Is soy good or bad for your heart? Let’s look at what science says.

Soybeans, a legume, are used to make a wide range of foods, from minimally processed tofu and tempeh to soy milk and more processed items like soybean oil and soy protein isolate. They’re rich in high-quality protein, fiber, and beneficial nutrients.

Research shows soy protein can lower LDL cholesterol by about 4%, which may translate to a 1-2% reduction in heart disease risk over time. These findings led the FDA, and later other countries, to approve heart-health claims for soy foods.

Beyond cholesterol, soy’s bioactive compounds may also help reduce high blood pressure, making soy a valuable addition to a heart-healthy diet.

Soy and Heart Health: The Research

A growing body of research suggests that soy foods and soy-derived nutrients may contribute to cardiovascular health, although the effects are modest and context-dependent.

Here are some takeaways from key studies on soy and heart health outcomes: 

• Several randomized controlled trials show that replacing animal protein with soy protein leads to reductions in LDL cholesterol and total cholesterol levels, generally on the order of 3-5%. 
• Population studies suggest that higher intake of soy foods or isoflavones may be associated with lower risk of coronary heart disease or cardiovascular disease events, though results vary by age, sex, menopausal status, and type of soy food. 
• Meta-analyses focusing on soy milk or the replacement of cow’s milk with soy milk indicate favorable effects on cardiometabolic risk factors (lipids, blood pressure, inflammation), especially when it replaces higher-saturated-fat dairy. 
• Some evidence highlights that effects may be stronger in individuals with elevated baseline risk (e.g., high blood pressure, type 2 diabetes, high LDL) rather than in broadly healthy populations. 

Overall, since the effects are modest and some studies have mixed or null results (especially in populations with low baseline risk), soy should be considered one component of a broader heart-healthy diet (like other healthy foods), not a standalone “magic bullet.”

Is Soybean Oil Bad for Your Heart?

The U.S. Food and Drug Administration has recognized soybean oil for its cardiovascular health benefits with a qualified health claim. The language allowed in support of the soybean oil health claim is stronger than the language for others that have similar health claims, stating: 

“Supportive but not conclusive scientific evidence suggests that eating about 1½ tablespoons (20.5 grams) daily of soybean oil, which contains unsaturated fat, may reduce the risk of coronary heart disease. To achieve this possible benefit, soybean oil is to replace saturated fat and not increase the total number of calories you eat in a day.”

However, the heart health impact of soybean oil depends heavily on how it’s processed and used. Highly refined soybean oil can be prone to oxidation, a chemical reaction that occurs when unsaturated fats are exposed to heat, light, or air. Oxidized oils can produce harmful compounds that may promote inflammation and damage blood vessels, counteracting potential heart benefits.

To minimize oxidation, choose fresh, high-quality soybean oil, store it in a cool, dark place, and avoid using it for repeated high-heat frying. If you enjoy soybean oil, using moderate amounts of unoxidized, unsaturated oils, alongside a diet rich in whole plant foods, has the most heart-protective benefits.

The Benefits of Soy Milk for Heart Health

Soy milk is a heart-healthy alternative to dairy milk thanks to its low saturated fat content and zero cholesterol. It provides high-quality protein (around 8 grams per cup, similar to dairy milk) and is often fortified with calcium, vitamin D, and B12 for added nutrition (but check the label). 

Research shows that replacing full-fat dairy with soy milk may help lower LDL and support healthier blood pressure levels. Plus, soy milk has naturally occurring isoflavones that can help improve blood vessel function, promoting overall cardiovascular health.

Soy Nutritional Content

Soybeans are nutrient-rich and contain many important nutrients that provide heart-healthy benefits, including: 

Folate

Folate can protect the heart because it is one of the B vitamins that helps break down homocysteine levels in the body. When folate is not adequately consumed, it can increase homocysteine levels, which are associated with heart disease.

The Daily Value (DV) for folate is 400 µg (mcg) DFE (Dietary Folate Equivalents). 

• 1 cup of cooked mature soybeans = 92.9 mcg
• 1 cup of edamame = 482 mcg 
• ¼ block of firm tofu = 23.5 mcg of folate
• 1 cup soy milk = 24.3 mcg 
• 1 cup of tempeh = 39.8 mcg
• 4-oz soy-based burger = 80.2 mcg

Potassium

Potassium can protect the heart because it helps maintain heartbeat regularity and helps to normalize blood pressure.  In one systematic review and meta-analysis of 22 randomized controlled trials and 11 cohort studies, increased potassium lowered the incidence of stroke by 24%.

The DV for potassium is 4,700 mg. 

• 1 cup of cooked mature soybeans = 886 mg
• 1 cup of edamame = 676 mg
• 4 oz soy-based burger = 699 mg
• ¼ block of firm tofu = 192 mg
• 1 cup soy milk = 299 mg
• 1 cup of tempeh = 684 mg 

Zinc

Because of its antioxidant and anti-inflammatory components, zinc is one of the nutrients that can help mitigate a common mechanism contributing to atherosclerosis. One of the main causes of atherosclerosis, the major cause of heart disease, is oxidative stress because it can lead to blood vessel damage and oxidation of LDL cholesterol.

The DV for zinc is 11 mg. While soy doesn’t contain a significant amount, it can contribute some to your overall diet. 

• 1 cup of cooked mature soybeans = 1.98 mg 
• ½ cup of black soybeans = 2.25 mg 
• 1 cup of edamame = 2.12 mg 
• ¼ block of firm tofu = 1.27 mg 
• 1 cup of tempeh = 1.89 mg

Magnesium

Magnesium is an essential mineral that is involved in more than 300 enzymatic reactions that help regulate blood pressure, blood sugar control, lipid oxidation, and antioxidant pathways. Magnesium is an important nutrient for cardiovascular health, and magnesium deficiency has been linked to high blood pressure, cardiomyopathy, heartbeat irregularities, atherosclerosis, abnormal lipid values, and diabetes.

The DV for magnesium is 420 mg. Again, while it may not be a magnesium powerhouse, soy does provide some that can contribute to your overall intake. 

• ½ cup of black soybeans = 59.8 mg 
• 1 cup of edamame = 99.2 mg 
• ¼ block of firm tofu = 47 mg 
• 1 cup of tempeh = 134 mg 

Fiber

Soy foods also contain, in varying amounts based on product, both insoluble and soluble fiber, which is beneficial for heart health. In one systematic review and meta-analysis, higher dietary fiber intakes have been shown to reduce the risk of cardiovascular disease, and lower certain heart disease risk factors such as high blood pressure, cholesterol, and body weight.

When soy foods are digested in the body, the gut ferments fiber and produces short-chain fatty acids like butyrate. Butyrate provides anti-inflammatory, antioxidant, and possibly even protective effects on atherosclerosis by reducing inflammation and oxidative stress, the underlying root causes of the plaque formation process.

Recommended daily fiber needs are 28 grams for women and 35 grams for men. 

• 1/2 cup edamame = 4 grams 
• 3 oz tempeh = 3-5 grams
• 3 oz firm tofu = 1 gram
• 1 cup unsweetened soy milk = 1 gram 

Phytochemicals

Phytochemicals, such as isoflavones and phytosterols, can also play a role in heart health. Soy is a uniquely rich source of isoflavones. Traditional soy foods contain approximately 3.5 mg of isoflavones per gram of protein or between 20-30 mg per serving.

Isoflavones may help lower blood pressure by helping the arteries relax and dilate. Soy isoflavones have been shown to help increase endogenous nitric oxide production, which improves blood flow. In one meta-analysis, daily intake of 65-153 mg of soy isoflavones for 1-12 months significantly decreased blood pressure (on average by 5.94 mmHg systolic and 3.35 mmHg diastolic) in individuals with high blood pressure. 

Research shows that soy may help reduce stiffness in the arteries in certain individuals who can metabolize daidzein, a specific isoflavone that is only found in soy foods, into equol. When the body produces equol as a metabolite from soybean production, it has been shown to improve blood vessel function, blood pressure, and arterial stiffness.

Is Soy Bad for Us? Common Concerns Addressed

There’s no doubt that soy is among the most controversial foods there are, with plenty of rumors that dissuade people from eating it. Here’s the truth about some common myths you may have heard about soy: 

• Hormones and phytoestrogens: Soy contains isoflavones, plant compounds that can weakly mimic estrogen but act very differently in the body. Studies show they a moderate intake of soy foods does not raise estrogen levels in men or women and does not cause feminizing effects like gynecomastia (enlarged breast tissue in men).
• Cancer risk: Contrary to popular belief, soy foods are linked to a lower risk of breast and prostate cancer, not higher. Some studies also show soy intake is associated with a higher survival rate and reduced recurrence rate among those already diagnosed. Isoflavones may protect cells from DNA damage and regulate hormone activity in ways that reduce cancer risk.
• Thyroid health: For people with normal thyroid function and adequate iodine intake, soy does not impair thyroid activity. Those on thyroid medication may simply need to take their medicine and soy foods at different times of day for optimal absorption, but the evidence behind this is minimal. Furthermore, cooking soy foods can help destroy compounds that may interfere with thyroid function.
• Heart health: Numerous studies show that soy protein can help lower LDL cholesterol, improve blood vessel function, and modestly reduce heart disease risk, especially when it replaces animal protein or saturated fats.

The best way to reap soy benefits is to choose whole and minimally processed options, and opt for USDA organic whenever possible, to reduce your intake of agricultural pollutants.

How to Eat More Soy Foods

Incorporating soy into your diet is simple and delicious. Here are some practical ways to enjoy heart-healthy soy foods:

• Tofu: Use firm tofu in stir-fries, soups, or on the grill. For a crispy texture, press out excess water before cooking and season generously.
• Tempeh: Slice and marinate before pan-searing or baking. Its nutty flavor pairs well with Asian sauces, tacos, or salads.
• Edamame: Enjoy steamed edamame pods as a snack or toss shelled edamame into grain bowls, pasta, or salads for extra protein and fiber.
• Soy milk: Pour over cereal, blend into smoothies, or use in coffee as a creamy, cholesterol-free alternative to dairy milk.

These easy swaps can help you add more protein, fiber, and heart-protective nutrients to your daily meals.

Soy and Heart Health FAQs

Can soy lower cholesterol?

Yes, studies show that soy protein may help reduce LDL cholesterol and total cholesterol, especially when it replaces animal protein. This effect can support overall heart health.

Is soy milk better than dairy milk for heart health?

Soy milk has no cholesterol, is lower in saturated fat than dairy milk, and may help improve cholesterol levels. Many varieties are fortified with calcium and vitamin D, making it a heart-friendly alternative.

How much soy is safe to eat daily?

Most research supports moderate soy intake, around about 1-2 servings per day (such as soy milk, tofu, or edamame), as safe and likely beneficial for heart health.

Soy and Your Heart: The Bottom Line

Soy foods are a good source of protein and may provide cardiovascular benefits from their rich vitamin and mineral content, to their dietary fiber and phytochemical makeup. Including edamame, tofu, tempeh, soymilk, and other soy foods in your diet is a great way to reap these benefits and contribute to a heart-healthy diet. If you don’t like soy, however, don’t worry. We can work together to personalize your diet and ensure you’re getting these nutrients from other foods. Click here to learn about my 1:1 nutrition services.

It is important to focus on what you are eating to support optimal heart health. To learn more about heart disease prevention through science-based nutrition, sign up for my email list here, and follow me on social media at heart.health.nutritionist.

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