Dear Mark: Carb Sources, Oxalates, Fiber, Vitamin D, MTHFR Mutations, Lowering ApoB, Choosing Cardio, and Non-Wine Alcohol

Here are my answers from the last round of Q&As.

Fredrik Prost asked:

Fruits, roots, and tubers are probably the safest carbohydrate sources.

And by “safest,” I mean a few things.

First, they’re whole foods. They aren’t refined, isolated, or processed down into “naked carbs” stripped of the stuff that helps you handle glucose, like fiber, polyphenols, potassium, and other minerals.

Second, they aren’t hyper-processed, so digestion tends to be slower and the glucose curve is usually more controlled. You’re not flooding your gut with a giant dose of acellular carbs.

Third, they’re generally lower in anti-nutrients and irritants. Fruit wants to be eaten. And roots and tubers are protected by the soil, so they don’t need the same chemical defenses as, say, leaves and seeds.

Most people tolerate these foods well. Almost everybody likes fruit. Put a bowl of fresh fruit in front of a baby who’s never seen it before and they’ll instinctively grab it and start gumming it.

I’d also include some grains in the “pretty safe for most people” category, especially white rice. A lot of people tolerate it well, and it’s a straightforward source of glucose if that’s what you need. And I’m not a militant about this. If you want a nice piece of bread or a bowl of beans and it’s high quality, tastes good, and agrees with you, those can be legitimate too. If you’re making them staples, you’ll usually do better with sourdough bread and soaked, sprouted, or well-cooked legumes.

I’m also not opposed to more “refined” carbs in specific contexts, like right after hard training. Things like tapioca syrup, waxy maize, or even chocolate milk can be great post-workout tools for replenishing glycogen.

As always, the context matters: your activity level, whether you just trained and you’re trying to restock muscle glycogen, and whether you personally tolerate grains and legumes.

But if I had to pick carb sources that are “safe” for almost everybody, it’s fruit, roots, tubers, and winter squash.

Nijan Datar asked:

I’m about the same. For the most part, I don’t eat raw fibrous leafy greens in large amounts. I definitely prefer romaine lettuce, butter lettuce, baby greens, and arugula which, while they don’t have the reputation of being very nutrient-dense, actually are. They’re a good source of folate and high in beneficial nitrates, which help with vasodilation and exercise performance and heart health by spurring the production of nitric oxide.

If I am going to eat kale or spinach, it is almost always cooked in liquid. Cooking the tougher leafy greens make them easier to digest and yes, it can reduce oxalate absorption, especially if you cook them with a calcium source.

This lines up with how these foods were traditionally prepared. I’m thinking things like stewed collard greens cooked with vinegar and a ham bone, with the vinegar pulling calcium from the bone, or creamed spinach, which is cooked with cream and cheese. The calcium (whether liberated from bone or found in dairy and cheese) can help bind to the oxalate and prevent absorption, and then they’re easily excreted.

That’s not to say that I worry about oxalates. Certain conditions, behaviors, or nutrient deficiencies, can make oxalates more of an issue:

• anyone with a history of kidney stones (especially calcium oxalate stones)

• people with gut issues or fat malabsorption (oxalate absorption can go up)

• people who do high-dose vitamin c regularly (some can convert to oxalate)

• anyone living on daily spinach smoothies, almond flour everything, and dark greens like it’s a competitive sport

• people who don’t eat enough calcium and magnesium

But the average person doesn’t have to make oxalate avoidance a cornerstone of their identity. Once again, the combination of ancestral reasoning, culinary wisdom, and modern research is a path for avoiding problems while still being able to enjoy some of these foods that are considered high in oxalate. I would say as long as you get enough magnesium and calcium, it should be pretty safe to have oxalate foods.

Dale Garman asked:

What’s my current take on fiber?

Well, what are you talking about? When you say “fiber,” I think too many fiber promoters and detractors speak about it as if it’s a monolith.

There’s viscous soluble fiber, fiber that is “softer,” absorbs water, forms “gels” and can help with diarrhea.

There’s non-viscous soluble fiber, fiber that dissolves in water but doesn’t gel up. This is often highly fermentable by gut bacteria, which can produce beneficial short chain fatty acids but also lots of gas and bloating if you’re susceptible.

There’s insoluble fiber, which actually physically scours the colon and can help with constipation. Sounds bad, but some “scouring” is normal. Just don’t go overboard, and don’t scour an already inflamed gut.

There’s also resistant starch, which isn’t a fiber but acts like one. It is indigestible by your digestive enzymes but highly fermentable by gut bacteria.

In general, if you’re eating a more standard carb-rich diet, even if it’s a “standard healthy diet” like whole grains, plenty of vegetables, lean meat, things like that, then fiber probably makes sense. My basic stance: if you’re eating foods that normally contain fiber, (as in, you find that food in nature and it contains fiber), you should probably eat the fiber. The fiber makes sense. Food is a system with many moving parts that synergize. If you’re eating a high-carb diet, it should probably have some fiber in there. Fiber will improve glucose tolerance. It can help you produce short-chain fatty acids as metabolic byproducts of fermenting fibers, which have been shown to improve insulin sensitivity. If you’re eating carbs, you want to be insulin sensitive.

I will say that most humans throughout history encountered fiber in their diet. The Hadza, which many people cite as a model for baseline human nutrition, eat upwards of 60-70 grams of fiber each day for certain periods of the year. But, then again, they live very different lives with very different genetics and very different gut bacteria than most reading this. What works for them won’t necessarily work for you.

I remember back in the old Mark’s Daily Apple days when resistant starch was getting big, and people were taking tablespoons of raw potato starch to get big doses of it, those who were on really low-carb diets didn’t see much benefit. They’d sometimes get constipated, missed out on the sleep and digestive benefits. Those who were eating more moderate amounts of carbs saw the big benefits. This makes sense, as natural sources of resistant starch also contain ample amounts of digestible carbs.

Fiber can constipate one person, give another person diarrhea, and make another feel great. It’s really hard to generalize, and it really depends on individual genetics, the landscape of the gut, which bacterial species you’re hosting, the type of fiber, and again, the underlying diet.

I don’t think you need to seek out large doses of supplemental fiber. That often makes things worse, particularly if you’re megadosing wheat bran and other forms of insoluble (“scouring”) fiber. You should just get fiber through eating food. To give you an idea of what you’re getting when you eat food, read on.

Sources of viscous soluble fiber

Food

• Oats

• Chia seeds

• Eggplant, okra

• Apples

• Legumes

Supplements

• Glucomannan

• Beta-glucan

• Psyllium husk

• Guar gum

• Pectin

Sources of non-viscous soluble fiber

Food

• Onions, garlic, leeks, and other alliums

• Asparagus

• Jerusalem artichokes

• Apples, pears, stone fruit

• Legumes (has both viscous and non-viscous)

• Mushrooms

• Seaweed

Supplements

• Inulin

• FOS and GOS

• Acacia fiber

• Partially hydrolyzed guar gum

• Resistant dextrin

• Soluble corn fiber

• Polydextrose

Sources of insoluble fiber

Food

• Cruciferous vegetables (cooked is much less harsh than raw, as the heat softens the insoluble fiber)

• Whole grains

• Wheat bran

• Leafy greens, especially kale, collards, and other “roughage”

• Nuts and seeds

• Fruit and vegtable skins

• Legumes (has it all)

Supplements

• Wheat bran

• Cellulose

• Whole husk psyllium

• Apple fiber

Based on your digestive response to these foods, you can begin gauging how you respond to “fiber.” If oats make you feel great, you can probably handle soluble viscous fiber. If cooked broccoli works better for you than raw broccoli or romaine than raw kale, you might be reacting to the insoluble fiber. Just know that you should figure out what you actually mean by “fiber,” because it can mean very different things.

gerrMy basic stance on fiber? If bathroom visits are easy, don’t worry. No need to experiment. Keep doing what you’re doing.

Paul Vahur asks:

It’s not “necessary” but it can be helpful. Sun exposure is the best way to get it, but not everyone is great at making vitamin D from sunlight. I spend a lot of time in the sun. I maintain a strong tan. I have for decades, and yet unless I supplement I have very low levels of vitamin D. Genetically, some just aren’t strong converters.

What’s going on?

My ancestral environment was sufficiently rich in dietary vitamin D via fish, mushrooms, and meat while being relatively lower in enough UVB to provoke vitamin D production from sunlight. I can still do it, it’s just not reliable.

Test your vitamin D and aim for a level between 30-50, maybe 40 ng/mL. Try to get there with sunlight. If that doesn’t work, you might need to supplement. When you do supplement, make sure to keep getting sunlight so you get all the benefits.

One reason vitamin D supplements often perform poorly in studies is because they don’t take vitamin K2 and vitamin A intake into account. The three nutrients all synergize. Many vitamin D-related benefits depend on A/K status, and vice versa. So that’s another thing to think about when supplementing; are you getting enough vitamin A and vitamin K2 to make the D “work”?

Jimmy E asks:

It’s not a bad idea. If you’ve established and confirmed they have the mutation, or one of the mutations, it’s reasonable, especially if they’re exhibiting the symptoms associated with the deficiency.

You can also try to get folate from food alone. It’s not that hard to build it in. Eat a couple eggs a day. Have a little romaine salad. Add some lentils if they tolerate them. That can be enough to cover a lot of ground. Pickiness makes it hard, of course.

But yeah, once you get the genetic results back, do a deeper dive on which forms would be best for your kid and give them a shot. They make tons of great gummy vitamins these days, and picky kids are far more likely to eat a gummy than a Romaine lettuce salad.

Carla Newport asks:

It really depends how high your ApoB is. Personally, I think mild elevations are fine and not worth panicking about, especially if overall metabolic health is good. But as I wrote a couple months ago, really high numbers simply do mean that potentially atherogenic lipoproteins are hanging around for long periods of time waiting to be oxidized and contribute to atherosclerosis. And even if the sky high ApoB doesn’t trigger atherosclerosis, it does indicate that something isn’t working for you. The numbers aren’t normal; they are evolutionarily novel. There was a guy in the previous Q&A who had astronomical numbers, and I recommended he go on a lower-fat diet. Some people simply don’t do well on that kind of diet.

That may be you. You might do better with moderate fat intakes, rather than high fat intakes. Often just increasing carbs to 100-150g per day can drastically normalize ApoB.

You can also change the fatty acids you eat. Switching from saturated fat to monounsaturated fat often lowers lipids.

The type of saturated fat you eat matters. Palmitic acid tends to raise ApoB more than stearic acid. Coconut oil tends to raise it less than butter.

Sometimes the changes aren’t what you’d expect. I’ve seen people who switched from butter to cream who saw big reductions. Same fat content, but cream has something called milk fat globule membrane that modulates blood lipids. You have to experiment.

Again: whether these changes are meaningful for health are up for debate. But if you want to lower cholesterol, this will often do it.

You can also look at thyroid function. Active thyroid hormone directly stimulates LDL receptor activity. Meaning: if your thyroid function is depressed, cholesterol may go up because the receptors for LDL particles aren’t as active, so the particles have more time to float around. In fact, in the old days, thyroid gland powder was a legitimate first-line approach for heart disease. It reliably lowered cholesterol.

I would also look into citrus bergamot, which is a sort of “mild statin.” Instead of fully blocking the enzyme responsible for cholesterol synthesis, it mildly inhibits it while also increasing LDL receptor activity. You can see a pretty decent reduction in ApoB levels—on the order of up to 15%—without the muscle-pain side effects you see with statins. It’s popular with bodybuilders, especially those taking steroids, because they’re trying to protect heart health. If it damaged muscle function, bodybuilders wouldn’t be taking it.

If you want to go the pharma route, probably the most effective one at lowering ApoB is going to be PCSK9 inhibition. This will raise LDL receptor activity and reliably clears circulating ApoB-containing lipoproteins. But you’d have to talk to your doctor about that.

Michael Whitener asks:

Apart from the three hours you’ve allotted for cardio, find time for 5–6 hours of low-level movement a week. That could be easy bike rides, hiking, walking to dinner. Essentially, a no-brainer way to do it is just walk for an hour a day. These are sessions where you can have an easy conversation. Full nasal breathing. Almost normal. Easy. You might not even sweat. I wouldn’t even place this in an “aerobic zone” because it’s not supposed to be exercise. It’s living. It’s the foundation.

Okay, now for the 3 hours.

2 hours of Zone 2 a week. This is training in the “180-minus age” HR zone. You take 180, subtract your age, and keep your heart rate below that number. This is an elevation, and you might be sweating, and your conversation will be a bit labored, but it’s maintainable. It doesn’t wreck you and you will probably end the session feeling great.

1 hour of “hard stuff.” This is cardio where you’re breathing really hard, muscles are sore, and you can’t have much of a conversation. What this looks like for me is an hour long session on the fat tire bike down the beach. Grueling, hot, sweating, intense, alive. Or it’s an hour or two on the paddle board. Not relaxing or leisurely, but really going for it. Abs burning, feet working hard (you’d be surprised how much it works your lower limbs). This could be high intensity intervals, where you do repeated high intensity bouts with incomplete recovery in between.

I’d also recommend sprinting once a week. Either take some time out of your “hard hour” or tack in on. I like one sprint session a week that is all-out sprinting, where you’re going to full effort, getting full recovery in between, and then going again. Depending on your age, your ability to recover, and your ability to generate power, that could be three or four sprints, or it could be up to ten.

Basically, the more powerful you are, the faster and harder you can go, the fewer sprints you actually need. Because your output is so high that recovery is harder, and the load on your central nervous system is that high.

For example, kids in middle school can sprint more often than kids in high school because they don’t yet have the power and muscle mass required to generate huge amounts of force. So they can recover quicker from their bouts because they just aren’t going as hard.

And sprints don’t have to be on flat ground. They don’t have to be running sprints. It could be on a stationary bike, on the rower, or one of my favorites, the rope pull-down machine, or the SkiErg, VersaClimber, StepMill. The key thing is giving maximum effort and getting real rest in between. Full recovery between bouts.

Wendy Brown asks:

They apply to any alcohol, but the reason wine is generally “safer” is because it’s so rich in polyphenols, thereby providing “in house” protection. Most other alcohols are not. Or maybe it’s that they haven’t been studied as much as wine.

We do know that single-malt whiskeys can be quite rich in polyphenols that have big ROS-scavenging activity. I’d expect most aged liquors to have some interesting things going on. Time to experiment!

Until next time.