The results of several recently published studies paint a confusing picture of the relationship between specific dietary components or foods and risk of cardiovascular disease (CVD). In the view of this author, this research highlights the importance of focusing on overall dietary pattern (rather than a certain food), especially those patterns in which soyfoods play a part.
As way of background, for more than 60 years the American Heart Association (AHA) has been recommending replacing saturated fat with polyunsaturated fatty acids (PUFA) as a means of reducing risk of CVD.1 Nevertheless, U.S. intake of saturated fat is above the upper limit of 10% of calories recommended by the AHA and has remained so over the past 20 years.2
One reason may be that despite the position of the AHA, there is conflicting evidence regarding the impact of PUFA intake on CVD risk. In fact, very recently, a team of researchers acting on behalf of the Lipid and Blood Pressure Meta-analysis Collaboration Group failed to find based on their analysis of randomized clinical trials that omega-6 PUFA supplementation significantly reduced risk of CVD morbidity and mortality.3
There is also controversy about the impact of red meat on CVD risk. A 2019 meta-analysis of 36 randomized clinical trials noted the many inconsistencies regarding the effects of red meat on CVD factors. The authors of this analysis attributed this, in part, to the composition of the comparison diet.4 More recently, Zheng et al.5 found that among postmenopausal women in the Women’s Health Initiative Cohorts, a relatively high red meat intake was associated with an increased risk of coronary heart disease; however, this association was largely attributable to dietary pattern, rather than to the consumption of meat per se. This finding aligns with sentiment expressed in a newly published editorial in the American Journal of Clinical Nutrition, which states that when it comes to meat, “it is not the amount of meat in the diet that is the culprit, but rather the quality of that meat and the quality of the diet as a whole.”6
There is no dispute that many foods can affect blood cholesterol levels. A recent review by Schoeneck and Iggman7 not only identified these foods but assessed the strength of the evidence supporting their effect. For example, it was concluded that there is high evidence that soy protein had a small to moderate cholesterol-lowering effect whereas there was moderate evidence that avocados and turmeric caused moderate to large reductions. However, cholesterol is but one CVD risk factor. In fact, elevated blood pressure is likely a more important factor than elevated cholesterol.8 Fortunately, in many instances the type of foods and diet that lower cholesterol also lower blood pressure. This point has been demonstrated clinically by studies evaluating the portfolio diet, which is a comprehensive dietary approach to lowering CVD risk.9,10 Soyfoods play a key role in the portfolio diet.
One reason some individuals may opt to make few dietary changes is because of the existence of cholesterol-lowering drugs. Statins are used by approximately 40 million Americans over age 4011 and are remarkably effective at lowering blood cholesterol levels.12 Depending on the dose and type, statins lower LDL-cholesterol by approximately 50%, according to a meta-analysis of 164 short-term randomized placebo-controlled trials.12 However, statins only target elevated cholesterol and CVD, not other CVD risk factors and chronic diseases. Furthermore, a recent meta-analysis that included 21 clinical trials found absolute risk reductions associated with statin use of only 0.8% for all-cause mortality, 1.3% for myocardial infarction, and 0.4% for stroke.13 Also, all drugs — including statins — have side effects.
For all sorts of reasons, diet should be the first approach to leading a healthy lifestyle, which will in turn help prevent and, in some cases, manage non-communicable disease risk. Soyfoods certainly warrant consideration as foods to be incorporated into diets aimed at reducing CVD risk as well as other chronic diseases. In addition to soy protein lowering cholesterol levels,14 there is speculative evidence that soy protein also lowers blood pressure15 and reduces inflammation,16 two effects that reduce CVD risk. There is also intriguing but still very speculative evidence that soy reduces risk of breast17 and prostate18 cancer. Remember also, that nutrients in soyfoods may provide health benefits by virtue of replacing less healthful foods in the diet.
- Dietary fat and its relation to heart attacks and strokes. Report by the Central Committee for Medical and Community Program of the American Heart Association. JAMA 1961;175:389-91.
- Shan Z, Rehm CD, Rogers G, Ruan M, Wang DD, Hu FB, Mozaffarian D, Zhang FF, Bhupathiraju SN. Trends in dietary carbohydrate, protein, and fat intake and diet quality among US adults, 1999-2016. JAMA 2019;322:1178-87.
- Mazidi M, Shekoohi N, Katsiki N, Banach M. Omega-6 fatty acids and the risk of cardiovascular disease: insights from a systematic review and meta-analysis of randomized controlled trials and a Mendelian randomization study. Arch Med Sci 2022;18:466-79.
- Guasch-Ferre M, Satija A, Blondin SA, Janiszewski M, Emlen E, O’Connor LE, Campbell WW, Hu FB, Willett WC, Stampfer MJ. Meta-analysis of randomized controlled trials of red meat consumption in comparison with various comparison diets on cardiovascular risk factors. Circulation 2019;139:1828-45.
- Zheng C, Pettinger M, Gowda GAN, Lampe JW, Raftery D, Tinker LF, Huang Y, Navarro SL, O’Brien DM, Snetselaar L, et al. Biomarker-calibrated red and combined red and processed meat intakes with chronic disease risk in a cohort of postmenopausal women. J Nutr 2022.
- Magkos F. Meat in the human diet: in transition from evolutionary hallmark to scapegoat. Am J Clinical Nutr 2022.
- Schoeneck M, Iggman D. The effects of foods on LDL cholesterol levels: A systematic review of the accumulated evidence from systematic reviews and meta-analyses of randomized controlled trials. Nutrition, metabolism, and cardiovascular diseases : NMCD 2021;31:1325-38.
- Bundy JD, Li C, Stuchlik P, Bu X, Kelly TN, Mills KT, He H, Chen J, Whelton PK, He J. Systolic blood pressure reduction and risk of cardiovascular disease and mortality: A systematic review and network meta-analysis. JAMA Cardiol 2017;2:775-81.
- Jenkins DJ, Jones PJ, Frohlich J, Lamarche B, Ireland C, Nishi SK, Srichaikul K, Galange P, Pellini C, Faulkner D, et al. The effect of a dietary portfolio compared to a DASH-type diet on blood pressure. Nutrition, metabolism, and cardiovascular diseases : NMCD 2015;25:1132-9.
- Chiavaroli L, Nishi SK, Khan TA, Braunstein CR, Glenn AJ, Mejia SB, Rahelic D, Kahleova H, Salas-Salvado J, Jenkins DJA, et al. Portfolio dietary pattern and cardiovascular disease: A systematic review and meta-analysis of controlled trials. Prog Cardiovasc Dis 2018;61:43-53.
- Salami JA, Warraich H, Valero-Elizondo J, Spatz ES, Desai NR, Rana JS, Virani SS, Blankstein R, Khera A, Blaha MJ, et al. National trends in statin use and expenditures in the US adult population from 2002 to 2013: Insights from the Medical Expenditure Panel Survey. JAMA Cardiol 2017;2:56-65.
- Law MR, Wald NJ, Rudnicka AR. Quantifying effect of statins on low density lipoprotein cholesterol, ischaemic heart disease, and stroke: systematic review and meta-analysis. BMJ 2003;326:1423.
- Byrne P, Demasi M, Jones M, Smith SM, O’Brien KK, DuBroff R. Evaluating the association between low-density lipoprotein cholesterol reduction and relative and absolute effects of statin treatment: A systematic review and meta-analysis. JAMA internal medicine 2022.
- Blanco Mejia S, Messina M, Li SS, Viguiliouk E, Chiavaroli L, Khan TA, Srichaikul K, Mirrahimi A, Sievenpiper JL, Kris-Etherton P, et al. A meta-analysis of 46 studies identified by the FDA demonstrates that soy protein decreases circulating LDL and total cholesterol concentrations in adults. J Nutr 2019;149:968-81.
- Mosallanezhad Z, Mahmoodi M, Ranjbar S, Hosseini R, Clark CCT, Carson-Chahhoud K, Norouzi Z, Abbasian A, Sohrabi Z, Jalali M. Soy intake is associated with lowering blood pressure in adults: A systematic review and meta-analysis of randomized double-blind placebo-controlled trials. Complement Thr Med 2021;59:102692.
- Asbaghi O, Yaghubi E, Nazarian B, Kelishadi MR, Khadem H, Moodi V, Naeini F, Ghaedi E. The effects of soy supplementation on inflammatory biomarkers: A systematic review and meta-analysis of randomized controlled trials. Cytokine 2020;136:155282.
- Okekunle AP, Gao J, Wu X, Feng R, Sun C. Higher dietary soy intake appears inversely related to breast cancer risk independent of estrogen receptor breast cancer phenotypes. Heliyon 2020;6:e04228.
- Applegate CC, Rowles JL, Ranard KM, Jeon S, Erdman JW. Soy consumption and the risk of prostate cancer: An updated systematic review and meta-analysis. Nutrients 2018;10.
This blog is sponsored by SNI Global and U.S. Soy.