- Click here for explanation of classification scheme.

To determine the effects of individual fatty acids on the ratios of total to HDL cholesterol and on serum lipoproteins.

• Original research studies
• English
• Published between 1/1970-12/1998
• Food intake thoroughly controlled and described
• Dietary fatty acids the sole variable
• Cholesterol intake constant
• Parallel, crossover or Latin square design
• Feeding periods long enough to allow steady-state conc. of serum lipids and lipoproteins, i.e. > 13d
• Adult subjects (>17y) who did not have disturbances of lipid metabolism or diabetes

• Not meeting inclusion criteria
• Studies focusing on very-long-chain (n-3) PUFA's
• Studies on medium chain fatty acids

Search procedures: computer-assisted literature search. Scanned reference lists. Performed hands-on searches of journals.

Populations included: Multinational, adult subjects (>17y) who did not have disturbances of lipid metabolism or diabetes

Types of interventions: original research studies w/dietary tx where cholesterol intake was constant and results reported changes in serum lipids and lipoproteins.

Outcomes Investigated: Change in the total chol:HDL or in serum lipid concentration when CHO intake decreases by 1% energy and that of a particular FA increases by the same amount.

Study quality: assessed by study design type (had to be parallel, crossover, Latin-square, or before-after w/control group); diet tx > 13 d to achieve steady state of serum lipids.  No required sample size for inclusion.

Information abstracted from articles: Each data point consisted of:

Independent variable - FA composition of a particular diet Dependant variable - mean ratio of serum total chol:HDL or mean serum lipid concentration at end of dietary period

Analytic methods used: Estimated regression coefficients are the predicted change in the total chol:HDL or in serum lipid concentration when CHO intake decreases by 1% energy and that of a particular FA increases by the same amount.

Model 1: estimated effects on a particular outcome of all FA w/in a category (SFA, MUFA, PUFA)

Model 2: estimated effects of individual SFA's (lauric, myristic, palmitic, stearic)

Validity examined by use of Cook's distance to detect outliers and excluded observations w/Cook's distances>0.3; Collinearity was quantitated as tolerance; visually inspected plots.

# articles included: N=60

# of articles identified: not specified

Type of studies reviewed: see inclusion criteria

Sample size of studies: 159 diet data points and 1762 total volunteers

Characteristics of the study participants

• Gender Ratio: 70M:30F
• Mean Age (n=51): 21-72 years
• Mean total cholesterol concentrations (n=40): 143.0-251.3 mg/dL (pre-intervention)

Location of Trials

• US: 34 studies
• Netherlands: 8 studies
• Denmark: 4 studies
• Canada: 3 studies
• Finland, Isreal, Malaysia, Norway: 2 studies each
• Germany, Italy, UK: 1 study each

Test diets fed for 13-91 days.

Regression coefficients for mean ? in LDL (mmol/L) when CHO constituing 1% dietary energy is replaced isoentergetically w/FA's (n=43)

	SFA	MUFA	PUFA
r	0.032	-0.009	-0.019
95%CI	0.025, 0.039	-0.014, -0.003	-0.025, -0.013
P	<0.001	0.004	<0.001

• The cis MUFA's and PUFA's had slight lowering effect on LDL when replacing CHO isoentergetically.
• SFA had slight LDL raising effect.

Regression coefficients for mean ? in LDL (mmol/L) when CHO constituing 1% dietary energy is replaced isoentergetically w/lauric, myristic, palmitic, and stearic acid (n=35)

	12:0	14:0	16:0	18.0
r	0.052	0.048	0.039	-0.004
95%CI	0.026, 0.078	0.027, 0.069	0.027, 0.051	-0.019, 0.011
P	<0.001	<0.001	<0.001	0.464

• Lauric (12:0), myristic (14:0), and palmitic (16:0) all had significant slight LDL raising effect when isoentergetically replacing CHO.
• Stearic (18:0) had slightly decreased LDL but not significantly.

Mean change in LDL when CHO constituting 1% of dietary energy replaced isoentergetically w/trans MUFA's (n=8):

r = 0.040 (0.020, 0.060), p=0.002

The replacement of trans fatty acids with unsaturated fatty acids from unhydrogenated oils is the single most effective measure for improving blood lipid profiles.

The effects on surrogate lipid markers, the epidemiologic findings, and the results of controlled clinical trials all suggest that replacement of SFA's w/cis unsaturated fatty acids reduces CAD risk.

Our results may apply only to population wide issues of lipid management and not to individual patients, whereas total:HDL cholesterol may not be useful for subjects w/specific lipid abnormalities such as greatly decreased HDL or increased LDL concentrations

Government:	Netherlands Organization for Scientific Research
Not-for-profit	0 Foundation associated with industry:

Race/ethnicity of included trials not specified which limits generalizability.

Good mix of men to women and multi-national trial samples.

Mean initial total cholesterol concentrations limit generalizability to moderate- to hypercholesterolemic individuals.

Number of articles identified not specified, nor is number of articles excluded from meta-analysis.

Did not make sample size part of inclusion criteria which makes the quality of the studies w/in the meta-analysis questionable.