Vitamin C on the radar screen again

When vitamin C first hit the public radar screen back in the 1960’s, it was touted as a miracle cure-all, preventing the common cold, flu, cancer and heart disease.  Research failed to prove any of that was true, but that hasn’t stopped the public from swallowing billions of vitamin C supplements over the years.  Vitamin stores have entire walls of vitamin C supplements.  Someone is buying all that stuff.

It’s interesting to note that studies on vitamin C absorption, excretion and tissue saturation show that about 200 mg/day is as much as the average person can absorb and utilize.  Anything above that amount is quickly excreted, without contributing any health advantage.  You can get approximately 200 mg/day from:

  • 2 glasses of grapefruit juice
  • 2 large oranges
  • 2 cups sliced strawberries
  • 1/2 large cantaloupe

Most other fruits and vegetables and juices have at least some vitamin C, so if you eat plenty of those everyday, your vitamin C intake adds up quickly.  Nevertheless, plenty of consumers are taking hundreds (or thousands?!) of milligrams of excess vitamin C everyday.

Recent research took a different approach to evaluating vitamin C.  Instead of over-dosing study subjects and looking for some benefits, the researchers evaluated people who weren’t taking any vitamin C at all.  They examined whether their diet-only vitamin C status was related to risk factors for inflammation and heart disease.  Conclusion in brief: it is related.

The subjects were young men – 8 lean and 8 obese.  They were tested for a wide array of markers for heart disease risk (triglycerides, cholesterol, etc), glucose, insulin, vitamin C status, and several markers for inflammation.  They were also tested for blood vessel function, and their diets were assessed for vitamin C intake and numerous other factors.  Findings included:

  • obese subjects had lower blood vitamin C, indicating deficiency.  While they ate only half as much C as the lean subjects, they did on average consume the recommended 75 mg/day.  Interesting.  Were they over-reporting intake of fruit and vegetables, to look “good”?  Or simply over-estimating portion sizes for those foods?
  • the lean subjects consumed on average 150 mg vitamin C/day, close to that 200 mg/day maximum usable dose, and twice the official recommended intake.
  • poor vascular function was linked to lower blood vitamin C status

Seems some of those guys were not eating many vegetables or fruit.  The obese subjects did have a higher sodium intake, which could be related to more processed foods.  The researchers were careful to note that the relationship they found between vitamin C status, inflammation and vascular health could be due to some other dietary factor not measured in this study.  Other adverse effects associated with obesity could be responsible for the vascular dysfunction and inflammation.  However, the study authors believe vitamin C status impacts many of these measurements, due to its unique metabolic behavior.

The next step would be to give subjects vitamin C supplements and see if these health risks improved, regardless of obesity or processed junky diet.   Unfortunately, if vitamin C supplements are shown to create any improvement at all in these inflammatory markers, the supplement pushers will have more PR ammunition to promote supplements as the alternative to a healthy diet.  The 200 mg maximum usable intake, shown by actual scientific studies, will be conveniently ignored.

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