Sweet Potato: Superfood for Thought

Popularity of the humble sweet potato has rocketed in recent years, with good reason too. The revolution behind this delicious vegetable goes beyond fries and mash. The tasty tuber is a superfood for both our dogs and us, here’s why:

Orange is the new black

As a general rule, highly coloured fruits and vegetables are better for us; partly because their pigments are rich in anti-oxidants including vitamins and minerals (1) (I don’t know if you’ve noticed, but sweet potatoes are pretty colourful).

Beta-carotene, a precursor of Vitamin A, is responsible for the bright orange colour of common sweet potatoes (2, 4). Dogs excrete a lot of vitamin A (13), so their daily intake must be sufficient. Evidence suggests that beta-carotene reduces the incidence of cardiovascular disease and age-related muscle degeneration in humans (7), while vitamin A plays a crucial role in for immunity and eye health for bothin humans and animals (8). Both compounds alone have anti-oxidant activity (3).

Anti-oxidants 101:

Free radicals are highly reactive atoms constantly formed in the body. These are necessary for biological processes, but if unregulated they can cause ‘oxidative stress’ and tissue damage.

Anti-oxidants regulate the production of these free radicals to prevent disease.

You may have noticed that some, less common varieties of sweet potato are purple. Along with carotenes (of which ‘beta’ is the most effective), anthocyanins and phenols are also abundant antioxidants in sweet potato. In humans, this powerful trio of compounds all promote normal cell proliferation, which can lead to cancer if not controlled (5,6). Research shows that anthocyanin and phenol content is significantly higher in purple varieties, along with overall anti-oxidant activity (4).

These pigments and other compounds give sweet potatoes anti-inflammatory properties in humans (16). Reducing inflammation can prevent tissue damage and maintain biological functions. For example: intestinal inflammation has various causes including dietary intolerances, this can compromise digestion and nutrient absorption.

Nutrient composition of sweet potatoes (without skin)

Adapted from the USDA food composition database (2015).

Boiled vs Roasted

As you can see, baked sweet potatoes retain more nutrients, vitamins and minerals than boiled. This is partly because during boiling (and steaming) they leach into the water.

Carbohydrate

Sweet potatoes are obviously high in carbohydrate, but contain fewer calories than regular potatoes. They also have a relatively low glycemic index (GI) compared to regular potatoes (approx. 70 vs. 100 in humans)(8). The GI describes the effect a food has on blood sugar levels. When we consume low GI foods (instead of high GI foods) it reduces ourthe risks of obesity, heart disease and diabetes (9).

Fibre

This is important for bulking out the stool and maintaining good intestinal health, this is great for us. When feeding to your dog, remember they have a limited capacity of fibre digestion, so my advice is to take the skin off.

Magnesium

Potassium, calcium and sodium are all involved in energy transfer (e.g. from food to the tissues). Magnesium is needed for many of these cellular reactions to occur and therefore, is essential for most biological processes that require energy. Every time your heart beats or you move a muscle, magnesium is involved.

Potassium

Sweet potatoes are high in potassium, an essential mineral that also helps to lower blood pressure in humans (10).

Calcium and Phosphorus

Being source of calcium and phosphorus means that these vegetables are good for strong bones. Both minerals are associated in the structure of bone; a deficiency in either can result in bone reabsorption.

Other vitamins in sweet potato

We all know that vitamin C is an essential part of our diet, being important for immune function. Dogs can synthesise their own Vitamin C(12), this does not mean that they don’t benefit from dietary supplementation. Over supplementation to dogs can result in diarrhoea, but tolerance varies between individuals (14).

Along with vitamin A, vitamin E is important for vision and eye health as well as immunity and healthy skin. A deficiency in vitamin E can damage the retina and eventually lead to blindness (14).

Vitamin K is essential for healing and helps blood to clot when we suffer an injury. Vitamin K is even used as remedy in dogs that accidentally consume anti-coagulants (e.g. rat poisons)(15).

B vitamins in sweet potato are involved in energy metabolism, nervous system function and skin/eye health. B6 specifically is used to help your blood carry oxygen, while folic acid is also essential for functioning red blood cells.

The take-home message

Sweet potatoes are an excellent source of anti-oxidants that can help to prevent many degenerative diseases, including cancer (as demonstrated in humans). A low glycemic index means that they provide energy with minimal impact on blood sugar levels. Additional vitamins and minerals promote various health benefits and support normal biological functions. Furthermore, you can benefit from anti-inflammatory properties. This is one of the best starchy foods for you and your dog.

Marco Crisci

References

1. Kaur, C. and Kapoor, H. (2001). Antioxidants in fruits and vegetables — the millennium’s health. International Journal of Food Science & Technology, 36(7), pp.703–725.
2. Low, J.W., Arimond, M., Osman, N., Cunguara, B., Zano, F. and Tschirley, D., 2007. A food-based approach introducing orange-fleshed sweet potatoes increased vitamin A intake and serum retinol concentrations in young children in rural Mozambique. The Journal of nutrition, 137(5), pp.1320–1327.
3. Blomhoff, R. (1994). Transport and Metabolism of Vitamin A. Nutrition Reviews, 52(2), pp.S13-S23.
4. Teow, C., Truong, V., McFeeters, R., Thompson, R., Pecota, K. and Yencho, G. (2007). Antioxidant activities, phenolic and β-carotene contents of sweet potato genotypes with varying flesh colours. Food Chemistry, 103(3), pp.829–838.
5. Lim, S., Xu, J., Kim, J., Chen, T., Su, X., Standard, J., Carey, E., Griffin, J., Herndon, B., Katz, B., Tomich, J. and Wang, W. (2013). Role of anthocyanin-enriched purple-fleshed sweet potato p40 in colorectal cancer prevention. Molecular Nutrition & Food Research, 57(11), pp.1908–1917.
6. Van Duyn, M. and Pivonka, E. (2000). Overview of the Health Benefits of Fruit and Vegetable Consumption for the Dietetics Professional. Journal of the American Dietetic Association, 100(12), pp.1511–1521.
7. Bovell‐Benjamin, A. (2007). Sweet Potato: A Review of its Past, Present, and Future Role in Human Nutrition. Advances in Food and Nutrition Research, 52, pp.1–59.
8. Jenkins, D., Wolever, T. and Jenkins, A. (1988). Starchy Foods and Glycemic Index. Diabetes Care, 11(2), pp.149–159.
9. Ludwig, D. (2002). The Glycemic Index: Physiological Mechanisms Relating to Obesity, Diabetes, and Cardiovascular Disease. JAMA, 287(18), pp.2414–2423.
10. Ward, E. (2010). Potassium Food Sources, Benefits, Deficiencies, and. [online] WebMD. Available at: http://www.webmd.com/food-recipes/features/potassium-sources-and-benefits#1 [Accessed 13 May 2017].
11. Chatterjee, I., Majumder, A., Nandi, B. and Subramanian, N. (1975). SYNTHESIS AND SOME MAJOR FUNCTIONS OF VITAMIN C IN ANIMALS. Annals of the New York Academy of Sciences, 258(1 Second Confer), pp.24–47.
12. Schweigert, F. and Bok, V. (2000). Vitamin A in Blood Plasma and Urine of Dogs is Affected by the Dietary Level of Vitamin A. International Journal for Vitamin and Nutrition Research, 70(3), pp.84–91.
13. Griswold, B. and Kerns, N. (1998). Benefits of Vitamin C to Your Dog. [online] Whole Dog Journal. Available at: https://www.whole-dog-journal.com/issues/1_7/features/Vitamin-C-for-Dogs_5309-1.html [Accessed 15 May 2017].
14. Riis, R.C., Sheffy, B.E., Loew, E., Kern, T.J. and Smith, J.S. (1981). Vitamin E deficiency retinopathy in dogs. American journal of veterinary research, 42(1), pp.74–86
15. Cornell University (2014). Vitamin K Therapy. [online] Cornell University College of Veterinary Medicine. Available at: https://ahdc.vet.cornell.edu/sects/coag/clinical/vitamk.cfm [Accessed 14 May 2017].
16. Bai, S., Lee, S., Na, H., Ha, K., Han, J., Lee, H., Kwon, Y., Chung, C. and Kim, Y. (2005). β-Carotene inhibits inflammatory gene expression in lipopolysaccharide-stimulated macrophages by suppressing redox-based NF-κB activation. Experimental & Molecular Medicine, 37(4), pp.323–334.