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Food Β· Β§360
Sweet Potatoes and Other Orange Tubers
A sweet potato is the cheapest fix for a vitamin A level most Western adults sit slightly below without knowing. The orange pigment is beta-carotene, which your body cuts into vitamin A on demand, so a food dose can't overdose you. Here's what you didn't know you didn't know: whether it's low-glycemic or spikes you like white rice comes down to one thing, and it isn't the variety. Eat a few a week, prepared right, and it works quietly on skin, gut, and blood pressure.
Do Β· Weekly Evidence Moderate Chapter Food

The vitamin A is the surest part. A medium orange-fleshed tuber, about 150 grams cooked, covers an adult day's requirement. Children fed boiled orange-fleshed sweet potato for eleven weeks raised their vitamin A liver stores; a white-fleshed control group didn't 1. Household rollouts cut vitamin A deficiency by about a third 2 3. The colour is the nutrient: white varieties carry fifty to a hundred times less.

The blood-sugar fact most people get wrong: boiled, sweet potato is genuinely low-glycemic, in the low forties to fifty. Baked or roasted dry, the same tuber scores in the eighties to mid-nineties, on par with white rice 4. The variety barely moves it; the cooking does.

The skin change is visible to other people in about six weeks. Carotenoid intake tracked against skin colour showed a warm undertone at three weeks and more at six 5. Strangers rated those faces as healthier and more attractive, beating a tan at moderate intensities 6 7.

A medium tuber, two or three times a week, is the sweet spot. That covers the vitamin A, drives the skin change, and nudges gut and blood pressure. More is fine; less helps.

First week: a boiled tuber doesn't set up the mid-afternoon dip a baguette or pasta bowl would. Just the absence of a slump you'd accepted as normal.

Third or fourth week: if you've kept the cooled-leftover habit, the gut quietens and post-meal bloating gets rare 8.

Around six weeks: your face picks up the faint warm undertone the carotenoid studies measure, and other people read it as health and rest 5 6.

Over years: the potassium nudges blood pressure down, and the steady vegetable portion adds to the lower CVD and death rates seen for people eating more colourful plants 9.

The fine print β€” when to skip it, and what people get wrong

"Yam" on a US label is almost always an orange sweet potato, a 1930s marketing holdover; true yams are a different plant with little pigment. White-fleshed sweet potato is a fine food but gives almost no vitamin A.

The two ways it fails: eating it fat-free wastes most of the vitamin A, and roasting it dry pushes it into white-rice territory 4. If the flesh is white or yellow inside, it's a different food nutritionally.

Heavy smokers: don't add a beta-carotene pill. At 20 to 30 mg/day it raised lung-cancer rates in smokers; food carotenoids haven't 10 11. With advanced kidney disease or oxalate stones, portion as your doctor advises.

References
  1. 1van Jaarsveld PJ, Faber M, Tanumihardjo SA, Nestel P, Lombard CJ, BenadΓ© AJS (2005). Ξ²-Carotene-rich orange-fleshed sweet potato improves the vitamin A status of primary school children assessed with the modified-relative-dose-response test. The American Journal of Clinical Nutrition. link
  2. 2Low JW, Arimond M, Osman N, Cunguara B, Zano F, 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. link
  3. 3Hotz C, Loechl C, Lubowa A, Tumwine JK, Ndeezi G, Masawi AN, Baingana R, Carriquiry A, de Brauw A, Meenakshi JV, Gilligan DO (2012). Introduction of Ξ²-carotene-rich orange sweet potato in rural Uganda resulted in increased vitamin A intakes among children and women and improved vitamin A status among children. The Journal of Nutrition. link
  4. 4Bahado-Singh PS, Riley CK, Wheatley AO, Lowe HIC (2011). Relationship between processing method and the glycemic indices of ten sweet potato (Ipomoea batatas) cultivars commonly consumed in Jamaica. Journal of Nutrition and Metabolism. link
  5. 5Whitehead RD, Re D, Xiao D, Ozakinci G, Perrett DI (2012). You are what you eat: within-subject increases in fruit and vegetable consumption confer beneficial skin-color changes. PLOS ONE. link
  6. 6Stephen ID, Coetzee V, Perrett DI (2011). Carotenoid and melanin pigment coloration affect perceived human health. Evolution and Human Behavior. link
  7. 7Lefevre CE, Perrett DI (2015). Fruit over sunbed: carotenoid skin colouration is found more attractive than melanin colouration. Quarterly Journal of Experimental Psychology. link
  8. 8Raatz SK, Idso L, Johnson LK, Jackson MI, Combs GF Jr (2016). Resistant starch analysis of commonly consumed potatoes: content varies by cooking method and service temperature but not by variety. Food Chemistry. link
  9. 9Aune D, Giovannucci E, Boffetta P, Fadnes LT, Keum N, Norat T, Greenwood DC, Riboli E, Vatten LJ, Tonstad S (2017). Fruit and vegetable intake and the risk of cardiovascular disease, total cancer and all-cause mortality - a systematic review and dose-response meta-analysis of prospective studies. International Journal of Epidemiology. link
  10. 10The Alpha-Tocopherol, Beta Carotene Cancer Prevention Study Group (1994). The effect of vitamin E and beta carotene on the incidence of lung cancer and other cancers in male smokers. New England Journal of Medicine. link
  11. 11Omenn GS, Goodman GE, Thornquist MD, Balmes J, Cullen MR, Glass A, Keogh JP, Meyskens FL, Valanis B, Williams JH, Barnhart S, Hammar S (1996). Effects of a combination of beta carotene and vitamin A on lung cancer and cardiovascular disease. New England Journal of Medicine. link
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