A Paleo/Low-and-Slow-Carb Approach to Produce: Which Fruits and Vegetables are Best?

6 03 2016

This is the product of my new-found obsession with dietary fiber – namely, making sure that I get enough of it, from the best possible dietary sources, coupled with safe amounts of digestible carbohydrates.

I compiled a list of popular vegetables, fruits, and nuts, and parsed through the USDA’s data to find fiber values for different measures of the food – i.e. grams of fiber per cup, and per 100 grams, and per pound. I also calculated the grams of digestible carbohydrate (i.e. {total carbs} – {fiber}) per gram of indigestible fiber, to enumerate those foods which I would consider the “slowest” carbohydrates (with the least digestible carbs per gram of fiber, or equivalently the most fiber per gram of digestible carbs).

My reasoning for this is that fiber acts as a “buffer” of sorts, slowing the digestion and uptake of digestible carbohydrates and minimizing their negative effects on the body’s insulin sensitivity, metabolic health, and the like (not to mention every other benefit fiber consumption has on our metabolic health, starting with our gut bacteria).

With no empirical evidence, but rather a strong hunch, informed by my knowledge of biochemical systems, I hypothesize: on average, a gram of fiber has some “digestible carbohydrate buffer capacity”; so all things being equal, a food with more digestible carbs per gram of fiber has a more negative effect, metabolically, than one with fewer digestible carbs, because the carbohydrates are released into the blood or liver more quickly.

(That’s not to say we shouldn’t eat foods with higher numbers of digestible carbs per fiber, but that the foundation of our copious vegetable consumption should be from foods with lower numbers).

As a quick point of conclusion, I found it pretty remarkable how the true Paleo diet emerges from the table when you sort it by grams of digestible carb per gram of fiber. The foods with the lowest numbers include berries, leafy greens, brassica/cole/cruciferous vegetables (cabbage, broccoli, etc), and nuts and coconuts (I included peanuts in here for arguments’ sake, but they are legumes and there are legitimate reasons to avoid them, beyond the scope of this post). These foods are the closest to their wild ancestors, the plant foods that our bodies evolved to eat (greens, berries, nuts, and tubers, which I’ll discuss below) before agriculture selected for higher levels of sugar at the expense of nutrients.

And without much further ado, I’ve uploaded the chart and made it available below. One discrepancy to point out: it was beyond my level of patience to tease out information about resistant starch – a type of non-fiber carbohydrate that ends up feeding our intestinal bacteria and not our fat cells. This is present in things like tubers (especially potatoes that are raw, or cooked and then cooled in the refrigerator) and onion family vegetables. I’ve made a note in the document, but it’s worth considering onions, leeks, scallions, garlic, and potatoes prepared as described above as having a much lower digestible carb/fiber measure than this table indicates. Eat onions every day, and tubers a few times a week.

Columns A, B, and C are self-explanatory. D through G are the grams of indigestible fiber per common volume or weight measurement of the food (typical “piece”, raw cup, raw 100g, raw 1 lb, respectively). H is the grams of digestible carbs (remember, this includes resistant starch and so skews the numbers of onions and tubers), and I is the important number, grams of digestible carbohydrate per gram of fiber. I have included highlighting – the greener the cell, the less carbs per gram of fiber and therefore, (as per my hypothesis), the better the food.

I urge you to peruse this chart and use it to make the healthiest food choices you can. The USDA (probably erroneously, but still) recommends 14 grams of fiber per 1000 Calorie food intake – about 25 grams per day for a typical woman, and 35 grams per day for a typical man. Armed with the information here, it’s easy to meet or surpass that number – and you’ll quickly see that watermelon probably isn’t the best way to do it.

Happy eating!

Vegetable Fiber Reference – Excel Document

Edit: Here is another version of the table (at the request of a friend of mine) with the rows sorted by grams of fiber per raw cup (first sheet) and grams of digestible carb per gram of fiber (second sheet). You can also change the sorting yourself.

Updated Vegetable Fiber Reference