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What are the effects of dietary stearic acid on LDL cholesterol?

Conclusion

Moderate evidence from a systematic review indicates that when stearic acid is substituted for other saturated fatty acids (SFA) or trans fatty acids, plasma LDL cholesterol (LDL-C) levels are decreased; when substituted for carbohydrates, LDL-C levels are unchanged; and when substituted for monounsaturated fatty acids (MUFA) or polyunsaturated fatty acids (PUFA), LDL-C levels are increased. Therefore, the impact of stearic acid replacement of other energy sources is variable regarding LDL-C, and the potential impact of changes in stearic acid intake on cardiovascular disease risk remains unclear.

Grade

Moderate

 

Evidence Summary Overview

A review of the evidence since 2000 resulted in one systematic review that covered all selected primary studies. This review was focused on the effect of stearic acid on cardiovascular disease (CVD) risks when substituted for saturated fat (SFA), trans fatty acids (TFA), monounsaturated fat (MUFA), polyunsaturated fat (PUFA) or carbohydrates (CHO) and provided the evidence to address this question (Hunter, 2010).

This systematic review covered 21 epidemiologic studies (three that assessed stearic acid specifically) and 22 randomized controlled trials (RCTs). Overall, the results showed that in comparison with SFA, stearic acid lowered LDL cholesterol (LDL-C), was neutral with respect to HDL cholesterol (HDL-C) and lowered the ratio of total to HDL-C. In comparison with unsaturated fatty acids, MUFA and PUFA, stearic acid tended to raise LDL-C, lower HDL-C and increase the ratio of total cholesterol (TC) to HDL-C. Replacing industrial trans fatty acids (iTFA) with stearic acid may increase stearic acid intake from 3% to 4-5% of energy in the US population.

Evidence Summary Paragraphs

Hunter et al, 2010 (neutral quality) This was a systematic review that examined the effect of stearic acid on blood LDL-C when substituted for SFA, MUFA, PUFACHO or TFA. This systematic review covered three epidemiologic studies that examined stearic acid specifically, and 20 RCTs that examined high stearic acid intake as a replacement of other dietary fats or CHO. The RCTs were grouped according to comparisons with:

  1. High SFA (palmitic acid, myristic acid, or butterfat)
  2. High CHO
  3. High unsaturated fat (oleic acid or linoleic acid)
  4. Baseline (or habitual) diet.

Four studies assessed the effect of substituting stearic acid for TFA in the diet. Both univariate and multivariate regression analysis was conducted with all selected studies. Overall, the results showed that in comparison with other SFA, stearic acid lowered LDL-C, was neutral with respect to HDL-C and lowered the ratio of TC to HDL-C. In comparison with unsaturated fatty acids (MUFA or PUFA) stearic acid tended to raise LDL-C, lower HDL-C and increase the ratio of TC to HDL-C. Univariate regression analysis of the data substituting stearic acid for cholesterol-raising SFA showed that the LDL-C concentration decreased as dietary stearic acid increased. The univariate regression coefficient for this relation was -0.036 (P=0.034). The regression coefficient suggests that for each 1% of energy increase in stearic acid, when substituted for cholesterol-raising SFA, the LDL-C concentration could decrease by 0.036mmol per L. When multivariate regression analysis was done, with adjustments for both between-study, and within-study, variation, the multivariate regression coefficient for this relation was 0.043 (<0.001), suggesting that for each 1% energy increase in cholesterol-raising SFA, when substituted for stearic acid, the LDL-C concentration would increase by 0.043mmol per L. Additionally, a one-to-one substitution of stearic acid for trans fatty acids showed a decrease or no effect on LDL-C, an increase or no effect on HDL-C and a decrease in the ratio of total to HDL-C. Replacing iTFA with stearic acid could increase stearic acid intake from 3% to 4-5% of energy in the US population. This systematic review provided broad qualitative and quantitative analysis, however, it was scored as methodologically neutral based on one limitation: The selected studies included in the review were not individually graded. Overall, this review provided the most updated evidence and covered all aspects of stearic acid replacements and risk/benefit outcomes related to LDL-C and CVD risk.



View table in new window
Author, Year,
Study Design,
Class,
Rating
Study Population/Location Intervention, Protocol/Exposure levels Significant Results Limitations
Hunter JE, Zhang J et al, 2010 

Study Design: Meta-analysis or Systematic Review

Class: M 

Rating: Neutral

International epidemiologic studies and RCTs.

 

Stearic acid and blood LDL-HDL-C and non HDL-C

Reviewed epidemiologic studies investigating stearic acid when substituted for SFA, MUFA, PUFA, CHO or TFA.

Conducted univariate and multivariate regression analysis with all selected studies.

Three epidemiologic studies that examined stearic acid specifically.

20 RCT that examined high stearic acid intake as a replacement of other dietary fats or CHO.

Four studies assessed effect of substituting stearic acid for TFAs in the diet.  

 

Comparison with other SFA, stearic acid:

  • LDL-C
  • Neutral with respect to HDL-C 
  • ↓ TC: HDL-C ratio.

Comparison with unsaturated FAs (MUFA or PUFA) stearic acid:

  • Tended to ↑ LDL-C
  • ↓ HDL-C
  • ↑ TC: HDL-C ratio.

Univariate regression analysis of the data substituting stearic acid for cholesterol-raising SFA:

LDL-C concentration ↓ as dietary stearic acid ↑ (univariate regression coefficient= -0.036 (P=0.034)

When multivariate regression (between- and within-study) multivariate regression coefficient=0.043 (<0.001)

One-to-one substitution of stearic acid for TFAs showed:

  • ↓ or no effect on LDL-C
  • ↑ or no effect on HDL-C
  • ↓ in the ratio of TC to HDL-C. 
 

Included studies were not graded.

 

Research Design and Implementation
For a summary of the Research Design and Implementation results, click here.