{"ok":true,"entry":{"slug":"vitamin-c","kind":"supplement","name":"vitamin c","aliases":["ascorbic acid","L-ascorbate","Gold C","Redoxon"],"brands_sg":["California Gold Nutrition","Life Extension","NOW Foods","Sunlipid","NeoCell"],"class":"vitamin","tags":["immune","skin-hair"],"use_for":"collagen formation for skin · normal immune function","use_after":"no timing rule given","use_duration":null,"take_with":"ascorbic acid absorbs as well as the vitamin c in food","pros":["rda 90 mg (men) · 75 mg (women); smokers +35 mg a day","humans can't make vitamin c — an essential nutrient","colds: modestly shorter — 8% adults, 14% children"],"cons":["above 1 g a day, absorption falls below 50%","high doses: diarrhea, nausea, cramps from unabsorbed c","doesn't cut cold risk in the general population"],"dose_note":"rda 90 mg a day for men and 75 mg for women (19+), 85 mg in pregnancy and 120 mg when breastfeeding; smokers need 35 mg a day more; the ul is 2,000 mg a day for adults; 70–90% is absorbed at 30–180 mg/day but under 50% above 1 g/day; hsa's limit for general-adult health supplements in singapore is 1,000 mg a day","dosage":{"ul":"2,000 mg","unit":"mg","fda_dv":"90 mg","rda_ai":"90 mg men · 75 mg women (19+) · +35 mg/day for smokers","ul_status":"established","population":"general adult","hsa_max_daily":"1,000 mg"},"ul_status":"established","sg_class":null,"cautions":["kidney stones or kidney disorders — high intakes could add to stone formation; ask your doctor first","hereditary hemochromatosis — chronic high doses could worsen iron overload","on chemotherapy or radiation — the sheet says to consult your oncologist first"],"clashes":[{"src":["nih_ods_vitc_rx"],"note":"vitamin c with other antioxidants may blunt the hdl rise from the combo","with":"niacin + simvastatin (zocor) combination therapy"},{"src":["nih_ods_vitc_rx"],"note":"oncologist consult advised before vitamin c or other antioxidant supplements","with":"chemotherapy or radiation"}],"sources":[{"id":"nih_ods_vitc_intro","url":"https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/","label":"NIH ODS — Vitamin C Fact Sheet for Health Professionals (updated July 31, 2025) — Introduction + Table 1 RDAs (19+ years row: male · female · pregnancy · lactation) + smokers note","quote":"Humans, unlike most animals, are unable to synthesize vitamin C endogenously, so it is an essential dietary component … 19+ years 90 mg 75 mg 85 mg 120 mg … require 35 mg/day more vitamin C","accessed":"2026-08-27"},{"id":"nih_ods_vitc_supp","url":"https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/","label":"NIH ODS — Vitamin C Fact Sheet for Health Professionals (updated July 31, 2025) — Sources of Vitamin C: Dietary supplements","quote":"Supplements typically contain vitamin C in the form of ascorbic acid, which has equivalent bioavailability to that of naturally occurring ascorbic acid in foods, such as orange juice and broccoli","accessed":"2026-08-27"},{"id":"nih_ods_vitc_abs","url":"https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/","label":"NIH ODS — Vitamin C Fact Sheet for Health Professionals (updated July 31, 2025) — Introduction (absorption)","quote":"Approximately 70% to 90% of vitamin C is absorbed at moderate intakes of 30 to 180 milligrams (mg)/day. However, at doses above 1 gram (g)/day, absorption falls to less than 50%","accessed":"2026-08-27"},{"id":"nih_ods_vitc_ul","url":"https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/","label":"NIH ODS — Vitamin C Fact Sheet for Health Professionals (updated July 31, 2025) — Table 3 ULs (19+ years row) + Health Risks from Excessive Vitamin C","quote":"19+ years 2,000 mg 2,000 mg 2,000 mg 2,000 mg … The most common complaints are diarrhea, nausea, abdominal cramps, and other gastrointestinal disturbances due to the osmotic effect of unabsorbed vitamin C in the gastrointestinal tract","accessed":"2026-08-27"},{"id":"nih_ods_vitc_risk","url":"https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/","label":"NIH ODS — Vitamin C Fact Sheet for Health Professionals (updated July 31, 2025) — Health Risks from Excessive Vitamin C (kidney stones; hemochromatosis)","quote":"High vitamin C intakes … could contribute to the formation of kidney stones, especially in individuals with renal disorders … in individuals with hereditary hemochromatosis, chronic consumption of high doses of vitamin C could exacerbate iron overload","accessed":"2026-08-27"},{"id":"nih_ods_vitc_rx","url":"https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/","label":"NIH ODS — Vitamin C Fact Sheet for Health Professionals (updated July 31, 2025) — Interactions with Medications (Chemotherapy and radiation; Statins and niacin)","quote":"undergoing chemotherapy or radiation should consult with their oncologist … Vitamin C, in combination with other antioxidants, may attenuate the increase in high-density lipoprotein levels that result from taking combination niacin/simvastatin (Zocor) therapy","accessed":"2026-08-27"},{"id":"nih_ods_vitc_cold","url":"https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/","label":"NIH ODS — Vitamin C Fact Sheet for Health Professionals (updated July 31, 2025) — Vitamin C and Health: Common cold","quote":"Prophylactic use of vitamin C did not significantly reduce the risk of developing a cold in the general population … the use of prophylactic vitamin C modestly reduced cold duration by 8% in adults and 14% in children","accessed":"2026-08-27"},{"id":"fda_dv","url":"https://www.fda.gov/food/nutrition-facts-label/daily-value-nutrition-and-supplement-facts-labels","label":"FDA — Daily Value on the Nutrition and Supplement Facts Labels, Reference Guide: Daily Values for Nutrients (content current as of 03/05/2024)","quote":"DVs are the recommended amounts of nutrients to consume or not to exceed each day … Vitamin C 90mg","accessed":"2026-08-27"},{"id":"hsa_hs_guidelines","url":"https://file.go.gov.sg/hsa-hs-guidelines.pdf","label":"HSA Singapore — Health Supplements Guidelines GL-CHPB-3-001 Rev. No. 020 (January 2026), s4.8 general-adult limits, Table 4 Vitamins Limits + List of Health Claims rows 19 + 70","quote":"Table 4: Vitamins Limits … Vitamin C 1000mg … Contribute to normal collagen formation for normal function of skin • Vitamin C … Help in the normal function of the immune system • Folic acid, vitamin A, B6, B12, C, D","accessed":"2026-08-27"},{"id":"hsa_prohibited_2025","url":"https://file.go.gov.sg/hsa-chp-prohibited-restricted-ing-guidelines.pdf","label":"HSA Singapore — Guidelines on Prohibited and Restricted Ingredients in Health Supplements and Traditional Medicines, GL-CHPB-1-012 Rev. 001 (October 2025), Annex A row 113","quote":"113. Vitamin C Restricted use in HS and TM Maximum Daily Dose When for oral use by general adult population, the maximum recommended daily dose should not provide more than 1000mg","accessed":"2026-08-27"},{"id":"iherb_sg","url":"https://sg.iherb.com/c/vitamin-c","label":"iHerb Singapore — Vitamin C category, default order (SGD pricing)","quote":"California Gold Nutrition, Gold C®, USP Grade Vitamin C, 1,000 mg … Life Extension, Glutathione, Cysteine & C … NOW Foods, Liposomal Vitamin C … Sunlipid, Liposomal Vitamin C with MCT Oil … NeoCell, Grassfed Collagen Peptides + Vitamin C & Biotin","accessed":"2026-08-27"}],"brand_certs":null,"updated_at":"2026-08-29T16:16:34.039038+08:00"},"disclaimer":"kozen-x is not a medical device and does not give medical advice. it lists what published sources have written down. absence of a record is not the same as safe."}