Can Including Soy in Your Diet Help Lower Your Cholesterol?

Soy and soy-containing foods like tofu have gained a reputation over the years for lowering cholesterol. Chief among these is the "bad" form of cholesterol known as low-density lipoprotein (LDL). This is the type that causes fatty deposits on the walls of arteries, known as plaque, leading to atherosclerosis ("hardening of the arteries") and coronary artery disease (CAD).

Based on evidence that soy can reduce these risks, the Food and Drug Administration (FDA) announced in 1999 that the heart health benefits of soy could be promoted on product labels. That decision is now being questioned.

This article takes a closer look at the current debate, what the body of research says, and what amount of soy may be potentially beneficial if you have high cholesterol.

What Is Soy?

Foods containing soy are derived from the soybean plant (Glycine max). Soy is a good source of plant-based protein as well as calcium, fiber, potassium, magnesium, copper, manganese, and polyunsaturated fats like omega-3 fatty acids.

Besides bringing protein into your diet, soy also contains estrogen-like compounds called isoflavones that have numerous health benefits. Among them, isoflavones have been touted by some for their cholesterol-lowering effects (mainly seen in animal studies).

Soy products, such as tofu, soy beverages, soybean burgers, and soy nuts, already have an established reputation for being a nutritious part of a balanced diet, particularly since they offer a healthy alternative to animal protein.

Can Soy Lower Cholesterol?

Scientists have identified one major component in soybeans that appears to have the potential to reduce cholesterol: soy protein.

Even so, there remains debate as to how significant the reduction is and whether it is enough to justify the claim that soy is a heart-healthy food.

Early Research

A review of studies published in Circulation in 2006 evaluated the effect of soybeans on cholesterol levels based on data from 22 human trials. What the researchers found was that soy protein, irrespective of all other components of soy, reduced LDL levels by around 3%.

Even so, the reduction was considered low. Moreover, soy protein appears to have little to no effect on either "good" high-density lipoprotein (HDL) or "bad" triglycerides.

The investigators also looked at the cholesterol-lowering effects of soy isoflavones and could not find any evidence that they helped in any way.

Reevaluation of Studies

Subsequent research published in the Journal of the American Heart Association in 2019 contested the FDA's decision to reverse its stance on soy. The researcher from the University of Toronto's Department of Nutritional Science argued that the LDL reduction induced by soy, while low, remained consistent over many years and well within the threshold established by the FDA.

The FDA's decision to review its 1999 ruling was based on conflicting evidence from 46 randomized controlled studies. The researchers in Toronto took it upon themselves to re-evaluate those studies and found that, after 14 years, the reduction in LDL among study participants remained well within the targets set by the FDA.

The FDA's 1999 ruling was based on evidence that soy protein could lower LDL by between 4.2 and 6.7 milligrams per deciliter (mg/dL) of blood. According to the Univerity of Toronto researchers, the average LDL reduction in the 14 years since the FDA ruling was 6.3 mg/dL.

The researchers further argued that reversing the 1999 ruling would unfairly target soy when other foods with equally modest cholesterol‐lowering effects (such as oats, psyllium, barley, and nuts) are allowed to be touted as "heart-healthy."

What Does This Mean For You?

At present, there is no change in the FDA's recommendations regarding the inclusion of soy in a heart-healthy diet.

According to the FDA, a daily intake of 25 grams (g) or more of soy protein is associated with a reduced risk of atherosclerosis and CAD. Some studies have suggested that 50 g or more per day is needed to achieve a beneficial effect.

Even so, it is important not to overstate the benefits of soy in reducing your risk of atherosclerosis or CAD.

Generally speaking, the risk of CAD increases when your LDL levels are 160 mg/dL or higher. While a reduction of 6.3 mg/dL is not insignificant, it is by no means a quick fix if you have high cholesterol.

Rather, soy should be considered a part of a holistic approach to lowering your cholesterol level, which should also involve routine exercise, weight loss if necessary, and a low-fat diet with minimal saturated fats.

Summary

Although the FDA allowed manufacturers of certain soy products to make heart health claims back in 1999, the evidence supporting their cholesterol-lowering effects remains shaky. Because of this, the FDA has considered whether to reverse its ruling.

Proponents argue that, while the reduction of "bad" LDL cholesterol is modest, the effect appears to be durable and does not lessen soy's benefit in a heart-healthy diet. The debate continues.

A Word From Verywell

Despite the small decreases in cholesterol levels, soy remains an ideal alternative to animal fats that are known to raise blood cholesterol levels.

In addition, soy products are high in fiber and low in saturated fat, both of which are essential to a heart-healthy diet.