Dr. Heather Blewett
Human Nutrition and Immunology, Canadian Centre for Agri-Food Research in Health and Medicine
Dr. Heather Blewett is a Research Scientist with Agriculture and Agri-Food Canada who leads the Human Nutrition and Immunology lab at the Canadian Centre for Agri-Food Research in Health and Medicine (CCARM). She uses her expertise in human nutrition to perform the necessary clinical trials to substantiate health claims for Canadian crops including cholesterol lowering (soy and flax), limiting the rise in blood sugar after a meal (barley and peas) and improving fullness and satisfaction after eating (buckwheat, barley and peas). Her research program also aims to investigate potential anti-nutrients and mitigate any adverse health effects they cause. Her background in immunology allows her to explore the effect of Canadian food products on immune function in the context of chronic diseases like high blood pressure. Because both Heather and her daughter have Celiac Disease, she is also interested in affordability and access to safe gluten-free food.
Why is this work important?
Health claims help to increase sales of Canadian crops, promote the development of new food products, and assist consumers in making healthier food choices in the grocery aisle.
Dysregulated immune function is a feature of many chronic diseases. Therefore, understanding how food choices influence the functioning of the immune system is the key to developing food products to support health.
What techniques and equipment are used in this laboratory?
In the lab:
- Flow cytometry: This technique allows the team to measure several properties of cells including their size, what they express either on their surface or internally, whether they are dying or multiplying, and their number.
- Pressure myography: This approach is used to study the function and structure of arteries.
- Ex vivo stimulation of immune cells: Some important functions of immune cells include their ability to multiply and release proteins called cytokines. By stimulating them outside of the body, the lab can assess how well they are functioning.
- Multi-array electrochemiluminescent assays using MSD imager: The group uses this instrument to quantify several components at the same time in the same sample (i.e., several cytokines or several appetite related hormones).
- Enzyme linked immunosorbant assays (ELISA): These are used to quantify proteins such as cytokines and hormones in blood samples from our studies.
- Flurometric/colorimetric assays: Same purpose as ELISA.
- High performance liquid chromatography (HPLC): This procedure is used to identify and quantify compounds in foods and biological samples (i.e. secoisolariciresinol diglucoside and vitamin B6).
In the clinic:
- Clinical trials involving food products.
- Post-prandial tests that involve collecting data over 2-3h after eating.
- Dietary intake analysis using a software program called Food Processor.
- Bioelectric Impedance Analysis (BIA) to measure lean and fat mass using the InBody 570
- Blood pressure measurement.
About Dr. Blewett
Dr. Blewett’s exposure to research started at a young age. Her mother worked as a lab technician in the Department of Anatomy at the University of Manitoba and as a consequence, her first exposure to laboratory science was when her mother would bring her in on the weekends to help feed and weigh the rats in her experiments. This first exposure to research inspired Dr. Blewett to follow a career path with the ultimate goal of conducting experiments aimed at improving the health of the population through food.
Dr. Blewett earned a Bachelor of Human Ecology majoring in Food and Nutrition and a minor in Management from the University of Manitoba in 1999. She went straight into the graduate program where she explored the effects of dietary zinc deficiency on T-cell maturation and function earning her doctorate in 2007.
She went on to work with the leading nutritional immunologist in Canada, Dr. Field, at the University of Alberta from 2006-2009. In her lab Dr. Blewett expanded both her nutritional and immunological training by studying the importance of amino acids and fatty acids for intestinal and immune defense against E. coli using a novel piglet model. She also discovered that the trans-fat vaccenic acid favorably alters the pro-inflammatory tendency of mesenteric lymphocytes in obesity.
As a Post-Doctoral Fellow in Dr. Zahradka’s lab from 2009-2011, she had the opportunity to gain valuable experience in clinical trials and vascular health.
Dr. Blewett accepted her dream job as a research scientist with Agriculture and Agri-Food Canada in 2011.
For more information, contact:
Heather Blewett, PhD
Burden of Celiac Disease
We published the following paper in 2021: Cost, Nutritional Content and Number of Gluten-Free Staple Foods Available in Winnipeg, Manitoba, Canada. We reported the median cost of 819 gluten-free products was $1.50/100g, compared to $0.65/100g for gluten-containing products. Gluten-free products in Manitoba were therefore more than 130% more expensive than gluten-containing products.
The paper was one of several food economic studies cited by Celiac Canada in an open letter to Parliament, urging political leaders to help ease the financial burden on Canadians who need gluten-free food simply to survive. https://www.celiac.ca/tax-fairness-and-affordability/
Effect of Barley on Blood Sugar Levels After a Meal
Barley can limit the rise in blood sugar levels after a meal; however there are several factors in food that can be manipulated to optimize its effect on blood sugar. After varying the amount of resistant starch, soluble fibre (β-glucan) and insoluble fibre, we discovered that the β-glucan content had the greatest effect on blood sugar levels after a meal. You can read the results here:
We designed a follow-up study to see what dose of β-glucan is needed to limit the rise in blood sugar levels after a meal. We found that as little as 2g β-glucan from barley per 30g digestible carbohydrates reduces the postprandial glycemic response by more than 20%. This work was presented at the American Society of Nutrition meeting in 2020 https://www.sciencedirect.com/science/article/pii/S2475299123081337
Pea Studies on Blood Sugar Levels After a Meal
Peas are high in resistant starch, fibre and protein, so we believed that replacing a portion of a high starch food like white rice or instant potato with peas would limit the rise in blood sugar levels after a meal (otherwise known as post-prandial glycaemic response). We have completed a trial comparing the post-prandial glycaemic response of white rice with and without three common market classes of peas (Golden: Whole yellow pea; Meadow: Split yellow pea; Striker: Split green pea) and repeated the trial with instant potatoes. We found that replacing just over half of the digestible carbohydrate from rice or instant potatoes with peas does limit the rise in blood sugar levels after a meal. There was no difference between the varieties of peas. The results of these trials were presented at the Canadian Nutrition Society Annual meeting in 2017.
We have designed three follow-up trials to determine if the same effect is seen when the peas are made into more complex foods (ie. Muffins, chili and soup). We were able to demonstrate that when peas replace part of the wheat in muffins, rice in soup or potatoes in soup, the rise in blood sugar levels after that meal are reduced by more than 20%. These results support a health claim related to the reduction in post-prandial glycaemic response for yellow peas. These results were presented at the Canadian Nutrition Society Annual meeting in 2019.
We are also interested in whether peas affect appetite by making a person feel fuller for longer, thus contributing to a reduced calorie intake. We are still analyzing the data on this, so stayed tuned…
Anti-nutrient mitigation in ground flaxseed
Flaxseed’s health benefits are attributed to high levels of soluble fibre and lignans (mainly secoisolariciresinol diglycoside (SDG)). However, flaxseed also contains a vitamin B6 antagonist (linatine) and cyanogenic glycosides (linustatin, neolinustatin). Our clinical trial found that consumption of 20g and 30g whole ground flaxseed in muffins negatively affected B6 status (presented at the American Society of Nutrition in 2018 https://profils-profiles.science.gc.ca/en/publication/daily-consumption-20-30-g-whole-ground-flaxseed-muffin-impairs-vitamin-b6-status ) providing an impetus to determine if the beneficial bioactives can be separated from the anti-nutrients to produce real health benefits. We postulated that if the health promoting bioactives (fibre, SDG) are concentrated in the hull, while the anti-nutrients (linatine, cyanogenic glycosides) are concentrated in the meal, de-hulling would separate the two. We recently finished the analysis of the samples and hope to share the results with you soon.
Evidence has shown that the immune system, in particular T-cells, play a role in high blood pressure. Anthocyanins are responsible for the red, blue and purple colors in plants, and we wondered how they might affect the response of T-cells in an animal model of high blood pressure. We found that the animals with high blood pressure had impaired T-cell function and a lower proportion of helper T-cell subsets. The first line drug treatment for high blood pressure is a diuretic called hydrochlorothiazide. The anthocyanin improved, while the drug impaired T-cell function further (see results here: https://pubs.rsc.org/en/content/articlelanding/2020/fo/d0fo01778g#). We conducted a similar study in an animal model of heart attack using an extract from ginseng berries as the treatment, but did not see any effect of treatment (see results here: https://www.mdpi.com/1422-0067/20/4/983).
With the rising incidence of overweight and obesity in developed countries, there is an interest in developing food products that may help control appetite and reduce caloric intake. Thirty-eight healthy adults were recruited to participate in our trial. The main objective was to determine if consuming snacks made from buckwheat would increase satiety and reduce energy intake. We found that neither buckwheat groats (32 g serving; 141 kcal) nor pita bread made from buckwheat flour (50 g serving; 135 kcal) changed appetite ratings or the number of calories consumed compared with reference snack products made from corn or rice flour. Here’s a link to the results: https://cdnsciencepub.com/doi/full/10.1139/apnm-2017-0295
LDL cholesterol lowering effect of whole soy
Other countries have approved a cholesterol lowering claim for soy, but Health Canada requires specific evidence before it will approve a similar claim in Canada. We designed a study to fill in the knowledge gaps, and also to see if people actually liked the look/smell/flavor/taste/texture of the muffins. Although muffins made with soy were liked by consumers, the results from a multi-centre trial looking into the cholesterol-lowering effect of whole soy in volunteers with high cholesterol showed no effect at the doses tested. Dr. Blewett lead the trial at CCARM, in collaboration with Dr. Wolever at GI Labs in Toronto, Dr. Duncan from the Human Nutraceutical Research Unit at the University of Guelph and Dr. Ramdath from the Guelph Research and Development Centre.
To read the scientific research reports from this study, please follow these links:
Manitoba Health Research Council Postdoctoral Fellowship (2009-2011)
Level: Provincial Value: $36 750/year
Dr. Elizabeth Feniak’s Award for Excellence in Technical Writing (2005)
Level: National Value: $500
Holmfidur Kristjansson Graduate Award in Nutrition (1999)
Level: Institutional Value: $2625
Xerox Canada University Education Scholarship (1995-1999)
Level: National Value: $6000
Blewett laboratory would like to gratefully acknowledge the following funding agencies and foundations:
- Agriculture and Agri-Food Canada
- Flax Council of Canada
- St. Boniface Hospital Foundation