Q&A with Sarah A. Johnson, PhD, RDN 


New Research Illustrates that Daily Consumption of Blueberries May Improve Endothelial Function in Postmenopausal Women with High Blood Pressure

The U.S. Highbush Blueberry Council is joined by Sarah A. Johnson, PhD, RDN, Associate Professor and Director of Functional Foods & Human Health Laboratory in the Department of Food Science and Human Nutrition at Colorado State University, to discuss her new study on how blueberries help to improve endothelial function in postmenopausal women with elevated blood pressure or stage 1-hypertension. Read below! 

Why did you decide to study blueberries?

In addition to their beautiful blue color and delicious taste, blueberries are rich in nutrients and phytochemicals called polyphenols. In particular, blueberries are abundant in anthocyanins, a type of polyphenol that gives blueberries their blue color and has been shown to be important for human health. Previous research strongly suggested the potential of polyphenols to reduce cardiovascular and metabolic disease risk, as well as the risk for other chronic diseases like cancer and neurodegenerative diseases.

Based on what was known about the health effects of blueberries at the time when I first became interested in them, as well as their high consumer acceptability and importance to United States agriculture, blueberries represented a promising food for promoting human health. I was fortunate to have the opportunity to pursue research on the cardiovascular-protective effects of blueberries for my PhD dissertation and have worked with blueberries ever since.

What are the key findings from your research?

Our recent study in estrogen-deficient postmenopausal women with above-normal blood pressure demonstrated that consuming the equivalent of 1 cup of fresh blueberries (provided as 22 grams of freeze-dried blueberry powder with water) daily for 12 weeks improved endothelial function. Endothelial function refers to how effectively the cells lining blood vessels regulate blood flow, clotting, and immunity. It is important for vascular health, particularly the arteries, and therefore is an important factor for overall heart health.

Further, endothelial function is a predictor of cardiovascular disease and associated mortality, and improvements are predictive of reduced risk independent of blood pressure (e.g., even if blood pressure remains stable, cardiovascular risk is reduced). Postmenopausal women with above-normal blood pressure have been shown to have impaired endothelial function, which is partially caused by oxidative stress (i.e., high free radicals without sufficient antioxidants in the body) due to the loss of estrogen production.

Our results showed that the improvements in endothelial function were due to improvements in oxidative stress, indicating that blueberries exert antioxidant effects in the body. We found increases in blood levels of polyphenol metabolites that are blueberry-derived, as well as products of gut microbial metabolism suggesting the important role of blueberries in supporting the gut microbiome. Though there were no major impacts on blood pressure and other measures of cardiovascular health, these results suggest that the antioxidant effects in blueberries can reduce cardiovascular disease risk, independent of blood pressure.

Improvements in endothelial function have been demonstrated consistently to be predictive of reduced risk of cardiovascular disease and related events (e.g., heart attack, stroke) and mortality. Therefore, these results suggest daily blueberry consumption can reduce cardiovascular disease risk in postmenopausal women with above-normal blood pressure. 

How do you personally enjoy blueberries in your everyday life?

I love adding blueberries to my morning oatmeal or to a salad for some natural sweetness. And if I’m on the run, filling a small container with fresh blueberries or mixing frozen blueberries into a smoothie is my go-to solution. I’ve also been introducing blueberries to my 2-year-old daughter and she’s a big fan!