Medical Nutrition Therapy Nutrient
What is the nutrient?
Zinc
What is the RDA/DRI for the nutrient?
The RDA and DRI’s for Zinc vary on the age and sex for each
person. The chart below summarizes the RDA and DRI
represented for each gender with age.
Age
Male
Female
0-6 months
2 mg*
2 mg*
7-12 months
3 mg
3 mg
1-3 years
3 mg
3 mg
4-8 years
5 mg
5 mg
9-13 years
8 mg
8 mg
14-18 years
11 mg
9 mg
(Pregnancy = 12mg)
(Lactation = 13mg)
19+ years
11 mg
8 mg
(Pregnancy = 11mg)
(Lactation = 12mg)
How is the nutrient metabolized?
When zinc is consumed, it is mainly absorbed in the small
intestine. When solid, whole foods are consumed, zinc is less
likely to be fully absorbed. This is due to the fact that zinc is not
stored in the body and is used as needed, when it enters the
body. When zinc is given to a fasting patient in aqueous
solutions, it is more readily absorbed, and efficiently absorbed
in comparison to a solid food diet.
What are food sources of the nutrient?
Zinc is present in a variety of foods that vary in quantity.
Oysters have the largest zinc content in comparison to all other
foods, but this is a food that is not typically consumed by many
Americans often. Americans generally obtain most of their zinc
from red meat sources, as well as poultry. Other sources
include, fortified cereals, nuts, beans, whole grains, beans,
legumes, crab, lobster and some dairy products. Other foods,
like grains, have a higher bioavailability because other vitamins
and minerals allow zinc to bind and be absorbed in the body.
What disease states alter the nutrients metabolism?
There are a few disease states that alter zinc metabolism. A few of
these diseases include; Crohn’s disease, Ulcerative Colitis, Short
Bowel Syndrome and other GI disorders or surgeries. These
diseases can drastically decrease zinc absorption (as well as other
vitamin and minerals), which in turn can result in a deficiency of
this nutrient. These diseases generally, let the nutrient bypass
through the entire GI tract. Other diseases that are sometimes
associated with zinc deficiency are, malabsorption, liver disease,
kidney disease, chronic diarrhea, diabetes and sickle cell disease.
What are the tests or procedures to assess the nutrient level
in the body?
There are a few examinations administered to test for zinc levels
in the body. A few of these tests include; the zinc taste test, the
serum zinc test, the plasma zinc test, the zinc tolerance test, and
the hair zinc test. The zinc taste test uses a zinc sulfate solution
for tasting and assess the patient’s responses that meet the
standards of the test. The easiest way of assessing zinc is by
measuring serum zinc but this form of testing tends to pose
inaccuracy of results because it only tests 250 µL of blood. The
most common test used is the plasma zinc test, which measures
the changes in plasma zinc after zinc is orally given to the
patient. The hair zinc test uses a sample of the patient’s hair, no
more than ½ gram, close to the scalp from the back of the head,
which is often used in research studies rather than specific
patient testing.
What is the drug –nutrient interactions?
There are some drug-nutrient interactions present with zinc. These
interactions may include; antibiotics, penicillamine and diuretics.
These pose problems if they are taken with a zinc supplement. The
absorption of zinc will be hindered if taken at the same time as
these medications and an increase of excretion will occur through
urination. To avoid deficiency when on antibiotics of
penicillamine, a zinc supplement should be taken a few hours prior
to the medication.
How is the nutrient measured?
This nutrient can be measured in multiple ways. The following
show the examinations that can measure zinc:
 Atomic absorption spectrometry (AAS)
 Atomic emission spectroscopy (AES
 Inductively coupled plasma-atomic emission spectroscopy
(ICP-AES)
 Flow injection analysis (FIA)
 Ammonium pyrolidine dithiocarbamate (APDC)
 Diethylammonium diethyldithiocarbamate (DDDC)
 Graphite furnace AAS (GF-AAS)
 Neutron activation analysis (NAA)
 Energy dispersive x-ray fluorescence (EDXRF)
 X-ray diffraction (XRD)
What is the Upper Tolerable Limits?
As seen with the RDA and DRI, the UL is also dependent on
gender and age. Below displays a chart of the UL for zinc:
Age
Male
Female
0-6 months
4 mg
4 mg
7-12 months
5 mg
5 mg
1-3 years
7 mg
7 mg
4-8 years
12 mg
12 mg
9-13 years
23 mg
23 mg
14-18 years
34 mg
34 mg
(Pregnancy = 34mg)
(Lactation = 34mg)
19+ years
40 mg
40 mg
(Pregnancy = 40mg)
(Lactation = 40mg)
What are the physical signs of deficiency?
Physical signs of deficiency:
 Growth retardation
 Impaired immune function
 Loss of appetite
 Diarrhea
Weight loss
 Delayed sexual maturation
 Hair loss
 Hypogonadism in males
 Skin lesions
 Delayed wound healing
What are physical signs of toxicity?
Physical signs of acute toxicity:
 Nausea, vomiting
 Loss of appetite
 Diarrhea
 Abdominal cramps
Chronic toxicity:
 Low copper status
 Altered iron absorption
Reduced immune function
 Reduced levels of HDL
References:
http://ods.od.nih.gov/factsheets/Zinc-HealthProfessional/
http://www.atsdr.cdc.gov/toxprofiles/tp60-c7.pdf
http://minerals.usgs.gov/minerals/pubs/commodity/zinc/
http://www.atsdr.cdc.gov/toxfaqs/tf.asp?id=301&tid=54
http://www.ars.usda.gov/is/ar/archive/mar02/zinc0302.htm