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males and just over 2,300 iU for adult females. intake of vitamin A may be greatly increased.
These values are based on studies conducted
in the general population, which is now recog- CoD lIVer oIl SuPPlIeS A BAlAnCe
nized to be largely deficient in vitamin D. Most Cod liver oil should not be seen as a cure-all or as a universal supple-
traditional diets likely supplied more vitamin A ment, but neither should cod liver oil be avoided out of fear. it is a valuable
than the current rDA. The greenland inuit diet and convenient way to obtain vitamins A and D together with omega-3
in 1953 supplied an average of 30,000 iU per fatty acids—all nutrients most Americans require in greater levels than
day. Other traditional diets where most of the they currently obtain through their diets.
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vitamin A came from dairy products likely pro- Does cod liver oil contain the ideal ratio of vitamins A and D? it is
vided lower levels. Price used three-quarters of a possible that there is an ideal dietary ratio of the two vitamins, but this is
teaspoon of high-vitamin cod liver oil per day and not necessarily the case. The body highly regulates its conversion of each
alternated between muscle meats and organ meats vitamin to the active form, and is capable of storing the portion it chooses
in the stews he used for his tooth decay reversal not to activate at any given time. it is more likely that there is a broad range
program. Together with whole milk, butter, and of acceptable dietary ratios and that harm comes when one or the other
carotenes from vegetables, his program probably vitamin is in unusually short supply.
provided over 10,000 iU of vitamin A per day, if there is an ideal ratio, it will vary from person to person and from
although this was to growing children who were season to season. People with darker skin may need extra vitamin D from
recovering from deficiency. fatty fish or vitamin D supplements year round, and others may need
regardless of whether or not the ideal in- extra vitamin D only in the winter. People should use recommendations
take of vitamin A is much higher than the rDA, as guidelines to help them experiment and find the amount of cod liver
over a quarter of Americans consume less than oil that works best for them, knowing that it has been a safe and valuable
half the rDA. if people eating diets this low in health-promoting food that for centuries has nourished both young and old.
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vitamin A begin supplementing with vitamin D
rather than cod liver oil, the danger of such a low

VITAMIn A AnD IncReASeD MORTAlITy

cannell cited a meta-analysis in his journal article and December newsletter showing that “vitamin A supplements”
1,2
increased the total mortality rate by 16 percent. while a typical meta-analysis pools together the results of many differ-
ent studies, this one examined the effects of a large number of antioxidants, and only one section dealt with vitamin A. By
the time Mercola published the claim on his web site, “vitamin A supplements” had been expanded to include “vitamin
3
A supplements in cod liver oil.” The original meta-analysis, however, obtained this figure by pooling together the results
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of only two studies on vitamin A given alone, neither of which even mentioned cod liver oil.
The first study was a double-blind intervention trial in which researchers administered either 25,000 IU of vitamin A
or a placebo to over 2,000 subjects at moderate risk for skin cancer for over four years. Vitamin A supplementation did
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not affect the risk of basal cell carcinoma, but it reduced the occurrence of squamous cell carcinoma by over 25 percent.
The median age of the subjects was 63 and over two thirds of them were male; consequently, the majority of the subjects
died by the end of the study. After 55 months, 35 percent in the vitamin A group and 36 percent in the placebo group
were still alive. The authors did not claim that vitamin A had any effect on mortality.
In the other study the researchers provided either a single dose of 200,000 IU of vitamin A or a placebo to just over
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100 elderly nursing home residents. They then observed the incidence of respiratory infections over the following 90
days. Vitamin A had no effect. four patients in the vitamin A group died while only two patients died in the placebo group.
The patients in the vitamin A group, however, were on average five years older than those in the placebo group and thus
much more likely to die of old age. The authors did not claim that vitamin A had any effect on mortality.
Meta-analyses can often help us see the big picture by examining the totality of the evidence. By pooling together
huge amounts of data they often achieve the statistical power necessary to verify associations between different factors
that smaller studies would miss. But they also have drawbacks. Studies may be lumped together when they differ in qual-
ity or were performed in different contexts. Much of the background information on each study can be lost. In this case,
citing a meta-analysis simply serves to obscure the basic facts about two small studies that offered no useful information
about the effect of vitamin A on mortality at all.

SPRING 2009 Wise Traditions 23