Dear Mark: Vitamin B and Lung Cancer, Folate Stability in Liver, and Less DNA Damage on No Produce

Dear_Mark_Inline_PhotoFor today’s edition of Dear Mark, I’m answering three questions from readers. First, what do I make of the recent study showing a link between lung cancer in men and supplementation with vitamin B6 and vitamin B12? Next, how stable is folate in liver? Other foods with high folate content before cooking, like legumes and greens, lose a lot during cooking. And finally, what’s my take on the old study where subjects’ markers of oxidative damage improved after eating a diet bereft of produce?

Let’s go:

Mark, I wonder if you’ve seen the study linking lung cancer in men with vitamin B supplementation:

What do you think?

Interesting study, thanks.

Supplementation with vitamin B6 or B12 was not associated with lung cancer risk in women.

Supplementation with vitamin B6 or B12 was associated with lung cancer risk in men, but only if those supplements were taken separately. If they supplemented with either vitamin as part of a multivitamin, the risk disappeared.

In other studies, vitamin B6 appears to be protective against most types of cancer, including lung cancer. Circulating levels of vitamin B6 protect against lung cancer. People with low “functional” vitamin B6 status—meaning they have low levels of active vitamin B6—have a greater risk of lung cancer.

Here’s what I think is going on: The study is capturing people with vitamin issues and disorders that cause deficiencies. People who take high dose vitamin B6 or B12 are more likely to have those disorders. They’re more likely to have low levels of the vitamins. They’re more likely to be prescribed vitamin supplements to make up for the deficiency. They’re probably even more likely to be unhealthy; many people take vitamins as an antidote to poor health.

Maybe supplementing isn’t good enough to overcome the inherent deficiency, or the condition causing the deficiency. Maybe these people aren’t converting supplemental vitamin B6 into the active, “functional” form that protects against cancer. Many of the participants were smokers at baseline, and the vitamin-mediated risk of cancer went up in those who smoked. Maybe they’re taking vitamins in response to an underlying disease state.

Those underlying disease states change how vitamin B6 acts in the body. In one study, “functional” B6 status was protective against lung cancer, while another type of biomarker measuring the catabolism of B6 due to inflammation, was linked to a rise in lung cancer. Low-grade inflammation is often high in states of disease or general unhealthiness, and B6 catabolism is a strong predictor of all-cause mortality.

It does seem that cooking affects these folate sources differently. If you compare cooked (boiled, drained) legumes, lentils come out on top! (Although liver is still king.)

This is true.

Animal-sourced folate is quite stable whether you freeze it or cook it.

I should say that overcooking your liver will deplete the folate. 12 minutes of frying in corn oil until 158°F/70°C caused a 50% loss of folate. 16 minutes of broiling until 158°F/70°C caused a 40% loss. That’s an obscene amount of cooking. Cooked liver should be pink inside. Creamy, not grainy. Even then, you still maintain at least half of the already generous amount of folate.

Older studies got better results, with fried beef liver losing between just 11-15% of folate. They probably weren’t overcooking it.

A ghost said:

I’d love to hear your opinion on this study:

Man, I wish I could get my hands on the full study. I’ll comment, but keep in mind that I’m only going off the abstract. Consider this fun speculation, not iron-clad conclusion.

Researchers took 8 smokers and 8 non-smokers, removed all concentrated sources of flavonoids from their diet, and fed them meat patties dosed with green tea extract for 10 weeks. This amounted to a “fruit-and-vegetable-free diet,” as produce is the richest source of flavonoids.

Green tea extract had some positive effects on postprandial oxidative stress, but they didn’t last. The half life of the extract in the body was 2 hours. As the subjects peed it out, the antioxidant capacity returned to normal.

What’s weird is that oxidative damage to DNA, lipids, and blood proteins all decreased over ten weeks despite the subjects eating no produce and the green tea extract only improving antioxidant capacity for a few hours postprandial.

Maybe the diet was dense with vitamins and minerals. After all, vitamins and minerals serve antioxidant functions and provide building blocks for the production of endogenous antioxidants like glutathione.

Maybe most of the oxidative damage our DNA, lipids, and blood proteins face occurs immediately after eating. If so, the postprandial increase in antioxidant capacity could have made all the difference.

We don’t know enough about the rest of the diet to say anything else or do anything but make guesses. They weren’t only eating the green tea meat patties. They ate other stuff, too—a “strictly controlled diet” absent fruits and vegetables. I really wish I could get my hands on the full paper.

That’s it for today, folks. Help out down below if you have anything to add, ask, or proclaim!

Take care, be well, and Grok on.


TAGS:  dear mark

About the Author

Mark Sisson is the founder of Mark’s Daily Apple, godfather to the Primal food and lifestyle movement, and the New York Times bestselling author of The Keto Reset Diet. His latest book is Keto for Life, where he discusses how he combines the keto diet with a Primal lifestyle for optimal health and longevity. Mark is the author of numerous other books as well, including The Primal Blueprint, which was credited with turbocharging the growth of the primal/paleo movement back in 2009. After spending three decades researching and educating folks on why food is the key component to achieving and maintaining optimal wellness, Mark launched Primal Kitchen, a real-food company that creates Primal/paleo, keto, and Whole30-friendly kitchen staples.

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19 thoughts on “Dear Mark: Vitamin B and Lung Cancer, Folate Stability in Liver, and Less DNA Damage on No Produce”

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  1. As far as the folate loss when cooking liver, I eat it raw. Totally gross, I know. I buy pastured beef liver from a local farmer and cut it into small pieces. Put in the freezer on a parchment lined baking sheet until frozen then pack up in a ziploc. Take one or two out in the morning and let it partially thaw while I’m doing my morning routine. Then I just swallow the liver whole. I take it with lemon water which helps to cut the taste. There is no point in cooking liver since I don’t know anyone else who will eat it. This is a way to get it in with very little effort, other than the original cutting it into small pieces. Which is not fun…a kitchen shears is helpful, as is good music or a podcast as a distraction!

    1. That’s a great idea! Cutting it up does sound like a pain though. I buy a liverwurst from whole foods by wellshire farms that has no sugar or grains added but I fry it in a pan until almost black before eating, so I imagine I decrease the folate content by quite a lot.

      1. Hey Tiffany, I wish I could find clean liverwurst…I actually enjoy that! But it’s hard to find in grocery stores around me, and usually has some crappy ingredients.

        1. Yeah it is literally the only pre-cooked liver product I’ve found that doesn’t have corn, wheat, sugar, or any other crap. It has nonfat dry milk but that’s okay with me. The brand is exclusive to Whole Foods, if you live near one. 🙂

          1. I FINALLY have a whole foods opening kind of near me…will definitely get some. And love that this community exists…where else could we be having such an in depth convo about liver lol?!

    2. Elizabeth, you’ve got more fortitude than I have. I don’t mind cooked chicken liver, but I find the taste and texture of ruminant liver flat-out disgusting, even when cooked. Incidentally, according to several websites I looked at, chicken liver compares favorably to beef liver with regard to nutrients. I think I’ll just stick with chicken liver pates, which even my ultra-picky family members will eat.

    3. I eat grass-fed-beef liver raw, too. However, since I’ve always loved the taste of liver (since I was a kid), I eat it in quantity. I have about 40-50 grams at a sitting and chew it up, savoring the flavor. My guess is that my affinity for liver comes from my MTFHR mutation… it’s just my body craving a good source of vitamin B. We eat fish raw, why not meat?

  2. What about the folate in sunflower seeds and leafy greens? How much does cooking affect those?

  3. The full paper is available for download by clicking “Full Text Links” in the upper right of the PubMed page, then clicking the PDF symbol button to the lower left of the extract at the BJN site.

    1. I hope he reads it. It had nothing to do with GTE as the effects were seen during the control period when it wasn’t given.

  4. Green tea has polyphenols, so they exert a hormetic response. Having them in the body even just a few hours a days should be enough to upregulate the body’s antioxidant production, explaining the positive results?

    Here’s the full study:

  5. For some years now I’ve been whizzing Ox Liver up in the blender and then adding it to vats of chilli or bolognaise. It gives an additional meaty taste, but I’ve been mostly (and smugly!) doing it for the nutrition. Based on the idea that pan-frying depletes folate, is the 2+ hours of cooking time I’m giving this dish going to make adding the liver completely redundant on the nutrition front?!