Vitamin E

[Guest guest]

Hi Folks:

Here is article from Dr. Alan Gaby sent to me by my dear friend Lyn Patrick,

NMD.

Andrew Weil also really questions the " marketing " of this study--

 

Does Vitamin E Cause Heart Failure?

by Alan R. Gaby, M.D.

Although vitamin E has long had a reputation of being " good for the heart, "

recent research has caused many to question not only its efficacy as a

heart-protective nutrient, but also its safety. However, virtually all of the

clinical research on vitamin E has used pure alpha-tocopherol, which is only one

of the four forms of vitamin E that occur naturally in food. While early

research suggested that most, if not all, of the biological activity of vitamin

E resides in the alpha- fraction, it is now known that at least one of the other

components – gamma-tocopherol -– has important functions. Furthermore, treatment

with large doses of alpha-tocopherol has been shown to deplete gamma-tocopherol,

thereby upsetting the natural balance of vitamin E isomers in the body. Reports

of potential adverse effects of high-dose alpha-tocopherol must be taken

seriously; however, there is still good reason to believe that " mixed

tocopherols " , which contain all four vitamin E isomers, will eventually be shown

to be both safe and effective for preventing and treating heart disease.

 

Alpha-tocopherol has a number of properties that might make it useful as a

cardioprotective nutrient. It inhibits platelet aggregation and possibly other

mechanisms of blood coagulation, inhibits the oxidation of LDL cholesterol,

prevents the development of atherosclerosis in experimental animals, and reduces

the deleterious effects of hypoxia in both animals and humans.

 

Alpha-tocopherol has been said to be beneficial in the treatment of many

different cardiovascular conditions, including angina pectoris, congestive heart

failure, intermittent claudication, ischemic ulcers, and gangrene, and in the

prevention of postoperative thrombophlebitis and pulmonary embolism. Much of the

evidence has been anecdotal, and reports have often been conflicting. On the

other hand, the effectiveness of alpha-tocopherol against intermittent

claudication and for preventing postoperative thromboembolism is supported by

controlled trials, and the results have been fairly consistent.

 

For many years, most doctors remained unconvinced about the claims regarding

alpha-tocopherol. Interest in this vitamin increased in the early 1990s,

however, when two large prospective studies (the Nurses' Health Study and the

Health Professionals Follow-up Study) showed that a high intake of vitamin E is

associated with a reduced risk of coronary heart disease in both men and women.

Those studies were followed by series of large, randomized, placebo-controlled

trials. While one such trial (the Cambridge Heart Antioxidant Study)

demonstrated a substantial reduction in incidence of myocardial infarctions in

heart patients treated with alpha-tocopherol, the data from the other trials

were for the most part disappointing. Consequently, many experts now regard

alpha-tocopherol as ineffective.

 

Moreover, two recently published studies suggested that alpha-tocopherol in

doses of 400 IU/day or more may actually be harmful for some people. In one

study, patients with vascular disease or diabetes were randomly assigned to

receive, in double-blind fashion, 400 IU/day of alpha-tocopherol or placebo for

seven years. Compared with placebo, alpha-tocopherol supplementation resulted in

a 19% increase in the risk of developing heart failure and a 40% increase in the

risk of being hospitalized for heart failure. This study came on the heels of a

meta-analysis of 19 clinical trials that showed that supplementation with 400

IU/day or more of alpha-tocopherol led to a small (4%) but statistically

significant increase in all-cause mortality. Because of these studies, many are

now questioning the wisdom of taking vitamin E for the purpose of preventing

heart disease.

 

I have pointed out previously that the meta-analysis suffered from serious

flaws. Specifically, in some of the largest studies included in the analysis,

patients were given other supplements in addition to alpha-tocopherol, and there

is reason to believe that the other supplements, not the alpha-tocopherol, may

have been responsible for at least some of the mortality increase. The study

showing an increase in the incidence of heart failure, on the other hand, was

well designed, and the results are difficult to ignore.

 

High-dose alpha-tocopherol may, indeed, have a negative effect in certain groups

of susceptible people. However, the same may not be true of " mixed tocopherols, "

which is a mixture of the four naturally occurring forms of vitamin E: alpha-,

beta-, gamma-, and delta-tocopherol. Approximately 70% of the vitamin E in food

is in the form of gamma-tocopherol. Most of " vitamin E " supplements on the

market, on the other hand, contain only alpha-tocopherol, although mixed

tocopherols are commercially available.

 

Recent studies have shown that gamma-tocopherol has important biological

functions. For example, the formation of nitric-oxide-derived free radicals,

which appears to be a factor in the pathogenesis of heart disease, is inhibited

to a greater extent by gamma-tocopherol than by alpha-tocopherol. In addition,

both mixed tocopherols and gamma-tocopherol have been found to be more potent

inhibitors of platelet aggregation than alpha-tocopherol. It is now known that

supplementing with large doses of alpha-tocopherol reduces blood levels of

gamma-tocopherol, apparently by accelerating its metabolism. Consequently,

whatever positive effects are produced by alpha-tocopherol supplementation might

be counterbalanced by a reduction of gamma-tocopherol levels in the body, a

reduction that would presumably be more pronounced when using higher doses of

pure alpha-tocopherol.

 

The potential for alpha-tocopherol to deplete gamma-tocopherol is particularly

relevant to the issue of congestive heart failure. Gamma-tocopherol is

metabolized largely to 2,7,8-trimethyl-2-(beta-carboxyethyl)-6-hydroxychroman

(gamma-CEHC), a compound that appears to function as a " natriuretic hormone. " It

has long been known that mammals respond to sodium-induced plasma-volume

expansion with a combination of sustained natriuresis (urinary sodium

excretion), inhibition of sodium transport, and increased vasoreactivity. It has

been assumed that these effects are due to the release of a " natriuretic

hormone, " but for many years scientists were unable to find an endogenous

compound that exerted all of these actions. In 1996, researchers at Loma Linda

University identified gamma-CEHC as such as substance and a year later found it

to be a metabolite of gamma-tocopherol. In that respect, gamma-tocopherol might

be considered a " pro-hormone, " a compound that plays a role in the regulation of

extracellular fluid and sodium balance, which is one factor involved in the

pathogenesis of congestive heart failure. It is possible that, for some people,

alpha-tocopherol-induced gamma-tocopherol deficiency would lead to impaired

regulation of sodium and water balance, thereby increasing the stress that every

salty meal or snack would place on the heart.

 

If high-dose alpha-tocopherol does adversely affect cardiac function in some

people, one might reasonably expect that “mixed tocopherols,” which contain all

four naturally occurring forms of vitamin E, would not have the same negative

effects. Although mixed tocopherols are more expensive, the available evidence

suggests that they are preferable to alpha-tocopherol, both in terms of safety

and efficacy. People who supplement with mixed tocopherols would presumably

derive the benefits of both alpha- and gamma-tocopherol, without creating an

imbalance in these two forms of vitamin E. While it may be many years before the

alpha-tocopherol research is repeated using mixed tocopherols, I predict that a

combination of the four naturally occurring tocopherols will eventually be shown

to effective both for preventing and treating heart disease.

 

 

 

 

Misha R. Cohen, OMD, L.Ac.

Visiting Researcher, UCSF Institute for Health & Aging

Research & Education Chair, Quan Yin Healing Arts Ctr., Chicken Soup

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