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Back to Fat

Saturated Fat and Cardiovascular Disease Risk Factors

Synopsis

Several studies including randomized clinical trials have investigated the role of saturated fat in cardiovascular disease risk factors, particularly blood lipid markers. The evidence suggests that saturated fat may not be detrimental to cardiovascular risk factors.

Highlights

  • Evidence suggests that saturated fat intake does not have a detrimental effect on blood lipids;
  • The impact of saturated fat on other cardiovascular risk factors such as inflammation and glucose intolerance needs to be confirmed.

The Evidence

A meta-analysis of long-term randomized controlled trials examined the effect of low-fat vs. high-fat diets on the blood lipid levels of overweight and obese patients. The high-fat diets consisted of >30% of total energy from fat and, in general, saturated fat made up 12% to 15% of total energy. The following observations were made:1

  • Lower total cholesterol and LDL cholesterol levels were observed with low-fat diets;
  • Higher HDL cholesterol levels were observed with high-fat diets;
  • Low-fat diets increased the total cholesterol to HDL cholesterol ratio more than high-fat diets;
  • Lower triglyceride levels were observed with high-fat diets.

In a randomized controlled trial, saturated fat intake did not appear to affect lipid or lipoprotein levels among overweight and obese adults. The study consisted of 158 participants, who were randomized to 1 of 4 diets:2

  • high protein intake (30% of total energy) and high saturated fat intake (15% of total energy);
  • high protein intake (30% of total energy) and low saturated fat intake (7% of total energy);
  • moderate protein intake (20% of total energy) and high saturated fat intake (15% of total energy);
  • moderate protein intake (20% of total energy) and low saturated fat intake (7% of total energy).

The following observations were made:

  • After 4 weeks, no substantial differences were observed between the 4 groups with regard to total cholesterol, LDL cholesterol, HDL cholesterol, triglyceride and lipoprotein levels;
  • No differences in insulin sensitivity and glucose metabolism were observed between the high vs. low saturated fat diets of similar protein intake;
  • In the context of the low saturated fat diets, there was an increase in glucose levels with high protein intake compared to low protein intake; however, this difference was not observed in the context of the high saturated fat diets.

In another randomized crossover controlled trial, the effect of saturated fat on plasma fatty composition was evaluated in the context of carbohydrate restriction. Two isocaloric carbohydrate restricted (12% of total energy from carbohydrates) diets were compared: one was higher in saturated fat (31% of total energy) and the other was higher in unsaturated fat. The participants were 8 men aged 35 to 58 years, who followed each diet for 6 weeks.3

  • For both diets, there was no significant change in the total cholesterol to HDL cholesterol ratio or the LDL cholesterol to HDL cholesterol ratio;
  • Both diets resulted in a substantial decrease in triglyceride levels and the triglyceride to HDL cholesterol ratio;
  • Blood glucose, insulin levels and insulin resistance were not significantly different from baseline or between diets;
  • There were no significant differences in any of the serum inflammatory markers between diets.

Furthermore, a systematic review was conducted by Santos et al. to investigate the role of saturated fat on inflammation. Fifteen observational studies, mainly of cross-sectional design, were included in the review. Some studies suggested a positive association between saturated fat and C-reactive protein, an inflammatory marker, while others found no association. The findings did not support an association with adipokines, which are proteins linked to inflammation.4

Finally, it appears that not all saturated fats have the same effect on blood lipids and cardiovascular risk factors. In this regard, the types of saturated fatty acids and the source of saturated fat may also be important.

Conclusion

Saturated fat per se does not appear to have an adverse effect on blood lipid levels. Additional randomized controlled dietary intervention studies, including mechanistic studies, are needed to provide more definitive conclusions.

Moreover, more research is needed to investigate and better understand the impact of saturated fat on insulin resistance and other non-traditional cardiovascular risk factors such as inflammation.

Keywords: saturated fat , cardiovascular risk factors , inflammation


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