Many Asian epidemiologic studies have examined the impact of soy intake on a variety of health outcomes. But surprisingly, until the results of the China Cardiometabolic Disease and Cancer Cohort [4C] study were published, no study had examined the relationship between soy intake and total CVD events and all-cause mortality in a Chinese population.1 Furthermore, many of the studies from China were focused on urban populations such as Shanghai,2,3 whereas the 4C study includes representatives from the entire population. The results of this study show that higher soyfood intake is associated with a reduced risk of total cardiovascular disease (CVD) events and all-cause mortality.
The 4C study recruited 193,846 men and women aged ≥ 40 years from 20 communities nationwide although the current analysis involved 97,940 participants. Of these, 66% were women and the average age was 56.15 years. During the mean follow-up period of 3.16 years, there were 2,523 total CVD events and 1,473 all-cause mortalities. Total CVD events include being hospitalized or treated for heart failure, non-fatal stroke, non-fatal myocardial infarction, and cardiovascular mortality.
Dietary intake was assessed via a food frequency questionnaire that included 16 items. To assess soy intake, participants were asked whether they regularly consumed soy during the year prior to study enrollment. Those who answered yes, were then asked to indicate how much and how often they consumed soy. For each participant, total soy consumption was referred to as the sum of all dietary soyfoods consumed per day and expressed as firm tofu equivalents.
Participants were divided into four soy intake categories according to the number of grams consumed per day:
- <15 grams – 50% of cohort
- 15-29 grams – 20% of cohort
- 30-59 grams – 18% of cohort
- ≥60 grams – 12% of cohort
The hazard ratios for these categories for total CVD events were 1.00 (reference), 1.03, 0.96 and 0.86, respectively, and the ratios for all-cause mortality were 1.00, 0.88, 0.86 and 0.83, respectively. In other words, risk of CVD events was reduced by 14% and risk of death by 17%. Both findings were statistically significant.
What is especially interesting about the findings is that they were adjusted for 17 factors: age, sex, education, urban/rural residence, healthy diet, total energy intake, smoking status, drinking status, physical activity, body mass index, systolic blood pressure, fasting high-density lipoprotein cholesterol, fasting low-density lipoprotein cholesterol, fasting total cholesterol, fasting triglycerides, and fasting plasma glucose. In observational studies, adjusting for these types of factors is common. However, several of these risk factors have been shown to be favorably affected by soy intake. For example, soy protein lowers blood cholesterol levels4,5 and may also lower blood pressure,6 although the evidence in support of the latter finding is less impressive. Soy may also favorably affect glucose levels.7
By controlling for these factors, it is possible the findings from the 4C study may have underestimated the potential for soy to reduce risk of CVD events and all-cause mortality. As to mechanisms, the authors of this report noted that soy contains isoflavones, phytosterols, lecithin, soluble fibers, saponins, and polysaccharides. It’s not clear that any one of these components was consumed in sufficiently large quantities to affect risk, which is why it is notable that the authors also suggested that these soy components may act collectively to confer unique health benefits.
- Xue T, Wen J, Wan Q, Qin G, Yan L, Wang G, Qin Y, Luo Z, Tang X, Huo Y, et al. Association of soy food with cardiovascular outcomes and all-cause mortality in a Chinese population: a nationwide prospective cohort study. Eur J Nutr 2022.
- Yang G, Shu XO, Jin F, Zhang X, Li HL, Li Q, Gao YT, Zheng W. Longitudinal study of soy food intake and blood pressure among middle-aged and elderly Chinese women. Am J Clin Nutr 2005;81:1012-7.
- Shu XO, Li H, Yang G, Gao J, Cai H, Takata Y, Zheng W, Xiang YB. Cohort profile: The Shanghai Men’s Health Study. Int J Epidemiol 2015;44:810-8.
- 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.
- Jenkins DJA, Blanco Mejia S, Chiavaroli L, Viguiliouk E, Li SS, Kendall CWC, Vuksan V, Sievenpiper JL. Cumulative meta-analysis of the soy effect over time. Journal of the American Heart Association 2019;8:e012458.
- 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.
- Mohammadifard N, Sajjadi F, Haghighatdoost F. Effects of soy consumption on metabolic parameters in patients with metabolic syndrome: A systematic review and meta-analysis. EXCLI journal 2021;20:665-85.
This blog is sponsored by SNI Global and the United Soybean Board.