vitamin K associated with lower risk of NHL

[Guest guest]

Greetings,

I was asked off list to comment on the report copied below - well actually

it was an LEF.org ad citing this report.

The findings are interesting and may be worth studying further, but it is

not a study on which to base conclusions - it is certainly not a

justification for vitamin K supplementation to fight lymphoma - as suggested

by LEF.org.

First, as noted within (and for any study), the findings need to be

replicated. If you did the same study 4 times, would each show a positive

association? Or one?

Next, the rate of use of vitamin K supplements in the NHL population and the

control is not stated ... my expectation is that it's probably very low.

How many people do you know that supplement with vitamin K? So the

findings (an association with k-foods and lower risk of NHL), are weak for

supplement use - which is noted by the investigator, but spun by LEF.org as

:

=> " When vitamin K from supplements was examined, *intake of the vitamin was

also shown to be protective up to a certain level,* above which increased

intake offered no additional benefit, suggesting that it is not necessary to

supplement with high doses for protection to occur. " <=

Yikes! Supplementation was NOT shown to be protective! This is classic

spin, and hype.

Back to the report: Described by the investigator as " a fairly strong

protective effect, " for a vitamin K *diet*, we are not provided with the

actual numbers by the researcher. And we don't see independent peer comment

- which tends to be more objective.

Further, it's a retrospective study, based on recall of food habits,

therefore subject to reporting bias. Those with NHL, for example, looking

for explanation might have a different recollection of past eating habits

than people who have not been diagnosed with a cancer. Perhaps.

Alright, let's assume that memory served us well, and the diets were

reported accurately. The weakness here is classic: the inclusion of lettuce

and spinach in ones' diet could easily be a marker for having a healthier

overall diet. Further, people who include such vegetables (because they are

concerned about health) may also exercise more than people who don't. Is it

the exercise, the healthier diet, or the lettuce, or the vitamin k in the

lettuce? Impossible to know.

Conversely, people who eat Twinkies daily may be at a higher risk for cancer

- but not because Twinkies cause cancer! ... but because such a daily habit

is a marker for having a relatively poor overall diet. Substitute, beer,

whisky, chips, ... you name it, for the Twinkies.

* Will vitamin companies make use of this report to promote sales of vitamin

K? Of course. Lef.org is already doing so. Good idea? Not unless your

deficient in it, and if so, better to eat more spinach.

* Will supplementing with vitamin K slow down an existing lymphoma or

prevent a relapse? Unfortunately I see nothing in this study to make such a

claim.

* Might such foods reduce risk of a first lymphoma? Maybe yes, maybe no.

I suppose the protective role of ANY vitamin would be very difficult to

prove without a very large prospective study.... where the participants are

randomized to receive a placebo, or vitamin K supplementation (or a diet

with lettuce and spinach, four times a week). The endpoint would be a

significant difference in incidence of lymphoma in the two groups in say 10

or 20 years.

You may recall that a similar study design - with many thousands of

participants - was done to determine the risks and effects of HRT in women -

which showed conclusively that HRT increased the risk of breast cancer.

Karl

==

Vitamin K May Protect Against Developing Non-Hodgkin's Lymphoma, Say Mayo

Clinic Researchers

ScienceDaily (Apr. 21, 2010) - In the first study of vitamin K and

Non-Hodgkin lymphoma risk, researchers at the Mayo Clinic campus in

Minnesota have found that people who have higher intakes of vitamin K from

their diet have a lower risk of developing Non-Hodgkin lymphoma. Non-Hodgkin

Lymphoma is a cancer of the immune system and is the most common hematologic

malignancy in the United States.

________________________________________

At the 101st Annual Meeting of the American Association for Cancer Research

(AACR), the researchers report that the risk of developing Non-Hodgkin

lymphoma was approximately 45 percent lower for participants who had vitamin

K intakes in the top quartile of intake in the study (>108 ug/day), compared

to participants who had intakes in the bottom quartile (<39 ug/day).

This association remained after accounting for other factors such as age,

sex, education, obesity, smoking, alcohol use and intake of foods with high

amounts of antioxidants.

Vitamin K is a fat-soluble vitamin and is derived from either plants

(phylloquinone or vitamin K1) or bacterial synthesis. This study estimated

intake of the plant form of vitamin K from diet and supplement use. The most

common sources of vitamin K1 in the diet include leaf lettuce and spinach,

with smaller amounts found in other vegetables, vegetable oils and some

fruits.

Researchers at the Mayo Comprehensive Cancer Center are studying the

connection between diet and Non-Hodgkin lymphoma risk, and they became

interested in a potential role for vitamin K. While vitamin K is best known

for its essential function in several proteins involved in blood clotting

(the name of the vitamin is derived from the German word " Koagulations " ), it

also appears to be important in other biological processes, including

inhibition of inflammatory cytokines thought to play a role in Non-Hodgkin

lymphoma, as well as pathways involved in cell cycle arrest and cell death.

" These results are provocative, since they are the first work we have done

on the connection between vitamin K and Non-Hodgkin lymphoma, and this is a

fairly strong protective effect, " says the study's lead investigator,

Cerhan, M.D., Ph.D., a cancer epidemiologist. " However, as with all new

findings, this will need to be replicated in other studies. "

The Mayo study enrolled 603 patients who were newly diagnosed with

Non-Hodgkin lymphoma as well as 1,007 matched cancer-free " control "

participants. Researchers asked the participants to answer a food

questionnaire about their usual intake of over 120 food items two years

prior to their cancer diagnosis or enrollment into the study (controls).

They also asked about use of a variety of supplements. Vitamin K intake was

estimated from this data.

While there was a clear trend showing that a greater intake of vitamin K

from dietary sources was associated with a lower risk of Non-Hodgkin

lymphoma, the use of vitamin K supplements presented a slightly different

picture. Increasing intake of vitamin K from supplements did protect against

Non-Hodgkin lymphoma, but reached a point where the highest intake offered

no reduction in risk. " The significance of this finding is unclear, " notes

Dr. Cerhan, " but suggests that taking high doses of supplements is unlikely

to be helpful. " Dr. Cerhan also notes that people taking certain oral

anticoagulants or seizure medications should closely follow their

physician's dietary recommendations with respect to vitamin K intake, since

vitamin K can interfere with these drugs.

" Whether the protective effect we observed is due to vitamin K intake, or

some other dietary or lifestyle exposure, cannot be definitely assessed in

this study, " notes Dr. Cerhan. " But these findings add to a lot of other

data that support a diet that includes plenty of green leafy vegetables in

order to prevent many cancers as well as other diseases. "

The study was funded by the National Cancer Institute.