Vitamin
A in Grass Fed Beef
C.A. Daley1, A.Abbott1, M. Basurto1, G. Nader2, and S. Larson2
College of Agriculture, California State University, Chico1
University of California Cooperative Extension Service2
ProVitamin A: Beta-Carotene:
Beta-carotene, derived from the Latin name for carrot, belongs
to a family of natural chemicals known as carotenes or carotenoids.
Carotenes produce the yellow and orange color found in fruits
and vegetables and is converted to vitamin A (retinol) by
the body. While excessive amounts of vitamin A in supplement
form can be toxic, the body will only convert as much vitamin
A from beta-carotene as it needs, thus beta-carotene is a
safe dietary source for vitamin A supplementation.(University
of Maryland Medicine, 2002)
Vitamin A is a critical fat-soluble vitamin that is important
for normal vision, bone growth, reproduction, cell division,
and cell differentiation (Stephens et al., 1996). Specifically,
it is responsible for maintaining the surface lining of the
eyes and also the lining of the respiratory, urinary, and
intestinal tracts. The overall integrity of skin and mucous
membranes is maintained by vitamin A, creating a barrier to
bacterial and viral infection (Semba, 1998; Harbige, 1996).
In addition, vitamin A is involved in the regulation of immune
function by supporting the production and function of white
blood cells (Ross, 1999; Gerster, 1997).
The current recommended intake of vitamin A is 3,000-5,000
IU (International Units) for men and 2,300-4,000 IU for women
(National Institute of Health Clinical Center, 2002; Harvard
School of Public Health) which is equivalent to 900 - 1500
micrograms (mg). While there is no recommended dietary allowance
(RDA) for beta-carotene or other pro-vitamin A carotenoids,
the Institute of Medicine report suggests that consuming 3
milligrams(mg) of beta-carotene daily to maintain plasma beta-carotene
in the range associated with normal function and a lowered
risk of chronic diseases (National Institute of Health Clinical
Center, 2002).
Recent data suggests dietary sources of beta-carotene (pro-vitamin
A) are superior to supplemental Vitamin A (retinol) because
of suspected interference with normal calcium absorption.
Dietary retinol (Vitamin A) intake greater than 1,500 mg/day
was associated with reduced bone mineral density and increase
risk of hip fracture as compared to women who consumed less
than 500 mg per day (Melhus et al., 1998). Thus, dietary sources
of beta-carotene continues to be a preferred method of meeting
daily requirements for Vitamin A.
Beef fed through conventional feedlots contains approximately
41 mg of beta-carotene/100 grams (g) of ground beef and approximately
36 mg in a typical ribeye steak. Cattle fattened predominately
on ryegrass effectively doubles the beta-carotene content
in both steak (64 mg) and groundbeef (87 mg) (Simonne, et
al., 1996).
Although beef is not a major source of beta-carotene, grass-fed
beef supplies two times the beta-carotene of conventional
beef. A typical 3 ounce (oz.) serving would provide 10% of
the recommended dietary allowance (RDA) for beta-carotene
for women as compared to 5 % supplied by conventional beef
(National Institute of Health Clinical Center, 2002).
There is currently no data available on the fluctuation of
beta-carotene content in beef from cattle fattened on various
forages. Likewise, there is no data available regarding seasonal
effects on beta-carotene content in grass-fed beef grazing
pasture or native grass.
References
Contact information: C.A.Daley, Associate
Professor, College of Agriculture, California State University,
Chico, Chico CA 95929, cdaley@csuchico.edu.
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