Agriculture Reference
In-Depth Information
AbstRAct
The history of the discovery of vitamins and essential minerals has been reviewed,
including particularly significant findings from the seventeenth to the late twenti-
eth century. Current knowledge of functions, absorption, metabolism, and dietary
sources of 4 fat-soluble vitamins, 9 water-soluble vitamins, and 15 mineral elements
required by humans and many animals is included. Quantitative requirements for
these nutrients at various ages, physiological states, levels of physical activity, and
environmental circumstances are regularly revised based on new data. Ranges of cur-
rently recommended allowances for these nutrients in human diets are presented.
vItAmIn begInnIngs
Identification of biologically vital elements in the late 1700s, during the “chemi-
cal revolution” in France, provided a foundation for subsequent discoveries of the
essential nutrients. In 1842, Justus von Liebig, a German organic chemist, stated that
protein was the only true nutrient, providing both the structure of muscle and the
energy for its contraction. However, an 1847 account of scurvy in Scottish prisoners
consuming ample protein (but no potatoes) and its prevention by lemon juice (con-
taining negligible nitrogen) belied Liebig's conclusion. In fact, James Lind showed
in 1746, in a controlled experiment, that citrus fruit, but not sulfuric acid or vinegar,
cured scurvy. Thus, the effectiveness of oranges, lemons, and limes was known for
almost 200 years before the active agent was finally identified in 1932 as ascorbic
acid, 4 years after its isolation from adrenal glands by Albert Szent-Györgi.
Rickets was common in young children in large industrialized cities in Western
Europe during the late 1800s, even when calcium intakes appeared adequate. Those
affected were often fed breast milk substitutes (which tended to be low in fat) and
had limited sun exposure due to airborne pollution. Walter Cheadle in 1888 con-
cluded that rickets could be prevented by cod liver oil, and Theobald Palm noted in
1890 that rickets was rare in regions with lots of sunlight. In 1924, it was established
that ultraviolet (UV) irradiation of rats or of their diet would prevent the disease.
The activated dietary factor was found to be lipid soluble, was named vitamin D
(because ascorbic acid had previously been designated vitamin C), and was crystal-
lized in 1931.
Other observations relevant to the vitamin story were made by the microbiolo-
gist Pekelharing in 1888 concerning beriberi in the army of the Dutch East India
colony. Although he thought an unusual bacterial infection might be responsible for
this condition, an infectious origin could not be confirmed. Knapp in 1909 observed
eye lesions (xerophthalmia and keratomalacia) that were responsive to cod liver oil
in rats fed a purified diet. Ultimately, the curative factor was identified and named
vitamin A.
Despite this early history and studies from 1900 to 1911 by Gerritt Grijns, who
concluded that a polyneuritis in chickens fed white rice was caused by a deficiency
of an unstable, water-soluble, organic compound, the vitamin era is commonly stated
to have begun in 1912 with the studies of beriberi in humans by Casimir Funk. He
isolated a water-soluble organic compound containing an amine group from rice
