Too Much Vitamin C Bad For Joints

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Too Much Vitamin C Bad For Joints

By E.J. Mundell

HealthDay Reporter

THURSDAY, June 3 (HealthDayNews) -- If a moderate amount of daily vitamin C

is good for bone health, then more must be even better, right?

Wrong.

" Everybody needs vitamin C in their diet, but taking supplements beyond the

recommended daily allowance is probably inadvisable " when it comes to

fighting arthritis, said Dr. Virginia Kraus, an associate professor of

medicine at Duke University and lead author of a study that challenges the

conventional wisdom on diet and osteoarthritis.

Millions of older Americans suffer from the pain and stiffness of

osteoarthritis -- a deterioration of bones and cartilage in the joints.

Unlike rheumatoid arthritis, which experts know is caused by inflammation

brought on by immune system dysfunction, the causes of osteoarthritis remain

unclear.

Seeking a deeper understanding of the disease, researchers are now focusing

on lifestyle and dietary factors as possible contributors to osteoarthritis.

In their study, published in the June issue of Arthritis & Rheumatism,

Kraus' team of researchers fed guinea pigs low, medium and high doses of

vitamin C as part of their daily diet.

" The guinea pig is the ideal animal in which to test this, " Kraus explained,

" because they require vitamin C in their diet, just like humans, and they

get an osteoarthritis of their knees that looks very similar to the type of

knee osteoarthritis that humans get. "

Arthritis specialists have long recommended that patients consume an

adequate daily amount of vitamin C because the nutrient is both a potent

antioxidant and a key player in the formation of joint cartilage. But would

higher doses of the vitamin make bones even stronger?

Not so, Kraus reports. " More is not better, " she said. " We found that the

more vitamin C given, the more osteoarthritis is apparent in the joints of

these animals that are predisposed to getting osteoarthritis. "

Guinea pigs fed low doses of vitamin C showed the least signs of knee

arthritis, Kraus said, but since they also tended to weigh much less than

the medium- or high-dose animals, reductions in weight might explain that

result.

Animals fed a medium dose of vitamin C -- roughly equivalent to the

recommended daily allowance in humans -- had slightly more signs of knee

damage. But it was the high-dose animals that fared worse, with obvious

signs of arthritis and an increase of bony outcroppings on the knee called

osteophytes or bone spurs.

The exact links between excess vitamin C and osteoarthritis remains unclear.

" One connection that we were able to make was that vitamin C activates a

protein called TGF-beta, " Kraus said. " When active, this protein seems to

increase bone spur or osteophyte formation. " Microscopic bone spurs roughen

the surface of joints, she explained, triggering the irritation and

inflammation that is a hallmark of arthritis.

Dr. H. Klippel, president of the American Arthritis Foundation, said

the findings " are challenging the common wisdom that increased doses of

vitamin C may be helpful or protective -- in fact, it seems to be quite the

opposite. " He believes more study is needed into possible links between diet

and bone health, especially since the origins of osteoarthritis remain a

mystery.

" This kind of research is so important because osteoarthritis is an

extremely common disease, " he said. " Therefore, it begs the question, are

there other dietary influences that in some way affect this disease? "

The study findings should not alter the standard dietary recommendation that

Americans eat five to six servings of fruits and vegetables per day to

obtain adequate doses of vitamin C, Kraus said. But for those who can't

always be sure they are getting enough vitamin C from their diet, taking a

daily multivitamin might be advisable, as well.

" What I tell my patients is that one multivitamin per day is a prudent thing

because it also has the daily allowance of vitamin D and other

micronutrients that might be important to bones, " she said.

But should folks take an extra vitamin C pill on top of that?

" Absolutely not, " Kraus said. " I try and emphasize to my patients that just

because something is natural doesn't mean that more is better for you. It

just goes to prove that the old adage that moderation is, for most things,

the best. "

More information

For more details on the connections between diet and arthritis, go to the

Arthritis Foundation.