquid chromatography-mass spectrometry is one of the analytical method used in
clinical chemistry to determine the concentration of compounds found in liquid or solution
[1]. LC-MS is an analytical method that combines the mass capabilities of mass spectrometry
and separation properties of liquid chromatography [4]. A critical analysis and review of the
literature provide comprehensive information on the important considerations to be applied in
the vitamin A testing process. The use of HPLC and LC-MS techniques in the measurement
and analysis of vitamin A are considered due to their efficacies and sensitivities [5]. The LC-
MS technique contains an interface used to transfer components that have been separated
from the LC column to the source of the mass spectrometry ions in the system.
The interface between the liquid chromatography and mass spectrometry is important
because the components may be incompatible. In most cases, the LC system comprises of
pressurized liquid and the MS analysers are normally operated in a vacuum. Research has
shown that it not easy to pump elute substances directly from the LC column [12]. In most
cases, the interface in the system is a simple mechanical part of the LC-MS technique that
normally transfers a maximum sample, preserves the chemical identity of the products and
removes a considerate portion of the mobile phase in the column.
The measurement and analysis of vitamin A levels in food and serum are normally
done using the high-performance liquid chromatography (HPLC) [8]. In analytical cases, the
preparative stages used for the sample include saponification. This saponification stage
involves the heat sensitivity of the sample to be analysed through the use of HPLC. The
HPLC method of vitamin A assessment is important because it is recommended and defined

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by the ISO standards [7]. The review of the literature is also essential because important
factor like time of saponification and the temperature of the sample is determined to ensure
the sensitivity in the analytical process. The temperature and time of the process are normally
expressed in values ranges to provide consistency since exact setting may lead to misleading
information and analytical errors.
Biochemistry of Vitamin A
Biochemists have mentioned that the term retinoid is used to describe any compound
that exhibits the activity of vitamin A in all biological systems of life. Vitamin A is a loose
terminology in the nutritional context because of the existence of different forms of the
biological compounds contributing to the total intake of vitamin A in diets. Retinoid is a
preferred term over vitamin A in the analytical process especially when it comes clinical
laboratory diagnosis. Vitamin A exists in serum in different forms that are tightly controlled
by the body processes [13]. Vitamin A also occurs in nature in various distinct forms like
retinoic acid, retinol, and retinyl esters. Retinol is the alcohol form of vitamin A that
predominates in the circulatory system. Retinol is not stored in the body because of its
toxicity. In some cases, the liver converts retinol into retinyl esters like palmitate for storage.
Adehyde component called retinal is the active form of vitamin A in the visual cycle.
Retinoic acid is the form of vitamin A in tissues that is responsible for initiating all
biological actions in the body. Retinol is the most measured form of vitamin A in the blood
serum [14]. Retinoid is easy to detect in serum because all of them contain a cyclohexane
ring in their structures. The ring is permanently attached to the tetra-isoprene chain. The main
reason for measuring the level of vitamin A in routine clinical practices is to determine if the
body has sufficient forms of retinoids to maintain the metabolic need in the body and prevent
diseases related to their accumulation and deficiencies. The interest of the assessment process

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is to determine the status of vitamin A but not its levels. In most cases, vitamin A status
relates to the metabolic requirements in the body [1]. The status of vitamin A in the blood
serum is one of the essential clinical issues in laboratory medicine because insufficient
amounts in the body lead to its deficiencies and the related health conditions.
According to results from the laboratory medicine practice, the level of retinol in
serum does not relate to the amount of retinyl ester stored in the liver. The amount of retinyl
ester stored in the liver tissues depends on the body need and the physiological processes.
Despite the limitation from the differences between the levels of retinol and retinyl esters,
retinol is a useful component of vitamin A because its levels will reduce if the levels supplied
from the liver decreases. Night blindness is manifested when the level of the retinol
decreased to an extent that result in vitamin A deficiency in the body [16]. Other serious
conditions are also manifested when the level of retinoic acid is decreased; therefore,
depleting the stored retinyl esters.
The dietary supplements of vitamin A have been common among some patients in
Australia. The supplements of vitamin A are normally recommended for children who are not
receiving breast milk from their mothers. World Health Organization (WHO) have also
recommended for the appropriate amount of supplements for people with vitamin A
deficiencies and related medical conditions especially in the developing countries [14]. Also,
it is pivotal to know that the fundamental amounts of vitamin A normally exists in narrow to
note that the beneficial range of vitamin A exists within a narrow range and its toxicity occurs
when the levels exceed the required ranges. Acute vitamin A toxicity occurs when the levels
of the components exceed the required ranges for maintenance of metabolic activities.
Consideration in Vitamin A Testing process

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From the research studies, it is clear that the measurement of vitamin A for nutritional
assessment involves various steps [7]. To determine the level of and status of the vitamin in
the blood serum and other body fluids, various considerations are used in the testing process.
The appropriate analytical process is also identified based on their sensitivities and the
expected outcomes. First, patient preparation is one of the considerations in the vitamin A
testing process. In routine laboratory medicine practice, vitamin A is collected from non-
fasting patients for the testing and analytical processes. The consumable vitamin A is
normally in the form of retinyl esters which are then hydrolysed during metabolic activities
into retinol [10]. The hydrolysis of the retinyl esters in the body makes it easy to detect even
low levels of retinol after a meal. Plant sources provide the nutrient in its precursor form
called pro-vitamin A. the precursor form is also called Beta-carotene that is then converted
through enzymatic activities to retinal. The formed retinal is then converted to retinal
following a series of enzymatic activities in the body.
Secondly, the collection is taken into consideration to ensure that the analytical and testing
processes are appropriate. Appropriate sample collection promotes the generation of relevant
results [13]. Two millilitres of heparinised or plan blood is collected using the venipuncture
method. Arterial phlebotomy technique may also be used in the sample collection provided
the required volume of blood is obtained. The blood is collected into an ethylene-diamine-
tetra-acetic acid (EDTA) tube, heparin tube or in a gel separator [11]. The third consideration
in the testing process is the sensitivity to temperature and light. Vitamin A has the highest
photosensitivity as compared to other fat-soluble vitamins in the blood; therefore, the
collected blood sample should be protected from any source of life. To protect the blood
sample from light, the tubes are wrapped using aluminium foil.
The fourth consideration in the vitamin A testing process is the transportation of the
collected sample. If possible the collected blood should be sent into an appropriate laboratory

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before the end of 48 hours. The transportation temperature should be 20 degree Celsius. In
most cases, chilling the collected whole blood may extend their stability period to a
maximum of four days. Also, storage contributes to the factors to be considered in the
vitamin A testing process. According to the critical analysis and evaluation of the literature,
the collected sample for the measurement of vitamin A must be frozen at -70 degree Celsius
[15]. Freezing of the blood sample at -70 degrees Celsius is important in avoiding
denaturation of vitamin A in high temperatures. According to the laboratory medicine report,
it is clear that vitamin A stabilizes with time without any alteration caused by the increasing
temperature and duration of sample storage.
Dietary Assessment of Vitamin A
Dietary assessment is one of the pivotal consideration in the toolkit of vitamin A
assessment process due to lack of appropriate and sensitive biomarkers. The use of dietary
assessment approach is also important since the laboratory medicine experts have not
identified appropriate long-term and short-term exposure coefficients for vitamin A. the
effective methods used in the dietary assessment of vitamin A include the 24-hour dietary
recall method, analysis and examination of dietary records, use of assessment dietary
instruments, and evaluation of diet history [6]. For effective dietary assessment of vitamin A,
researchers have applied more efforts on the evaluation of the sources of the nutrient and the
nature of fortification used in the respective countries. Seasonality of the potential sources of
vitamin A also affects the process of dietary assessment.
The deficiency of vitamin A manifests through various symptoms like night blindness
and dermatological conditions when dietary intake is limited; therefore, failing to meet the
body needs. Vitamin A toxicity does not occur when an individual consumes a lot of fruits
and vegetables because the body can down-regulate the level of vitamin A by inhibiting the

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activation of precursor forms. Research has also shown that increases concentration of
vitamin A in diets and the retinyl esters in the liver also increases the levels of vitamin A in
the blood plasma [5]. Vitamin A has various roles in the body, especially when in the
maintenance of normal physiological functions and prevention of illnesses. Different tools are
used in laboratory medicine to assess and evaluate the essential biological/physiological
functions of vitamin A in the body.
To conclude, the main takeaways in the measurement of vitamin A for nutritional
assessment is important in determining the prevalence and incidences of diseases related to
vitamin A deficiency. Vitamin A is also assessed to determine how they function as
biomarkers in the diagnostic procedures.

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