antistress formula’). In most cases, however, the
claims for vitamin products are limited to state-
ments of nutrient content (e.g. ‘provides 100% of
the RDA for seven important vitamins’).
The benefits of vitamin supplementation in
cases of borderline or frank vitamin deficiency
are well accepted (Clarkson 1991). Under these
circumstances, health status and performance
are improved when the deficiency is corrected.
Whether ingestion of vitamins in amounts far
exceeding the recommended dietary allowances
confer benefits to physically active people
remains a topic of much discussion and interest
(see Chapters 20–22). Future research will
undoubtedly determine if vitamin supplementa-
tion provides specific benefits to human struc-
ture and function, or serves merely as a way for
physically active people to assure adequate
micronutrient intake. Additional information on
vitamin supplementation can be found in Chap-
ters 20–22 of this text and in review articles by
Armstrong and Maresh (1996), Clarkson (1991),
Haymes (1991), Rosenbloomet al.(1992), Sobal
and Marquart (1994) and Williams (1984).
Mineral supplements
As with vitamins, minerals are also sold singly
(e.g. chromium) or in combination (multimineral
tablets). Chapters 23–25 provide a detailed
review of mineral requirements in physically
active people, as do review articles by Armstrong
and Maresh (1996), Clarkson (1991) and Haymes
(1991). Acute or chronic deficiencies of minerals
such as sodium, calcium and iron can occur as a
result of physical activity and inadequate dietary
intake. Advertising claims for the benefits of
minerals such as boron, chromium, molybde-
num, selenium and zinc have not been borne out
by scientific research (Clarkson 1991; Haymes
1991). Armstrong and Maresh (1996) identified a
number of flaws in the experimental designs of
supplementation studies that can render the data
suspect or useless. Among these are the inability
to control for mineral status of the subjects, the
absence of placebo groups, and the choice of
inappropriate assessment criteria. Some of the
studies that report positive structural or func-
tional effects of mineral supplementation suffer
from one or more of the design flaws noted by
Armstrong and Maresh (1996).Protein and amino-acid supplements
The advertising for protein and amino-acid
supplements is often based upon the notion that
physically active people, particularly body-
builders and power lifters, require large amounts
of dietary protein. Claims for these products tout
benefits such as, ‘promotes anticatabolic activ-
ity’, ‘pack on some solid, rock-hard mass’, and
‘increases lean muscle mass and promotes fat
loss’. There is little in the way of scientific evi-
dence to indicate that ingesting protein supple-
ments will fulfil these promises. As indicated in
Chapters 9 and 10, although physical activity
increases the dietary requirement for protein, the
increase is easily met by consuming a normal
diet. In brief, protein and amino-acid supple-
ments are expensive substitutes for protein-rich
foods that are readily available in the diet
(Lemon 1995).
In recent years, attention has been paid to the
effects of ingesting individual amino acids such
as glycine and glutamine or combinations of
amino acids such as the branched-chain amino
acids (leucine, isoleucine and valine) for pur-
poses ranging from stimulating growth hormone
release to altering serotonin production in the
brain. Although future research may generate
evidence of benefits associated with the inges-
tion of amino acids, the current data are not com-
pelling. In addition, the ingestion of amino-acid
supplements is not without risk (Butterfield
1991; Beltz & Doering 1993).Putative promoters of muscle growth
A number of other substances have been adver-
tised as being able to promote the growth
of muscle tissue. Dibencozide, g-oryzanol,
yohimbe, phosphatidylserine and vanadyl sul-
phate are among the ingredients that can be
found in current products promoted as having