Epidemiology Shows That Vitamin C Helps Us Live Longer

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Epidemiology Shows That Vitamin C Helps Us Live Longer

 

© Interview With

Interviewed By Richard A. Passwater Ph.D.

 

In May, very exciting nutrition headlines captured the

interest of nearly everyone. [1,2] A long-time

colleague and friend of mine, Dr. James E. Enstrom of

the UCLA School of Public Health, published his latest

research on how men taking vitamin C, about 300

milligrams or more per day, on average live six years

longer than those who receive less than 50 milligrams

of vitamin C daily. [3] The scientific journal also

included an editorial by Dr. Gladys Block that

concluded, " The results of Enstrom et al indicate that

increased attention should be given not only to

dietary sources of these nutrients, but also to the

possible benefits of vitamin supplements. [4]

 

I called Dr. Enstrom to congratulate him, and I

thought that you might like to share in that

conversation.

 

James E. Enstrom, Ph.D., M.P.H.

 

Dr. James E. Enstrom is an Associate Research

Professor and Epidemiologist at the University of

California School of Public Health in Los Angeles. He

received his Ph.D. in Physics from Stanford in 1970

and a M.P.H. in Epidemiology from UCLA in 1976. He has

been conducting epidemiologic research at the UCLA

School of Public Health and Jonsson Comprehensive

Cancer Center since 1974. Also, he has been a

consulting epidemiologist for the Linus Pauling

Institute of Science and Medicine.

 

Passwater: Congratulations, Dr. Enstrom, your latest

study made national headlines and may have been just

the impetus needed to get more researchers excited

about studying the role of nutrients and health beyond

deficiencies.

 

The headlines concentrated on the longer lifespans of

those taking vitamin C, but I see several other

interesting revelations in your article.

 

I often refer to the fact that 30 million Americans

have been taking vitamin C and vitamin E supplements

for decades now, and heart disease has decreased in

step with this. You also point out, " the last 20 years

of large increases in the consumption of supplements

containing vitamin C and large declines in

age-adjusted death rates (total, cardiovascular

disease and stomach cancer) in the general population

that are only partially explained by established risk

factors. " Would you elaborate on this point?

 

Enstrom: One line of evidence that must be used in

assessing epidemiologic associations is temporal

changes in etiologic (causative) factors and disease

rates, such as, the changes that have occurred in

cigarette smoking and lung cancer rates during this

century. In this regard, it's worth noting that there

has been about a ten-fold increase in consumption of

vitamin supplements, particularly vitamin C, during

the past 25 years and the age-adjusted death rates for

Americans have declined since 1970 by about 30% for

all causes, 45% for all cardiovascular diseases, and

40% for stomach cancer.

 

Obviously, time trends themselves do not prove an

association. However, since changes in the established

risk factors for cardiovascular diseases (e. g.

smoking, serum cholesterol and blood pressure) do not

fully explain the changes in cardiovascular disease

death rates, it is reasonable to look at other

potential risk factors such as vitamin C as a partial

explanation. [5]

 

Passwater: I have been stressing in this column for

years that antioxidant nutrient intake is more

important than cholesterol intake for the average

healthy person. You note that " the inverse relation of

total mortality to vitamin C intake is stronger and

more consistent in this population than the relation

of total mortality to serum cholesterol and dietary

fat intake, two variables on which strong public

health guidelines have been issued over the years. "

Would you mind telling me more about this point?

 

Enstrom: Serum cholesterol was measured very carefully

in the HANES I Epidemiologic Follow-up Study (NHEFS)

cohort (group) and its relationship to mortality is a

U-shaped curve, with the total death rate being

highest at the highest and lowest serum cholesterol

levels. Even though the bulk of epidemiological data

indicate no benefits of low serum cholesterol with

respect to total mortality in the population as a

whole, these data have been largely ignored in the

heart disease community, which prefers to focus on the

positive relationship between serum cholesterol and

coronary heart disease among middle-aged white men.

 

Two major books in the last four years have been

written which point out many weaknesses in the serum

cholesterol - heart disease data. [6,7] Even if serum

cholesterol has a positive relation to coronary heart

disease in some segments of the population, serum

cholesterol does not have a positive relation to total

mortality and this lessens its importance to overall

health.

 

Passwater: Your study actually showed a benefit in

taking supplements beyond that of the " adequate "

intake from foods. Do you think that this fact will be

noticed by others in the nutrition community?

 

Enstrom: It is hard to know what the nutrition

community will do with this study, but I have been

surprised with the relative lack of criticism. I hope

I have stated my findings in such a qualified

 

way that they will not invite criticism. The

healthiest persons were those who consumed substantial

dietary vitamin C and used supplements containing

vitamin C on a daily basis. However, the supplement

usage in this study involved more than just vitamin C

pills because most supplement users consumed

multivitamin pills which contain several basic

nutrients. The use of supplements may be a marker for

other healthy behavior, but my results suggest an

effect for vitamin C even after controlling for ten

potentially confounding variables in addition to age

and sex (smoking, alcohol consumption, recreational

exercise, dietary fat, dietary calories, serum

cholesterol, dietary vitamin A, disease history,

education and race).

 

Passwater: Your study concentrated on vitamin C -- why

did you select vitamin C?

 

Enstrom: Vitamin C was selected because of theories

proposed by Dr. Linus Pauling related to the fact that

vitamin C is not naturally produced in the human body

and may be beneficial to humans in amounts greater

than those needed to prevent a deficiency disease like

scurvy. Very little epidemiologic research has been

done on vitamin C and total mortality, and this makes

it an area worthy of more investigation. Another

reason for investigating vitamin C is the fact that it

is relatively easy to change this risk factor if it is

shown to have value.

 

Passwater: What about the other antioxidant vitamins.

Does your data allow a study of vitamins A or E? If

so, will we be treated to a companion article on them?

 

Enstrom: The NHEFS did measure all the foods consumed

during a 24 hour period before the initial interview.

Calculations were done to convert these food lists

into dietary vitamin C and dietary vitamin A intake as

part of the original data processing using standard

food conversion tables. Similarly, it is possible to

calculate intake levels of beta carotene and vitamin E

from these same foods. I am in the process of doing

this now. It is my intention to construct an

antioxidant index and reanalyze the mortality data

with regard to the antioxidant hypothesis.

 

Passwater: That will be a major advance! There are so

many studies out there that miss the point. They look

at the quintiles of one antioxidant without regard for

the confounding actions of the other antioxidants.

Thus, they miss the protective effects of the

antioxidants not being studied -- which will distort

the quintile rankings -- and they will miss their

synergistic effects. I hope other investigators will

follow your lead and fine-tune their published data

with your antioxidant index to extract more

information.

 

Will you also examine the effects pro-oxidants? There

is an urgent question now concerning blood ferritin

levels and possibly dietary iron intake.

 

Enstrom: I will examine pro-oxidants like iron to the

extent possible with the data collected in the NHEFS.

If the recently reported relationships between

cardiovascular diseases and vitamin C and iron hold up

in subsequent studies, they could represent major new

risk factors.

 

Passwater: You did a study similar to the NHEFS study

earlier with Linus Pauling. That study, published in

the Proceedings of the National Academy of Sciences

(PNAS) used data from my 1974 Prevention study. [8]

Yet, when your study was published in 1982, it

received very little attention. Do you think the

attitudes have changed or do you think it's just the

strength of the data?

 

Enstrom: My 1982 paper in PNAS with Linus Pauling

involved a highly selected cohort of 479 elderly

California Prevention rs who completed a very

simple questionnaire. Thus, the data were very limited

and inconclusive, and this probably explains the

relative lack of attention that this paper received.

Also, the scientific community seems more receptive to

this area of investigation now.

 

Passwater: What did the 1982 data show?

 

Enstrom: The 1982 paper showed that this cohort of 479

elderly (65+ years) Prevention magazine rs

was substantially healthier than the general

population (with a total death rate about two-thirds

that of similarly aged Americans). Also, this cohort

was healthier than typical nonsmokers, but tended to

be similar to the health conscious nonsmokers in some

other questionnaire surveys. It was hard to analyze

the selection factors for this group because it

included persons who were very health conscious

currently -- but many of them had poor health in the

past. The results were inconclusive with regard to

benefits of vitamin E supplements because there were

so few (14) non-users of supplements. Also, the total

number of deaths (107) was too small to do any

detailed analyses.

 

Passwater: How did your recent study improve upon

this?

 

Enstrom: The NHEFS was a far better study because it

involved a nationally representative sample with many

more persons (11,348) and many more follow-up deaths

(1,809). It collected much more information about the

dietary habits and health characteristics of the

persons studied. Thus, it was possible to make

detailed analyses which showed a significant

beneficial effect for vitamin C among men even after

controlling for ten potential confounding variables.

 

Passwater: How well do the two studies correlate?

 

Enstrom: Precise comparison is difficult because of

the much different way the cohorts were assembled.

Roughly speaking, the Prevention cohort as a whole is

healthier than the elderly NHEFS nonsmokers, but

fairly similar to the elderly NHEFS non-smokers who

had high vitamin C intake. The females appear to be

much healthier than the males in the Prevention cohort

compared with sex differences in the NHEFS cohort.

 

Passwater: I remember sorting through the 17,894

responses by hand in my 1974 study for one variable at

a time. Now you use computers and sophisticated

analytical programs. Is there a chance that you can go

back and use these new tools to extract more

information from the old data? Can you follow up any

of the respondents from that study?

 

Enstrom: It would be difficult to follow the nearly

18,000 persons you questioned in 1974 because of the

limited identifying information that you collected.

However, I have continued to follow the California

portion (those in my 1982 PNAS paper) to a limited

extent and the results remain roughly similar. The

main problem with analyzing the specific effect of

vitamin supplements in this cohort is that there were

very few non-users of supplements to serve as a

control group.

 

Passwater: Will there be a follow-up study of the

NHANES participants, and, if so, when will you have

access to the data to do a follow-up of your present

study?

 

Enstrom: There is ongoing follow-up of the NHEFS

cohort, and I am now conducting an analysis of

follow-up through 1987 -- along with an analysis of

disease incidence in the cohort.

 

Passwater: In my books, I write about your studies

showing the benefits of a moderate lifestyle. You have

done several studies -- what are the main points

learned from these studies?

 

Enstrom: My studies on Mormons, Prevention magazine

readers, Alameda County residents practicing good

health habits, physicians who have stopped smoking,

and the NHEFS cohort have all been analyzed with

respect to major lifestyle variables with the goal of

identifying lifestyles that result in a low overall

death rate. [3, 8-11] I think that they indicate

substantial benefits of non-smoking, family structure,

health consciousness, good health habits, and vitamin

C intake in reducing premature deaths.

 

Passwater: Can we assume that you will be continuing

to follow these same groups?

 

Enstrom: Yes, I am continuing to follow these groups.

I believe in long-term studies of overall health in

well defined populations. More results from these

studies will be forthcoming in the next few years.

 

Passwater: What will you be looking into next?

 

Enstrom: Recently I have begun a collaboration with

the American Cancer Society to conduct a follow-up of

their 1959 Cancer Prevention Study through 1991. I

will then analyze the Cancer Prevention Study data

over a 32 year period (1960-1991) to determine

mortality trends in relation to smoking cessation and

to identify the most important lifestyle factors

associated with reduced mortality over a long period

of time.

 

Passwater: Wow! Are you one busy scientist. Thanks for

taking the time to chat about your research.

 

NOTE !!!

 

Since Dr. Enstrom's research was published, a Harvard

research team has published an abstract that vitamin C

reduces the risk for heart disease. [12]

 

REFERENCES

 

1. Take your vitamins -- and you may live

longer. FitzGerald, Susan Philadelphia Inquirer 1 (May

8, 1992)

 

2. Live longer with vitamin C. Cowley, Geoffrey

& Church, Vernon Newsweek 60 (May 18, 1992)

 

3. Vitamin C intake and mortality among a sample

of the United States population. Enstrom, James E.;

Kanim, Linda E. & Klein, Morton A. Epidemiol.

3(3):194-202 (May 1992)

 

4. Vitamin C and reduced mortality. Block,

Gladys Epidemiol. 3(3):189-91 (May 1992)

 

5. The decline in ischemic heart disease

mortality: Prospective evidence from the Alameda

County STudy. Kaplan, G. A.; Cohn, B. A.; Cohen, R. D.

& Guralnik, J. Amer. J. Epidemiol. 127:1131-42 (1988)

 

6. Heart Failure Moore, Thomas J. Random, NY

(1989) Simon & Schuster, NY (1990) ISBN 0-394-56958-X

 

7. Diet, Blood Cholesterol and Coronary Heart

Disease: A Critical Review of the Literature. Smith,

Russell L. Vector Enterprises, Santa Monica, CA (1988)

Also see " The Cholesterol Conspiracy " Smith Russell L.

Green, NY (1991) ISBN 0-87527-476-5

 

8. Mortality among health-conscious elderly

Californians. Enstrom, James E. & Pauling, Linus

Proceed. Natl. Acad. Sci. 79:6023-7 (Oct. 1982)

 

9. Persistence of health habits and their

relationship to mortality. Breslow, Lester and

Enstrom, James E. Preventive Med. 9:469-83 (1980)

 

10. Trends in mortality among California

physicians after giving up smoking: 1950-79. Enstrom,

James E. Br. Med. J. 286:1101-5 (1982)

 

11. Health practices and cancer mortality among

active California Mormons. Enstrom, James E. J. Nat.

Cancer Inst. 91:1807-14 (1989)

 

12. A prospective study of vitamin C and

incidence of coronary heart disease in women. Manson,

J.; Stampfer, Meir,; Willett, Walter; et al

Circulation 85:865 (abstract) (1992)

 

 

All rights, including electronic and print media, to

this article are copyrighted to © Richard A.

Passwater, Ph.D. and Whole Foods magazine (WFC Inc.).