130
Daily reference value of vitamin C is 60 mg according to the 2013 FDA food-labeling guidelines.
What Are the Recommended Dietary Allowances for Vitamin C?
| 1–3 years | 15 mg |
| 4–8 years | 25 mg |
| 9–13 years | 45 mg |
| 14–18 years | 75 mg (boys); 65 mg (girls) |
| 19 years and older | 90 mg (men); 75 mg (women) |
The upper daily intake limit of vitamin C is 2,000 mg.
Vitamin C Supplements
• Dosage. The most common dosages of vitamin C supplements are 50–1,000 mg. Vitamin C supplementation has beneficial effects on health, but high-dose vitamin C supplements can cause diarrhea and other digestive problems. Avoid taking more than 2,000 mg of vitamin C per day.
• Types. Various vitamin C supplements are available in the marketplace. Although there are many different kinds, they are all similar in regard to bioavailability. There is no evidence that one product is better than the other in terms of their absorption or efficacy. Ascorbic acid and sodium ascorbate are the two most common vitamin C supplements. Vitamin C palmitate converts to vitamin C and palmitate in the intestines. Some manufacturers claim that their products contain a 100% “reduced form” of vitamin C. The fact is that all vitamin C supplements contain only the “reduced form” if manufactured properly.
• Liposomal vitamin C. Liposomal vitamin C is a lipid formulation in which water-soluble vitamin C is encapsulated in liposomes made of phospholipids. The logic behind the design was that the encapsulation of vitamin C in a liposomal form could enhance its absorption in the intestines, thereby elevating the blood level of vitamin C. However, the clinical data so far do not seem to support such claims. If you need to take a vitamin C supplement, choose ascorbic or sodium ascorbate. You do not need to purchase expensive products like liposomal vitamin C.
• Cataracts. Vitamin C may prevent cataracts and mitigate the condition. Studies from England have shown that taking a vitamin C supplement at a dose of 250 mg daily for 10 years curtailed the risk of cataracts.
• Smoking. Cigarette smoke can deplete vitamin C in the lungs as well as the rest of the body, causing insufficient vitamin C and free radical–mediated oxidative stress. It is imperative that smokers take vitamin C supplementation to avoid vitamin C insufficiency and its deleterious consequences.
• Hypertension. Vitamin C supplementation can lower blood pressure, and this beneficial effect is more robust in hypertensive patients. Vitamin C reduces blood pressure through inhibition of endothelin-1, a vasoactive protein that elevates blood pressure.
• Gout. Vitamin C supplements may alleviate gout symptoms. The suggested daily dose is 500 mg of vitamin C.
• Premature mortality. Vitamin C may decrease the risk of premature death and increase life expectancy. Studies from the US have shown that vitamin C supplementation or sufficient dietary intake of vitamin C could prolong one’s life-span. The suggested daily dose is 500 mg of vitamin C.
• Preeclampsia. Vitamin C taken together with vitamin E can lower the risk of preeclampsia in pregnant women. Symptoms of preeclampsia include hypertension, edema, and renal problems. The suggested daily doses are 500 mg of vitamin C and 100 IU of vitamin E.
• Bruises. Vitamin C supplements can help prevent bruising. The suggested daily dose is 500 mg of vitamin C.
• Cancers. High-dose intravenous vitamin C therapy is effective in treating certain types of cancers, particularly in terminally ill cancer patients who have refused any further chemotherapy. (See chapter 47, “Breast Cancer,” for details.)
Safety Issues
• Side effects. High-dose vitamin C supplementation may increase the risk of cataracts and kidney stones. Vitamin C can be converted to oxalate, which forms oxalate crystals, leading to kidney stones. Studies from Switzerland have shown that taking a vitamin C supplement at a daily dose of 1,000 mg increases one’s risk of kidney stones by 66%. Another study from Sweden shows that taking a vitamin C supplement at a dose of 1,000 mg for 10 years increases the risk of cataracts by 25%.
• Iron. Vitamin C boosts the absorption of iron by the intestines. People who take iron supplements together with vitamin C supplements need to monitor their blood iron levels to avoid problems associated with iron overload.
What Types of Drugs May Interact with Vitamin C?
• Oral contraceptives and aspirin. Both oral contraceptives and aspirin can reduce the blood level of vitamin C.
• Acetaminophen (Tylenol). Vitamin C increases the blood level of acetaminophen and exacerbates acetaminophen-induced liver damage. People who take vitamin C supplements together with acetaminophen need to be aware of the potential problems associated with liver damage.
• Anticoagulants. Vitamin C decreases the efficacy of anticoagulant drugs such as warfarin and heparin.
Vitamin D is also known as the sunshine vitamin. The history of vitamin D is associated with rickets. In the late 17th century, Dutch physicians noticed the prevalence of rickets, a condition characterized by bent and deformed bones and enlarged joints in the hands and feet. In severe cases, patients with rickets had difficulty breathing. In the mid-19th century, many countries in Europe were in the midst of the Industrial Revolution, during which factory buildings were widespread and an abundance of coal was burned in public places as well as in houses for
