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Recommendations Summary

DLM: Carbohydrate, Protein and Fiber 2011

Click here to see the explanation of recommendation ratings (Strong, Fair, Weak, Consensus, Insufficient Evidence) and labels (Imperative or Conditional). To see more detail on the evidence from which the following recommendations were drawn, use the hyperlinks in the Supporting Evidence Section below.


  • Recommendation(s)

    DLM: Carbohydrates and Protein in the Cardioprotective Diet

    The Registered Dietitian (RD) should consider replacing saturated fat and trans-fatty acids with unsaturated fatty acids, complex carbohydrates and/or protein in the cardioprotective dietary pattern. Saturated and trans fatty acids should be as low as possible. Studies are needed to determine the ideal percentages of these macronutrients as replacements for saturated fat.

    Rating: Strong
    Imperative

    DLM: Fiber in the Cardioprotective Diet

    The Registered Dietitian (RD) should incorporate fiber-rich foods that contribute at least 25g to 30g of fiber per day, with special emphasis on soluble fiber sources (7g to 13g) into the cardioprotective dietary pattern. These foods rich in soluble fiber include: fruits, vegetables and whole grains, especially high-fiber cereals, oatmeal, and legumes, especially beans.

    Risk factors associated with coronary heart disease (CHD) and cardiovascular disease (CVD) are decreased as dietary fiber intake increases. Diets high in total and soluble fiber, as part of a cardioprotective diet, can further reduce total cholesterol (TC) by 2% to 3% and low-density lipoprotein cholesterol (LDL-C) up to 7%. 

    Rating: Strong
    Imperative

    • Risks/Harms of Implementing This Recommendation

      There are no potential risks or harms associated with the application of this recommendation.

    • Conditions of Application

      In cases where protein restriction could be indicated (e.g., renal insufficiency, liver disease), this macronutrient distribution may need to be modified. 

    • Potential Costs Associated with Application

      There are no obvious costs associated with the application of this recommendation.

    • Recommendation Narrative

      Replacing Saturated Fat with Carbohydrates or Protein

      • Data on the ideal isocaloric substitution of carbohydrate and protein to maximize LDL-C lowering are limited. Traditionally, a low-fat diet is one in which total fat and saturated fat calories are replaced by carbohydrates, such as the Step I and II diet, the Therapeutic Lifestyle Changes (TLC) diet, or the DASH diet.
      • Although not all studies report percentage of calories from carbohydrates, two positive quality randomized controlled trials (RCTs) (Ginsberg et al, 1998; Lichtenstein, 2002) did compare a Western-type diet to a low-fat/saturated fat diet, higher in carbohydrates, and found reductions in TC and LDL-C
      • A neutral quality meta-analysis (Yu-Poth et al, 1999) found that when cholesterol-raising saturated fatty acids (lauric, myristic, and plamitic acids) were replaced with carbohydrates, LDL was reduced. Similarly, a different neutral quality meta-analysis (Mensink et al, 2003) found replacing carbohydrates isoenergetically with saturated fat was associated with an increase in LDL-C.
      • No studies compared varying levels of protein
      • Studies included two positive quality RCTs (Ginsberg et al, 1998; Lichtenstein, 2002) and two neutral quality meta-analyses (Mensink et al, 2003; Yu-Poth et al, 1999).

      Dietary Fiber

      • Seven studies provide evidence that consuming diets high in total dietary fiber (greater than 25g per day) is associated with decreased risk for CHD and CVD
        • Studies included three positive quality cohort studies (Liu et al, 1999; Liu et al, 2002; Wolk et al, 1999); two neutral quality cohort studies (Bazzano et al 2003; Merchant et al, 2003); one neutral quality meta-analysis of pooled analysis of cohort (Pereira et al, 2004) and one negative quality consensus statement (Van Horn et al, 1997)
      • Six studies provide evidence that consuming diets high in total fiber (17g to 30g per day) and soluble fiber (7g to 13g per day) as part of a diet low in saturated fat and cholesterol can further reduced TC by 2-3% and LDL up to 7%
        • Studies included two positive quality RCTs (Jenkins et al, 2002; Van Horn et al, 2001),  one positive quality cohort study (Ludwig et al, 1999),  one positive quality meta-analysis (Brown et al, 1999),  and two neutral quality RCTs (Davy et al, 2002; Saltzman et al, 2001)
      • Six studies provide evidence that limited research indicates that other risk factors for CHD may be modified by a diet low in saturated fat and cholesterol and high in total and soluble fiber. These risk factors include blood pressure, lipoprotein subclasses and particle sizes, and fasting and post-prandial insulin.
        • Studies included two positive quality RCTs (Jenkins et al, 2002; Van Horn et al, 2001),  one positive quality cohort study (Ludwig et al, 1999),  one positive quality meta-analysis (Brown et al, 1999), and two neutral RCTs (Davy et al, 2002; Saltzman et al, 2001). 
      • Five population-based cohort studies (three neutral quality and two positive quality) and one neutral quality meta-analysis found dietary fiber was inversely associated with risk of CHD,  peripheral artery disease (PAD) and/or CVD
      • A neutral quality meta-analysis (Pereira et al, 2004) reported 2g to 10g of soluble fiber was associated with reductions in TC. This was confirmed by two positive quality RCTs (Jenkins et al, 2002; Van Horn et al, 2001) that found either two servings of oats, or a diet that contained 30g total and 13g soluble fiber, reduced TC and LDL-C independent of a low-saturated fat diet. One of these studies (Jenkins et al, 2002) also reported reductions in TG, TC/HDL, and LDL/HDL. A neutral quality RCT (Saltzman et al, 2001) also found reductions in TC and LDL-C with 16g total and 7g soluble fiber diet, however the reported reductions in TC and LDL-C were not independent of a low-saturated fat diet.
      • Two studies (Davy et al, 2002; Ludwig et al, 1999) examined the impact of fiber-containing foods on other risk factors for CVD. One neutral quality RCT (Davy et al, 2002) found a diet rich in oats not only reduced LDL-C and LDL/HDL, but also reduced small-LDL subclass and LDL particle number. A positive quality cohort study (Ludwig et al, 1999) found a linear association from the lowest to highest intake of fiber with regards to body weight, waist-to-hip ratio, fasting insulin, and two-hour post-glucose insulin. Fiber was also inversely associated with blood pressure, fibrinogen, and levels of TG, HDL, and LDL. 
      • Results of this evidence analysis were supplemented by a later review of the literature dated January 2008. There may be some overlap in the included studies.
        • A total of thirty-seven studies provide evidence that dietary fiber intake from whole foods or supplements may lower blood pressure, improve serum lipids and reduce indicators of inflammation. Benefits may occur with intakes of 12g to 33g per day from whole foods or up to 42.5g of fiber per day from supplements.
        • Sixteen studies provide evidence that: 
          • High-fiber diets may be associated with lower blood pressure when consumed at doses of 12g to 22g of fiber per day and with lower serum lipids when consumed at 12g to 33g of fiber per day. These diets may also be associated with improvements in apolipoproteins and inflammation. The sources and types of fiber cannot be specified because different fiber sources and combinations of fiber-rich foods were used. Further study is required to identify specific recommendations for optimal dosage and types of fiber.
            • Studies included four positive quality RCTs (Davy et al, 2002; Juntunen et al, 2003; King et al, 2007; Pins et al, 2002), two positive quality cross-sectional studies (Qi et al, 2006; McKeown et al, 2004), one positive quality non-randomized trial (Jacobs et al, 2002), one positive quality cohort study (Mozaffarian et al, 2003), one positive quality meta-analysis (Kelly et al, 2007), two neutral quality meta-analyses (Pereira et al, 2004; Ripsin et al, 1992), one neutral quality RCT (Pittaway et al, 2006), one neutral quality cross-sectional study (Lairon et al, 2005), one negative quality review (Glore et al,  1994), and one negative quality RCT (Anderson et al, 1995)
        • Twenty-three studies provide evidence that:
          • Fiber supplements in doses of 4g to 24g per day may be associated with lower blood pressure. Plasma lipids improved with doses of up to 42.5g per day, with greater reduction of LDL-C from soluble fiber than insoluble fiber. Fiber supplements may also be beneficial in improving measures of inflammation such as C-reactive protein and improving apolipoprotein levels. There is some evidence that cereal and fruit fibers reduce the risk of fatal and non-fatal CVD events. In addition, in some studies, the concurrent interventions of reduced energy or lower-fat diets or the presence of adiposity may have impacted the outcomes. Further study is required to identify specific recommendations for optimal dosage and types of fiber.
          • Studies included twelve positive quality RCTs (Alles et al, 1999; Demark-Wahnefried et al, 1990; Kashtan et al, 1992; Keenan et al, 1991; King et al, 2007; Knopp et al, 1999; Rossner et al,  1987; Ryttig et al, 1989; Schwab et al,  2006; Shane and Walker, 1995; Sola et al, 2007; Vuksan et al,  1999), nine neutral quality RCTs (Birketvedt et al, 2000; Frape and Jones, 1995; Jenkins et al, 2002; Jenkins et al, 1993; Kirsten et al, 1992; Nami et al, 1995; Robitaille et al,   2005; Solum et al, 1987; Tai et al, 1999), one neutral quality time series (Nicolosi et al, 1999), and one negative quality non-randomized trial (Stasse-Wolthuis et al, 1980).

    • Recommendation Strength Rationale

      Replacing Saturated Fat with Carbohydrates or Protein

      • An historical approach to a low-fat diet provides evidence to support the recommendation of replacing saturated fat with carbohydrates. The historical approach is supported by two positive quality RCT feeding studies and two neutral quality meta-analyses.
      • The ideal substitution of protein for fat components is an option for individuals at all risk levels, since the evidence is still evolving
      • One consensus document reports the Acceptable Macronutrient Distribution Ranges (AMDRs) for adults for fat, protein, and carbohydrates are estimated to be 20% to 35%, 10% to 35%, and 45% to 65% of energy, respectively (IOM, 2002)
      • Conclusion statement is Grade III based on based on two positive quality RCTs and two neutral quality meta-analyses.

      Fiber

      • Consistency across multiple cohort studies, high-quality RCTs, and meta-analyses. Studies were of men and women. Although ethnicities were not reported in all studies, one study (Ludwig et al, 1999) separated findings for white and black individuals and found similar results.
      • Two methodologies of measuring dietary fiber intake were used (i.e., food record and research-controlled diet intake approaches)
      • In addition, studies reporting biological changes that lead to CHD and CVD risks support recommendation
      • Conclusion statements are as follows:
        • Grade II for the Relationship between Fiber Intake and CHD Outcomes, based on three positive quality cohort studies, two neutral quality cohort studies,  one neutral quality pooled analysis of cohort, and one negative quality consensus statement   
        • Grade I for Consuming High Fiber Foods as Part of a Diet Low in Saturated Fat/Cholesterol to Reduce Total Cholesterol and LDL More Than a Diet Low in Saturated Fat/Cholesterol Alone, based on two positive quality RCTs,  one positive quality cohort study, one positive quality meta-analysis, and two neutral RCTs
        • Grade III for Modification of Risk Factors for CHD by a Low Saturated fat/Cholesterol,  High Total/Soluble Fiber Diet, based on the same six studies as above
        • Grade II for Dietary Fiber from Whole Foods and Dietary Supplements in Cardiovascular Disease, based on fifteen positive quality RCTs, ten neutral quality RCTs, two positive quality cross-sectional studies, one positive quality non-randomized trial, one positive quality cohort study, one positive quality meta-analysis, two neutral quality meta-analyses, one neutral quality cross-sectional study, one neutral quality time series, one negative quality non-randomized trial, one negative quality RCT, and one negative quality review.

    • Minority Opinions

      None.