The habitual pattern of consumption of food and drink.
That which supplies a deficiency or fulfills a need.
semantically inclined will, no doubt, perceive an element of inconsistency
in the title of this contribution. Any food(stuff) ingested for
a nutritional purpose is, it could be argued, ipso facto a dietary
component. To refer to "nonfood dietary supplements" would,
therefore, be meaningless.
the other hand, foods are often defined in traditional historical
terms, and it is apparent that there are a substantial number of
"nutritionally significant" substances which, although
not ordinarily components of a diet, may nevertheless be ingested
in special circumstances. Whether such "foreign" substances
are then described as food(stuffs) or as dietary nonfood(stuffs)
is very much a matter of opinion.
issue is further clouded by a tendency to regard foods as being
of natural origin, whereas certain dietary supplements, although
having a clearly definable nutritional role, may nevertheless have
a "nonnatural" (synthetic) origin. And whereas "true"
foods are rarely challenged in terms of potential toxicity, this
is not the case with supplements as evidenced, for example,
by the American report on the safety of amino acids used as dietary
supplements (Anderson, Fisher, and Raiten 1993).
one must distinguish between nonfoods as dietary supplements and
nonfoods as dietary components. Geophagists, picaists, and drug
addicts may, in certain circumstances, ingest large amounts of nonfood
materials, but these fall outside the scope of this discussion.
Supplementation implies that the additional material is introduced
intentionally for an avowedly dietary reason and is a substance
that could not, in normal circumstances, be supplied by realistic
the purpose of dietary supplementation is to improve the nutritional
status of the subject (thus distinguishing dietary supplements from
pharmacological treatments), its practice must be congruous with
generally accepted nutritional thought which, in turn, implies
that the intentional use of dietary supplements is a development
of fairly recent origin. Consequently, the significance attributed
to many nonfood supplements has, in recent years, ebbed and flowed,
thereby reflecting the kaleidoscopic nature of orthodox nutritional
the same token, it is equally apparent that the concept of nonfood
dietary supplements is a relative one, with the lines of categorization
shifting from community to community. Thus dietary fiber, a widely
advocated nonfood dietary supplement in the Western European diet,
would have no such status in many African communities. Equally difficult
to define is the distinction between the use of a supplement in
a dietary capacity and its use as a pharmacological agent. Megadoses
of ascorbic acid (vitamin C) may, in this respect, be contrasted
with the more moderate levels used for orthodox dietary supplementation;
and the use of arginine to modify immunity and intestinal carrier
systems could, it may be argued, reflect a pharmacological, rather
than a nutritional, role for supplementation (Hirst 1993; Park 1993).
the late nineteenth century, the categorization of foods in functional
terms had progressed considerably. Foods were described as "body-building"
(nitrogenous) or "energy-forming" (nonnitrogenous), and
there was, consequently, a tendency to simplify dietary concepts
and to limit precepts to recognizably bona fide members of these
two groups. However, by the turn of the century, the recognition
of the role of vitamins nonfoods in a quantitative sense
and the blurring of the lines of demarcation between "energy"
and "growth" foods provided a more flexible conceptual
framework for the proliferation of ideas about the usefulness of
chapter therefore deals with substances that, without falling into
the conventional categories of dietary components (protein, energy
sources, vitamins, and minerals), are nevertheless believed to enhance
dietary effectiveness. They would not, in normal circumstances,
be supplied by customary dietary components either because
the foods containing them are ingested in supposedly inadequate
amounts (as in the case of dietary fiber in certain communities)
or because the substance in question is not readily available from
food(stuff) sources. This latter category is, in evolutionary terms,
less likely to exist and, it could be argued, implies more of a
pharmacological relationship than a nutritional one. Perhaps with
this in mind, Michele Sadler, in a recent discussion of dietary
supplements, has referred to them as "Functional Foods"
and has defined them as lying between foods and pharmaceuticals
examples of "nonfood" dietary supplements are discussed
below. All have achieved, at different times, some significance
as supplements during the last 40 years or so, and they represent
three "etiologically" different categories.
term "bioflavonoids" has been widely used to refer to
those flavonoids that are believed to have pharmacological or nutritional
properties. They have no apparently essential role in nutrition
and, consequently, no daily requirement can be specified. Nevertheless,
for a period of some 30 years they were held to have an "adjuvant"
role in maintaining good health possibly by enhancing the
activity of vitamin C.
flavonoids are a large group of plant compounds based on a C6C3C6
skeleton. They are of widespread distribution in the plant kingdom,
being virtually ubiquitous in angiosperms and also existing in more
primitive groups, such as green algae, and Bryophyta, including
Hepaticae. It has been estimated that in the West, the average per
capita daily intake of bioflavonoids is approximately 1 gram (g)
(Middleton 1988). Higher animals have, perforce, evolved in an environment
in which, of necessity, their feeding habits exposed them to a wide
range of flavonoid material, ingested as "secondary" components
of foodstuffs. It is, therefore, quite conceivable that this evolutionary
exposure to a wide range of flavonoids has elicited physiological
and biochemical responses in higher animals. Certainly some bioflavonoid
features, such as their ability to chelate with metals and the antioxidant
activity associated with hydroxyl groups, indicate a considerable
potential for biochemical involvements.
first attracted the attention of nutritionists in the 1930s when
Hungarian workers reported that certain vegetables and fruits (notably
citrus) contained substances capable of enhancing the antiscorbutic
properties of ascorbic acid (vitamin C) and even of partially substituting
for it. It was claimed that "the age-old beneficial effect
of fruit juice is partly due to its vitamin P [sic] content"
(Bentsáth, Rusznyák, and Szent-Györgyi 1937:
327); it was also suggested that "citrin," a flavonoid
preparation, could prolong the survival period of scorbutic guinea
pigs and that extracts of Citrus limon and Capsicum annuum
could correct capillary fragility a condition characteristic
of ascorbic acid deficiency (Bentsáth, Rusznyák, and
Szent-Györgyi 1936). The new factor(s) was regarded as separate
from vitamin C and was designated "vitamin P" (Rusznyák
and Szent-Györgyi 1936), and sometimes was named, primarily
by French workers, the "C2" factor. However, the true
nature of the relationship (if any) between the bioflavonoids and
vitamin C was unclear, and later work indicated that some of the
earlier results were probably attributable to traces of vitamin
C in the flavonoid preparations. Nevertheless, by the late 1930s
the bioflavonoids had acquired a niche, albeit a minor one, in the
annals of vitaminology. But considerable reservations remained about
their real nutritional significance (Harris 1938: 28).
1949 Harold Scarborough and A. L. Bacharach published an important
review article summarizing the work done between 1935 and 1949,
and dismissing any suggestion that vitamin P could generally substitute
for vitamin C. They centered their attention on the influence of
bioflavonoids on capillary resistance and quoted with approval an
earlier statement that "guinea pigs placed on a scorbutic diet
supplemented with adequate amounts of ascorbic acid show a decline
in capillary strength . . . restorable by vitamin P"
(Scarborough and Bacharach 1949: 11).
consensus of opinion in 1950 was that flavonoids were of physiological
significance and that their main influence (on capillary resistance)
was mediated independently of vitamin C. Nevertheless, the Joint
Committee on Biochemical Nomenclature (United States) recommended
in 1950 that the term "vitamin P" be replaced by the designation
"bioflavonoids"; and in 1980 the (U.K.) Committee on Dietary
Allowances of the Food and Nutrition Board (COMA) indicated that
the bioflavonoids should be regarded as pharmacological, rather
than as nutritional, agents.
in the possible nutritional significance of bioflavonoids forged
ahead during the 1950s (see Table VII.11.1), with a continuing emphasis
upon their possible adjuvant relationship with vitamin C. It is
interesting to note that almost half of the bioflavonoid papers
published during the period from 1948 to 1957 dealt with the specific
bioflavonoid rutin (quercetin-3-rutinoside). Rutin was widely used
at the time in model experimental systems and is still sold as a
dietary supplement, sometimes in the form of extracts of buckwheat
(Fagopyrum esculentum), one of its principal natural sources.
Other specific compounds to receive attention by nutritionists were
quercetin and hesperidin.
on bioflavonoids was extended in the 1950s and 1960s to include
a wide range of supposed physiological and biochemical involvements.
Possibly for historical reasons, workers in Eastern European countries
were particularly active in this respect. K. Böhm, in his 1968
monograph, cited some 40 definable influences of flavonoids in humans
although the evidence for many of these was weak and sometimes
contradictory. M. Gabor, in his 1972 monograph, dealt almost exclusively
with one of these suggested areas, namely the supposed anti-inflammatory
effect of flavonoids. Other, and more overtly nutritional, areas
where bioflavonoids were believed to have a role were hepatic detoxication
and lipid utilization (Hughes 1978).
by the 1960s, interest in a nutritional role for bioflavonoids had
peaked, along with their associated use as dietary supplements (see
Table VII.11.1). Thereafter the main nutritional interest in bioflavonoids
centered on their supposed synergistic relationship with vitamin
C and their possible role as antioxidants. There was substantial
evidence that bioflavonoids could "enhance" the ascorbic
acid status of hypovitaminotic C guinea pigs, and much work in the
1960s and 1970s was aimed at elucidating the nature of this relationship.
Discussions centered on whether bioflavonoids could actually substitute
for (or synergistically assist) vitamin C in some of its roles,
or whether they increased the availability of vitamin C either by
protecting it from oxidative breakdown in the tissues or by enhancing
its absorption from the gastrointestinal tract (Hughes and Wilson
aspects of flavonoid metabolism attracted some attention
their antioxidant capacity and, in some cases, an apparent mutagenicity.
But studies of the nutritional significance of these features gave
inconsistent and difficult-to-interpret results. For example, one
study dealing with mice indicated that, whereas a dietary supplement
of quercetin shortened life span, a flavonoid-rich extract of black
currants (containing quercetin together with other flavonoids) extended
it (Jones and Hughes 1982). Moreover, none of these studies provided
any incontrovertible evidence of an essential role for bioflavonoids
in nutrition, and a recent reviewer opined that their function in
health and disease as natural biological response modifiers still
needed to be determined (Middleton 1988). M. M. Cody, in a contribution
to the Handbook of Vitamins, dealt with bioflavonoids under
the heading "Substances without vitamin status" (Cody
there remains a certain amount of residual evidence favoring the
use of bioflavonoids as a dietary supplement to enhance the absorption
of vitamin C from the gastrointestinal tract and, possibly, its
subsequent retention by the tissues (Hughes and Wilson 1977). As
a consequence, to advocate the ingestion of "natural"
vitamin C (as, for example, in the form of bioflavonoid-rich black
currant juice) rather than the synthetic "tablet"
form of the vitamin by persons otherwise recalcitrant to
vitamin C absorption (such as the elderly) is not entirely without
the decade 19809, however, only 30 "nutritionally orientated"
bioflavonoid publications could be identified, and general interest
in the erstwhile suspected nutritional role of bioflavonoids and
in their consequent use in dietary supplementation would now appear
to be waning.
recent COMA report dismissed them as an "unnecessary substance"
and made no recommendation for their use as a supplement.
were many "latent" references to dietary fiber before
it was identified and characterized as a specific dietary component.
Early writers on diet, such as Thomas Elyot (The Castel of Helth
. . . ), Ludovicus Nonnius (De Re Cibaria
), and Thomas Moffet (Healths Improvements ),
who referred to the laxative property of whole-meal bread (when
compared with lower-extraction-rate breads), were in reality commenting
on the fiber content.
Cogan, the Elizabethan dietitian, wrote in his The Haven of Health:
"Browne bread made of the coursest of wheate floure, having
in it much branne . . . shortly descendeth from the stomacke
[and] . . . such as have beene used to fine bread, when
they have beene costive, by eating browne bread and butter have
been made soluble" (1612: 25).
Thomas Venner, the Bath physician, wrote of whole-meal bread in
his Via Recta ad Vitam Longam that
reason of some part of the bran which is contained in it, it doth
sooner descend and move the belly, for there is a kind of abstersive
[laxative] faculty in the bran: wherefore for those that are healthy,
and yet subject to costiveness, and also for such as would not
wax grosse, it is most profitable (1638: 25).
comment is curiously congruous with the standpoint adopted by present-day
Trowell, in his extensive bibliography Dietary Fibre in Human
Nutrition (1979), mentions a paper written in 1919 as the earliest
to deal with definable fiber (cellulose) per se. Arthur Rendle-Short,
a British surgeon, argued in the 1920s that epidemiological evidence
suggested a relationship between lack of dietary cellulose and the
incidence of appendicitis. The earliest title in Trowells
bibliography to contain the term "fibre" was one by M.
A. Bloom, published in 1930.
was not until the 1970s, however, that a wide interest emerged in
the nutritional significance of what had been regarded, until then,
merely as dietary "roughage," or waste material. Three
names are usually associated with this phase in the history of fiber.
One is that of T. L. Cleave, a British naval doctor, who argued
(1974) that a number of pathological conditions were probably attributable
to an increased intake of refined sugar and starch. Although Cleave
did not emphasize the mirror image of his thesis namely,
that an increasingly refined diet was in reality a low-fiber one
he has, nevertheless, been widely, and somewhat incorrectly,
hailed as a pioneer of current dietary fiber hypotheses.
more overt and direct link between fiber lack and disease was promulgated
in the 1970s by Hugh Trowell (1979; see also 1985) and by Denis
Burkitt (1971), and the genesis of modern fiber studies has become
almost synonymous with their names. Burkitt himself, in tracing
the early history of thought on fiber, has included a fourth name,
that of A. R. Walker of South Africa. The number of identifiable
publications on the subject of dietary fiber rose from an annual
average of 10 in the late 1960s to 125 in the early 1970s; 10 years
later (in 1983), the average had risen to well over 500. Trowells
original thesis (1960) stemmed from his observation that a number
of diseases that appeared to be characteristic of affluent Western
technological communities were rare or absent in the more "primitive"
parts of Africa with which he was familiar. He drew particular attention
to the differential incidence of diseases of the gastrointestinal
tract and suggested that a high consumption of fiber-rich foods
was protective against noninfective diseases of the large bowel.
Similarly, and independently, Burkitt (in 1971) published his evidence
that dietary fiber might be protective against colorectal cancer.
that time, however, there was no generally accepted definition of
dietary fiber, and much confusion stemmed from the use of values
for "crude" fiber (the residue left after serial extraction
with acid and alkali). This was a measure that excluded the bulk
of the cellulose and hemicellulose material, both important components
of dietary fiber. The problem of definition was, of course, inextricably
linked to difficulties in the development of a method for the accurate
determination of fiber (Englyst and Cummings 1990). Trowell, in
1971, defined dietary fiber as the plant cell material that was
resistant to digestion by the gastrointestinal enzymes, and this
became the accepted definition. More recently the term "dietary
fiber" has been displaced by the resurrected form "nonstarch
polysaccharide material," which reflects current analytic procedures.
original "dietary fiber hypothesis" was soon extended
by other workers to embrace suggested relationships between dietary
fiber and nongastrointestinal diseases, particularly cardiovascular
disorders (for example, Judd 1985; Kritchevsky 1988). Epidemiological
studies indicated a negative correlation between fiber intake and
the incidence of cardiovascular disease, and experimental studies
showed that certain types of dietary fiber were potent hypocholesterolemic
agents. However, relationships of this type posed a problem. By
definition, dietary fiber was a substance that did not leave the
gastrointestinal tract. How then could one explain its supposed
was it always easy to distinguish between a direct protective effect
of fiber and a displacement effect on "harmful" dietary
components. Mechanisms based on a fiber-mediated inhibition of cholesterol
absorption or an increased bile acid excretion were among those
mooted. But much of the epidemiological work related to fruit and
vegetable intake and not to intake of fiber per se. M. L. Burr and
P. M. Sweetnam (1982), however, found that in Wales, a vegetarian
lifestyle could be correlated with a reduced incidence of heart
disease, but fiber intake could not.
picture was further complicated by the interrelationships now known
to exist between dietary fiber and the intestinal flora. This is
a complex two-way relationship. Not only are certain types of fiber
subject to degradation by colonic bacteria, but there is also increasing
evidence that fiber itself may, in turn, modify the nature and metabolic
activity of the colonic flora, with consequent modifications to
the formation and absorption of a wide range of metabolites. Considerations
of this type have led to suggestions that dietary fiber may modify
the estrogen status in females, with consequent implications for
a protective role for fiber in breast cancer and, possibly, other
cancers (Hughes 1990; Adlercreutz 1991).
current consensus would appear to favor an increased fiber intake
in the Western-type diet, but an optimal intake has yet to be clearly
delineated. Appeals to primitive dietary patterns are of little
help in this respect, as the fiber intake of humans has fluctuated
substantially during their stay on earth. Estimates based on coprolite
analysis have indicated substantially higher ingestion of dietary
fiber by primitive peoples than by their present-day descendants,
with daily intakes of 100 to 200 grams occurring at certain periods.
In addition, there have been significant changes in fiber intake
at critical points in the socioeconomic development of humanity,
such as during the "neolithic transition" (Eaton 1990).
years after the birth of the fiber hypothesis, Rodney H. Taylor,
in a leading article in the British Medical Journal (1984),
questioned the prophylactic usefulness of high-fiber diets except
for improving colonic function and alleviating constipation. Recent
dietary precepts are almost equally noncommittal in their advocacy
of dietary fiber. The most recent COMA recommendation (1991) echoed
Taylors doubts. Although advocating an increase in NSP (nonstarch
polysaccharides) from the current average intake of 13 g/day to
18 g/day to improve bowel function, the committee was unable to
find sufficient evidence for a direct mediating influence of fiber
in other suggested areas, such as diabetes and cardiovascular disease.
Moreover, the increased intake, it was suggested, should be attained
by dietary manipulation, rather than by overt supplementation. It
is possible that after a quarter of a century of often frenzied
investigative activity, the dietary fiber movement is beginning
was discovered at the beginning of this century when its presence
in Liebigs meat extract at the time a popular dietary
supplement was reported. Twenty years later its structure
was elucidated, and it was shown to be (beta-hydroxy-gamma-(trimethylamino)-butyric
acid. But it attracted little biochemical or nutritional attention
until the late 1950s when its role in the metabolism of fats was
described. Reviewing the situation at that time, G. Fraenkel and
S. Friedman wrote that "a small amount of evidence has been
pieced together indicating that carnitine may be active in the metabolism
of fats or their derivatives" (1957: 104).
in vivo studies with labeled fatty acids confirmed this conclusion,
and within a few years the role of carnitine in stimulating the
mitochondrial oxidation of fatty acids was generally accepted (Olson
1966). Subsequent investigations revealed the nature of the mechanism
of this stimulation when it was shown that carnitine acts as a transport
molecule for the movement of long-chain fatty acid molecules into
the mitochondrial matrix. A number of situations in which carnitine
has a derived or secondary role as a buffering agent for acyl groups
have also been described (Cerretelli and Marconi 1990).
lack of carnitine, or a reduced or defective activity of one or
more of the transport enzymes, would therefore reduce the availability
of fat as a source of energy. This could be significant in cases
where it is believed that a substantial proportion of the energy
metabolism is derived from fat as in the newly born infant
or in cardiac muscle metabolism. It would appear, however, that
in the short term, substantial falls in carnitine are required before
an impairment of fatty acid oxidation becomes apparent (Carroll,
Carter, and Perlman 1987).
body is able to biosynthesize carnitine, and by the 1980s the biosynthetic
pathway had been elucidated. It was shown that the precursor molecules
were lysine and methionine, two essential dietary amino acids. The
lysine is methylated by the methionine to form the protein-bound
trimethyllysine, which is then hydroxylated to form beta-hydroxy-N-trimethyllysine.
This is converted, first to gamma-butyrobetaine and then to carnitine
(Rebouche and Paulson 1986).
deficiency diseases, resulting from a defect in the biosynthetic
pathway, have been described. Such a condition was first reported
by A. G. Engel and C. Angelini in 1973, and since then a number
of apparently different types of carnitine deficiency have been
noted and discussed in the literature. Two basic types are sometimes
recognized systemic carnitine deficiency (characterized by
a general reduction of carnitine in the tissues, including the liver)
and muscle or myopathic deficiency, in which the reduction in carnitine
occurs in the muscles. In such cases, carnitine replacement therapy
is a recognized mode of treatment; supplementation must take the
form of L-carnitine, the DL/D form being ineffective and, in some
cases, further exacerbating the condition.
are also a number of secondary or noncongenital syndromes that respond
to treatment with carnitine, some of which are side effects of other
clinical conditions (Rebouche and Paulson 1986; Smith and Dippenaar
1990). Carnitine levels are, in general, lower at birth than in
adulthood, and there is evidence that some newly born infants may
have a reduced capacity for carnitine biosynthesis. At birth, too,
fatty acids become increasingly important as an energy source (Smith
and Dippenaar 1990), and it has been suggested that all infants
should receive carnitine supplements at least until the end of their
first year of life (Olson, Nelson, and Rebouche 1989; Giovannini,
Agostoni, and Salari 1991). A recent COMA report accepted that carnitine
supplements could be necessary "for low birth weight or preterm
infants" (Committee on Medical Aspects of Food Policy 1991:
135). Barbara Bowman, in a recent review, has pointed out that carnitine
"appears to be a conditionally essential nutrient in malnutrition
and in newborns, pregnant and lactating women, patients receiving
dialysis or total parenteral nutrition, and patients with liver
disease" (1992: 142).
of these examples of carnitine supplementation presumably stem from
the correction of an abnormal feature of carnitine metabolism or
by restoring a defective carnitine status to normal. Others are
more overtly pharmacological than nutritional in nature. A striking
example of the pharmacological use of [acetyl]carnitine was the
report of a double-blind, randomized, controlled clinical trial
in which the progression of Alzheimers disease was significantly
delayed by the ingestion of 2 grams of acetylcarnitine daily for
a year (Spagnoli et al. 1991).
carnitine supplementation has a role in normal or "nonclinical"
nutrition is more debatable. Much of the discussion in this respect
has centered on the possibility of using carnitine supplements to
enhance aerobic power and the capacity for physical exercise (Cerretelli
and Marconi 1990). Theoretically, such supplementation could be
advantageous in a situation characterized by an increased demand
for "physical energy" and, more specifically, in circumstances
characterized by (1) an increased use of fatty acids as an energy
source, and (2) a depression in the biosynthetic capacity of the
depressed biosynthetic capacity might, in turn, result from a reduced
availability of the essential nutrients involved in the biosynthetic
pathway. This latter consideration the influence of other
dietary factors on carnitine status could be of some significance
and is central to the concept of carnitine as a conditionally essential
hydroxylation reactions in the formation of carnitine from lysine
and methionine require ascorbic acid (vitamin C) as a cofactor;
in addition, two members of the vitamin B complex (niacin and pyridoxine)
are involved, as is iron. The endogenous formation of carnitine,
therefore, involves the participation of six obligatory dietary
components a requirement that places it in a "high risk"
category with respect to inadequate supporting diets. A review has
underlined this point:
the exogenous supply of carnitine is temporarily cut off, and
provided the subject is not suffering from protein hypo- or malnutrition
(as may happen in vegetarianism) plasma carnitine concentrations
do not shift . . . [but] however, drop sharply if the
co-factors essential for carnitine synthesis are lacking (Giovannini,
Agostoni, and Salari 1991: 88).
the essential cofactors, lysine (often the limiting amino acid in
poor-quality diets and frequently present in a physiologically unavailable
form [Helmut 1989]) and ascorbic acid (vitamin C) are probably the
most critically important ones. There is evidence, both experimental
and circumstantial, that a reduced availability of one or both of
these essential nutrients results in a fall of carnitine and possibly
a reduction of carnitine-mediated energy release. Thus, the intake
of three compounds preformed carnitine, lysine, and vitamin
C (the three forming the "carnitine base") will
determine the carnitine status of an individual, and one can point
to a number of historically significant situations where a reduced
carnitine base has resulted in the emergence of a stage consistent
with what we now know to be the physiological consequences of carnitine
deficiency: primarily a reduced capacity for sustained muscular
exercise (Hughes 1993).
there are grounds for believing that the fatigue and lassitude,
invariably present in the early stages of scurvy, could have resulted
from the impairment of carnitine synthesis, which in turn would
have resulted from a deficiency of vitamin C (Hughes 1981, 1993;
see also Figures VII.11.1 and VII.11.2). It is tempting to speculate
that the lowered aptitude for physical labor displayed by potato-eating
Irish and by vegetable-eating French peoples and commented on by
a number of observers in the last century was, at least in part,
attributable to a reduced carnitine base (Young 1780; Lewes 1859;
Bennet 1877; Williams 1885). A diet that centered almost exclusively
on potatoes (as was eaten in Ireland during the nineteenth century)
would contain virtually no preformed carnitine. Moreover, 20 pounds
of potatoes would have to be eaten to obtain the amount of lysine
present in half a pound of meat.
remarks of George Henry Lewes in 1859 are interestingly pertinent
in this respect. Describing the relative capacities of the French
and the English for physical work he wrote:
is worth noting that the popular idea of one Englishman being
equal to three Frenchmen, was found by contractors to be tolerably
accurate, one Englishman really doing the work of two and a half
men; and M. Payen remarks that the consumption of mutton in England
is three times as much as that in France. . . .
[B]y giving the Frenchmen as ample a ration of meat as that eaten
by the Englishman, the difference was soon reduced to a mere nothing
(1859, 1: 174).
reference to mutton was, in this respect, a strikingly apt one,
for of all meats and fishes analyzed to date, mutton has by far
the highest carnitine concentration (Smith and Dippenaar 1990).
belief in a positive correlation between animal protein intake and
capacity for physical work was a central feature of dietary thought
until disproved by the biochemical reductionism of the post-Liebigean
era. H. Letheby summarized some of this anecdotal evidence in his
Cantor Lectures in 1868:
is always a relation between the amount of nitrogen contained
[in] the food and the labor value of it. Carnivorous animals,
for example, are . . . stronger and more capable of
prolonged exertion than herbivores. . . . The bears
of India and America, says Playfair, which feed on acorns, are
mild and tractable whilst those of the polar regions, which consume
flesh, are savage and untameable. The Peruvians whom Pizarro found
in the country at its conquest were gentle and inoffensive in
their habits, and they subsisted chiefly on vegetable food; whilst
their brethren in Mexico, when found by Cortes, were a warlike
and fierce race, feeding for the most part on animal diet. . . .
The Hindoo navvies also who were employed in making the tunnel
of the Bhore Ghat Railway, and who had very laborious work to
perform, found it impossible to sustain their health on a vegetable
diet; and being left at liberty by their caste to eat as they
pleased they took the common food of the English navigators, and
were then able to work as vigorously (1870: 79).
seventy years later, Robert McCarrison (also in a series of Cantor
Lectures) made almost the same point by comparing the diets and
physical capabilities of different Indian races (McCarrison 1944).
In general, however, by the beginning of the twentieth century,
advances in our knowledge of muscle biochemistry were beginning
to undermine the belief in a necessary relationship between animal
protein intake and physical activity (Hutchinson 1902: 38).
is interesting to note that the same biochemical reductionism that
dismissed the supposed relationship between activity and a "strong"
(animal protein) diet now prompts us to reconsider this anecdotal
evidence from the standpoint of "carnitine base" status.
Many of the "weak" or "poor" diets referred
in this section would almost certainly be found wanting in this
respect. By the same token, it has been suggested that certain significant
socioeconomic changes could imply a change in carnitine base availability.
Thus the "Neolithic transition," although leading to an
improved supply and availability of food, almost certainly resulted
in a reduction in dietary quality and, particularly, in that of
the "carnitine base" (Cohen 1990; Hughes 1993).
considerations are of direct interest vis-à-vis carnitine
supplementation. In more general terms, they underline the importance
in supplementation studies of considering each situation on its
own merits. Any reduction in one or more of the components of the
dietary carnitine base could indicate a need for carnitine supplementation.
A sudden fall in the animal protein intake or in the availability
of the lysine component or in vitamin C intake (as would appear
to occur in the institutionalized elderly where the tissue concentrations
of vitamin C are significantly below those believed to be functionally
desirable in younger subjects) could result in a reduction in endogenously
formed carnitine (Hughes 1993).
entire issue of dietary supplementation is clouded by adventitious
circumstances and considerations. Thus it will be apparent that
certain intellectual environments or passing paradigms of scientific
thought can be particularly favorable to the concept of dietary
supplementation. The burgeoning interest in bioflavonoids in the
late 1940s and 1950s (and in fiber in the 1970s) was probably not
unassociated with two acceptable features of nutritional thought
at the time: (1) the belief in "subclinical" manifestations
of deficiency diseases (which, in some undefined way, were believed
to exist despite a normal intake of accepted nutrients); and (2)
the conviction that supplementation of foodstuffs with micronutrients
was nutritionally appropriate a belief that, in cases such
as the supplementation of low-extraction flour, carried the seal
of government approval.
is true that there have always been those who advocated supplementation
for scientifically inadequate reasons. Such persons belong to the
same category as those who, also for nonscientific reasons (such
as folklore or romantic naturalism), favored brown (whole-meal)
bread rather than low-extraction breads (McCance and Widdowson 1956).
Where arguments for supplementation stem from external sources of
this nature and are, consequently, difficult to accommodate within
the current framework of scientific thought, they should always
be treated with proper scientific skepticism and subjected to the
appropriate scientific scrutiny. If it turns out that the advocacy
of a supplement is consonant with current biochemical thought, then
the arguments for its use can be that much more convincing.
three examples outlined in this essay represent, in this respect,
cases of dietary supplementation with three quite different origins.
The suggested use of bioflavonoids stemmed, in essence, from a mixture
of folklore and weak anecdotal evidence, supported originally by
unconfirmed laboratory reports, and was enthusiastically embraced
by believers in the value of natural foods as contrasted with manufactured
ones. There are many other erstwhile dietary supplements that belong
to this category "vitamin B15" (pangamic acid),
"vitamin B17" (laetrile), sea salt, and a host of herbal
preparations. These supplements, for the most part, entered the
nutritional field, as it were, from "outside" and for
nonscientific reasons. Their alleged efficacy was, consequently,
more easily disproved by accepted experimental and statistical techniques,
and their use was frequently subjected to criticism and, sometimes,
ridicule by scientifically orientated "establishment"
nutritionists (see, for example, Bender 1985).
belongs to a somewhat different category of nonfood supplements,
as its appearance as a candidate for dietary status was the consequence
of epidemiological studies, although it must be admitted that in
a nutritional context, it is not always easy to distinguish between
"strong anecdotal evidence" (as presented, for example,
by Trowell in his early studies) and statistically acceptable epidemiological
evidence. Unlike the bioflavonoids, however, dietary fiber has achieved
a foothold in current nutritional thought mainly because of strong
correlative evidence coupled with the results of some experimental
studies. Dietary intervention studies with fiber have been somewhat
less successful, and accommodating the purported advantages of fiber
supplementation within the current ambit of biochemical thought
still poses considerable problems.
represents a third etiologic category of potential dietary supplements.
Its emergence as a factor of possible nutritional significance,
in contrast to the two other examples discussed, was an "internal"
event; it was not thrust upon nutritional thought, as it were, from
the outside. Arguments for its acceptance in certain circumstances
as a dietary supplement placed no conceptual strain on contemporary
nutritional thought. In scientific terms it belongs, therefore,
to a more acceptable category than the other two examples discussed.
Other putative supplements whose emergence has reflected the current
state of the art, rather than external and unrelated circumstances
are taurine (which, alongside carnitine, receives conditional acceptance
as a supplement in the current COMA report), inositol, para-amino
benzoic acid, and specific amino acids. In all such cases of putative
dietary supplements, the final verdict must await extensive experimental
work and intervention studies.
brief survey of the recent history of three "nonfood"
dietary supplements should serve to illustrate three important and
cautionary facts. First, it is useful, as far as possible, to distinguish
between a pharmacological role and a nutritional role for supplements.
Second, one should exercise caution before accepting claims based
on anecdotal evidence or derived from statements or arguments external
to (and sometimes in open contradiction to) current scientific thought.
Third, and most importantly, dietary supplementation must be defined
in terms of lacunae and imbalances in the existing dietary pattern,
rather than in terms of absolute requirements the concept
of "conditional essentiality."
nutrition derived much of its strength (and lately, some of its
weaknesses) from generalizations based on an essentially reductionist
and unitary approach to dietary components. A necessary condition
for its success was the virtual exclusion of any conceptually extraneous
matter, such as the possible importance of nonobligatory dietary
components, the significance of dietary interactions, and the importance
of the changing balance between tissue demands and nutrient availability.
There are signs that current nutritional thought is shedding at
least some of its traditional absolutism (Hughes 1993: 401).
Future studies will presumably be designed not so much to prove
in absolute terms the usefulness of specific supplements but to
define the nutritional circumstances in which such conditionally
essential nutrients as carnitine and fiber would be deemed to be
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