Sweet Potatoes: One of nature’s truly great gifts!
Sweet potatoes are one of the oldest foods in the human diet. Their starch content is similar in every way to other root vegetables and tubers that have played prominent roles in human development. These starches have provided humans with a critical source of carbohydrates that has allowed for expansion of our brain size as a species and has been supportive of human health and the health of hundreds of human generations. Sweet potatoes are a great source of numerous nutrients that range from trace minerals to vitamin E, and from fermentable fiber to an array of carotenoids. In all, one cup of sweet potato contains more than 20% of the DRI for at least 10 nutrients. They can be a staple of a healthy diet and are the true definition of a "superfood" if such a thing exists!
Although both sweet and an incredibly rich source of carbohydrates, the glycemic index of sweet potatoes is moderate (46 if boiled or steamed and 82 if baked) to low depending upon the cooking method and temperature. While steaming or lower heat cooking techniques generate significantly lower glycemic indexes, eating sweet potatoes raw is not better yet. In fact, research suggests that some heat is best. Just several minutes of steaming, for instance, inactivates peroxidase enzymes in sweet potatoes that would otherwise degrade the variety of pigments present and can render them less beneficial to our health.
The greatest benefits derived from sweet potatoes may be found in some of the unique phytonutrients that they contain. One of those phytonutrients is sporamin, a unique storage protein that helps sweet potatoes heal when injured or damaged in the ground. This molecule, in synergy with other phytonutrients, has significant antioxidant value, anti-inflammatory properties, and has also been shown to lower fibrinogen levels in individuals.
Additionally, animals given purple sweet potatoes as a regular part of their diet exhibited marked drop offs in their uric acid levels and circulating xanthine oxidase activity, both biomarkers that are consistently associated with conditions such as heart disease and gout.
While all sweet potatoes are extremely concentrated in carotenoids, purple sweet potatoes are exceptionally high in their anthocyanin content. In fact, antioxidant research has shown that the purple pigments peonidin and cyanidin provide purple sweet potatoes with an ORAC value that is 3.2x higher than blueberries on a per weight basis!
Famous Blue Zone and healthy populations that eat sweet potatoes as a regular part of their diet include the Okinawans and the New Guinea Highlanders. These and other populations have great levels of health from so many excellent lifestyle characteristics and sweet potatoes are just one more of these.
- Ahmad MH, Morrison EY, Asemota HN. Food processing methods influence the glycemic indices of some commonly eaten West Indian carbohydrate-rich foods. Br J Nutr. 2006 Sep;96(3):476-81. 2006.
- Bahado-Singh PS, Wheatley AO et al. Food processing methods influence the glycemic indices of some commonly eaten West Indian carbohydrate-rich foods. Br J Nutr. 2006 Sep;96(3):476-81. 2006.
- Chang WH, Huang YF, Yeh TS et al. *Effect of purple sweet potato leaves consumption on exercise-induced oxidative stress, and IL-6 and HSP72 levels. *J Appl Physiol. 2010 Sep 23. [Epub ahead of print]. 2010.
- Choi JH, Choi CY, Lee KJ et al. Hepatoprotective effects of an anthocyanin fraction from purple-fleshed sweet potato against acetaminophen-induced liver damage in mice. J Med Food. 2009 Apr;12(2):320-6. 2009.
- Han KH, Matsumoto A, Shimada K et al. Effects of anthocyanin-rich purple potato flakes on antioxidant status in F344 rats fed a cholesterol-rich diet. Br J Nutr. 2007 Nov;98(5):914-21. Epub 2007 Jun 11. 2007.
- Hwang YP, Choi JH, Yun HJ et al. Anthocyanins from purple sweet potato attenuate dimethylnitrosamine-induced liver injury in rats by inducing Nrf2-mediated antioxidant enzymes and reducing COX-2 and iNOS expression. Food Chem Toxicol. 2010 Oct 8. [Epub ahead of print]. 2010.
- Ludvik B, Hanefeld M, and Pacini G. Improved metabolic control by Ipomoea batatas (Caiapo) is associated with increased adiponectin and decreased fibrinogen levels in type 2 diabetic subjects. Diabetes Obes Metab. 2008 Jul;10(7):586-92. Epub 2007 Jul 21.
- Philpott M, Ferguson LR, Gould KS et al. Anthocyanidin-containing compounds occur in the periderm cell walls of the storage roots of sweet potato (Ipomoea batatas). J Plant Physiol. 2009 Jul 1;166(10):1112-7. Epub 2009 Feb 6. 2009.
- Sugata M, Lin CY, and Shih YC. Anti-Inflammatory and Anticancer Activities of Taiwanese Purple-Fleshed Sweet Potatoes (Ipomoea batatas L. Lam) Extracts. Biomed Res Int. 2015;2015:768093. Epub 2015 Oct 5.
- Wang YJ, Zheng YL, Lu J et al. Purple sweet potato color suppresses lipopolysaccharide-induced acute inflammatory response in mouse brain. Neurochem Int. 2010 Feb;56(3):424-30. Epub 2009 Nov 24. 2010.
- Xie J, Han YT, Wang CB et al. Purple sweet potato pigments protect murine thymocytes from (60)Co gamma-ray-induced mitochondria-mediated apoptosis. Int J Radiat Biol. 2010 Aug 10. [Epub ahead of print]. 2010.
- Zhang ZF, Fan SH, Zheng YL et al. Purple sweet potato color attenuates oxidative stress and inflammatory response induced by d-galactose in mouse liver. Food Chem Toxicol. 2009 Feb;47(2):496-501. Epub 2008 Dec 13. 2009.
- Zhang ZC et al. Effects of anthocyanins from purple sweet potato (Ipomoea batatas L. cultivar Eshu No. 8) on the serum uric acid level and xanthine oxidase activity in hyperuricemic mice. Food Funct. 2015 Sep 2;6(9):3045-55. doi: 10.1039/c5fo00499c.