For today’s edition of Dear Mark, I’m answering three questions. You guys had more questions about folate. Since it’s such an important vitamin, I answer those first. Then I discuss the study mentioned in last week’s Dear Mark in which removing polyphenol-rich fruits and vegetables from the diet improved oxidative stress markers instead of worsening them. I got my hands on the full study, so I have more to say on the subject.
First, Tiffany asked:
What about the folate in sunflower seeds and leafy greens? How much does cooking affect those?
“Cooked” sunflower seeds are roasted sunflower seeds. According to USDA nutritional data, both roasted and raw sunflower seeds have the same amount of folate. You’re probably safe there.
For greens, how much folate you retain depends on how you cook them.
Boiling spinach or broccoli causes about 50% folate loss. Steamed spinach or broccoli lose almost zero folate. For what it’s worth, potato folate is impervious to boiling.
Another study found similar results: Cooking in water causes leafy green folate loss.
Overall, folate loss from vegetables is primarily due to leaching (into cooking water) rather than degradation by heat.
Even though you didn’t mention them, legumes is where it gets interesting.
In one study, cooking beans without soaking retained 60% of folate. A quick pre-soak (boiled for 2 minutes, covered for an hour, then drained) followed by 20 minutes of cooking retained 18% folate; followed by 90 minutes of cooking, 31%. A long soak (16 hours in water overnight) followed by 20 minutes of cooking retained 35% folate; followed by 90 minutes of cooking, 42%. Oddly, how you soaked the beans didn’t matter when you cooked the beans for 150 minutes. A quick soak retained 41%, a long soak 44%. I suspect the longer cooking times give the folate more time to be re-absorbed.
Another study found that pressure cooking was better for folate retention than boiling, and that chickpea folate was more resilient than field pea folate.
Steph Windmill asked:
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?!
Wet cooking will deplete folate, but as in the case of beans, it ends up in the cooking water. Since you’re consuming the cooking liquid, it shouldn’t be a problem.
Still, if you want to be really sure, I have a solution. Classic bolognese sauce recipes call for chopped or pureed liver to be added in the last ten minutes of cooking, not right away. Try that instead of dropping it in at the beginning. Liver cooks really quickly, so ten minutes is plenty of time.
Time Traveler swooped in with assistance:
Hey Mark, here’s the link to the full smokers study, if you wish analyze thoroughly. It took me 2 seconds to find (-:
Very interesting. The full paper clears up a lot of questions I had.
The fruit and vegetable-free diet was decent, as lab diets go, drawn from standard Danish foods:
Is it Primal? Not exactly, but you could definitely cobble together a nice Primal diet by removing some foods. And everything is “real,” not processed or overly refined.
They do point to other studies in which removal of fruits and vegetables had the effect of increasing oxidative stress, so the effect is equivocal.
The 16 subjects of the study were young, lean, and—besides half of them smoking—quite healthy males. If you’ve ever fit that category, it’s a good time to be alive. You don’t worry about much. You’re focused on the day at hand. You have very low stress levels. You’re living for the moment. Old enough to reap the benefits of adulthood, young enough to avoid the consequences.
I’ve always maintained that polyphenols and other phytonutrients found in fruits and vegetables are most critical for people undergoing significant oxidative stress. These include the obese and overweight, the diabetic, the old and sedentary, the chronically stressed. The overworked athlete who needs an edge for recovery.
And one big reason I emphasize produce and even sell a powerful antioxidant/mineral/vitamin supplement is that most people come to this site to improve their health. Many of us got into Primal because we were trying to fix something broken in us. We were starting from a health deficit. We needed (and still need) extra help.
The subjects in this study weren’t really the target audience for phytonutrients. What really throws me for a loop is that their oxidative stress markers were worse on the habitual diet with more polyphenols. It wasn’t that removing polyphenols had no effect. It actually improved their oxidative status.
Here’s a thought that could explain it: Denmark isn’t known for its natural bounty of high-polyphenol plant foods. We know from previous posts that our genetic ancestry can partially determine our nutrient requirements and how we respond to foods. If these were ethnic Danes (as of 2017, 86% of the country is ethnically Danish; the study was in 2002, so Denmark was probably even more homogeneous), and ethnic Danes have a genetic adaptation to the historically lower levels of dietary phytonutrients available in the area, this could explain the results.
Interesting study to hypothesize about. Maybe I should pursue this ancestry angle further—thoughts?
That’s it for me, folks. Thanks for reading, thanks for writing in, and be sure to keep it going down below!