A. Venket Rao, PhD

A. Venket Rao, PhD


Dr. Rao completed his M. Sc. and Ph. D. degrees in Food Science from Oregon State University, USA. After being a Full Professor in the Department of Nutritional Sciences, Faculty of Medicine, he currently holds the position of Professor Emeritus at the University of Toronto.  He also served as the Director of the Program in Food Safety, Nutrition and Regulatory Affairs, Director of the Collaborative Program in Toxicology, and Member of the Institute of Environmental Studies. He is a member of several national and international scientific and professional organizations.

He has established a major focus in the area of diet and health with particular emphasis on the role of dietary phytochemicals and intestinal microflora. More recently his research has focused on the role of oxidative stress and antioxidants in the causation, prevention and treatment of chronic diseases, with particular emphasis on the role of dietary carotenoids and polyphenols in human health. He was instrumental in bringing international interest in lycopene, a naturally occurring carotenoid antioxidant in tomatoes, in the prevention of cancer and cardiovascular disease. He is now actively engaged in basic and clinical research to investigate the health benefits of fruits and in particular berries such as raspberries.

Another important area of his research activity includes the role probiotics and prebiotics in human health.  He is also interested in the applications of biotechnology in the agri-food-health industries. He has published well over hundred publications in scientific journals and participated in many national and international scientific conferences. More recently he authored a chapter entitled ‘Lycopene’ in Advances in Food and Nutrition Research and edited and contributed chapters to a book entitled ‘Tomato Lycopene and Human Health’.

Dr. Rao is a member of the Provincial and National Expert Committees in Canada in the areas of nutrition, health, food safety and agriculture. He has a distinguished career as an educator and a researcher. He serves as a Senior Scientific Consultant to provincial and federal government agencies and food and pharmaceutical industries globally. He is popularly sought by the international media to express his opinions on the subjects of nutrition, health and food safety.


Raspberries and Human Health: Time for Recognition

Venket Rao & Dawn Snyder Department of Nutritional Sciences, Faculty of Medicine, University of Toronto, Canada

Dietary guidelines around the world recommend increased consumption of fruits and vegetables for the prevention of chronic diseases. Fruits and in particular berries are good sources of several compounds that contribute towards good health. Red raspberries are among the most popularly consumed berries. In addition to their attractive color and appealing flavour, red raspberries contain several essential nutrients and beneficial phytochemicals. They can be considered a healthy food choice since they are low in total calories and fat, contain no cholesterol, are high in dietary fiber and a good source of vitamin C, folate, potassium and magnesium with very low amounts of sodium.

Red raspberries are rated among the top ten commonly consumed fruits and vegetables in the American diet in terms of their antioxidant potential. They contain high levels of beneficial phytochemicals including anthocyanins, hydrolyzable tannins and phenolic acids. They are a particularly rich source of cyanidin and are unique among the berries for their high ellagitannin content, which can be hydrolyzed to yield ellagic acid.

There is a growing body of scientific evidence to support the health benefits of consuming raspberries. Listed among these health benefits are their potential role in the prevention of cancer, cardiovascular diseases, diabetes, obesity, neurodegenerative diseases and aging. To understand the role of raspberries in human health, one must recognise the significance of dietary components on cellular functioning in the aetiology of human disease.

Several mechanisms of action are known to be involved in mediating the disease process. Important among them are the mechanisms of oxidative stress, inflammation, immune function and metabolism. The nutritional profile of raspberries and the presence of beneficial phytochemicals, provide them the ability to influence several of these mechanisms and thereby health outcomes. For example, the low energy, low fat, no cholesterol and high fiber content of raspberries is consistent with nutritional profiles of foods that support healthy heart function, and promote satiety and weight loss. High potassium and low sodium content of raspberries may also help reduce hypertension.

Similarly, their phytochemical composition and antioxidant properties may function as anti-inflammatory and anti-atherosclerotic agents via the inhibition of NO and TNF, and protect against LDL oxidation, reducing cardiovascular diseases Additionally these compounds may support a role in the prevention of cancer by protecting against oxidative DNA damage. ,Their possible role in diabetes prevention and maintenance may be mediated via the inhibition of the digestive enzymes resulting in a reduction in post-prandial glucose levels and improved insulin response.

Most of the studies showing the beneficial effects of raspberries have so far been done in vitro in tissue culture or using animal models and have looked at individual phytochemicals. Ellagic acid and cyanidin have been shown to inhibit the growth of several cancer cells in both in vitro and animal studies. Animal studies have also supported the ability of ellagic acid in the prevention of cancer. The protective properties of these phytochemicals could be attributed to their structural similarity to other endogenous biological compounds. Studies have demonstrated that ellagic acid is absorbed into the body readily. Another unique feature of raspberries is the presence of ketones.

Raspberry ketones are structurally similar to capsacin in red peppers, synephrine in citrus peel and zingerone in ginger extract, all of which have been shown to have health benefits. In a recent animal study, raspberry ketones were shown to prevent high fat diet induced elevation in body, liver and visceral adipose tissue weights as well as high fat induced elevation in hepatic triglycerides and an increase in norephinephrine induced lipolysis. Based on these observations it has been suggested that raspberry ketones may prevent obesity and fatty liver in the rat model. No human studies have been done so far to confirm these observations and its safety at high levels of intake.

Although several human intervention studies have been reported in the literature with fruits and berries such as pomegranate, black currents, blueberries, strawberries, black raspberries, cranberries and buckthorn berries, there has been no human intervention studies published on the health benefits of red raspberries. There is convincing scientific evidence to substantiate the health benefits of red raspberries attributable to their nutritional profile and the biological activity of their individual phytochemical components.

Pharmokinetic studies have demonstrated that ellagitannins and anthocyanins are hydrolyzed into ellagic acid and anthocyanidins, which are absorbed into the body in their bioactive form. However, in the opinion of nutritionists and other health professionals, consumption of whole foods given the advantage of complimentary and synergistic effects amoung their components, far outweighs consuming individual phytochemicals. With this in view we have undertaken a clinical study to investigate the effect of consuming frozen whole red raspberries on several health biomarkers in healthy human subjects.

The consumption of red raspberries in our study have been kept to a realistic quantity of one-cup individually quick frozen berries per day for a period of four weeks. This study is in progress at present.

Weighing the current body of scientific evidence, it would be prudent to include consumption of red raspberries as a regular part of a healthy diet for the maintenance of a high quality life and the prevention of chronic diseases.


Aiyer HS, Vadhanam MV, Stoyanova R, Caprio GD, Clapper ML, Gupta RC (2008) Dietary berries and ellagic acid prevent oxidative DNA damage and modulate expression of DNA repair genes. International Journal of Molecular Sciences 9: 327-341

Anttonen MJ, Karjalainen RO (2005) Environmental and genetic variation of phenolic compounds in red raspberry. Journal of Food Composition and Analysis 18: 759-769

Beekwilder J, Jonker H, Meesters P, Hall RD, van der Meer IM, Ric de Vos CH (2005) Antioxidants in raspberry: on-line analysis links antioxidant activity to a diversity of individual metabolites. J Agric Food Chem 53: 3313-20

de Ancos B, Gonzalez EM, Cano MP (2000) Ellagic acid, vitamin C, and total phenolic contents and radical scavenging capacity affected by freezing and frozen storage in raspberry fruit. J Agric Food Chem 48: 4565-70

Halvorsen BL, Carlsen MH, Phillips KM, Bhn SK, Holte K, Jacobs Jr DR, Blomhoff R (2006) Content of redox-active compounds (ie, antioxidants) in foods consumed in the United States. American Journal of Clinical Nutrition 84: 95-135

Liu M, Li XQ, Weber C, Lee CY, Brown J, Liu RH (2002) Antioxidant and antiproliferative activities of raspberries. J Agric Food Chem 50: 2926-30McDougall GJ, Stewart D (2005) The inhibitory effects of berry polyphenols on digestive enzymes. Biofactors 23: 189-195

Mullen W, Stewart AJ, Lean MEJ, Gardner P, Duthie GG, Crozier A (2002) Effect of freezing and storage on the phenolics, ellagitannins, flavonoids, and antioxidant capacity of red raspberries. Journal of Agricultural and Food Chemistry 50: 5197-5201

Prior RL, Wu X, Gu L, Hager TJ, Hager A, Howard LR (2008) Whole berries versus berry anthocyanins: Interactions with dietary fat levels in the C57BL/6J mouse model of obesity. Journal of Agricultural and Food Chemistry 56: 647-653

Washington Red Raspberry Commision(2007). www.raspberryinfo.com/articles/SummaryRaspNutrition.doc