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Cholesterol Levels Coming Down, But Dietary Changes Still Needed

May 5, 2020

by Dr. Mark Messina

Cardiovascular disease (CVD) kills more Americans than any other disease. Coronary heart disease (CHD) accounts for the largest share of the diseases that fall under the umbrella of CVD as it is responsible for 13% of all U.S. deaths (~365,000/year).1 Elevated cholesterol is an important CHD risk factor – so a recent report from the Centers for Disease Control (CDC) is good news for the health of the American public.2

According to the CDC,* in recent years the number of American adults with elevated total cholesterol and low levels of high density lipoprotein cholesterol (HDL-C) has markedly declined.2 Soy protein and soybean oil, both of which have FDA approved heart health claims, are two dietary factors that clinical studies show can lower total and LDL-cholesterol (LDL-C).3,4  Soy protein may also raise HDL-C. While these effects on cholesterol are important, blood cholesterol is just one among many CHD risk factors. In fact, a large cohort of U.S. patients hospitalized with CHD found that almost half had LDL-C below the recommended upper limit of <100 mg/dl.5  Although the effects of soy on cholesterol has taken center stage, there is evidence that soy protein or other soybean components favorably affect more than one CHD risk factor.

In 1999-2000, the age adjusted prevalence of high total cholesterol (³240 mg/dl) was 18.3% whereas in 2017-2018 it was 10.5%.2 The prevalence of low HDL-C (<40 mg/dl) was 22.2% in 2007-2008 (data for earlier years not reported due to changes in laboratories and methods) whereas it was 16.0% in 2017-2018. Changes over time were statistically significant for both total and HDL-C.2

The CDC did not discuss the reasons for these declines. The evidence that statins played a role in reducing total cholesterol is impressive considering that statin use among U.S. adults 40 years of age and older in the general population increased 79.8% from 21.8 million individuals (17.9%) in 2002-2003 (134 million prescriptions) to 39.2 million individuals (27.8%) in 2012-2013 (221 million prescriptions).6

Despite the widespread use of statins and other cholesterol-lowering drugs,7 diet therapy remains the first line of approach for reducing elevated cholesterol and risk of CHD. Clinical studies show both soy protein8-10 and soybean oil11,12 lower total and LDL-C. In addition, some evidence indicates soy protein raises HDL-C and lowers blood triglyceride levels, the latter being another CHD risk factor.10 However, to markedly lower elevated cholesterol levels via diet requires adopting a comprehensive approach, the efficacy of which has demonstrated clinically by David Jenkins and colleagues from the University of Toronto through the use of the portfolio diet.13,14 Soyfoods and soy protein play a prominent role in this diet. 13,14

The portfolio diet has also been shown to lower blood pressure15 and some evidence indicates that soy protein may do likewise.16,17 These findings are important because reducing elevated blood pressure has been proven to reduce risk of death and CVD,18 thus confirming there is a lot more to CHD than elevated cholesterol.

In addition to elevated blood pressure and cholesterol, obesity and diabetes are also independent CHD risk factors. While achieving long-term weight loss has been proven difficult, there is some evidence that higher-protein diets may be helpful in this regard.19 Soybeans are higher in protein than other legumes and come without the amounts of saturated fat typically found in commonly consumed sources of protein in the U.S. diet.20 There is also evidence that soy helps regulate glucose levels, which over time, might help to reduce risk of developing diabetes.21

The reduction in blood cholesterol levels among Americans that has occurred over the past two decades is certainly a notable and welcomed achievement. Ideally, a reduction in cholesterol occurs as a result of making appropriate dietary changes because the changes that lower cholesterol are often the same as those that lower blood pressure and risk of other chronic diseases. Eating soyfoods is a step in the right direction.

*Data from the National Health and Nutrition Examination Survey (NHANES) from 1999–2000 through 2017–2018 were used for these analyses. Data from NHANES 2015–2018 were used to test differences between subgroups. Ten 2-year cycles (1999–2018) were used in testing for trends in the prevalence of high total cholesterol, and six 2-year cycles (2007–2018) were used for prevalence of low HDL-C.

References

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