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months, vitamin A levels don’t even budge. So DETERMINING VITAMIN A DEFICIENCY
don’t depend on leafy greens, even if you think Blood tests for serum or plasma retinol are not very helpful because
you are a good carotenoid converter. the liver stores 70-90 percent of the body’s vitamin A and keeps blood
Not only is converting carotenoids to vita- levels tightly regulated between 45-65 µg/dL. This number does not indi-
min A difficult, it is also difficult to extract the cate your overall vitamin A status—or how much vitamin A you have in
carotenoids from vegetables that are raw. It is reserve. Your blood level of retinol will not drop below 20 µg/dL unless
easier to extract them from cooked vegetables, you are severely depleted. Blood testing can indicate only whether liver
and easier to make the conversion if you put stores are either depleted or filled to capacity.
butter or cream or other traditional fats on To determine either deficiency or excess states, you should measure
your cooked vegetables. A good source of pro- both serum retinol (or serum vitamin A) and serum retinyl esters (serum
vitamin A is unrefined palm oil—the orange A palmitate); serum retinol should ideally be in the middle or upper half
palm oil—where the carotenoids are in the fat. of the reference range and not less than 30 μg/L, and the serum retinyl
Low-protein diets, lowfat diets, high-fiber diets esters should not be above 10 percent of the sum of the retinol and retinyl
and diets high in raw plant foods all make this esters. Measuring fasting retinyl esters is done to check whether the ca-
conversion difficult. pacity of the liver to store vitamin A has been exceeded, an uncommon
Iron and zinc deficiency also inhibit the but possible occurrence.
conversion of carotenoids to vitamin A. Iron Obesity causes blood levels to rise even during a physiological tissue
is needed to convert beta-carotene into retinol, deficiency, while infection and inflammation can depress blood levels.
and zinc is needed for all aspects of vitamin A Vitamin A levels in blood vary with “fed” status, that is, how recently
metabolism, including its transport around your you ate. If you are going to get tested, please get tested while fasting.
body. If you have a lot of toxins in your body, es-
pecially toxic metals, conversion will be difficult.
Gut dysbiosis inhibits conversion. If you FIGURE 1: Forms of Vitamin A
have had your gallbladder removed, conversion
will be difficult because you don’t have much
bile, and you need bile to convert carotenes to
vitamin A. If you have hypothyroidism, if you
are very old or very young, or you’re supple-
menting with another source of carotenoids such
as lycopene, these can also block the conversion.
In my practice, I find that only a minority
of my patients do well without including vitamin
A as retinol in their diet. However, about one in
every three or four of my patients has physical
signs of vitamin A deficiency despite consuming
colorful vegetables routinely. Because the conver-
sion rate of carotenoids to vitamin A can be as low
as 10 percent or less, this does not surprise me.
On the other hand, there are people who
make this conversion very effectively, up to 90
percent in some cases; I suspect this is not com-
mon in my own patient population because the
majority do better when their diet or supplement
regimen includes a source of retinol.
Genetics definitely play a governing role in
our ability to convert carotenoids. The list of all the
genes that affect your vitamin A metabolism and
how you carry it through your body is a long one.
The inability to convert carotenoids seems to be
more common among those of European descent.

SPRING 2020 Wise Traditions 17