How does sweet potato baking compare to boiling and steaming, and should we eat the skin?
Flashback Friday: The Best Way to Cook Sweet Potatoes
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Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
The only potential downside of eating sweet potatoes is if you eat too much, you could get a yellow nose. It’s called carotenemia. It’s a common, harmless condition due to elevated levels of beta-carotene in the blood, first noticed a century ago, when carrots were introduced into infant diets. It’s treated mostly by just reassuring parents that it’s harmless. But, if you don’t want your child’s nose to be yellow, you can decrease their beta-carotene intake, and in a few months, it will be gone.
But, color is what we’re looking for when picking out varieties at the supermarket. “The intensity of the yellow or orange flesh color of the sweet potato is directly correlated to [its nutritional] content.” So, the more intense, the better. Though, if you really want intensity, “sweet potato varieties…[range not only] from white [to] yellow…[and] orange, [but to] pink [and] “very to deep purple”—the natural pigments of which may have special anticancer effects of their own.
What’s the best way to cook sweet potatoes? Boiling may actually best retain the antioxidant power of sweet potatoes, compared to roasting and steaming. If you compare baking to boiling, microscopically, boiling helps thin out the cell walls and gelatinize the starch, which may enhance the bioavailability of nutrients, while at the same time the glycemic index of boiled sweet potatoes was found to be only about half that of baking or roasting. So, boiled gives one less of a blood sugar spike.
Make sure to keep the skin on, though. The peel of a sweet potato has nearly ten times the antioxidant power as the flesh—an antioxidant capacity “comparable [to] that of blueberries,” though it really takes a hit when baked, wiping out over two-thirds, whereas microwaving or boiling was comparatively much gentler. The same with the rest of the sweet potato. Baking can cause an 80% drop in vitamin A levels—twice as much as boiling. So, “from a nutritional standpoint, boiling rather than baking can be recommended for sweet potato cooking.”
Boiling may be best, but sweet potatoes are so incredibly healthy, the best way to prepare them is whichever way will get you to eat the most of them—with the exception of deep frying, which can lead to the formation of acrylamide, a potential human carcinogen.
Please consider volunteering to help out on the site.
- A C Bovell-Benjamin. Sweet potato: A review of its past, present, and future role in human nutrition. Adv Food Nutr Res 2007 52:1 – 59.
- A Drewnowski. New metrics of affordable nutrition: Which vegetables provide most nutrients for least cost? J Acad Nutr Diet 2013 113(9):1182 – 1187.
- K Ren, J Qiu, X Wang, F Niu, T Jiang. The effect of a sweet potato, footbath, and acupressure intervention in preventing constipation in hospitalized patients with acute coronary syndromes. Gastroenterol Nurs 2012 35(4):271 – 277.
- P G Li, T H Mu, L Deng. Anticancer effects of sweet potato protein on human colorectal cancer cells. World J Gastroenterol. 2013 19(21):3300 – 3308.
- P S Bahado-Singh, C K Riley, A O Wheatley, H I C Lowe. Relationship between Processing Method and the Glycemic Indices of Ten Sweet Potato (Ipomoea batatas) Cultivars Commonly Consumed in Jamaica. J Nutr Metab 2011 2011:584832.
- G A Tumuhimbise, A Namutebi, J H Muyonga. Microstructure and in vitro beta carotene bioaccessibility of heat processed orange fleshed sweet potato. Plant Foods Hum Nutr 2009 64(4):312 – 318.
- C Dincer, M Karaoglan, F Erden, N Tetik, A Topuz, F Ozdemir. Effects of baking and boiling on the nutritional and antioxidant properties of sweet potato [Ipomoea batatas (L.) Lam.] Cultivars. Plant Foods Hum Nutr 2011 66(4):341 – 347.
- C M Donado-Pestana, J M Salgado, A de Oliveira Rios, P R dos Santos, A Jablonski. Stability of carotenoids, total phenolics and in vitro antioxidant capacity in the thermal processing of orange-fleshed sweet potato (Ipomoea batatas Lam.) Cultivars grown in Brazil. Plant Foods Hum Nutr 2012 67(3):262 – 270.
- M S Padda, D H Picha. Phenolic composition and antioxidant capacity of different heat-processed forms of sweetpotato cv. 'Beauregard'. Int J Food Sci Tech 2008 43(8):1404 – 1409.
- S Lim, J Xu, J Kim, T Y Chen, X Su, J Standard, E Carey, J Griffin, B Herndon, B Katz, J Tomich, W Wang. Role of anthocyanin-enriched purple-fleshed sweet potato p40 in colorectal cancer prevention. Mol Nutr Food Res 2013 57(11):1908 – 1917.
- M Eltayeb. A toddler with a yellow nose and excessive intake of sweet potato. BMJ Case Rep 2011.
- P K Lim, S Jinap, M Sanny, C P Tan, A Khatib. The influence of deep frying using various vegetable oils on acrylamide formation in sweet potato (Ipomoea batatas L. Lam) chips. J. Food Sci. 2014 79(1):T115 – 21.
- R Senthilkumar, K W Yeh. Multiple biological functions of sporamin related to stress tolerance in sweet potato (Ipomoea batatas Lam). Biotechnol. Adv. 2012 30(6):1309 – 1317.
- M Pandey, V K Shukla. Diet and gallbladder cancer: A case-control study. Euro J Canc Prev 2002 11(4):365 – 368.
- V Arya, J Grzybowski, R Schwartz. Carotenemia in infancy and its association with prevalent feeding practices. Pediatr Dermatol 2006 23(6):441 – 442.
- H Kobayashi, T Yagyu, K Inagaki, T Kondo, M Suzuki, N Kanayama, T Terao. Therapeutic efficacy of once-daily oral administration of a Kunitz-type protease inhibitor, bikunin, in a mouse model and in human cancer. Cancer 2004 100(4):869 – 877.
- J Yao, C Qian. Sporamin induce apoptosis in human tongue carcinoma cells by down-regulating Akt/GSK-3 signaling. Fundam Clin Pharmacol 2011 25(2):229 – 236.
- G J Huang, M J Sheu, H J Chen, Y S Chang, Y H. Lin. Growth inhibition and induction of apoptosis in NB4 promyelocytic leukemia cells by trypsin inhibitor from sweet potato storage roots. J. Agric. Food. Chem. 2007 55(7):2548 – 2553.
- M A Ameny, P W Wilson. Relationship between Hunter Color Values and b-Carotene Contents in White-Fleshed African Sweet potatoes (Ipomoea batatas Lam). J Sci Food Agric 1997 73:301 – 306.
Images thanks to Jim Hickcox and Alpha via flickr
Below is an approximation of this video’s audio content. To see any graphs, charts, graphics, images, and quotes to which Dr. Greger may be referring, watch the above video.
The only potential downside of eating sweet potatoes is if you eat too much, you could get a yellow nose. It’s called carotenemia. It’s a common, harmless condition due to elevated levels of beta-carotene in the blood, first noticed a century ago, when carrots were introduced into infant diets. It’s treated mostly by just reassuring parents that it’s harmless. But, if you don’t want your child’s nose to be yellow, you can decrease their beta-carotene intake, and in a few months, it will be gone.
But, color is what we’re looking for when picking out varieties at the supermarket. “The intensity of the yellow or orange flesh color of the sweet potato is directly correlated to [its nutritional] content.” So, the more intense, the better. Though, if you really want intensity, “sweet potato varieties…[range not only] from white [to] yellow…[and] orange, [but to] pink [and] “very to deep purple”—the natural pigments of which may have special anticancer effects of their own.
What’s the best way to cook sweet potatoes? Boiling may actually best retain the antioxidant power of sweet potatoes, compared to roasting and steaming. If you compare baking to boiling, microscopically, boiling helps thin out the cell walls and gelatinize the starch, which may enhance the bioavailability of nutrients, while at the same time the glycemic index of boiled sweet potatoes was found to be only about half that of baking or roasting. So, boiled gives one less of a blood sugar spike.
Make sure to keep the skin on, though. The peel of a sweet potato has nearly ten times the antioxidant power as the flesh—an antioxidant capacity “comparable [to] that of blueberries,” though it really takes a hit when baked, wiping out over two-thirds, whereas microwaving or boiling was comparatively much gentler. The same with the rest of the sweet potato. Baking can cause an 80% drop in vitamin A levels—twice as much as boiling. So, “from a nutritional standpoint, boiling rather than baking can be recommended for sweet potato cooking.”
Boiling may be best, but sweet potatoes are so incredibly healthy, the best way to prepare them is whichever way will get you to eat the most of them—with the exception of deep frying, which can lead to the formation of acrylamide, a potential human carcinogen.
Please consider volunteering to help out on the site.
- A C Bovell-Benjamin. Sweet potato: A review of its past, present, and future role in human nutrition. Adv Food Nutr Res 2007 52:1 – 59.
- A Drewnowski. New metrics of affordable nutrition: Which vegetables provide most nutrients for least cost? J Acad Nutr Diet 2013 113(9):1182 – 1187.
- K Ren, J Qiu, X Wang, F Niu, T Jiang. The effect of a sweet potato, footbath, and acupressure intervention in preventing constipation in hospitalized patients with acute coronary syndromes. Gastroenterol Nurs 2012 35(4):271 – 277.
- P G Li, T H Mu, L Deng. Anticancer effects of sweet potato protein on human colorectal cancer cells. World J Gastroenterol. 2013 19(21):3300 – 3308.
- P S Bahado-Singh, C K Riley, A O Wheatley, H I C Lowe. Relationship between Processing Method and the Glycemic Indices of Ten Sweet Potato (Ipomoea batatas) Cultivars Commonly Consumed in Jamaica. J Nutr Metab 2011 2011:584832.
- G A Tumuhimbise, A Namutebi, J H Muyonga. Microstructure and in vitro beta carotene bioaccessibility of heat processed orange fleshed sweet potato. Plant Foods Hum Nutr 2009 64(4):312 – 318.
- C Dincer, M Karaoglan, F Erden, N Tetik, A Topuz, F Ozdemir. Effects of baking and boiling on the nutritional and antioxidant properties of sweet potato [Ipomoea batatas (L.) Lam.] Cultivars. Plant Foods Hum Nutr 2011 66(4):341 – 347.
- C M Donado-Pestana, J M Salgado, A de Oliveira Rios, P R dos Santos, A Jablonski. Stability of carotenoids, total phenolics and in vitro antioxidant capacity in the thermal processing of orange-fleshed sweet potato (Ipomoea batatas Lam.) Cultivars grown in Brazil. Plant Foods Hum Nutr 2012 67(3):262 – 270.
- M S Padda, D H Picha. Phenolic composition and antioxidant capacity of different heat-processed forms of sweetpotato cv. 'Beauregard'. Int J Food Sci Tech 2008 43(8):1404 – 1409.
- S Lim, J Xu, J Kim, T Y Chen, X Su, J Standard, E Carey, J Griffin, B Herndon, B Katz, J Tomich, W Wang. Role of anthocyanin-enriched purple-fleshed sweet potato p40 in colorectal cancer prevention. Mol Nutr Food Res 2013 57(11):1908 – 1917.
- M Eltayeb. A toddler with a yellow nose and excessive intake of sweet potato. BMJ Case Rep 2011.
- P K Lim, S Jinap, M Sanny, C P Tan, A Khatib. The influence of deep frying using various vegetable oils on acrylamide formation in sweet potato (Ipomoea batatas L. Lam) chips. J. Food Sci. 2014 79(1):T115 – 21.
- R Senthilkumar, K W Yeh. Multiple biological functions of sporamin related to stress tolerance in sweet potato (Ipomoea batatas Lam). Biotechnol. Adv. 2012 30(6):1309 – 1317.
- M Pandey, V K Shukla. Diet and gallbladder cancer: A case-control study. Euro J Canc Prev 2002 11(4):365 – 368.
- V Arya, J Grzybowski, R Schwartz. Carotenemia in infancy and its association with prevalent feeding practices. Pediatr Dermatol 2006 23(6):441 – 442.
- H Kobayashi, T Yagyu, K Inagaki, T Kondo, M Suzuki, N Kanayama, T Terao. Therapeutic efficacy of once-daily oral administration of a Kunitz-type protease inhibitor, bikunin, in a mouse model and in human cancer. Cancer 2004 100(4):869 – 877.
- J Yao, C Qian. Sporamin induce apoptosis in human tongue carcinoma cells by down-regulating Akt/GSK-3 signaling. Fundam Clin Pharmacol 2011 25(2):229 – 236.
- G J Huang, M J Sheu, H J Chen, Y S Chang, Y H. Lin. Growth inhibition and induction of apoptosis in NB4 promyelocytic leukemia cells by trypsin inhibitor from sweet potato storage roots. J. Agric. Food. Chem. 2007 55(7):2548 – 2553.
- M A Ameny, P W Wilson. Relationship between Hunter Color Values and b-Carotene Contents in White-Fleshed African Sweet potatoes (Ipomoea batatas Lam). J Sci Food Agric 1997 73:301 – 306.
Images thanks to Jim Hickcox and Alpha via flickr
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Title
Flashback Friday: The Best Way to Cook Sweet Potatoes
LicenseCreative Commons Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)
Content URLDoctor's Note
Next up in our Flashback Friday series: Sweet potatoes are cheap, healthy, nutrient powerhouses—check out Anticancer Potential of Sweet Potato Proteins. What if most of what you ate was sweet potatoes? Find out in my video The Okinawa Diet: Living to Be 100.
What about cooking methods for other vegetables? See Best Cooking Method.
Want more information about acrylamide, the potential crispy carb carcinogen? See Cancer Risk from French Fries. And, for why deep frying, in general, might not be good, see Carcinogens in the Smell of Frying Bacon.
Since this video first aired, I’ve got some more cooking method videos:
- Are Microwaves Safe?
- The Effects of Radiation Leaking from Microwave Ovens
- The Benefits of Kale & Cabbage for Cholesterol
- How to Reduce Cholesterol Oxidation
- How to Cook Greens
- Best Way to Cook Vegetables
-
Glycemic Index of Potatoes: Why You Should Chill and Reheat Them
And how about a bonus recipe? Yum: Stuffed Sweet Potatoes with Balsamic Glaze.
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