Experiments That Changed Nutritional Thinking - TUUM EST

1026S
SUPPLEMENT
TABLE 2
the body, certainly under ordinary conditions of life’’ (p. 475,
Chittenden 1904).
Perhaps it ought to be noted that these experiments did
not actually establish an average, minimum physiological re-
quirement for dietary protein in these groups of subjects because
1) the low protein diets were freely chosen by the professional
group, 2) the athletes were instructed to diminish the
intake of protein but without imposition of a specific diet,
and 3) the soldiers were given meals that contained lowered
amounts of protein than provided by ordinary army rations
and apparently with some reduction in the total ‘‘fuel value’’
of the food. The food given to each soldier was weighed, and
at the close of every meal the uneaten food was determined
and subtracted from the initial weight.
Although there has been some concern about the precision
and accuracy of the nitrogen balance data generated from
Chittenden’s experiments (McCay 1912, Carpenter 1994), including
the reliability of the urine and fecal collections and
determination of nitrogen intake, the results of these series of
experiments were coherent and dramatic. They presented a
strong case that the physiological needs for protein were much
lower than values represented by free-choice intakes of dietary
protein.
Chittenden’s conclusions were neither quickly nor univer-
sally accepted. For example, McCay (1912) referred to the
onslaught to Chittenden’s findings and ideas, but he used his
own data from dietary surveys of Bengalis, as well as the data of
others, to reach a conclusion that ‘‘Voit stands today absolutely
vindicated.’’ Although Cathcart (1911) was in ‘‘complete
agreement with Professor Chittenden’s statement that life can
be maintained and frequently maintained at a high level on
relatively low protein intake,’’ he was not sure if it was desir-
able to keep a low intake as a general rule, and he expressed
concern about the quality of protein. Later, he (Cathcart 1921)
voiced reservations that were related to the lowered resistance
to disease in persons consuming low protein diets. However,
Chittenden (1911) had already argued that the problem with
McCay’s studies was that the diets of the populations studied
in India lacked unidentified trace nutrients. This was probably
true, in retrospect, given the public health problems of iron,
vitamin A and iodine deficiencies that are prevalent in south-
east Asia today.
The protein standards for healthy individuals continued
to be set by the opinions of individuals until national and
international committees were convened to establish dietary
recommendations. An early international committee was set
up by the League of Nations, and in 1936 the recommendation
was that ‘‘the protein intake for all adults should not fall below
1 gramme of protein per kilogramme of body weight . . .’’
(League of Nations 1936). No scientific justification was presented
in support of the recommendation. In 1943 the U.S.
Food and Nutrition Board of the National Academy of Sci-
ences issued its first Recommended Dietary Allowances, and
in this report 66 g of protein daily was recommended. These
early figures proposed by expert groups were somewhat higher
than those found to be sufficient by Chittenden, but they were
far below the liberal standards that had been widely adopted
during the middle 19th and on into the early part of the
20th century. It seems clear, however, that by the 1950s the
metabolic approach used by Chittenden and others for establishing
protein requirements had been well embraced, to the
exclusion of the dietary intake approach followed by Voit,
Atwater and others. For example, at the Princeton Conference
in 1955, W. R. Aykroyd, the director of the nutrition division
of the Food and Agriculture Organization, stated: ‘‘We need
A typical day’s record of R. H. Chittenden’s diet and nitrogen
balance after 18 mo on his self-imposed experiment1
Sunday, June 26, 1904
Diet
Breakfast: Coffee 122 g, cream 31 g, sugar 8 g.
Dinner: Roast lamb 50 g, baked potato 52 g, peas 64 g, biscuit
82 g, butter 12 g, lettuce salad 43 g, cream cheese 21 g,
toasted crackers 23 g, blanc mange 164 g.
Supper: Iced tea 225 g, sugar 29 g, lettuce sandwich 51 g,
strawberries 130 g, sugar 22 g, cream 40 g, sponge cake 31 g.
Body weight Å 57.4 kg (initial weight in November 1902 Å 65 kg.
Age 47 y)
Protein intake Å 0.64 g/kg
N balance Å00.07 g N
Energy intake Å 1549 kcal
1 Data from Chittenden (1904).
Back then was no different than today, in that Chittenden
needed financial support for the conduct of his investigations.
He secured funds from the Carnegie Institution of Washington
and the Bache Fund of the National Academy of Sciences,
and he also received large donations from Fletcher and John
H. Patterson of Dayton, Ohio.
The overall investigation consisted of three major experi-
ments, each characterized by a long-term period of dietary
protein restriction combined with nitrogen excretion measure-
ments and supplemented in some studies with assessments of
physical and mental well-being. Chittenden (1904) states
‘‘The writer, fully impressed with his responsibility in the conduct
of an experiment of this kind, began with himself in
November 1902.’’ He therefore served as one of the subjects
in his study of five university professors and instructors, includ-
ing his former student Lafayette Mendel, who by that time
had become professor.
On the basis of his own experience (Table 2), including the
disappearance of the rheumatic problem he had been having
in his knee joint and the findings with the other four Yale
professionals, Chittenden concluded that the minimum ‘‘proteid’’
requirement was 93–103 mg N/kg body wt (about 0.6–
0.64 g proteinrkg 01 rd), which anticipates, by 80 years, the
mean requirement figure of 0.6 g proteinrkg 01 rd 01 propos-
ed by FAO/WHO/UNU (1985)!
The next two series of studies confirmed and strengthened
these initial findings; one of these was with 13 members of a
detachment from the U.S. Army Hospital Corps, who were
housed in Vanderbilt Square at Yale for 6 mo. The study
included measures of physical and mental condition and of
blood composition in addition to nitrogen excretion and bal-
ance over the 6-mo period. The conclusion was that 50 g of
protein daily can establish nitrogen equilibrium and that there
is, at this approximate intake, a maintenance of physical
strength and vigor and an ability to respond to sensory stimuli.
In a follow-up letter written to Chittenden by one of the
participants, Private First Class J. Steltz, and on behalf of the
other men, he stated: ‘‘The men are all in first-class condition.
. . . We eat very little meat now as a rule, and would willingly
go on another test.’’ The extensive findings in a third series
involving eight Yale University athletes merely served to repli-
cate all of these data and the interpretations that had been
drawn from them.
Thus, Chittenden concluded that one-half of the 118 g of
protein called for daily by the ordinary dietary standards is
quite sufficient to meet all the real physiological needs of
/ 4p09$$0062 04-07-97 14:02:12 nutras LP: J Nut May Suppl
Downloaded from jn.nutrition.org by on June 3, 2010