Sweet potato leaves: a vitamin K green tested in three small trials

In a randomized crossover trial in 16 healthy adults, eating 7.1 oz (200 g) of purple sweet potato leaves a day for 2 weeks raised immune cell proliferation, IL-2 and IL-4 secretion and natural killer cell activity in blood samples. These are laboratory markers, and the authors say they do not yet know which part of the leaves is responsible or whether the changes matter biologically. The same diet raised polyphenols in urine, while the rise in plasma did not reach significance. A second trial of 200 g a day, in 15 elite basketball players, raised plasma polyphenols and vitamins C and E over 2 weeks, again in a small group of athletes and again in markers only. On the plate the leaves are above all a vitamin K food. The USDA record for raw leaves lists 302.2 mcg per 3.5 oz (100 g), from a single record with no sampling spread.

The numbers, per 3.5 oz (100 g)

How much is actually in it

• Raw sweet potato leaves contain 302.2 mcg vitamin K, 189 mcg vitamin A (RAE) and 0.345 mg riboflavin per 3.5 oz (100 g) in the USDA reference record. — food composition record, raw leaves Evidence E source
  Vitamin K 302.2 mcg/100 g; across 3 USDA records (raw, steamed) 108.6-302.2 mcg

What a real portion looks like

• In the US survey food codes, one cup of cooked sweet potato or similar leaves weighs 2.4 oz (69 g) and an unspecified serving 1.2 oz (35 g). — FNDDS food code shared by sweet potato, squash, pumpkin, chrysanthemum and bean leaves, cooked Evidence E source
  1 cup = 69 g; quantity not specified = 35 g

What your body absorbs

• In a randomized crossover trial in 16 adults eating 7.1 oz (200 g) of purple sweet potato leaves daily for 2 weeks, plasma polyphenols did not rise significantly but urinary polyphenols did. — 16 healthy non-smoking adults of normal weight, 2-week periods (n = 16) Evidence B source
  Plasma polyphenols no significant rise; urinary polyphenols significantly elevated; plasma beta-carotene rose in both arms
• Laboratory data suggest that total polyphenols of sweet potato leaves fall during simulated digestion, with trends differing between five varieties. — five sweet potato leaf varieties, INFOGEST simulated oral-gastric-intestinal digestion Evidence D source
  TPC after digestion significantly lower than original; variety X1 27.07, 14.77 and 19.35 mg GAE/g DW in oral, gastric and intestinal phases

What cooking and storage change

• For leafy greens boiled in a little water and drained, USDA retention factors keep 60% of vitamin C, 65% of folate and 95% of riboflavin. — USDA group factor, Vegetables and Vegetable Products, greens boiled in little water, drained Evidence E source
  Vitamin C 60%, folate 65%, thiamin 85%, riboflavin 95%, iron 95% retained
• For steamed vegetables, USDA retention factors keep 85% of vitamin C and folate and all of the minerals, so steaming loses less than boiling. — USDA group factor, Vegetables and Vegetable Products, other vegetables steamed Evidence E source
  Vitamin C 85%, folate 85%, riboflavin 95%, minerals 100% retained

What it does to your health

• In a randomized crossover trial in 16 adults, 7.1 oz (200 g) of purple sweet potato leaves daily for 2 weeks raised blood immune cell proliferation, IL-2 and IL-4 secretion and natural killer cell activity. — 16 healthy non-smoking adults of normal weight, 2-week periods (n = 16) Evidence B source
  Significant increases in PBMC proliferation, IL-2, IL-4 and NK lytic activity; clinical relevance not shown
• In a controlled crossover trial in 15 untrained young men, a 7-day high-polyphenol diet based on purple sweet potato leaves lowered exercise-induced oxidative damage markers and plasma IL-6. — 15 healthy untrained young men, 7-day diet periods, 1 h treadmill run (n = 15) Evidence C source
  Lower plasma TBARS, protein carbonyl and IL-6 after exercise; no difference in HSP72
• Observational data from Taiwan link the highest intake of sweet potato leaves with lower odds of lung cancer (adjusted OR 0.43-0.65). — 301 incident lung cancer cases, 602 hospital and 602 neighborhood controls, Taiwan (n = 1505) Evidence C source
  AOR highest vs lowest tertile 0.43-0.65, 95% CI 0.28-0.96, p linear trend <= 0.03

Safety, limits and interactions

• According to NIH ODS, people taking warfarin need a consistent vitamin K intake, which matters for leaves as rich in vitamin K as sweet potato leaves. — people taking warfarin or similar anticoagulants Evidence E source
  Sudden changes in vitamin K intake can increase or decrease the anticoagulant effect

What people believe that the data does not support

• The EU authorizes the claim that vitamin K contributes to normal blood clotting, while no EU or US 21 CFR claim names sweet potato leaves themselves. — EU nutrition and health claims register Evidence E source
  Authorized claim for vitamin K; none registered for the leaves

Who this works differently for

• In a randomized crossover trial in 15 elite basketball players, 7.1 oz (200 g) of purple sweet potato leaves daily for 2 weeks raised plasma polyphenols and vitamins E and C. — 15 elite basketball players during training, 2-week diet period (n = 15) Evidence B source
  Significant rise in plasma polyphenols, vitamin E and C; longer LDL lag time; lower urinary 8-OHdG; no change in GSH, TAS or MDA

What is still unknown

• After a 2-week trial of 200 g daily in 16 adults, the authors state that which components of sweet potato leaves cause the immune changes, and whether they matter biologically, is still unknown. — 16 healthy non-smoking adults, 2-week periods (n = 16) Evidence B source
  Open question stated by the trial authors

The bottom line

The one observational finding comes from Taiwan, in a case-control study of 301 people with lung cancer against 602 hospital and 602 neighborhood controls. The highest third of sweet potato leaf intake was linked with lower odds of lung cancer, an adjusted odds ratio of 0.43 to 0.65 with confidence limits from 0.28 to 0.96. The design relies on people recalling what they ate. It shows an association, and an association is not an effect. In 15 untrained young men, a 7-day diet built on the leaves lowered markers of oxidative damage and plasma IL-6 after a 1 hour treadmill run, in a controlled trial that does not say it was randomized. Cooking matters for the vitamins that leak into water. USDA factors for greens boiled in a little water and drained keep 60 percent of vitamin C and 65 percent of folate. For steamed vegetables they keep 85 percent of both. These are group factors that were never measured on sweet potato leaves, and vitamin K is missing from the table. A cooked cup weighs 2.4 oz (69 g) in US survey data. In simulated digestion in the laboratory, total polyphenols of five leaf varieties ended lower than where they started. If you take warfarin or a similar anticoagulant, NIH advises keeping vitamin K intake consistent, because sudden changes can raise or lower the effect of the drug. That advice covers vitamin K in general. Raw leaves carry 302 mcg per 3.5 oz (100 g), so starting or stopping them is the kind of change it describes. We found no study of the leaves in pregnancy, in children or in kidney disease. The EU authorizes the claim that vitamin K contributes to normal blood clotting, and no EU or US claim names the leaves themselves.

Sources

1. spleav-daily-r6-01 · USDA SR Legacy dataset
   Sweet potato leaves, raw, SR Legacy FDC 169303: vitamin K 302.2 UG, vitamin A RAE 189 UG, riboflavin 0.345 MG per 100 g
   USDA FoodData Central, SR Legacy 2018, FDC 169303 (Sweet potato leaves, raw) · checked 2026-09-30
2. spleav-daily-r6-04 · USDA FNDDS dataset
   Sweet potato, squash, pumpkin, chrysanthemum, or bean leaves, cooked, FNDDS code 72133201, fdc_id 2709642: 1 cup 69 g; Quantity not specified 35 g
   USDA FNDDS, food code 72133201 (FDC 2709642) · checked 2026-09-30
3. spleav-daily-r6-05 · randomized crossover trial
   Although plasma polyphenol levels did not significantly increase in the PSPL group at the end of the study, they were significantly elevated in urine.
   World J Gastroenterol, 2005 · checked 2026-09-30
4. spleav-daily-r6-11 · in vitro digestion study
   As shown in Figure 1C and Figure 3A, the TPC after in vitro digestion was significantly lower than the original.
   Antioxidants, 2024 · checked 2026-09-30
5. spleav-daily-r6-02 · USDA retention factors dataset
   USDA-RETN-R6:3004 VEG,GREENS,BOILD,LITTLE WATER DRAIN, group Vegetables and Vegetable Products: vitamin_c_mg 60% retained, folate_total_ug 65%, thiamin_mg 85%, riboflavin_mg 95%, iron_mg 95%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), code 3004 · checked 2026-09-30
6. spleav-daily-r6-03 · USDA retention factors dataset
   USDA-RETN-R6:3784 VEG,OTHER,STEAMED, group Vegetables and Vegetable Products: vitamin_c_mg 85% retained, folate_total_ug 85%, riboflavin_mg 95%, calcium_mg 100%, iron_mg 100%, potassium_mg 100%
   USDA Table of Nutrient Retention Factors, Release 6 (2007), code 3784 · checked 2026-09-30
7. spleav-daily-r6-06 · randomized crossover trial
   Consumption of PSPL modulates various immune functions including increased proliferation responsiveness of PBMC, secretion of cytokines IL-2 and IL-4, and the lytic activity of NK cells.
   World J Gastroenterol, 2005 · checked 2026-09-30
8. spleav-daily-r6-08 · controlled crossover trial
   The markers of oxidative damage, plasma TBARS and protein carbonyl, significantly decreased. Plasma IL-6 concentration also decreased.
   J Appl Physiol (1985), 2010 · checked 2026-09-30
9. spleav-daily-r6-09 · case-control study
   sweet potato leaves (AOR for the highest versus the lowest tertile = 0.43-0.65, 95% CI = 0.28-0.96, (plinear trend )<= 0.03) were associated with the reduced risk for lung cancer.
   Asia Pac J Clin Nutr, 2007 · checked 2026-09-30
10. spleav-daily-r6-10 · agency fact sheet
    People taking warfarin and similar anticoagulants need to maintain a consistent intake of vitamin K from food and supplements because sudden changes in vitamin K intakes can increase or decrease the anticoagulant effect
    NIH Office of Dietary Supplements, Vitamin K Health Professional Fact Sheet · checked 2026-09-30
11. spleav-daily-r6-12 · regulatory register
    POL-HC-6523 Vitamin K Vitamin K contributes to normal blood clotting Authorised
    EU Register on nutrition and health claims, claim POL-HC-6523, snapshot 2026-09-21 · checked 2026-09-30
12. spleav-daily-r6-07 · randomized crossover trial
    Compared with the control group, the results showed that PSPLs consumption led to a significant increase of plasma polyphenol concentration and vitamin E and C levels.
    Asia Pac J Clin Nutr, 2007 · checked 2026-09-30
13. spleav-daily-r6-13 · randomized crossover trial
    The responsible determinants of PSPL remain to be elucidated, as does the biological significance of the present observations.
    World J Gastroenterol, 2005 · checked 2026-09-30