CHIRON NOTES Editor: Donald S. McLaren, MD, PhD
Erratum
In May 2001, Nutrition: The International Journal of Applied and Basic Nutritional Sciences received from Professor Donald S.
McLaren the following article, a review of current literature that is, by definition, highly time sensitive. Most unfortunately, this paper
was held up in the publication process for many months, and is only now being published in this issue. We are greatly distressed by
the error and extend our sincere apologies to Professor McLaren.
A Trawl Through the Current
Nutrition Literature
There seems little doubt that it has become exceedingly difficult in
recent years for expert groups to agree on the form and content of
their recommendations concerning dietary requirements of nutri-
ents. In the United States the responsible bodies are the Food and
Nutrition Board, the Institute of Medicine, and the National acad-
emies in Washington, DC. On previous occasions a single mono-
graph covered all micro- and macronutrients at the same time. The
Institute of Medicine is in the process of publishing a series of
documents, five of which have been published in recent years and
several more are promised in the near future.
1–5
It might be easy to
miss one or more of them. Things are made much more compli-
cated this time by major changes in terminology. The familiar
recommended dietary allowance (RDA) is not being used in a
general sense but has been retained for specific use; in an overall
sense, RDA has been replaced by the dietary reference intake.
Another complicating feature is the use of four kinds of dietary
reference intake: RDA, adequate intake, tolerable upper-intake
level, and estimated average requirement. RDA and adequate
intake are mutually exclusive. RDA is defined as “the average
daily dietary intake level that is sufficient to meet the nutrient
requirement of nearly all (97–98%) healthy individuals in a par-
ticular life stage and gender group.” Adequate intake is “a recom-
mended intake value based on observed or experimentally deter-
mined approximations or estimates of nutrient intake by a group
(or groups) of healthy people that are assumed to be adequate—
used when a RDA cannot be determined.” The tolerable upper-
intake level is self-explanatory: “the highest level of daily nutrient
that is likely to pose no risk of adverse health effects for almost all
individuals in the general population.” Estimated average require-
ment is “a daily nutrient intake value that is estimated to meet the
requirement of half of the healthy individuals in a life stage and
gender group.” The estimated average requirement is used “to
examine the probability that usual intake is inadequate” for an
individual and “to estimate the prevalence of inadequate intakes
within a group” for a group.
The grouping of nutrients in particular documents is quite
unhelpful. Selections of some vitamins and minerals are mixed
together. Vitamin A and carotenoids are found in different
documents.
Close examination of the text for a particular nutrient of inter-
est, vitamin A in my case, shows a number of inadequacies and
suggests that these are widespread. In Table 5 in the review by
Trumbo et al.,
6
under adverse effects for vitamin A, only terato-
logic effects and liver toxicity are listed. There are many more
adverse effects of hypervitaminosis A: in the acute form, nausea,
vomiting, headache, vertigo, stupor, blurred vision, papilledema,
pseudotumor cerebri, fontanelle bulging (infants), fever, peeling,
drying, itching and scaling of skin; in the chronic form, anorexia,
weight loss, alopecia, coarsening of hair, splenomegaly, anemia,
bone changes, and gingival discoloration. In Figure 2 of the same
paper,
6
the criterion of adequacy for vitamin A is given as “main-
tenance of adequate body vitamin A stores as indicated by liver
biopsy.” Are the experts who wrote this report serious in making
this suggestion? It is clearly unethical to carry out this potentially
dangerous procedure in healthy people. Studies published decades
ago showed that autopsy data could not be relied on.
Perhaps the most significant change to appear in these reports
thus far concerns the efficacy of dietary carotenoids as sources of
vitamin A. This change is largely the result of the research carried
out by Clive West and Seskia de Pee and their group at the
Agricultural University of Wageningen in The Netherlands over
the past decade or so. In a series of careful studies, they have
shown that the bioavailability of

-carotene and other provitamin
A carotenoids is reduced by a variety of dietary and host factors
and is several-fold lower than had been assumed by the values
given in retinol equivalents, which have been used worldwide for
the past 40 y or so. Provitamin A in dark-green leafy vegetables,
the main source of vitamin A for most populations in the 71
developing countries where vitamin A deficiency has been identi-
fied as a public-health problem, has an especially low bioavail-
ability. Consequently, in the report the old conversion factors for

-carotene (1/6) and other provitamin A carotenoids (1/12) have
been halved (to 1/12 and 1/24, respectively). The term retinol
equivalent has been replaced by retinol-activity equivalent, one
unit of which is only half as potent as one unit of the former.
In his most recent review West
7
proposed that, from a mixed-
vegetable diet, the old figure of 6
gof

-carotene ϭ 1 retinol
equivalent should be modified even further to 21
gof

-carotene.
The implications for programs aimed at controlling vitamin A
deficiency in developing countries are serious. Estimates of daily
per-capita intake of vitamin A in Africa, South America, and Asia,
expressed as retinol-activity equivalents are reduced from 895,
599, and 667, respectively, to 371, 372, and 258, respectively.
These intakes are well below the former recommended daily intake
of 600 retinol equivalents for adult males, but the discrepancy is
made even greater by the fact that the present recommendation has
been raised by 50% to 900 retinol-activity equivalents.
Evidently a panel of experts is currently reviewing protein,
amino acids, fats and fatty acids, carbohydrates and fiber, and
energy expenditure using the dietary reference-intake framework.
That report, which sounds like an enormous undertaking, is due to
be published by the end of 2001. Other groups are due to start work
on electrolytes and water, food components such as phytoestrogens
and other phytochemicals in relation to risk of chronic disease and
health, and the role of alcohol in health and disease. As Trumbo et
al.
6
commented rather wryly, “perhaps even before these panels
start, it will be time to review the data on some of the vitamins or
Correspondence to: Donald S. McLaren, MD, PhD, Nutritional Blindness
Prevention Program, 12 Offington Avenue, Worthing, West Sussex BN14
9PE, UK. E-mail: sce_ltd@compuserve.com
Nutrition 18:447–449, 2002 0899-9007/02/$22.00
©Elsevier Science Inc., 2002. Printed in the United States. All rights reserved. PII S0899-9007(01)00635-9