The China Study by Thomas Campbell

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366 TH E (H I NA STU DY

CHART C.3: ROLE OF THE PARATHYROID HORMONE
IN THE REGULATION OF SUPERCHARGED 1,25 D

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  • must be maintained within a fairly narrow range. The 1,25 D keeps the
    blood levels of calcium operating within this narrow range by moni-
    toring and regulating how much calcium is absorbed from food being
    digested in the intestine, how much calcium is excreted in the urine and
    feces and how much is exchanged with the bone, the big supply tank
    for the body's calcium. For example, if there is too much calcium in the
    blood, 1,25 D becomes less active, less calcium is absorbed and more
    calcium is excreted. It is a very sensitive balancing act in our bodies.
    As blood calcium goes up, 1,25 D goes down, and when blood calcium
    goes down, 1,25 D goes Up.10. 24 Here's the kicker: if calcium consump-
    tion is unnecessarily high, it lowers the activity of the kidney enzyme
    and, as a consequence, the level of 1,25 D .1. 25 In other words, routinely
    consuming high-calcium diets is not in our best interests.
    The blood levels of 1,25 D therefore are depressed both by consum-
    ing too much animal protein and too much calcium. Animal-based
    food, with its protein, depresses 1,25 D. Cow's milk, however, is high
    both in protein and calcium. In fact, in one of the more extensive stud-
    ies on MS that is associated with lower levels of 1,25 D, cow's milk
    was found to be as important a factor as latitude mentioned earlier. 26
    For example, the association of MS with latitude and sunshine shown
    in Chart C.2 also is seen with animal-based foods shown in Chart
    C.4.14
    One could hypothesize that diseases like MS are due, at least in part,
    to a lack of sunshine and lower vitamin D status. This is supported by the
    observation that northern people living along coastlines (e.g., Norway



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