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The National Institutes of Health's Office of Dietary Supplements states that the recommended daily amount of Vitamin C for an adult male is 90 mg. The highest recommended dose is 120 mg for breastfeeding women. The upper limit does of Vitamin C for adults is 2,000 mg.

The book "Prescription for Natural Healing" (5th ed.), however, recommends an optimum daily intake of 1,000 to 3,000 mg of "Vitamin C with mineral ascorbates (Ester-C)". I don't have much experience with the book and I'm trying to gauge how helpful it is.

Am I right to see a conflict here? Or are they talking about different things? Is this really as simple as the book making a wildly bad recommendation, or is there reason to think a higher dose is good?

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  • @David I'm not asking anyone to read the book - I'm just curious if there is indeed a conflict here or if I'm missing a distinction somewhere. – Tom Hamming Apr 20 '18 at 15:16
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    There is a conflict; the NIH is not trying to get you to spend lots of money in the alt-health business. The book is. – swbarnes2 Apr 20 '18 at 16:21
  • I edited your question to remove the link to Amazon. If someone wants to buy the book I'm sure they can find it without a direct link here. – Carey Gregory Apr 23 '18 at 14:16
  • @CareyGregory thanks - I didn't mean to suggest that people buy it. I was just clearly indicating what book I was talking about. – Tom Hamming Apr 23 '18 at 14:50
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    You will get different numbers from different sources on many nutritional recommendations. Read the reason for the high number and determine for yourself if you consider it credible. – paparazzo Apr 23 '18 at 15:03
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Here are few aspects of high-dose vitamin C supplements.

The upper limit(UL) 2,000 mg for vitamin C is not some sort of recommendation, but a dose, which, if exceeded, can cause nausea and diarrhea, for example.

Does it make sense to take vitamin C supplements?

Vitamin C supplements can correct vitamin C deficiency and improve the absorption of iron from plant foods. But there is no convincing evidence that vitamin C would help to prevent or treat common cold, cancer, heart disease, stroke or age-related macular degeneration.

Are higher doses more effective?

Approximately 70%–90% of vitamin C is absorbed at moderate intakes of 30–180 mg/day. However, at doses above 1 g/day, absorption falls to less than 50% and absorbed, unmetabolized ascorbic acid is excreted in the urine.

There is no convincing evidence that high-dose (oral) vitamin C would prevent or treat cancer or other diseases.

Can high-dose vitamin C be dangerous?

High-dose vitamin C might increase the risk of oxalate kidney stones in some individuals.

Reference: https://ods.od.nih.gov/factsheets/VitaminC-HealthProfessional/

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