B vitamins prevent macular degeneration: Logic fails, then succeeds for leading cause of blindness

by James Hubbard, M.D., M.P.H.

A new JAMA study is very interesting for two reasons.  It gives us hope for preventing a leading cause of blindness in the U.S.  But it’s also a great example of why, while the popular “association” studies give us valuable information, they never prove causation. You need more-focused studies for that.

First, the great news:A combination of B vitamins taken daily can prevent acute macular degeneration, a disease that severely affects the vision of 1.75 million aging Americans.  (Another seven million have early disease.)  Up until now, the only two known alterable risks factors were our old standbys, smoking and obesity.  Aging, being female and heredity also play a role.


WHEN LOGIC IS WRONG … AND THEN RIGHT

Investigators first suspected B vitamins might affect AMD when a large women’s study showed an association of high homocysteine levels with heart disease and, by the way, AMD.  High homocysteine levels are associated with B vitamin deficiencies, so increasing B vitamins should lower heart disease risk, right?

Wrong.

A randomized, placebo-controlled,  double-blind study (the best kind) showed no difference in heart disease in those taking B vitamin versus placebo.

Then they took a large subset of these women–all who had no sign of AMD–and followed them over seven years.  The ones who took the B vitamins had about 40 percent less AMD.  They also measured a smaller subset of follow-up blood homocysteine levels, finding a decrease in the treatment group.

That is how studies are supposed to be done: Start general, get suppositions, then get specific.

By the way, the treatment group received 2.5 mg of folic acid, 50 mg of pyridoxine (B-6) and 1 mg of cyanocobalmin (B-12) per day.

Any questions?  Has anyone been affected by macular degeneration?

Doctors and business owners: Send customized issues of James Hubbard’s My Family Doctor to your customers or patients. E-mail publisher-at-familydoctormag.com for details.

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10 Responses to “B vitamins prevent macular degeneration: Logic fails, then succeeds for leading cause of blindness”

  1. Riley & Tiki's Mom Says:

    My mom has macular degeneration. Lack of B vitamins seem reasonable, although in her case I always assumed it was her terrible eating habits in general. She is 68 years old, 90 pounds (has always been too thin), never smoked, and is/was a regular vitamin taker. She refuses to eat most food and really only likes sweets. If it were up to her, she would eat cinnamon sugar toast for breakfast, vitamins for lunch and dinner, and then have dessert.

    My take on this is vitamins are a fine supplement, but you need to start with real food.

    Riley & Tiki’s Moms last blog post..I got an award!

  2. James Hubbard, M.D., M.P.H. Says:

    Thanks Riley and Tiki’s Mom, I agree and have posted on that subject before. Supplements don’t take the place of good nutrition.

  3. ocbody.com doc Says:

    Vitamin and supplement studies are frequently difficult to interpret particularly when contradictory or inconclusive results pop up so often in later studies.

    ocbody.com docs last blog post..Links & Comments

  4. Sagan Says:

    Yep- sticking with the real food. All the controversies surrounding vitamin supplements confuse the hell out of me!

    Sagans last blog post..Book Review: “The New Rules of Lifting for Women” by Lou Schuler

  5. Steve Parker, M.D. Says:

    Is there a multivitamin that has that combination? I was thinking Foltx, but it has 2 mg B12 instead of 1 mg. The other two ingredients were spot on.

    -Steve

    Steve Parker, M.D.s last blog post..Which Diet Is Better for Weight Loss: Low-Carb or Low-Fat?

  6. James Hubbard, M.D., M.P.H. Says:

    Ocbody that is true, but the opposite in this case.

  7. James Hubbard, M.D., M.P.H. Says:

    Dr. Parker, I think there is, but I don’t know the name.

  8. James Hubbard, M.D., M.P.H. Says:

    Good idea Sagan. Eat your vegetables.

  9. James Hubbard’s My Family Doctor Blog » Blog Archive » Vitamin D fights off colds, obesity, cancer … really? The newest miracle vitamin. Says:

    [...] Probably not.  Most of these are association studies.  For the past year or two, scientists have been seemingly obsessed with finding vitamin D associations. I’ve explained that this does not prove causation, which more-focused studies must determine. [...]

  10. Macular Degeneration Support Canada Says:

    Antioxidants provided through these types of dietary supplements can make a difference.

    Great article.

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