Thursday, November 19, 2009

Folic Acid Supplements May Increase Cancer Risk

This post is going to say much the same as my post about omega-3 fatty acids (fish oil) and cancer. I'll recycle the last sentence of that post:
"Like most nutrients, there appears to be an ideal range for omega-3 fatty acids folate in the body, above and below which an individual can experience poor health."
A new study in JAMA this week is reporting an increased cancer risk among those who took folic acid supplements:
Cancer Incidence and Mortality After Treatment With Folic Acid and Vitamin B12, Journal of the American Medical Association, November 2009

The risk was not high (21% increased risk for getting cancer, 38% increased risk of dying from cancer) but it was statistically significant. Lung cancers dominated.

Patients who experienced increased risk were taking 800 micrograms/day (mcg/d) of folic acid.1 (They also took 400 mcg/d of vitamin B12 and/or 40 mg/d of vitamin B6.)

The recommended allowance (or DRI: Dietary Reference Intake) for folic acid in this country is 400 mcg/d. So they were taking twice the DRI. Yet they fell short of the tolerable upper intake of 1000 mcg/d.

In our body, folate is used in DNA replication - it's needed for cell growth and repair. Cancer cells also use it for growth.

Two items of note:
  1. Participants in this combined analysis lived in Norway where there is no fortification of foods with folic acid. The US embarked on a mandatory fortification program in 1998 - flour and grain products here contain added folic acid. That's in addition to the folic acid added to our breakfast cereals, often 400 mcg/serving. (A bowl of cereal and a typical vitamin pill can easily put you at 800 mcg. Eat anything made with folic-acid-fortified-flour and you'll surpass their intake.)

  2. One mechanism put forth for the increased cancer rates was reduced activity of our immune system's natural killer cells in the presence of high levels of folic acid.2 Coincidentally, high intakes of omega-3 (about 1 gram/day) were also seen to reduce the amount and activity of natural killer cells.
Taking vitamins is not as innocent as supplement manufacturers lead us to believe.
1 Folate found naturally in food hasn't been shown to be harmful. Green leafy vegs are a great source - about 270 mcg folate in 1 cup cooked spinach.
2 Unmetabolized Folic Acid in Plasma Is Associated with Reduced Natural Killer Cell Cytotoxicity among Postmenopausal Women, Journal of Nutrition, 2006


Perovskia said...

Yeah, I came across this in my first Nutrition course; most of our everyday foods are fortified (like you said, breads, cereals, flour, etc) that we don't need supplements for said fortified vitamins. It's definitely something to be mindful of.

Perovskia said...

Hmm.. I thought I wrote something a while ago about fortified foods. Even just in the case of the numbers, citing percentages of how much something is fortified could be incorrect..

Jim Purdy said...

The only supplement that ever caused me to really notice bad side-effects was long ago, with excessive iron ... which is very wrong for males. These days, I try to avoid mega-doses of anything

Bix said...

Jim, you had side effects from iron? Were they gastrointestinal?

Was wondering ... have you ever taken chromium?

Bix said...

Perovskia, that article, the one that says, "pasta, breads and cereals can contain anywhere between 90% and 377% of folic acid claimed on the product label" is troubling.

Add to that ... many people consume some form of folate-fortified wheat flour (bread/crackers/cookies/baked goods/cereal/pasta/noodles) at every meal. And they want to double the fortification amount!

Jim Purdy said...

Bix, many years ago, I started taking high doses of iron because I thought iron would help my near-anemia. With hindsight, I think my low blood iron levels were caused by my drinking a lot of tea, which apparently can reduce iron levels. Anyway, the excess iron intake caused my skin to break out everywhere with little red pimple-like things, which apparently was my body's attempt to get rid of the excess iron. I learned to be very careful of mega-doses of supplements.

By the way, I really enjoy your blog.

Bix said...

Thanks, Jim.

How about that. There's a lot of good anecdotal evidence out there.

I asked about chromium because, as I recall, you have diabetes?, and it's a popular supplement since it supposedly enhances glucose uptake. I've also seen some evidence about its ability to reduce carb cravings, e.g.

"A Double-Blind, Placebo-Controlled, Exploratory Trial of Chromium Picolinate in Atypical Depression: Effect on Carbohydrate Craving",_Placebo_Controlled,_Exploratory.4.aspx

"In a population of adults with atypical depression, most of whom were overweight or obese, CrPic produced improvement on ... appetite increase, increased eating, carbohydrate craving, and diurnal [daytime] variation of feelings."

Just curious.

Jim Purdy said...

"There's a lot of good anecdotal evidence out there."

The adjective "anecdotal" is used derisively by shameless BigPharma shills ... oops, I mean mainstream doctors ... to describe the adverse effects reported by their own patients, while accepting as valid the sloppy statistics from BigPharga funded "studies" that get reviewed by other BigPharma shills ... I mean their peers ... and then published in advertising publications ... I mean professional journals ... which make huge profits by selling reprints of those articles back to the BigPharma companies from whose marketing departments they originated.

After the way the NEJM shamelessly promoted and profited from its original Vioxx article, why would anybody ever trust medical journals?

Chromium? I don't know whether it works. I've tried it, with no obvious results. When it comes to putting pills and other chemicals in my body, I consider them guilty until proven innocent.

Bix said...

I appreciate the response, Jim. Chromium is interesting. Seems some people respond to it, others not at all. Any benefit could be correcting a deficiency or suboptimum state - especially in people with diabetes or prediabetes, since chromium losses are higher when glucose and insulin are high. Anyway .... thanks!

Perovskia said...

Jim.. did you take vitamin C while taking the iron? The tea would have counter-acted the iron, but the vit. C would have helped absorption.

Bix... Ugh, troubling, indeed. People aren't as educated about what's in their food and how it may affect them and then adding supplements on top of that. Because it's 'silent', we don't see what it's doing.

I'm thankful for my doctor because she'll suggest what types of foods to eat for raising certain vitamin levels in my body, before advising supplements. Except for iron. I'm taking an iron supplement right now for a kick-start and it's helped a lot (a slight bit more energy and has helped with my breathing problems).