Fast Facts: Vitamin C

Vitamin C is one of the best known micronutrients. However, the average daily intake is often lower than expected. You might not be getting as much as you think.

Vitamin C is perhaps best known for immune system support. Interestingly, while some immune cells need vitamin C to function (and you may be more susceptible to illness if deficient), there is no concrete scientific proof that increasing your intake makes a significant difference in the duration or severity of colds. Of course, if you’re otherwise generally healthy, it’s also not likely to do you any harm, as our bodies are excellent at secreting excess.

Vitamin C is also an antioxidant, working to help balance the body’s chemical reactions and prevent cellular damage from free radicals. It helps your body absorb iron and protects levels of vitamin E, and is needed to produce collagen (a key structural protein) and several neurotransmitters (the chemicals that carry signals throughout your brain and nervous system). It also plays an active role in cholesterol management, helping to convert cholesterol to bile acids, which in turn lowers cholesterol levels.

Much of the research on vitamin C has shown greater health benefits when you get your C through food rather than tablets or pills. Of course, eating whole foods provides you with many other nutrients as well, so food is almost always a better option than supplementation. Individual variation exists of course, so it’s worth trying a few approaches to find the right method for you.

Vitamin C is involved in:
  • Protecting cells from free radical damage, as an antioxidant
  • Improving dietary iron absorption
  • Regenerating vitamin E levels
  • Building collagen, an important structural protein
  • Production of norepinephrine and serotonin
  • Chemical transformation of cholesterol to bile acids
  • Maintaining the functional ability of some immune cells
Food sources of vitamin C include:
  • Citrus fruits (lemon, orange, lime, tangerine, etc.)
  • Cruciferous vegetables (cauliflower, broccoli, Brussels sprouts, cabbage, etc.)
  • Leafy green vegetables
  • Berries and melons
  • Squashes and carrots
  • …and most other fresh fruits and vegetables!
  • Organ meat, if that’s your thing
Getting too much vitamin C can lead to:
  • Diarrhea
  • Gas and/or upset stomach
  • Increased risk of kidney stones

There is little to no evidence that high vitamin C intake from food sources leads to any signs and symptoms of excess intake.

Not getting enough vitamin C can lead to:
  • Poor wound and structural repair
  • Poor dental health
  • Poor immune response
More on vitamin C:
  • Vitamin C levels in food are quickly reduced by heat, oxygen, and storage. You can slow these losses by refrigerating your fruit and veggies and storing them whole.
  • Nicotine decreases the effectiveness of vitamin C, and smoking in particular leads to higher levels of free radicals, so tobacco users may need greater dietary intakes of vitamin C
  • Some research has shown that vitamin C may help slow plaque buildup in arteries and keep blood vessels more elastic, leading to decreased risks of heart attack and stroke. However, this research needs more support, and there is no evidence that taking vitamin C supplements will help (it needs to come from food sources to be protective).
  • Evidence also shows that people who eat diets rich in vitamin C are less likely to be diagnosed with arthritis, though there is no specific evidence that vitamin C supplements will help treat or prevent this.
Vitamin C combined with other medications and health conditions:

Taking vitamins may have adverse effects when combined with some over the counter or prescription medications, and some medications can decrease vitamin absorption. Some health conditions can be impacted by high vitamin C intakes. Talk to your doctor prior to increasing your vitamin C intake if you have or are taking:

  • Kidney problems
  • Regular use of aspirin and non-steroidal anti-inflammatory drugs (NSAIDS) like ibuprofen – These can increase vitamin C excretion. Somewhat confusingly, high vitamin C intakes can decrease drug excretion, leading to increased blood levels of the drug.
  • Regular use of acetaminophen (Tylenol) – High vitamin C intakes can decrease drug excretion, leading to increased blood levels of the drug.
  • Antacids containing aluminum – Vitamin C can increase aluminum absorption, which can make medication side effects worse. Aluminum-containing antacids include Mylanta, Maalox and Gaviscon.
  • Barbiturates – Including phenobarbital and others, these may decrease vitamin C effectiveness.
  • Chemotherapy drugs – Vitamin C may interfere with some chemotherapy drugs, though it is also speculated that vitamin C may make them more effective. Don’t increase vitamin C intake (or any other supplement) without talking to your oncologist!
  • Oral contraceptives (birth control pills) and hormone replacement therapy (HRT) – When taken with these drugs, vitamin C can increase estrogen levels; Oral estrogens can decrease vitamin C effectiveness.

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