In yesterday's Part 1 about nutrient deficiencies in the gluten-free population, I posed four critiques and questions that I promised to answer in today's part 2. Without further ado, here we go...
Critique #1 questioned the small sample size of the research. I can't do anything about that, and there's not much to be said about it, so let's move on.
Next, I think it's easiest to address critique #3: How did nutrient deficiencies in the GF population compare to Americans as a whole? To answer that question, I pulled data regarding nationwide averages from the USDA's Community Nutrition Mapping Project. If I amend yesterday's table that showed the percent of the GF population who are deficient in given nutrients, and add to it a column for the national averages, this is what you find:
|Nutrient||GF Deficiency||Nationwide Deficiency|
These numbers change the perspective a bit, I think. It's not simply that the GF population is nutrient deficient. When you compare us to the national averages, it gets slightly more complex. In some cases, such as folate, riboflavin, thiamin, and iron, we're two or more times as deficient (as a group) than the nation. However, in other cases, such as B12, B6, and calcium, we still have greater rates of deficiencies, but we're also in the same ballpark as the national averages. And in one case - fiber - we're actually LESS deficient than the national average. Interesting.
Which brings me to critiques #2 and #4: are there differentiations within the GF community (processed GF foods, whole grains, fresh fruits and veggies and meat and fish), and is the GF diet to blame or are other factors (i.e. nutrient malabsorption) to blame?
First, it's important to note that if you're an undiagnosed Celiac, or if you're a newly diagnosed Celiac whose villi haven't had a chance to heal in the small intestine, then nutrient malabsorption is undoubtedly a factor to consider. Even those who have been on a gluten-free diet for prolonged periods of time may have persistent nutrient malabsorption problems, especially with fats, certain vitamins, and calcium (whose absorption rate is impacted by the vitamins).
Second, it's also important to note that for many Celiacs (as well as for some with gluten intolerance), the gluten restriction is also coincident with lactose intolerance, casein intolerance, or both. This leads to a natural shift away from dairy products such as milk, cheese and yogurt, all which can be good sources of calcium. Unless you diet is rich in non-dairy sources of calcium, and unless you take a multivitamin supplement, it wouldn't be surprising to find that you're calcium deficient. (And as you may know, bone density loss and osteoporosis are both secondary health concerns for those with Celiac.)
That's as much as I'll say about contributing factors other than the GF diet itself. As for the GF diet, this is where the rubber really meets the road, as they say. I was curious whether the GF diet was indeed nutrient deficient when compared to a "standard" gluten diet. The primary distinction between gluten and gluten-free diets is of course the gluten. And so that's where I focused my attention - by comparing a baseline wheat flour (all-purpose enriched unbleached wheat flour [W]) with a range of gluten-free substitutes (cornstarch [C], brown rice flour [BRF], potato flour [PF], tapioca/cassava [T/C], arrowroot flour [AF], sorghum [S], cooked quinoa [Q], cooked amaranth grain [AG] and cooked millet [M] ). Once again, I pulled my data from the USDA's National Nutrient Database. (A couple words of note. In the following table, I've rounded decimals for space. Also, the USDA database does not include sorghum flour, so I've used plain sorghum. Ditto for the quinoa. Tapioca starch isn't listed either, so I've included both raw cassava and tapioca pearls. In all cases, the values are for one cup of the given food. Because I couldn't compare equivalent starches/flours across the board, it's not a perfect comparison, but it gives a very good general sense of things...)
Whew. That's a lot of numbers. What does it all mean? Well, first take a look at the first row, which lists the values for fiber. Remember how fiber was the one nutritional component measured in the study where the GF population was less deficient than the national average? Suddenly that doesn't seem too surprising. With only a few exceptions, the broad suite of gluten-free grains contain more fiber than the wheat baseline.
Secondly, take a look at the second row, which lists the values for calcium. Again, with only a few rare exceptions, the broad suite of gluten-free grains contain higher levels of calcium than the wheat baseline. Now hold on a minute. The GF population is more calcium deficient than the national average, not less. What gives? The data here tell me that the calcium deficiency is not due to the gluten-free diet. I'd be willing to wager that our higher prevalence of calcium deficiency is due to two factors: an avoidance of dairy products due to lactose/casein intolerance, and calcium malabsorption. Never the less, it's not the fault of the gluten-free diet.
Thirdly, take a look at the rows for B6 and B12. You'll immediately see that B12 has zeroes across the board. That's because B12 isn't available via plants. It comes primarily from meat, poultry, dairy, etc. Then there's B6. As you can see, wheat is pretty poor source of it. The ancient grains - quinoa, amaranth, and millet - are comparatively much better. But best of all are the brown rice flour and potato flour. It just so happens that brown rice and potatoes are decent sources of B vitamins. So again, the gluten-free diet itself doesn't seem to be to blame here.
Lastly for my analysis, I think it's very useful to recall my differentiation beteween various types of GF diets. First, there's the GF analog of the standard American diet, comprised primarily of heavily processed foods. The GF components of those foods are typically corn, rice, tapioca, and to a lesser degree, potato. You'll find those all in columns 2-5. As you can see, cornstarch and tapioca especially are poor sources of nutrition. They offer very little. Is it any surprise, then, that a diet heavily dependent upon these starches would be nutrient deficient? Brown rice flour and potato flour aren't as bad. They're actually pretty decent in their nutrition (especially when compared to cornstarch and tapioca!)?
Then, what if we consider my second grouping, which includes a GF diet that incorporates more whole grains and the "ancient" alternative grains (sorghum, quinoa, millet, amaranth)? Then the nutritional picture starts to look even better. As a group they're more nutrient dense than the first group. Plus, many of the ancient grains offer the complete set of amino acids. That's a big added bonus.
The most striking to me, though, is that the gluten-free alternatives to wheat aren't necessarily all that different from the wheat flour baseline. In some cases, they're actually preferred from a nutrition standpoint.
But even more important to recognize is that none of these grains - from wheat right down to the ancient grains - are great sources of the nutrients which the research study focused on. You shouldn't be making these starches - whether you eat gluten or not - as the basis of your nutrition. Sure, they can be a good source of carbs. But when it comes to rounding out the nutrient intake, look elsewhere.
And that brings me to the third of my three groupings: the GF set who eat a high percentage of fresh fruits and vegetables, as well as whole meats, fish, etc. They're going to be the best off nutritionally. If you look at the government's Dietary Guidelines for Americans, you'll find that the best dietary sources of various nutrients have nothing to do with wheat or cornstarch or, for the most part, any of the other grains I profiled. Here's a sampling of the best dietary sources of different nutrients:
iron - soy, beef, beans, lentils, spinach, chickpeas, tomato, some seafood
calcium - tofu, salmon, molasses, spinach, soy, beans, kale, yogurt, milk, cheese
fiber - beans, peas, lentils, soy, fruits and vegetables (including banana, orange), sweet potato, whole grains, nuts and seeds
B6/B12 - meat, chicken, eggs, asparagus, broccoli, spinach, bananas, potatoes, milk, cheese, nuts, fish, brown rice
You know what I notice? That entire list is naturally gluten-free. The million dollar take home message is thus: if more gluten-free people ate a diet well-rounded with whole GF grains, including the ancient grains, and rooted that diet in fresh fruits and vegetables, and whole meats and fish, it would go a very long way toward battling nutrient deficiency in the GF diet. Keep that in mind the next time you're at the grocery store, or planning a meal.