Page 24 - Fall2010

Our bodies After five months of the safflower oil formula, the DHA than those of infants fed formulas devoid
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use the same girl experienced episodes of numbness, tingling, of the fatty acid. When a mother improves her
DHA status by supplementing with cod liver oil
weakness, inability to walk, leg pain, psychologi-
enzymes to cal disturbances and blurred vision—symptoms during pregnancy and the first three months of
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convert ALA that researchers had never seen in essential fatty lactation, it improves her child’s IQ at four years
acid deficient animals or in humans receiving fat-
of age, although the effect is drowned out by other
to DHA as free TPN. Her blood levels of omega-3 fatty acids factors as the child grows older.
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The requirement for DHA is likely to be most
were low. When her physicians switched her to the
they use soybean oil formula, her omega-3 fatty acid levels critical during pregnancy, lactation, early develop-
to convert returned to normal and her neurological symptoms ment, and other periods of growth, tissue repair,
linoleic acid disappeared. or diseases involving the oxidative destruction of
lipids. People who consume linoleic acid-rich
Animal experiments suggest that great ex-

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to arachidonic cesses of linoleic acid are required to cause de- vegetable oils are likely to have greatly decreased
ficiencies in omega-3 fatty acids. In every organ, conversion of ALA to DHA. Since this is the norm
acid. A great the concentration of DHA vastly outweighs the on the standard American diet, most Americans
excess of one concentration of any other omega-3 fatty acid, but eating a standard diet may be vulnerable to DHA
levels of DHA are especially high in the brain and deficiency. People who convert ALA to DHA
precursor retina, where its concentration is tightly regulated. 35 poorly or strict vegetarians whose diets are com-
can therefore In the early development of these tissues, small pletely devoid of DHA may benefit from consuming
amounts of omega-3 fatty acids are required to sources of preformed DHA such as cod liver oil or
outcompete provide maximal DHA content; after this window egg yolks from pastured chickens. Small amounts
the other for is closed, however, the brain and retina are very of cod liver oil are also useful in a broader range
the enzymatic resistant to the effects of deficiency, just as mature of circumstances to provide vitamins A and D.
animals and adult humans are resistant to the ef-
machinery. fects of arachidonic acid deficiency under ordinary THE OMEGA-6-TO-OMEGA-3 RATIO
circumstances. An often-cited animal experiment suggested
Even during early development, however, great that the ideal ratio of omega-6 linoleic acid to
excesses of omega-6 linoleic acid are required to omega-3 ALA is four-to-one, but this experiment
cause substantial decreases in the omega-3 DHA injected rats with free fatty acids rather than feed-
content of the brain and retina. When fed to wean- ing them dietary oils. A more realistic experiment
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ling rats, the classic sucrose-casein essential fatty that fed rats a mix of various vegetable oils in a
acid-deficient diet only depletes retinal DHA con- broad range of different proportions showed that a
tent by 15 percent. The addition of ten percent of ratio of nine-to-one maximized tissue DHA content
calories as safflower oil, however, causes a much just as well as lower ratios. The precise ratio is
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more dramatic 50 percent depletion. Feeding rats likely to be of much less importance, however,
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two percent of their calories as purified linoleic when there is preformed arachidonic acid and DHA
acid depletes the DHA content of the retina by 62 in the diet. Nevertheless, people who consume
percent in the first generation and 92 percent in the standard American diet rich in vegetable oils
the second generation. Similar effects occur in may face adverse consequences from consuming
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the brain. 38-39 Depletion of retinal and brain DHA excess linoleic acid and people who consume large
using linoleic acid-rich vegetable oils causes visual amounts of fatty fish, fish oil or cod liver oil may
and possibly learning defects in rats and rhesus face adverse consequences from consuming an
monkeys. 40-42 excess of the omega-3 fatty acid eicosapentaenoic
Our bodies use the same enzymes to convert acid (EPA).
ALA to DHA as they use to convert linoleic acid to Among ten populations studied from five dif-
arachidonic acid. A great excess of one precursor ferent continents, American adults have the highest
can therefore outcompete the other for the enzy- blood levels of omega-6 fatty acids and American
matic machinery. Large amounts of any PUFA, infants have the lowest blood levels of omega-3
moreover, will cause the cell to make less of this fatty acids. Up until the 1930s, Americans con-
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enzymatic machinery by convincing the cell that it sumed on average about 15 grams (one tablespoon)
is no longer needed. This competition and cellular of PUFA per day. Since the 1930s, this value has
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confusion can be avoided altogether by providing more than doubled to over 35 grams per day as
small amounts of preformed arachidonic acid and Americans have increased their intake of vegetable
DHA in the diet. Even though the concentration oils rich in the omega-6 linoleic acid (see Figure 2).
2
of DHA in breast milk is very small, the brains of Most of this increase occurred after 1961 when the
breast-fed infants accumulate fifty percent more American Heart Association began recommending
24 Wise Traditions FALL 2010