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Upper
Limit Vitamin C and E Intake Michael Lam, MD, MPH
www.DrLam.com
(READING TIPS: For
fast reading, scan through the topic headings in BOLD BLACK, important conclusions
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| Before You Begin
Information presented here is for general
educational purposes only. Each one of us is biochemically and metabolically
different. If you have a specific health concern and wish my personalized
nutritional recommendation, write to me by clicking
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Contents
Introduction
Vitamin E
Vitamin C
Primer on Free Radicals and Antioxidants
From Hoax to Science
How Much Is Too Much?
When Should I Start Taking Supplements?
Introduction
The Antioxidant Panel of the Food
and Nutrition Board, Institute of Medicine, National Academy of Sciences (NAS),
announced in 2000 the new recommended dietary allowances (RDA) for Vitamin C
and E. For Vitamin E, the new RDA for both men and women has been raised to
15 mg, up from 8 mg for men and 6.4 mg for women.
The newly established upper level, assuming the source is from supplementation,
is as high as 1,000 mg of Vitamin E (alpha-tocopherol per day). This is equivalent
to roughly 1,500 IU of "d-alpha-tocopherol." For Vitamin C, the new RDA is 90
mg for men and 75 mg for women, up from 65 mg. The newly established upper limit
for Vitamin C is 2,000 mg per day.
Vitamin E
 In
view of the mounting evidence that Vitamin E is a powerful antioxidant with
significant health benefits, the NAS panel
virtually doubled their old recommendation to 15 mg of d-alpha-tocopherol (the
natural form of Vitamin E and the basis for the new RDAs) per day for both men
and women.
The old RDA had rated natural Vitamin E as being only 36% more active than the
synthetic form. This report confirms that the difference is much greater. In
fact, the NAS panel has determined that natural
Vitamin E is twice as potent as the synthetic version.
The form of Vitamin E that is best used and
retained by the body is the RRR-tocopherol (alpha). In the process
of making synthetic Vitamin E from petroleum chemicals, fully one half of synthetic
Vitamin E is in the form of tocotrienols, and beta-, gamma- and delta-tocopherol,
all of which the body does not recognize and preferentially excretes. On the
other hand, 100% of natural-source Vitamin E, purified from plant sources, is
in the RRR-tocopherol (alpha) form recognized and used by the body.
Another highlight of the report for Vitamin
E includes the establishment of an upper intake level (UL).
This UL for Vitamin E is 1,000 milligrams daily. This is equivalent to approximately
1,500 international units of natural-source Vitamin E or 1,100 IU of synthetic
Vitamin E. The difference in limits for natural-source and synthetic
forms of Vitamin E underscores the importance of the NAS finding that synthetic
Vitamin E contains compounds with no Vitamin E activity. The UL also establishes
that Vitamin E is safe in amounts much greater (67 times) than even the new
RDAs.
There have been many studies showing the benefits of Vitamin E. The following
two will demonstrate some of them, as well as give you some insight into the
reasons on which the NAS based their decision to increase the RDA and establish
such a high upper limit.
In our first study, which was published in Lancet in 1996, 2002 patients with
angiographically proven coronary atherosclerosis were enrolled in a Vitamin
E supplementation program and followed for a median of 510 days. These patients
were given alpha-tocopherol capsules containing 800 IU a day for the first 546
days and 400 IU daily for the remainder. Results showed that
alpha-tocopherol treatment substantially reduced the rate of non-fatal MI (heart
attacks), with beneficial effects apparent after 1 year of treatment.
In the second study, published in Journal of the American Medical Association
(JAMA), in 1995, 156 men aged 40-59 with previous coronary artery bypass graft
surgery were supplemented with 100 IU of Vitamin E per day and compared to those
men whose intake was less than 100 IU per day. After the treatment,
subjects receiving 100 IU demonstrated less coronary artery lesion progression
than did subjects with intake of less than 100 IU per day, as determined by
angiography.
Studies determining the efficacy between various forms of Vitamin E are less
clear, especially as it relates to alpha- vs. gamma -Tocopherol. Some studies
have suggested that gamma-Tocopherol is more effective, while others show that
a mixed blend of alpha- and gamma- appears to be the best. Until more research
is available, it is clear that the standard form of Tocopherol should be alpha-Tocopherol.
Studies have already determined that Vitamin E derived from natural source ("d"form)
is better than synthetic form ("dl"form).
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