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Newsletters & Publications
| Volume
16 - Number 4 |
Winter 1999 |
COMMON ABBREVIATIONS
BMI: body mass index (kg/m2)
CAD: coronary artery disease
CHD: coronary heart disease
CHO: carbohydrate
CI: confidence interval
CVD: cardiovascular disease
ene: energy
HDL: high density lipoprotein
LDL: low density lipoprotein
Lp(a): lipoprotein (a)
MI: myocardial infarction
MUFA: monounsaturated fatty acids
NCEP: National Cholesterol Education Program
P:S: dietary polyunsaturated:saturated fat ratio
PUFA: polyunsaturated fatty acids
RR: relative risk
SFA: saturated fatty acids
TAG: triacylglycerol
VLDL: very low density lipoprotein
For the past several years, nutritionists
have been promoting the "5-A-Day" campaign to increase fruit and
vegetable intake as an intervention to lower CVD and cancer in
the population. And findings from a new study by Joshipura et al.
strongly supports the role of fruits and vegetables in protecting
against chronic illness. Based on the dietary habits of female
nurses and male health professionals in the Nurses' Health Study
(NHS) and the Health Professionals Follow-up Study (HPFS), eating
5 servings a day of fruits and vegetables was associated with a
significantly decreased incidence of ischemic stroke.
In these prospective cohort studies with 75,596
females and 38,683 males, 366 and 204 cases of ischemic stroke
were reported in women and men, respectively, during the follow-up
period. The median intake of total fruits and vegetables was 5.8
servings per day in women and 5.1 serving per day in men. The prevalence
of ischemic stroke was 31% lower in the quintile with the highest
fruit and vegetable intakes (9.7 servings) compared with the lowest
quintile (2.7 servings). Each serving of fruits and vegetables
was associated with a 6% lower risk of ischemic stroke. It was
also observed that higher fruit and vegetable intakes were associated
with a healthy lifestyle as indicated by higher rates of physical
activity and multivitamin supplement intake, and lower rates of
smoking. The protective role of fruits and vegetables against ischemic
stroke persisted even after controlling for multiple CVD risk confounders.
High intakes of cruciferous vegetable (broccoli
and cabbage), green leafy vegetables, citrus fruit juices, and
vitamin C-rich fruits and vegetables were especially protective
against ischemic stroke. The multivariate RRs of ischemic stroke
per 1 serving of cruciferous vegetable was 0.68 (95% CI, 0.49-0.94),
green leafy vegetable 0.79 (95% CI, 0.62-0.99), citrus fruit juices
0.75 (95% CI, 0.62-0.99), and vitamin C-rich fruits and vegetables
0.87 (95% CI, 0.61-0.96). However, "analyses of individual fruit
and vegetable items that constituted the composite items did not
show any single fruit or vegetable that was strikingly more protective
than others." Potatoes and legumes did not protect against ischemic
stroke, the RR values were 1.21 and 1.09, respectively.
The benefits associated with fruit and vegetable
intake against ischemic stroke were stronger in current smokers
and non-supplement users. However, the actual cases of ischemic
stroke were still much smaller in supplement users and non-smokers.
The strength of this relationship found in smokers and non-supplement
uses was probably the result of an attenuated relationship following
adjustment for standard CVD risk factors in the vitamin users and
non-smokers. Current findings also affirm the 5-A-Day campaign.
It showed that eating 5-5.9 servings of fruits and vegetables resulted
in maximum benefit. Eating more than this amount did not yield
further benefit.
The data from these 2 large epidemiological
studies strongly encourage increased fruit and vegetable consumption
for ischemic stroke risk reduction. It seems that 5 servings of
cruciferous and green leafy vegetables and citrus fruits and juices
are especially beneficial in protecting against ischemic stroke.
Joshipura KJ, Ascherio A, Manson JE, et al.
Fruit and vegetable intake in relation to risk of ischemic stroke. JAMA. 1999;282:1233-1239.
Key Messages
- Fruit and vegetable intake is associated with lower ischemic
stroke.
- People with higher fruit and vegetable intake also had lower
CVD risk factors.
- 5-6 servings of fruits and vegetables were associated with
maximum CVD benefit.
- Cruciferous leafy green vegetables, and citrus fruits and
juices were especially protective against ischemic stroke.
Table of Contents
Previous studies have firmly established a
cardioprotective role of dietary fiber in humans. For instance,
high fiber consumption is associated with achieving a healthy body
weight, blood pressure, blood cholesterol level, and normal blood
clotting factors. According to a new study by Ludwig Ludwig
od clotting factors. According to a new study by Ludwig and colleagues,
one possible mechanism behind this effect is lower insulin levels
following high fiber intake.
In this multi-centered, prospective study with
2,909 young adults between the ages of 18-30 years, the investigators
examined the role of fiber consumption and its association with
insulin levels, body weight, and other CVD risk factors as related
to other dietary components. Based on dietary histories taken during
the 7th year of this 10 year study, it was evident that fiber intake
was directly associated with positive lifestyle factors such as
a higher fitness level and vitamin supplement use, and inversely
associated with smoking. Fat intake, on the other hand, was associated
with smoking, inactivity, and lower vitamin supplement use. Dietary
fiber intake was higher among females and older study participants.
Aside from the healthier lifestyle factors, people with higher
fiber intakes, also had lower body weights, waist-to-hip ratios,
and fasting and 2 hour post-glucose insulin levels compared to
the group with the lowest fiber intake. The difference in body
weight between the lowest quintile (10 gm) and the highest quintile
(25 gm) of dietary fiber was 8.1 lbs in whites and 8.0 lbs in blacks.
The mean difference in waist-to-hip ratio, fasting insulin, and
2 hour post-glucose insulin levels for all subjects were -0.011,
-1.1 µU/ml, and -9.9 µU/ml, respectively, between quintiles 1 and
5. Other dietary factors, total fat, saturated and unsaturated
fat, and CHO, did not show significant differences in these 2 groups.
In addition to the physical changes noted
above, the highest fiber intake was also associated with improved
blood pressure and lipid parameters. The systolic blood pressure
decreased by 1.2 mm Hg, TAG decreased by 0.6 mg/dl, HDL cholesterol
increased by 1.3 mg/dl, LDL cholesterol decreased by 4.3 mg/dl,
and fibrinogen decreased by 7.2 mg/dl. These changes were much
larger before adjusting for fasting insulin. Dietary fats were
not associated with such change in CVD risk factors.
The inverse relationship noted between dietary
fiber and body weight, fasting insulin, lipids, and fibrinogen
levels in the current study, along with similar findings from the
Health Professional's Follow-up Study, lead Ludwig and colleagues
to conclude that "fiber may play a greater role in determining
CVD risk than total or saturated fat intake." This theory is based
on the premise that a high fiber intake results in lower blood
insulin levels due to lower glycemic index associated with dietary
fiber. Thus, by lowering insulin levels it is possible to alter
metabolic mechanisms associated with desire to consume excess food.
Also, independent of its effect on insulin, dietary fiber intake
has been shown to decrease body weight, in part due to low energy
density of these foods resulting in lower insulin resistance as
well as other CVD risk factors.
Ludwig DS, Pereira MA, Kroenke CH, et al.
Dietary fiber, weight gain, and cardiovascular risk factors in
young adults. JAMA. 1999;282:1539-1546.
Table of Contents
Weight loss and diet therapy have long been used
to counter elevated serum lipids, lipoproteins, and glucose concentrations
associated with many chronic maladies such as CHD, diabetes, and
hypertension. In a new study by Mori et al., overweight adults
achieved reduction in these measurements when these 2 treatment
modalities were simultaneously incorporated. In this investigation,
the researchers tested the independent and combined effects of
weight loss and omega-3 rich fish intake on serum lipids, glucose,
and insulin levels in 63 hypertensive subjects. During the 16-week
intervention, all subjects concurrently received antihypertensive
treatment along with one of the following dietary modifications:
weight maintenance diet (control group), weight maintenance diet
with daily fish intake (fish group), weight loss diet (weight loss
group), and weight loss diet with daily fish intake diet (combined
group). Subjects on the 2 fish diets were provided with Greenland
turbot, canned sardine, canned tuna, and canned salmon in order
to increase omega-3 fatty acid intake by 3.65 gm/day. The
baseline clinical and biochemical measurements were similar among
the study groups. However, post-treatment concentrations were vastly
different. For example, as expected, the cohorts in the 2 weight
loss diets lost more weight than the 2 weight maintenance groups.
The net difference in mean weight loss was 12 pounds compared to
no weight change in the 2 weight maintenance groups. Also, in these
groups, the total energy and percent of total fat, SFA, and MUFA
intakes were lower. The fish diets were associated with a significantly
higher intake of protein and PUFA. The 2 fish diets also resulted
in a 5.4% increase in plasma omega-3 fatty acid levels and 2.4%
decrease in plasma omega-6 fatty acids. All other macronutrient
intakes were similar among the groups.
After
treatment, the weight loss diet was associated with a 29% (4.05
pmol/l) reduction in fasting insulin levels and 28% and 8% reductions
in the area under the curve (AUC) for insulin and glucose during
an oral-glucose-tolerance-test, respectively. The fish diet alone
did not result in changes in fasting blood glucose and insulin
levels, however, following the combined treatment, these concentrations
were significantly lower. For example, the fasting insulin level
deceased by 33% (4.28 pmol/l) and ACU for glucose and insulin during
the oral-glucose-tolerance-test decreased by 9% (81 mmol/l) and
32% (2,846 mmol/l), respectively, indicating improve glucose metabolism. The
effects of weight loss and fish intake combined on the serum lipid
and lipoprotein levels were much greater than weight loss or fish
intake separately. For example, plasma TAG decreased by 67 gm/dl
(38%) compared to -22 mg/dl in the fish group and -20 mg/dl in
the weight loss group. Also, the increase in plasma HDL2 cholesterol
following combined treatment was significantly higher than with
the other 3 test diets. The increases in plasma total cholesterol,
LDL cholesterol, and HDL cholesterol levels during the fish diet
were not statistically different. Weight loss was associated with
a decrease in total cholesterol and increase in HDL and LDL cholesterol
concentrations. In addition to improvement in glucose metabolism
and serum lipid parameters, this combined therapy was also effective
in lowering blood pressure in these hypertensive adults. The systolic
and diastolic blood pressures decreased by 13 and 9.3 mm Hg, respectively.
This was approximately two times more than the changes noted following
the fish and weight loss diets separately.
The
data from the study by Mori et al. indicate that adding fish to
a low caloric diet is an effective way to control blood glucose,
insulin and lipid metabolism as well as blood pressure. Even though
dietary omega-3 fatty acids are associated with increase in glycemia,
secondary to hepatic glucose production and diminished insulin
secretion, combining it with a weight loss diet can lead to a synergistic
effect on lowering blood glucose concentrations. Finally, omega-3
fatty acid intake along with a reduced calorie diet might be a
safe treatment for high blood pressure without the negative side-effects
associated with some anti-hypertension drugs.
Mori TA, Bao DQ, Burke V, et al. Dietary fish
as a major component of a weight-loss diet: effect on serum lipids,
glucose, and insulin metabolism in overweight hypertensive subjects. Am
J Clin Nutr. 1999;70:817-825.
Table of Contents
In the family of grape products, purple grape
juice has been overshadowed by cardioprotective roles of red wine.
However, the tide is beginning to turn. According to Stein et al.,
like red wine, flavonoids found in purple grape juice improve endothelial
function and lower LDL oxidation rates, independent of alcohol.
In this 2-week clinical trial, 15 adults with
a history of CHD consumed 8 ml of purple grape juice per kg of body
weight, daily. All other fruit products, tea, and alcoholic beverage
consumption were prohibited. However, no changes were recommended
regarding the subjects' lipid lowering medication and dietary supplemental
practices.
The effects of purple grape juice on the flow-mediated
vasodilation (FMD) were measured using high-resolution brachial
artery ultrasonography. Baseline FMD measurement revealed that
subjects had impaired initial FMD values (2.2 ± 2.9%) which increased
to 6.4 ± 4.7% after 2 weeks of purple grape juice consumption.
The susceptibility of LDL to oxidation was also improved following
grape juice consumption which increased the lag time of conjugated
diene formation by 34.5% (87 ± 29 min to 117 ± 23 min). These CVD
protective effects were seen in spite of an increase in plasma
total cholesterol, LDL cholesterol, HDL cholesterol, TAG, total
cholesterol/HDL cholesterol ratio, and insulin levels following
grape juice intake.
The results from this investigation show that
drinking purple grape juice is associated with improved endothelial
function as well as reduced LDL oxidation. These cardioprotective
effects were evident in spite of subjects' lipid lowering and antioxidant
supplement use. Also, the fact that this relationship was evident
in the presence of increased plasma lipids suggests that grape
juice could be a relatively strong protective factor tool against
CVD. The authors concluded that "improved endothelium-dependent
vasodilation and prevention of LDL oxidation are potential mechanisms
by which flavonoids in purple grape products may prevent cardiovascular
events, independent of alcohol content."
Stein JH, Keevil JG, Wiebe DA. et al. Purple
grape juice improves endothelial function and reduces the susceptibility
of LDL cholesterol to oxidation in patients with coronary artery
disease. Circulation. 1999;100:1050-1055.
Table of Contents
The findings from Wannamethee and Shaper's investigation
add further evidence to a growing body of knowledge that regular
alcohol intake is associated with lower CHD risk. In this prospective
study, researchers compared the drinking habits of 7,272 middle-aged
men in the British Regional Heart Study with CHD events and all-cause
mortality rates during a 16.8 years follow-up period. During the
initial screening, the subjects' daily alcohol habits (frequency,
quantity, and type of alcoholic beverage) as well as other lifestyle
behaviors and medical history were recorded by a research nurse.
Based on this information, subjects were classified into 5 different
alcohol intake groups: none, occasional (less than 1 drink per
week), light (1-15 drinks per week), moderate (16-42 drinks per
week), and heavy (more than 6 drinks per day). There were 901 cases
of CHD events, 456 nonfatal and 445 fatal; and 1308 deaths from
all-causes, 595 cardiovascular and 713 noncardiovascular.
These
data indicated a U-shaped relationship between alcohol intake and
age adjusted major CHD events and all-cause mortality, with the
lowest rates seen in light drinkers. However, when other CHD risk
factors were included in the analysis, the RR for CHD events and
all-cause mortality was not different among the light, moderate,
and heavy drinkers. The researchers combined the data into 1 collective
group termed regular drinkers and compared this group to occasional
alcohol drinkers. The regular drinkers had a 23% lower risk of
CHD events; however, this advantage was not observed with all-cause
mortality. Type of alcoholic beverages consumed by the study cohorts
was a factor in the observed outcome. For example, the lower CHD
risk was observed only in men who regularly drank beer, spirits,
or beer and spirits. In the case of all-cause death, type of alcohol
beverage consumed did not alter the relationship. This unexpected
outcome might be due to a lower age-adjusted absolute rate of both
CHD events and all-cause mortality. However, when the effects of
different types of alcoholic beverages on CHD events and all-cause
mortality were separated, wine consumption was associated with
lower risk compared to both beer and spirits. One possible explanation
for lower CHD events and all-cause mortality in wind drinkers is
that as a group, they had a much healthier lifestyle and were in
better physical health.
This
study shows that enjoying a moderate amount of alcohol can be beneficial
to the heart, but does not protect against all-cause mortality.
Wine consumption was slightly better at decreasing CHD risk than
beer and spirit.
Wannamethee SG, Shaper AG. Type of alcoholic
drink and risk of major coronary heart disease events and all-cause
mortality. Am J Public Health. 1999;89:685-690.
Table of Contents
Ever since people became olive oil consumption has dramatically increased in the USA.
But according to Ramirez-Tortohealth conscious about their diets,
olive oil consumption has dramatically increased in the USA. But
according to Ramirez-Tortosa et al., not all olive oils are created
equal. It seems that extra-virgin olive oils, which undergo less
processing than refined olive oil, contain more alpha-tocopherol
and phenolic compounds, and are more protective against CVD. The
investigators tested this theory in 24 older, Spanish men with
peripheral vascular disease. In this crossover study, subjects
replaced visible saturated fat with either extra-virgin olive oil
or refined olive oil for a 3 month period each. There was a 3-month
washout period in between the dietary trials. Dietary composition
between the extra-virgin olive oil diet phase and the refined olive
oil diet phase were similar expect for alpha-tocopherol intake.
Extra virgin olive oil contained higher alpha-tocopherol levels
than refined olive oil. Also, the unsaponifiable matter in extra
virgin olive oil had higher concentrations of alpha-tocopherol
and polyphenols, while the fatty acid composition was similar between
the 2 olive oils. Plasma TAG levels were higher following the extra
virgin olive oil diet whereas all other plasma lipid and lipoprotein
levels were similar between the 2 diets. The susceptibility of
LDL to oxidize was less during the extra virgin olive oil phase.
Also, macrophage uptake of oxidized LDL was greater for LDL obtained
during the refined olive oil diet phase. While this study did not
show an improvement in plasma lipids and lipoproteins following
either type of olive oil intake, the reduced LDL oxidation susceptibility
with extra virgin olive oil indicates potential benefit in people
with a high risk of CVD. It is thought that extra virgin olive
oil reduces LDL oxidation due to its high content of polyphenolic
antioxidants.
Ramirez-Tortosa MC, Urbano G, Lopez-Jurado
M, et al. Extra-virgin olive oil increases the resistance of LDL
to oxidation more than refined olive oil in free-living men with
peripheral vascular disease. J Nutr. 1999;129:2177-2183
Table of Contents
In for this intercorrelation using multiple regression
analysis the mist of conflicting outcomes, the latest tea study
shows an inverse relationship between black tea intake and aortic
atherosclerosis in adults over 55 years old. Based on data from
the Rotterdam Study of 3,454 Dutch subjects, drinking black tea
was associated with less calcification of the aorta. Eighty-four
percent of men and 91% of women in the study drank approximately
3 cups and 3.5 cups of tea per day, respectively. And compared
to non-tea drinkers in the study, tea drinkers were leaner, and
less likely to smoke, drink alcohol and coffee, and eat fatty foods.
The tea drinkers were also more likely to take antioxidant supplements
and have a higher education level. The change in atherosclerosis
progression in the abdominal aorta from baseline to follow-up (2-3
years) was measured using lateral radiographic films. The abdominal
aorta calcification was present in 1,900 cases and was classified
in three groups: 641 mild (<1 cm), 1,061 moderate (1-5 cm),
and 198 severe (>5 cm). No calcification was found in 1,554
subjects who drank 2.9 cups/day of tea compared with 2.4 cups/day
of tea in the group with severe calcification. Based on multivariate,
logistic regression analyses, tea consumption was associated with
lower atherosclerosis risk in only the severe atherosclerosis group.
No significant relationship was found in the mild and moderate
atherosclerosis groups, after adjusting for confounding variables.
The odds ratios across categories of tea intake in the severe atherosclerosis
group were 0.54, 0.47, and 0.31 for 1-2 cups, 3-4 cups, and greater
than 4 cups, respectively. This association was especially strong
in women with severe atherosclerosis. The age-adjusted odds ratio
for severe atherosclerosis was 0.23 in the highest tea drinkers.
Findings from this study indicate that drinking a nice hot cup
of black tea is not only relaxing, but it may also protect the
heart due to antioxidant effects of flavonoids found in the tea.
Finally, Geleijnse et al. speculated that their outcome was different
from the Caerphilly Study in Welsh subjects possibly due to the
fact that Welsh subjects added milk to their tea. The added milk
was thought to reduce the bioavailability of flavonoids.
Hertog MG, Sweetnam PM, Fehily AM, et al.
Antioxidant flavonols and ischemic heart disease in a Welsh population
of men: the Caerphilly Study. Am J Clin Nutr. 1997;65: 1489-1494.
Geleijnse JM, Launer LJ, Hofman A, et al.
Tea flavonoids may protect against atherosclerosis. Arch Intern
Med. 1999;159: 2170-2174.
Table of Contents
The following briefs cover some of the many abstracts
presented at the 72th Scientific Sessions of the American
Heart Association (AHA) held in Atlanta, Georgia this past November.
Abstracts are published in Circulation, AHA's bimonthly
journal.
Eggs, Insulin Resistance and Obesity. To
determine if differences in the plasma cholesterol response to
dietary cholesterol were related to insulin sensitivity, Knopp
et al. studied the effects on plasma lipoproteins of adding 2 or
4 eggs per day to the diets of lean insulin-sensitive (LIS n=65),
lean insulin-resistant (LIR n=75) and obese insulin-resistant (OIR
n=58) subjects. Plasma LDL cholesterol was not significantly increased
in any group with 2 eggs/day but was increased in the lean groups
with 4 eggs/day. The OIR did not change. Changes in plasma HDL
cholesterol mimicked changes in LDL cholesterol and the LDL:HDL
ratio was unchanged with either level of egg feeding. Insulin sensitivity
was not a factor in the plasma cholesterol response to dietary
cholesterol whereas obesity attenuated the observed increases in
LDL and HDL cholesterol levels during the 4 eggs/day feeding phase. Knopp
et al. Effects of insulin resistance and obesity on the LDL response
to egg ingestion. Circulation. 1999;100 (suppl 1):I-116.
Xanthophylls and CHD Risk. Genetic
polymorphisms of HDL associated human serum paroxonase (PON) were
tested to determine potential effects on CHD risk. The authors
investigated gene-diet interactions between PON and xanthophylls,
another HDL associated antioxidants. The study population consisted
of 375 cases of MI and 273 matched controls. The authors observed
no significant differences in dietary carotenoid intakes between
PON 1 and PON2 genotypes but adipose levels were significantly
different for the genotypes (lutein and zeaxanthin only). Surprisingly,
the investigators found that adipose tissue levels of lutein-zeaxanthin
was positively associated with significantly lower incidences of
MI in both PON1 and PON2 genotypes. This relationship was not found
for adipose tissue levels of lycopene and alpha-carotene. The higher
levels of lutein-zeaxanthin in the PON2 group suggests differences
in xanthophyll metabolism in this group. The data also suggest
potential benefits from increased intakes of lutein and zeaxanthin
in lowering the risk of MI. Sen et al. Gene-diet interaction between
the paraoxonase 192 polymorphism and xanthophylls. Circulation.
1999;100 (suppl 1):I-659.
Cholesterol Absorption, Insulin Resistance
and Obesity. Obesity is associated with higher rates
of endogenous cholesterol synthesis which can result in lower
fractional absorption rates of cholesterol. In this study of
16 obese type 2 diabetic subjects (BMI 32) and 11 normoglycemic
obese controls, the investigators found a lower absorption
of cholesterol in the diabetics (30%) compared to controls
(42%). They also reported that obese diabetic subjects had
higher rates of cholesterol synthesis as well as higher rates
of fecal bile acid and neutral steroid excretion. The authors
concluded that diabetes has a marked influence on cholesterol
absorption efficiency, and low cholesterol absorption is part
of the insulin resistance syndrome. Simonen et al. Insulin
resistance contributes to lowering cholesterol absorption efficiency
in obesity. Circulation. 1999;100 (suppl 1):I-116.
Vitamins E and C and Carotid Atherosclerosis. The
Antioxidant Supplement in Atherosclerosis Prevention (ASAP) Study tests the efficacy of vitamin E and C supplementation
on the progression of carotid atherosclerosis in 520 smoking and
non-smoking men and postmenopausal women aged 45-69 years with
hypercholesterolemia. Subjects received either 200 mg/day d-alpha-tocopherol,
500 mg slow-release vitamin C, both vitamins, or placebo for 3
years. The average increases in carotid intima-media thickness
were: 0.020 mm/yr in men on placebo, 0.018 vit E, 0.017 vit C,
and 0.011 in vit E+C. In women the values were 0.016, 0.015, 0.017
and 0.016mm/yr respectively. The protective effect of the double
vitamin intake was greatest in smoking men and absent in women.
The data suggest that reasonable doses of both vitamin E and vitamin
C can retard the progression of common carotid atherosclerosis
especially in regularly smoking hypercholesterolemic men. Salonen
et al. The effect of vitamin E and vitamin C on carotid atherosclerotic
progression: The Antioxidant Supplementation in Atherosclerosis
Prevention (ASAP) Study. Circulation. 1999;100 (suppl 1):I-238.
CHD Risk During Menopause. The
Women's Healthy Lifestyle Project is a lifestyle intervention trial
in peri and postmenopausal women followed for 5 years. In this
study, 535 women (275 controls and 260 lifestyle interventions)
were studied to determine the efficacy of non-pharmacological interventions
to minimize the increase in plasma LDL cholesterol and weight associated
with peri and postmenopause. The lifestyle intervention included
reductions in total fat (25% of calories), saturated fat (7% of
calories), dietary cholesterol (100 mg/day), total calories (1300
kcal/day), and exercise (1000-1500 kcal/wk). The increases in LDL
cholesterol for control and intervention groups were: postmenopause
- 12 vs 3.8 mg/dl; with hormone replacement therapy (HRT) - 2.8
vs 2.1 mg/dl; without HRT 11.6 vs 6.3 mg/dl. While the authors
concluded that lifestyle interventions can effectively blunt the
rise in plasma LDL associated with menopause, the data indicate
that this is primarily true only in women not on HRT. Kuller et
al. A randomized clinical trial of risk factor modification in
535 healthy women during menopause. Circulation. 1999;100
(suppl 1):I-522.
Fish Consumption and ApoB Metabolism. Studies
have shown that fish consumption lowers CVD risk probably by multiple
mechanisms including effects on thrombosis and lipoprotein metabolism.
In this study, investigators determined the effects of fish consumption
on the rates of production of apoB-48 and apoB-100 in the non-fasting
state. A high fish diet was associated with a decreased production
rate of apoB-48 and apoB-100 in triglyceride rich lipoproteins
(TRL) with change in the fractional catabolic rate (FCR). These
changes resulted in a reduced TRL pool size. The high fish diet
also lowered the LDL apoB-100 pool size through an increase in
the production rate coupled with and increase in the FCR. The authors
concluded that a diet high in fish (n-3 fatty acids) blunts the
postprandial rise in plasma triacylglycerols due to a decrease
in TRL apoB production with little effect on the FCR. Lichtenstein
et al. Fish consumption decreases TRL apoB-48 & apoB-100 production
rates. Circulation. 1999;100 (suppl 1):I-659.
Dietary Fat and Weight Loss. To
determine effects of fat type and amount on CVD risk factors during
weight loss, 62 subjects were studied using 3 energy restricted
(-35%) test diets for 12 weeks: very low fat (10% ene fat); high
SFA (32% ene fat, 17% ene SFA); or low SFA (32% ene fat, 6% SFA). Plasma
LDL was lowest with the very low and low SFA diets; however, the
fall in plasma HDL levels was less with both 32% fat diets. All
diet groups had similar caloric intakes and comparable weight losses
and reductions in waist circumference over the 12 week test period.
Comparable changes in the plasma glucose response and fasting plasma
insulin levels were noted in all 3 diet groups. The fall in blood
pressure was least with the low fat diet. The authors concluded
that all energy restricted diets improve overall CVD risk factors
but that the low SFA diet appeared to confer maximal benefits.
Noakes & Clifton. Dietary fats in energy restricted diets:
effects on cardiovascular risk factors. Circulation. 1999;100(supp1):I-66
Central Adiposity and Carotid Atherosclerosis. Studies
were carried out to determine the associations between overall
obesity (BMI) and central adiposity (waist-to-hip ratio, WHR) with
the 4 year increase in mean and maximal intima-media thickness
(IMT) of the common carotid arteries. The study population involved
774 men 42-60 years of age. BMI
was not associated with the increase in mean and maximal IMT using
multiple regression analysis whereas WHR was directly related.
Men with WHR of <0.91, 0.91-0.96 and >0.96 had an increase
in mean IMT of 0.097, 0.110 and 0.123 mm/4 years. WHR was not associated
with the IMT increase in men with LDL cholesterol levels less than
150 mg/dl. The authors concluded that central adiposity accelerates
the progression of early atherosclerosis in middle-aged men, especially
in those with elevated serum LDL cholesterol. The data would indicate
that excess body weight per se is not necessarily a risk factor
for carotid atherosclerosis unless associated with central adiposity
and an elevated plasma LDL level. Lakka et al. Central obesity
and the progression of early carotid atherosclerosis in middle-aged
men. Circulation. 1999;100 (suppl 1):I-741.
Table of Contents
Over the past years there have been numerous
epidemiological surveys showing a null relationship between dietary
cholesterol and CVD incidence. These reports appear to contradict
many studies published in the 60s and 70s reporting significant
relationships between cholesterol in the diet and heart disease.
Even today some studies suggest significant relationships between
dietary cholesterol and CHD. Why do these various reports from
epidemiological surveys appear to be contradictory? The fact is,
they really aren't. This apparent conflict can easily
by explained by inspection of a report from the Twenty Countries
Study by Kromhout et al. (1995). These authors concluded that dietary
cholesterol, saturated fat (SFA), and trans-fatty acids were significantly
related with CHD incidence as determined by simple correlation.
In the case of dietary cholesterol, simple regression analysis
indicated a positive correlation between dietary cholesterol and
CHD mortality with a r value of 0.55 (P= 0.029). In a similar manner,
SFA calories also had a significant relationship of r = 0.88 (P < 0.0001).
At first glance it seems that both dietary cholesterol and SFA
are positively correlated with CHD rates. The problem
is that most cholesterol containing foods are high in SFA (eggs
are an exception), and these two nutrients are intercorrelated.
In the Twenty Countries Study there was a significant correlation
between dietary SFA and cholesterol (r = 0.62, P = 0.011). With
multiple regression analysis the only significant dietary correlation
is with SFA (P = 0.010) not dietary cholesterol (P = 0.895).
Is dietary cholesterol significantly related
to CHD rates in this study population? The answer is yes, and no.
Yes, based on simple correlation and no, following correction for
the colinearity of SFA and cholesterol in the diet. Kromhout and
colleagues stated that: "In the present study, a significant association
between average dietary cholesterol intake and long-term mortality
rates from coronary heart disease was also found. This correlation
was not independent of saturated and trans-fatty acids due to strong
intercorrelations.
Clearly, it is easy to document a simple relationship
between dietary cholesterol and CHD but such relationships only
obscure significant factors such as dietary SFA which do contribute
to CHD risk. This becomes clear when it is noted that no studies
in the 90s have found a significant relationship between dietary
cholesterol and CHD when correcting for this intercorrelation using
multiple regression analysis.
Kromhout D, Menotti A, Bloemberg B, et al.
Dietary saturated and trans fatty acids and cholesterol and 25-year
mortality from coronary heart disease: the Seven Countries Study. Prev
Med. 1995;24:308-15.
Donald J. McNamara, Ph.D.
Executive Editor, Nutrition Close-Up
Table of Contents
 Executive
Editor: Donald J. McNamara, Ph.D.
Writer/Editor: Linda Min, M.S., R.D.
Nutrition Close-Up is published quarterly
by the Egg Nutrition Center. Nutrition Close-Up presents
up-to-date reviews, summaries and commentaries on the latest research
investigating the role of nutrition in health promotion and disease
prevention, and the contributions of eggs to a nutritious and healthful
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