Soya - HEART UK

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Research has extensively explored the relationship between soya and CVD, focussing on its ability to lower LDL cholesterol^2–4. The benefits are often attributed to its favourable nutritional composition.

Take home messages

Soya foods and drinks have a beneficial nutrient profile: they are naturally low in saturated fat, provide unsaturated fat and fibre, and soya protein is of high quality.
Consuming soya foods and drinks daily has been proven to lower LDL cholesterol by up to 10%.
The cholesterol-lowering properties of soya have been attributed to:
- soya foods are often consumed instead of full fat milk and meat which are high in saturated fat
- the unique protein structure of soya has been shown to up-regulate LDL receptors within the liver, so more cholesterol is removed from the body.
Cholesterol lowering can be achieved with 15g of soya protein per day, which is equivalent to two large glasses of soya drink or 100g of fresh young edamame beans
Higher soya food intakes have also been associated with lower blood pressure and improved endothelial function.

Research has extensively explored the relationship between soya and CVD, with a specific focus on its ability to lower LDL cholesterol^2–4. The cardio-protective benefits are often attributed to its favourable nutritional composition.

Soya's nutrition profile

Soya beans and soya-based foods and drinks are typically low in saturated fat and are valuable sources of essential unsaturated fatty acids, namely linolenic acid (LA) and alpha-linoleic acid (ALA)^4,5. This is significant because the fat profile of diets plays a pivotal role in CVD risk^6–9. Additionally, soya beans provide a mixture of fibres, vitamins and minerals.

The evidence

Soya and its low saturated fat profile

Extensive research highlights the vital role of reducing saturated fat intake for lowering LDL cholesterol and improving CVD outcomes^7,8. The choice of nutrient for replacing saturated fat is important, with unsaturated fats offering optimal results^7,9. The most recent WHO meta-analysis found that substituting saturated fat with polyunsaturated fats reduces the incidence of CHD by 11%, and monounsaturated fats reduces CHD incidence by 17%⁹.

Unsurprisingly, dietary recommendations from the European Society of Cardiology, the European Atherosclerosis Society, and the American Heart Association for CVD prevention emphasise reducing dietary saturated fat in favour of unsaturated fats^6,10.

Soya and cholesterol

In 2019, a comprehensive meta-analysis of 46 RCTs with a total of 2,607 participants, reported on the impact of a median 25g daily soya protein intake compared to a healthful low fat and very low saturated fat diet. Over a 6-week period, 25g daily soya resulted in a modest yet statistically significant reduction in LDL cholesterol of 0.12 mmol/L (equivalent to 3.2%) and a decrease in total cholesterol of 0.17 mmol/L (2.8%) compared to the control group^11,12. This effect was ascribed to the intrinsic properties of soya, with the observation that more significant reductions could be attained when soya foods replace saturated fat-rich foods. Furthermore, dose-response analysis revealed no discernible effect across the range used in the 46 trials (12.5g to 75g of soya protein a day). Consequently, it is plausible to suggest that intakes below 25g may be equally effective.

This observation is in line with the findings of a previous systematic review and meta-analysis which found a 7.9-10.3% decrease in LDL cholesterol levels when 13-58g of animal-based foods high in saturated fat and cholesterol were replaced with an equivalent quantity of soya foods¹³. This study also found no dose-dependent relationship. Those who ate as little as 15g soya protein a day had a similar impact on cholesterol to those with higher intakes.

Proposed mechanism

In summary, the cholesterol-lowering benefits of soya foods have been attributed to two main factors:

Extrinsic factor: soya displaces animal foods in the diet which contain more saturated fats. Soya is low in saturated fats and higher in unsaturated fats. This fat profile is one of the most influential dietary elements for reducing LDL cholesterol and lowering cardiovascular risk^7,9,12,13.
Intrinsic factor: soya protein itself has been shown to directly reduce serum cholesterol. The precise mechanism remains under investigation, but it is suggested that the 7S globulin fraction of soya protein can upregulate liver LDL receptors, reducing blood cholesterol^11,13–15.

Other cardioprotective benefits of soya

High blood pressure, a major modifiable risk factor for cardiovascular disease, is responsible for over half of CVD-related deaths¹⁶. Research suggests that soya foods may mildly reduce blood pressure but more evidence is needed¹⁷.

Other evolving evidence supports an association between the anti-inflammatory properties of soya isoflavones and improved endothelial function, decreased inflammatory markers, and reduced arterial stiffness^4,18.

Effective dose: 15g-25g soya protein daily

Achieving 15g-25g soya protein daily

Those who are not familiar with soya foods would benefit from a gradual introduction where they would gain the benefits of displacing saturated fat and build up slowly to the 25g effective dose.

Start with 1 serving daily and build up to 2-3 servings

Soya food/drink	Serving	Soya protein (g) per serving	Notes
Soya drinks	Large glass – 250ml	7.5-8g	Choose unsweetened fortified varieties
Soya alternatives to yogurt (plain)	Average serving – 150g	5g	Choose unsweetened fortified varieties
Edamame: green/young soya beans	3-4 tbsp – 80g	13g	Can be found with chilled salads or in the frozen section of supermarkets
Tofu	½ block – 90g	11g	Calcium-set varieties are exceptionally rich in calcium
Tempeh: fermented tofu with a higher protein concentration	½ block – 80g	17g	Check salt levels
Soya mince	100g	19g	Can be found with chilled alternative meat proteins or in the frozen section of supermarkets
Soya burgers Soya sausages	1 – 90g 2 – 80g	17g 12g	Nutritional quality will depend on other added ingredients. Always check labels. Using front of pack nutrition labels, opt for varieties showing green for salt and saturated fat, or if using the ingredients list, avoid those with added coconut or palm fats

Watch our CPD e-module: The four cholesterol lowering foods

Read about the other cholesterol-lowering foods

Nuts Oats and barley Sterols and stanol esters

References

Rizzo G, Baroni L. Soy, Soy Foods and Their Role in Vegetarian Diets. Nutrients. 2018;10(1):43. doi:10.3390/nu10010043
Lou D, Li Y, Yan G, Bu J, Wang H. Soy Consumption with Risk of Coronary Heart Disease and Stroke: A Meta-Analysis of Observational Studies. Neuroepidemiology. 2016;46(4):242-252. doi:10.1159/000444324
Nachvak SM, Moradi S, Anjom-shoae J, et al. Soy, Soy Isoflavones, and Protein Intake in Relation to Mortality from All Causes, Cancers, and Cardiovascular Diseases: A Systematic Review and Dose–Response Meta-Analysis of Prospective Cohort Studies. Journal of the Academy of Nutrition and Dietetics. 2019;119(9):1483-1500.e17. doi:10.1016/j.jand.2019.04.011
Messina M. Soy and Health Update: Evaluation of the Clinical and Epidemiologic Literature. Nutrients. 2016;8(12):754. doi:10.3390/nu8120754
Messina M, Duncan A, Messina V, Lynch H, Kiel J, Erdman JW. The health effects of soy: A reference guide for health professionals. Front Nutr. 2022;9:970364. doi:10.3389/fnut.2022.970364
Mach F, Baigent C, Catapano AL, et al. 2019 ESC/EAS Guidelines for the management of dyslipidaemias: lipid modification to reduce cardiovascular risk: The Task Force for the management of dyslipidaemias of the European Society of Cardiology (ESC) and European Atherosclerosis Society (EAS). European Heart Journal. 2020;41(1):111-188. doi:10.1093/eurheartj/ehz455
SACN. Saturated fats and health. GOV.UK. Published August 2019. Accessed October 16, 2023. https://www.gov.uk/government/publications/saturated-fats-and-health-sacn-report
Mensink RP, World Health Organization. Effects of Saturated Fatty Acids on Serum Lipids and Lipoproteins: A Systematic Review and Regression Analysis. World Health Organization; 2016. Accessed October 16, 2023. https://iris.who.int/handle/10665/246104
Reynolds AN, Hodson L, de Souza R, Pham HTD, Vlietstra L, Mann J. Saturated fat and trans-fat intakes and their replacement with other macronutrients: a systematic review and meta-analysis of prospective observational studies.
Arnett DK, Blumenthal RS, Albert MA, et al. 2019 ACC/AHA Guideline on the Primary Prevention of Cardiovascular Disease: A Report of the American College of Cardiology/American Heart Association Task Force on Clinical Practice Guidelines. Circulation. 2019;140(11):e596-e646. doi:10.1161/CIR.0000000000000678
Blanco Mejia S, Messina M, Li SS, 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. The Journal of Nutrition. 2019;149(6):968-981. doi:10.1093/jn/nxz020
Jenkins DJA, Blanco Mejia S, Chiavaroli L, et al. Cumulative Meta‐Analysis of the Soy Effect Over Time. Journal of the American Heart Association. 2019;8(13):e012458. doi:10.1161/JAHA.119.012458
Jenkins DJA, Mirrahimi A, Srichaikul K, et al. Soy Protein Reduces Serum Cholesterol by Both Intrinsic and Food Displacement Mechanisms, ,. The Journal of Nutrition. 2010;140(12):2302S-2311S. doi:10.3945/jn.110.124958
Cho SJ, Juillerat MA, Lee CH. Cholesterol Lowering Mechanism of Soybean Protein Hydrolysate. J Agric Food Chem. 2007;55(26):10599-10604. doi:10.1021/jf071903f
Arnoldi A, Kurowska E, Carroll KK, et al. Soy Protein Peptides Regulate Cholesterol Homeostasis in Hep G2 Cells. The Journal of Nutrition. 2000;130(10):2543-2549. doi:10.1093/jn/130.10.2543
Global Burden of Disease Collaborative Network. Global Burden of Disease 2019. Institute for Health Metrics and Evaluation. Published 2019. Accessed October 16, 2023. https://vizhub.healthdata.org/gbd-results
Mosallanezhad Z, Mahmoodi M, Ranjbar S, et al. Soy intake is associated with lowering blood pressure in adults: A systematic review and meta-analysis of randomized double-blind placebo-controlled trials. Complementary Therapies in Medicine. 2021;59:102692. doi:10.1016/j.ctim.2021.102692
Ramdath DD, Padhi EMT, Sarfaraz S, Renwick S, Duncan AM. Beyond the Cholesterol-Lowering Effect of Soy Protein: A Review of the Effects of Dietary Soy and Its Constituents on Risk Factors for Cardiovascular Disease. Nutrients. 2017;9(4):324. doi:10.3390/nu9040324

Published: June 2024