New Study Examines Which Foods Affect LDL Cholesterol

To help make sense of individual foods and their impact on LDL cholesterol and heart health, researchers recently completed a systematic review and meta-analysis, which was published in the journal Nutrition, Metabolism and Cardiovascular Diseases.

This meta-analysis includes data from 37 guidelines, 108 systematic reviews, and 20 randomized controlled trials. The aim of the research was to evaluate the evidence on how foods affect LDL cholesterol and compare the findings with current guidelines.

Studying how different foods and beverages impact cholesterol levels is important for overall heart health. Elevated levels of LDL (or “bad”) cholesterol are a known risk factor for cardiovascular disease.

“Heart disease risk is evaluated based on many biomarkers,” says Rosanne Rust, author, registered dietitian and blogger at Chew the Facts. “LDL is one of them, along with other blood lipids, blood pressure, body weight, age, presence of other disease, and family history.”

Rust says that dietary changes absolutely can make a difference in cholesterol levels. 

While many studies focus on the overall dietary pattern that’s important for heart disease prevention, this study looked more closely at the individual foods within dietary patterns. The whole dietary pattern is more important than any one food, and the findings in this paper are not meant to replace any current dietary guidelines. 

David Iggman, a researcher at Svärdsjö Health Care Center at Uppsala University in Sweden and one of the researchers on this study, explains that the paper summarizes the current knowledge, but does not provide nutrition recommendations.

“We did not consider dietary patterns, individual nutrients, or supplements, only foods,” says Iggman. “However, in the included guidelines, a Mediterranean dietary pattern (or several similar others) is most often recommended.”  

If you’re looking for a dietary pattern for heart health, you’ll want to read more about the  Mediterranean diet  and the DASH diet, or any similar dietary pattern that’s high in fruits, vegetables, fish, nuts, non-tropical oils, legumes, whole grains and high-fiber foods.

Today’s summary focuses on individual foods and beverages that have positive or negative effects on LDL cholesterol.

What Did the Study Look At?

For this study, the researchers reviewed guidelines and systematic reviews and conducted a systematic review and meta-analysis of randomized controlled trials. The studies they looked at had to meet the following parameters:

• Target population was adults.
• Target population were not being treated with lipid-lowering medications.
• The studies were about foods, not supplements, weight-loss diets, or dietary patterns.
• Studies were not more than 10 years old.

Different foods were studied and were categorized by their impact on LDL cholesterol levels. Some foods had no effect, others contributed to small, moderate, or large reductions in LDL cholesterol, and some contributed to small, moderate, or large increases in LDL cholesterol levels.

The impacts of each food were judged based on their GRADE evidence. GRADE is an acronym for Grading of Recommendations Assessment, Development, and Evaluation. It’s a transparent approach for grading the quality or certainty of scientific evidence, and looks at whether the outcome was close to or far from the researcher’s hypothesis.

In science, high or moderate GRADE levels give the researchers more confidence in the strength of their recommendations, compared to studies with low or very low results.  

What Did the Study Find?

Some foods and beverages were shown to have no impact on LDL cholesterol levels. These all had high or moderate GRADE levels. Foods with no effect include:

• Fish
• Fructose to replace sucrose or glucose
• Decaffeinated coffee in place of regular coffee
• Filtered coffee

Foods and beverages that have high or moderate GRADES to support a reduction in LDL cholesterol levels include:

• Foods high in soluble fiber, such as psyllium, oats and barley
• Whole grains
• Flaxseeds
• Soy protein
• Tomatoes
• Avocados
• Foods with added plant sterols or stanols
• Almonds, walnuts and hazelnuts
• Legumes, such as beans and lentils
• Oils that are high in mono or poly-unsaturated fats, such as olive or canola oil
• Turmeric
• Green tea

Iggman notes that it is interesting to find tomatoes and turmeric on the list of foods that may help lower LDL cholesterol, since they were not previously highlighted in the guidelines.

The rest of the list is not surprising, as it mirrors many of the foods that are recommended in heart-healthy dietary patterns, such as the Mediterranean and DASH diets. 

“There is plenty of research that has shown that a dietary pattern that is low in saturated fat and includes plenty of vegetables and wholesome grains is beneficial,” says Rust. “Replacing the saturated fat with healthy monounsaturated fats (including olive oil, avocado, canola oil) can be beneficial to reducing blood cholesterol.”

Dietary Fat and LDL Cholesterol

Many studies and dietary guidelines recommend replacing saturated and trans fat with monounsaturated and polyunsaturated fats. However, not every health professional agrees with this recommendation.

Some recent studies found no beneficial effects of reducing saturated fat intake on cardiovascular disease. While saturated fats do increase LDL cholesterol, it usually affects larger LDL particles, which are less strongly related to CVD risk. It’s the small, dense LDL particles that are more problematic. 

This particular study did not break down the effects of food and beverage on small vs. large LDL cholesterol particles, so there is definitely more to learn in this area of science.

Can Foods Raise LDL Cholesterol?

There were also some foods and beverages that were shown to increase LDL cholesterol levels.

“In line with current guidelines, solid fats like butter increase LDL cholesterol, especially compared with fats high in unsaturated fatty acids,” says Iggman. “Sugar also seems to have a slight detrimental effect.”

Iggman also explains that the meta-analysis demonstrated a clear increase in LDL cholesterol by unfiltered coffee intake (such as Scandinavian-style boiled coffee). Interestingly, this was not the case with filtered coffee or decaffeinated coffee, which have no effect on LDL cholesterol levels.

There was also a low or very low GRADE level to show that these foods can reduce LDL cholesterol levels:

• Garlic and garlic powder
• Probiotics and prebiotics
• Cumin
• Ginger
• Berries
• Dark chocolate
• Black tea

There were some foods that showed no clear effects, but at a very low grade levels. These include dairy products, fruit juice, red meat and sweeteners.

Heart Smart Dietary Advice

VeryWell Fit asked dietitian Rosanne Rust about her recommendations to clients who are trying to manage cholesterol levels and reduce heart disease risk.

“My top recommendation is to take a look at saturated fat by getting into the habit of reading package labels,” says Rust. She also recommends reducing the total amount of meat, and adding more fiber into meals by eating more vegetables, fruits and whole grains. 

“There are no magic foods that treat specific diseases, however your overall dietary pattern or framework can impact your overall disease risk,” says Rust. “A diet low in saturated fat, sugars and refined carbohydrates, and high in fiber can help reduce the risk of heart disease.”

What's Next?

Iggman’s paper notes that “future studies should further investigate foods whose effects showed moderate (e.g. turmeric and green tea) or low evidence (e.g. eggs, garlic, cumin, ginger, and probiotics).” More research needs to be done in this areas.