Potato: chilling it, and the enzyme before surgery

Cooling a cooked potato does change what it does to you, and it changes less than you have been told. In premenopausal women with raised fasting glucose, chilled potato cut insulin at 15 and 30 minutes by about a quarter against boiled potato, and the area under the glucose curve did not differ between them at all. Insulin fell. Blood sugar did not. Read the method before you plan your week around it. That potato was baked at 218 degrees for ninety minutes and then held at 4 degrees for five full days, a schedule chosen to build as much resistant starch as possible, and the potato it was compared against had been peeled before boiling. Two things changed at once, so the chilling cannot take all the credit. The wider picture is calmer than the argument. The one systematic review that went looking found no convincing link between eating potatoes and obesity, diabetes or heart disease, and every study that pulled French fries out separately found a worse picture for the fries.

The numbers, per 100 g

How much is actually in it

• Boil a potato in its skin and it keeps nine tenths of its folate. Peel it first and pour the water away, and a quarter of the folate goes down the sink. Bake it in the skin and the potassium stays put entirely. — Vegetables and Vegetable Products, potato methods (n = 270 group-by-method combinations in the table, 16 nutrients parsed of the 26 the table carries) Evidence E source
  POTATOES,BOILED IN SKIN (3307): folate 90%, potassium 90%, vitamin C 75%, thiamin 80%. POTATOES,BOILED(PARED)DRAIN (3308): folate 75%, potassium 90%, vitamin C 75%, thiamin 80%. POTATOES,BOILED(PARED) WATER USED (3309): folate 90%, potassium 100%, vitamin C 80%. POTATOES,BAKED IN SKIN (3301): folate 90%, potassium 100%, vitamin C 80%, thiamin 85%. POTATOES,FRIED (3315): folate 75%, vitamin C 80%, thiamin 80%, potassium 100%

What a real portion looks like

• A medium baked potato weighs 285 grams and a medium boiled one weighs 170. Same word, same vegetable, and nearly double the food on the plate. — White potatoes, baked or boiled (n = FNDDS 5,432 foods and 22,046 household measures) Evidence E source
  Potato, baked, NFS (fdc_id 2709383): small 230 g, medium 285 g, large 400 g, 1 cup 130 g. Potato, boiled, NFS (fdc_id 2709385): baby potato 60 g, new potato 60 g, small 130 g, medium 170 g, large 300 g, 1 cup 160 g

What your body absorbs

• Baked-then-chilled potato cut the insulin response by about a quarter against boiled potato in women with raised fasting glucose, while the overall glucose curve did not move at all. — premenopausal overweight and obese women aged 18 to 45 with a mean BMI of 32.8, fasting glucose 110.5 mg/dL and insulin 10.3 microIU/L at baseline (n = 30 women, each acting as her own control) Evidence B source
  At 15 and 30 minutes the chilled potato lowered glucose by 4.8% and 9.2%, insulin by 25.8% and 22.6% and glucose-dependent insulinotropic peptide by 41.1% and 37.6%; area under the curve was significantly lower for insulin and GIP, but showed no difference for glucose, GLP-1, peptide YY or subjective satiety
• Potassium from potato is absorbed as completely as potassium from a supplement, better than 94 per cent either way, and after the potato more of it comes out in the urine. — healthy normotensive men and women with a mean age of 29.7 years and mean BMI of 24.3, eating a basal diet of about 60 mEq potassium (n = 35 adults) Evidence B source
  Added potassium of 20, 40 and 60 mEq/day as unfried white potato with skin or as potassium gluconate, plus 40 mEq as French fries; serum potassium area under the curve rose with dose (P < 0.0001) and did not differ by source (P = 0.53), cumulative 24-hour urinary potassium rose with dose (P < 0.0001) and was greater with potato than with the supplement (P < 0.0001), absorption efficiency exceeded 94% across all interventions, and neither blood pressure nor augmentation index changed with source or dose

What cooking and storage change

• The chilled potato in that trial took five days to make. It was baked for ninety minutes, then held at 4 degrees for five full days, and the authors picked five days on purpose to build up as much resistant starch as they could. — russet potatoes of similar size bought from the same shop before each intervention (n = two preparations compared, boiled and baked-then-chilled) Evidence B source
  The chilled arm was washed, wrapped in foil, baked at 218 degrees Celsius for 90 minutes, sealed and stored at 4 degrees Celsius for five days, with the skin left on through baking and chilling and removed only just before eating; the boiled arm was peeled first, diced into 2.54 cm cubes and boiled 15 minutes

Safety, limits and interactions

• Acrylamide, which forms when potatoes are fried or baked hot, tracks with cardiovascular death in population surveys. The same surveys have it running backwards against diabetes and obesity, which is a sign the picture is not settled. — general population samples, predominantly from US NHANES, with acrylamide and its metabolite glycidamide measured as haemoglobin adducts (n = 28 studies, predominantly cross-sectional) Evidence C source
  Higher acrylamide exposure was associated with increased cardiovascular mortality but inversely associated with glucose and lipid levels and with diabetes, obesity and metabolic syndrome, while glycidamide was positively associated with raised glucose and lipids, higher systolic blood pressure and greater obesity prevalence

What people believe that the data does not support

• The one systematic review that went looking found no convincing link between eating potatoes and obesity, diabetes or heart disease. Every study that separated out French fries found a worse picture for the fries. — apparently healthy adults with no known illness at baseline (n = 13 eligible studies, all observational: 5 on obesity, 7 on type 2 diabetes, 1 on cardiovascular disease) Evidence B source
  Potatoes excluding French fries were neutral for adiposity in 2 studies and positively associated in 2; French fries were positively associated with adiposity in 3 of 3 studies; for type 2 diabetes 2 studies showed a positive association and 5 showed none or a negative one, while French fries were positively associated in 3 of 3 studies that separated them; no association was seen for cardiovascular disease
• In a twelve week trial everyone ate five to seven servings of potato a week, and everyone still lost weight. Cutting calories did the work, and the potato did not get in the way. — free-living overweight men and women with a mean BMI of 29.6, choosing and preparing their own food (n = 90 adults) Evidence B source
  No significant differences in weight loss or body composition between the three groups, modest weight loss and body composition change from week 0 to week 12 in all groups (P < 0.05), and no change within or between treatments in fasting triglycerides, glucose tolerance, insulin or insulin sensitivity; the authors report that achieving the prescribed glycaemic index diets was difficult in this free-living setting
• Europe has turned down every health claim ever filed for potato. All four were about feeling full or losing weight, and none of them got through. — claims filed for authorisation on potato-derived substances in the European Union (n = 4 claims found for potato out of 2,330 in the register: 0 authorised, 4 non-authorised, 0 revoked) Evidence E source
  POL-HC-7796 potato protein isolate for satiety, appetite and weight control, POL-HC-8425 Slendesta potato extract for reduction of body weight in overweight individuals, and POL-HC-7966 and POL-HC-7967 standardised potato extract for supporting the body's natural satiety response, all recorded as Non-authorised; by contrast potassium itself carries three authorised claims in the same register, including maintenance of normal blood pressure

Who this works differently for

• Potatoes block the enzyme that clears a common anaesthetic muscle relaxant, and a normal portion eaten in the last meal before surgery measurably stretched out both the block and the waking up. — adults undergoing elective surgery under thiopental, fentanyl and sevoflurane with succinylcholine 1 mg/kg for intubation (n = 44 patients, 21 eating potatoes and 23 eating food without glycoalkaloids) Evidence C source
  Duration of succinylcholine-induced neuromuscular block, awakening time and recovery time were all significantly longer in the potato group (P < 0.05); serum butyrylcholinesterase fell at 6 hours after eating in the potato group, but none of the differences in enzyme levels reached statistical significance
• Europe assessed the natural toxins in potato and found a health concern for babies and toddlers at ordinary intakes, and for adults only at the high end. Peeling removes a quarter to three quarters of them. — European population by age group, with infants and toddlers assessed separately (n = EFSA Journal 2020, risk assessment covering mean and high consumers across age groups) Evidence E source
  EFSA derived a lowest observed adverse effect level of 1 mg per kg of body weight per day for acute effects; a health concern was identified for infants and toddlers at both mean and high consumption, and for adults at high consumption only; peeling reduces glycoalkaloid content by 25 to 75%, boiling in water by 5 to 65% and frying in oil by 20 to 90%

What is still unknown

• Nobody has published a spread for the composition of a plain potato. The USDA variability dataset covers potato flour and stops there, so how much a potato varies from field to field is a question we cannot answer. — potato entries in the Foundation Foods variability release (n = the only potato entry is Flour, potato, with 8 samples across 25 nutrients) Evidence E source
  Flour, potato shows ranges of 70.7 to 1790 mg potassium per 100 g (spread 135%), 16.6 to 58.9 µg total folate (103%), 58.36 to 72.94 g starch (23%) and 0.0 to 86.3 mg iron (721%) across 8 samples; no entry for the raw or cooked tuber exists in this layer, and CoFID likewise has no plain boiled or baked potato, only crisps, chips, curries, scones, duchesse and potato powder
• A 2026 trial is titled for improving glucose across two meals, and its own abstract says the effect did not reach the second meal. The title and the result disagree, and the result is the part that counts. — adults eating rice and potato mixed meals (n = acute crossover trial, participant count not given in the abstract and the full text reports it in the staple food substitution section) Evidence C source
  Hard-cooked potato retained more resistant starch and total phenolics than soft-cooked, and with rice it reduced glucose iAUC, peak glucose, glycaemic excursion, insulin iAUC, peak insulin and the insulin resistance index; the hypoglycaemic effect did not extend to the second meal, although the composite glucose iAUC over 540 minutes was reduced

The bottom line

Cook it in its skin. Boiled in the skin, a potato keeps 90 percent of its folate. Peeled first with the water poured away, it keeps 75. Baked in the skin it keeps all of its potassium, and that potassium is as usable as the kind in a pill, absorbed at better than 94 percent from either, with more of it turning up in the urine after the potato. Blood pressure did not change with either source. Potatoes are also not the thing stopping people from losing weight. Over twelve weeks everyone in one trial ate five to seven servings a week, everyone cut calories, and everyone lost weight. Two warnings belong to real people rather than to the food in general. Europe assessed the natural toxins in potato, the glycoalkaloids, and found a health concern for infants and toddlers at ordinary intakes and for adults only at the high end. Peeling removes a quarter to three quarters of them, which is the one time peeling is the better choice. And if you have surgery coming, a normal portion of potato in the last meal before anaesthesia measurably stretched out both the block from a common muscle relaxant and the waking up afterwards. Mention it to your anaesthetist rather than lying awake about it. Frying has an argument of its own. Acrylamide tracks with cardiovascular death in population surveys and runs backwards against diabetes and obesity in the same surveys, which is what an unsettled picture looks like. Europe turned down all four health claims ever filed for potato, and all four were about feeling full or losing weight. One gap is worth naming out loud. Nobody has published how much a plain potato varies from field to field. The USDA variability dataset covers potato flour and stops there.

Sources

1. pot-f-10 · reference dataset
   USDA-RETN-R6:3307 POTATOES,BOILED IN SKIN — folate_total_ug 90% · potassium_mg 90% · vitamin_c_mg 75% · thiamin_mg 80% || USDA-RETN-R6:3308 POTATOES,BOILED(PARED)DRAIN — folate_total_ug 75% · potassium_mg 90% || USDA-RETN-R6:3309 POTATOES,BOILED(PARED) WATER USED — folate_total_ug 90% · potassium_mg 100% || USDA-RETN-R6:3301 POTATOES,BAKED IN SKIN — folate_total_ug 90% · potassium_mg 100% · thiamin_mg 85% || USDA-RETN-R6:3315 POTATOES,FRIED — folate_total_ug 75% · potassium_mg 100%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), Agricultural Research Service · checked 2026-09-21
2. pot-f-11 · reference dataset
   FNDDS 2709383 Potato, baked, NFS (71100100) — 1 small 230 г · 1 medium 285 г · 1 large 400 г · 1 cup 130 г || FNDDS 2709385 Potato, boiled, NFS (71102980) — 1 baby potato 60 г · 1 new potato 60 г · 1 small 130 г · 1 medium 170 г · 1 large 300 г · 1 cup 160 г
   USDA FNDDS 2021-2023, FoodData Central · checked 2026-09-21
3. pot-f-01 · randomised crossover trial
   Results showed that the chilled potato elicited significant reductions at 15 and 30 min in glucose (4.8% and 9.2%), insulin (25.8% and 22.6%), and glucose-dependent insulinotropic peptide (GIP) (41.1% and 37.6%), respectively.
   Patterson et al., Nutrients, 2019 · checked 2026-09-21
4. pot-f-03 · randomised crossover dose-response trial
   The serum potassium AUC increased with the dose (P < 0.0001) and did not differ because of the source (P = 0.53). Cumulative 24-h urinary potassium also increased with the dose (P < 0.0001) and was greater with the potato than with the supplement (P < 0.0001). The kinetic analysis showed the absorption efficiency was high across all interventions (>94% ± 12%).
   Macdonald-Clarke et al., American Journal of Clinical Nutrition, 2016 · checked 2026-09-21
5. pot-f-02 · randomised crossover trial
   The potatoes were chilled five days to maximize RS3 formation, which is similar to a protocol used previously [20] where potatoes were chilled for six days.
   Patterson et al., Nutrients, 2019 · checked 2026-09-21
6. pot-f-07 · systematic review of observational studies
   Higher acrylamide exposure was associated with an increased risk of cardiovascular mortality but was inversely associated with glucose and lipid levels, as well as key cardiovascular risk factors such as diabetes, obesity, and metabolic syndrome.
   Nutrients, 2024 · checked 2026-09-21
7. pot-f-04 · systematic review of observational studies
   The identified studies do not provide convincing evidence to suggest an association between intake of potatoes and risks of obesity, T2D, or CVD. French fries may be associated with increased risks of obesity and T2D although confounding may be present.
   Borch et al., American Journal of Clinical Nutrition, 2016 · checked 2026-09-21
8. pot-f-05 · randomised controlled trial
   Potato intake did not cause weight gain and following either a high- or low-GI dietary prescription was difficult for free-living subjects, emphasizing the complex nature of changing dietary patterns.
   Randolph et al., Journal of the American College of Nutrition, 2014 · checked 2026-09-21
9. pot-f-08 · regulatory register
   POL-HC-8425 Slendesta® Potato Extract Slendesta® contributes to the reduction of body weight in overweight individuals -/- Non-authorised
   EU Register on nutrition and health claims, European Commission · checked 2026-09-21
10. pot-f-06 · randomised controlled trial
    This study suggests that potatoes eaten before anesthesia can prolong the duration of succinylcholine-induced neuromuscular block and delay recovery from anesthesia.
    Krivoy et al., Journal of Clinical Monitoring and Computing, 2013 · checked 2026-09-21
11. pot-f-09 · agency risk assessment
    Experts identified a health concern for infants and toddlers, considering both mean and high consumers...Peeling potatoes can reduce their content by between 25 and 75%, boiling in water between 5 and 65%, and frying in oil between 20 and 90%.
    EFSA, Glycoalkaloids in potatoes: public health risks assessed, 2020 · checked 2026-09-21
12. pot-f-12 · reference dataset
    Flour, potato — Potassium, K 1269.0 MG діапазон 70.7–1790.0 (медіана 1525.0), зразків 8, розкид 135% · Folate, total 41.15 UG діапазон 16.6–58.9, зразків 8, розкид 103% · Starch 62.67 G діапазон 58.36–72.94, зразків 8, розкид 23% · Iron, Fe 11.97 MG діапазон 0.0–86.3, зразків 8, розкид 721%
    USDA FoodData Central, Foundation Foods, release 2026-04-30; CoFID 2021, Public Health England / OGL v3.0 · checked 2026-09-21
13. pot-f-13 · randomised controlled acute trial
    The hypoglycemic effect did not extend to the second meal, though composite iAUCglucose over 540 min was reduced.
    Nutrients, 2026 · checked 2026-09-21