(Looking at the Science on Raw vs. Cooked Foods--continued, Part 2H)
Does cooking render minerals "inorganic"
or less assimilable?
One claim made by a number of raw "experts" is that "cooking makes all minerals inorganic," i.e., cooking converts all the (organic) minerals in food into an inorganic form. The further claim is then made that the inorganic form cannot be used by the body. This section will examine the validity (or lack thereof) of the first claim, as the second (regarding assimilation of inorganic minerals) depends somewhat on the first.
An old claim, but what is its origin? The idea that cooking converts organic minerals to an inorganic form is fairly common in rawist circles--one can find natural hygienists, fruitarians, and others making the claim. It is sometimes attributed to Herbert Shelton or T.C. Fry (raw/predominantly raw diet advocates of the past), but apparently neither actually originated the claim. The earliest citation for the claim that could be located for the present write-up is one found in the book Uncooked Foods and How to Use Them, by Mr. and Mrs. Eugene Christian, published in 1904. From pp. 77-78:
When we apply it [fire] to our food in the process of cooking, it results in such a change as destroys the elementary plant form, and the mineral elements return to their inorganic condition.
Thus it appears that the claim originated long ago, before the days of Shelton or Fry, though the above book could be described as having (approximately) a "traditional" natural hygiene orientation. This suggests the claim may have originated in the 1800s (or earlier), perhaps as part of the nature cure movement, or in the earliest days of the natural hygiene movement. (If any reader is aware of citation(s) regarding an earlier origin for this claim, don't hesitate to forward the information to one of the site editors.)
What is actually meant by
"organic" vs. "inorganic" minerals? |
The first point to note is that the claim about the difference between "organic" vs. "inorganic" minerals is relatively vague. The terms used are never defined, thus many readers--or raw-fooders themselves--may not know exactly what the claim means. So let's begin by defining terms.
- Organic: The standard chemistry definition is that a molecule is organic if it includes at least one carbon atom.
- Inorganic: The standard chemistry definition is any molecule that is not organic, i.e., has no carbon atoms at all.
- Cooking: Heating food to a minimum temperature. The precise value of the minimum temperature is subject to discussion; details below.
- Mineral: (1) something that is neither animal nor vegetable matter, (2) a crystalline substance formed via inorganic processes.
[Detailed definitions are available via http://www.m-w.com/.]
The term mineral is still not as precise as one would like; one might ask whether metals are minerals or not. By definition (1) under the last bullet above, metals are minerals, but by definition (2) they might not be. Because of this fine point, we give counterexamples below for both metals and minerals.
Another fine point concerns the value of the minimum temperature in the definition of cooking. A few potential minimum temperatures that come to mind are:
- The boiling point of water: 100°C (212°F).
- The temperature at which foods are said to become "leukocytic" per Kouchakoff (the limitations/problems inherent in this approach are discussed elsewhere in this paper): approximately 90°C (194°F), though this temperature is said to vary with the particular food in question.
- The temperature at which foods are steamed (but not pressure-steamed): varies with the conditions the foods are steamed under, but may be near 100°C (212°F).
Thus one can argue for a definition of "cooked" in the range 90-100°C (194-212°F). For convenience here, we will adopt 95°C (203°F) as the standard for cooked food: at this temperature, food is "cooked" according to criteria that many raw-fooders share: most enzymes are degraded, and the food is leukocytic if one believes old research by Kouchakoff [1930, 1937].
Restating the claim in more precise language
We can now clarify the claim: Cooking food--heating it to 95°C (203°F)--will cause chemical changes to any/all organic molecules (present in the food) that include or are chemically bound to minerals, such that all the minerals in the organic compound(s) are converted into inorganic form (i.e., inorganic compounds and/or free ions). The term "mineral" as used here can follow either definition above.
At this point most readers with even a limited knowledge of organic chemistry are probably chuckling with mirth, as the claim is, quite frankly, ridiculous. However, let's continue to take it seriously, and thoroughly assess it.
Because the claim alleges that ALL minerals are converted to inorganic form, all that is needed to disprove it is a counterexample of an organic compound that includes a mineral (or metal) that is at least partially heat-stable at 95°C (203°F), i.e., can be heated to 95°C and does not completely break down. A few select counterexamples follow.
Metals
Cobalt is a metal, hence a mineral by definition (1) above, but not necessarily by definition (2) above. Cobalt is an essential part of cobalamin, a compound better known as vitamin B-12. Herbert et al. [1984] reports that vitamin B-12 was heated to 200°C (392°F) for 6 days, with only 15% loss. That is, 85% of the vitamin B-12 survived the heating. This is a counterexample to the claim above, since if the claim were true, 100% of the B-12 should degrade due to loss of cobalt.
Copper: For an example from the plant world, Neumann et al. [1995] discuss how the plant Armeria maritima binds a heavy metal (copper, from natural copper in the soil near a copper mine) into heat-stress proteins within the plant, which are stable and extracted for analysis at 95°C.
Non-metallic minerals
Sulfur: Two important sulfur-containing amino acids, methionine and cysteine (both found in many plant foods, see Giovanelli [1987]) survive--to a large extent--after cooking. See Clemente et al. [1998] and Chau et al. [1997] for two research papers reporting the survival of these amino acids with cooking. Note that although there is some loss of sulfur-based amino acids in cooking, the claim the cooking makes minerals inorganic, if it were true, would require (nearly) 100% loss of methionine and cysteine. As that does not happen, these two common amino acids are counterexamples to the claim. (Note: the claim, if it were true, would require the consumption of at least some raw (rather than cooked) protein, as otherwise all the sulfur-based amino acids would be lost, including methionine, an essential amino acid.)
Additional examples
Phytates and tannins are common antinutrient compounds in certain plant foods. Phytate contains phosphorus (a metal), and also forms complexes with metal ions. Phytates and the phytic acid-metal ion complex are only partially destroyed by heat. Similarly, various tannins are known for forming complexes with minerals/metals, especially iron, and for being at least partially heat-resistant. We conclude, in this case, that cooking makes part, but not all, of the minerals inorganic.
Without evidence, claims are simply speculation. The above counterexamples neatly disprove the claim. However, one might argue that disproof is not required here, because the promoters of the claim have never put forth any credible proof FOR the claim--they are simply speculating. Strictly speaking, the burden of proof is on those who make the claim, and in this case, no proof has ever been presented.
In order to understand this point, consider what credible proof for such a claim would look like. Basically, proof for the claim should be a voluminous database, whose entries would show:
- Chemical compound name.
- Specification of the minerals the compound contains--type(s), number of atoms of each mineral.
- Specification of the foods that contain the compound--with reference citations.
- Reference citations proving the compound degrades at (or below) a specific minimum cooking temperature, into inorganic compounds/ions and organic compounds that do not contain any minerals.
- The database should contain all known organic compounds that contain mineral atoms, in all foods of interest.
Obviously, developing such a database would be a very large research project. However, instead of the above credible proof, what the raw-fooder receives/offers as "proof" are the unsupported/unscientific assertions of alleged raw "experts."
Old, speculative, and/or unscientific claims often accepted as "raw truth" without evidence or proof. Now consider the apparent age of the claim, and that the claim has been not only uncritically accepted but, further, actively promulgated down to the present day by raw "experts," despite the apparent lack of even a semblance of legitimate scientific proof. Consider the credibility of the raw diet "experts" who promote as "fact" what is really unsupported speculation on their part. What does this suggest about their credibility on other points, especially if they claim that their raw diets are cure-alls, will work for everyone, are "ideal," etc.?
The above is just one example of the burden of proof--when you hear raw "experts" claiming that "spices are toxic," "wheatgrass juice is toxic," etc., the burden of proof is on those making the claims. Also, due to the prevalence of crank science in raw, it is wise to check any "proofs" offered up by the "experts," if any are given. An interesting situation highlighted by the issue of burden-of-proof is that some of the allegedly "scientific" raw vegan "experts" accept the claim above with no proof whatsoever, while simultaneously angrily demanding "proof" for every criticism of their diet. Is that irony, hypocrisy, or both?
| Rationalizations to defend the claim |
As convenient rationalizations are easily spun when idealistic theories are at issue, two potential rationalizations to watch for here are:
RATIONALIZATION: The counterexamples cited above were not heated high enough. If you heat something hot enough, it will turn to ash and the minerals will then be inorganic.
REPLY: This is an attempt to change the claim. The claim is that cooking converts minerals to inorganic form, not that incineration converts minerals to inorganic form. It is true that given enough heat, carbon can be driven off and one gets an inorganic molecule. However, there is a big difference between cooking something via baking, and heating it to the point that the item is incinerated. As mentioned above, phytate is an antinutrient that contains phosphorus. Phytate is common in wheat, and sufficiently heat-stable that significant quantities of phytate can and do survive the bread-baking process [Buonocore et al. 1977]. Hence phytate provides a counterexample to the claim.
RATIONALIZATION: The claim is not ALL minerals, but only that MOST minerals are converted to inorganic form by cooking.
REPLY: This is really speculation; once again, the burden of proof is on those who make this claim. Without a comprehensive database of organic compounds in foods that contain minerals, and information on the temperatures at which they break down into inorganic forms, one cannot even say "MOST."
Absorption of organic and inorganic
minerals in the human body |
It is appropriate to briefly comment on the topic of minerals in the human body. The human body includes both:
- Organic minerals, e.g., hemoglobin contains iron; many amino acids and proteins contain sulfur; as well as
- Inorganic minerals, e.g., salt--sodium chloride--in the blood, lymph, and many other body fluids.
Obviously, you would die without hemoglobin (organic iron) and salt (inorganic sodium, a metal/mineral). Additionally, the body can certainly use inorganic iron; see Fomon et al. [1995], Abrams et al. [1996], and Cook and Reddy [1995] for experimental verification.
Thus we note that the body needs and/or can use both organic and inorganic minerals, and the raw-foodist claim that the body cannot use any/all inorganic minerals is simply nonsense. Once again, the burden of proof applies to those who make this claim.
Are inorganic minerals "toxic"? Some raw-fooders make the extreme claim that all inorganic minerals are "toxic." (And note here that, as with the failure to define "organic" vs. "inorganic," advocates are usually also quite sloppy in their use of the word "toxic.") Such claims are an example of the narrow, binary thinking common in the raw community. The fact that a substance (e.g., a specific inorganic mineral) is toxic in isolation and in huge doses does not mean it is toxic at the levels encountered in a particular food, nor does it mean the food is "toxic." One should beware of the raw "experts" who see toxins everywhere, except, of course, in the very few foods they promote.
Conclusion on the nutritiousness
of raw vs. cooked food
Considering trade-offs rather than spurious black-and-white divisions. We see from the many considerations above that there is no clear-cut conclusion that can be stated with confidence about the question of raw vs. cooked foods as a whole. However, if we break the question down into simpler aspects, there are several general observations that can be made. First, the two major overarching considerations are:
- Amount of nutrients in a food (the potential "benefit"). First, virtually all foods contain more nutrients in the raw state. On the other hand, the differences are not very great: ranging from approximately 10-25% in the case of most vitamins, while the difference is negligible (almost zero) with respect to minerals.
- "Cost" to obtain the nutrients. However, there are also digestibility, antinutrients/toxicity, and bioavailability to take into consideration when assessing how many nutrients can actually be assimiliated from a particular food. Cooking can affect these considerations positively or negatively, depending on the circumstance.
"Net value" of a food depends on assessing the cost/benefit trade-offs. Putting the two above points together means that one must consider the cost/benefit trade-offs--that is, the nutrients present vs. the "cost" to get them--the latter determined by both absorbability and antinutrient concerns.
- Fruits can and do contain tannins, which are potent enzyme inhibitors and can cause unwanted side-effects when consumed in large quantities [Mehansho et al. 1987, as cited in Etzel 1993]. However, the levels of tannins in ripe juicy fruits are generally low, and as cooking decreases the vitamin content and has only limited impact on tannin content, these will be better eaten raw.
- Meat. The organs of many animals (as well as human blood and urine) contain proteinase inhibitors [Vogel et al. 1968]. This suggests that raw (muscle) meats may contain some proteinase inhibitors as well. However overall, whether cooked or raw, meat is generally easy to digest especially when considered in terms of the high bioavailability of a range of nutrients (iron, zinc, vitamin A, taurine, protein, essential fatty acids). Raw meat can also contain parasites. However, the cooking of meats creates substances such as HCAs with potential carcinogenicity, though this is probably a concern primarily with high-temperature cooking. Aged or cured meats are said to be particularly easy to digest, and are prized in some cultures. Hence the tradeoff, raw vs. cooked, is not so clear for meat. More research would be desirable here.
- With vegetables it depends on the specific item in question. One consideration here is that bioavailability of beta-carotene is generally low from raw vegetables and is improved by steaming (i.e., in carrots for example). However, one must also weigh this against cooking's effects in decreasing other vitamin levels, though since the effect is relatively modest (perhaps a 10-25% loss) in most cases, the decision is not always a clear one.
- Virtually all grains, legumes, and starchy tubers (potatoes, sweet potatoes) have a better net value when cooked. (Sprouting is another possibility, but may also greatly change nutrient composition. For example, while on a dry-weight basis [i.e., measured after complete dehydration], sprouting of wheat increases protein content (and also vitamin content), on a wet-weight (fresh) basis, protein content considerably decreases, as does caloric value, for example. The situation is difficult to evaluate because of somewhat limited available data on sprouts. But in general, the basic picture is that while sprouting may increase the digestibility of a range of nutrients, at the same time it also increases water levels which dilutes their concentration [Vanderstoep 1981].
- Nuts can contain trypsin inhibitors, lectins, saponin, and phytate; see Makkar et al. [1998] for a specific example. Conservative cooking may increase protein digestibility by deactivating heat-labile antinutrients (trypsin inhibitors, lectins), and by increasing protein digestibility. Sprouting of nuts (when feasible) should have an effect similar to that observed with grains and legumes, but nutritional data on sprouted nuts are not available to confirm. Overall, however, it is unclear at what level trypsin inhibitors, lectins, saponin, and phytate occur in nuts generally, and thus whether they constitute much of a problem, considering that most people seem to handle nuts well raw, with some exceptions of course. The antinutrient question with nuts is an area we hope to be able to resolve in more detail at a future date, at which time an update and/or new section on them for this paper will be provided.
- No one-size-fits-all answer. The nutritiousness of a given food may or may not be improved by cooking, or only by certain methods of cooking. There may be an ideal temperature, or an ideal cooking time.
- Caloric considerations on high-bulk all-raw diets. An additional issue is the difficulty on all-raw vegan diets of getting enough calories due to bulk. (See The Calorie Paradox of Raw Veganism for an examination of this problem, and why so many raw-fooders end up emaciated or hungry all the time.) Cooking coarse veggies makes them softer, and easier to eat more. While this might make overeating easier, it also allows one to get more nutrients as well. Most vegetables provide, on a caloric basis, relatively little nutrition and thus require consumption of very large amounts daily if one bases their diet primarily around them. It is hard to eat nutritionally significant amounts of coarse veggies when raw--but it's easier when cooked.
- Cooking's role given safety issues under modern conditions. In our modern day and age with less-than-ideal livestock practices, there can be obvious safety considerations with eating meats raw (even though the nutritional content and bioavailability is higher) due to concerns about parasites or bacteria when eaten uncooked. Thus, some compromise may be necessary. (Also, as we will see in Part 3, hunter-gatherers typically cook most of their meats, and have excellent general health.)
- Raw idealism about nature vs. real-world practicalities encountered by actual hunter-gatherers. Some will say that if a food cannot be eaten raw, it should be avoided. However, as we will see in Part 3 with hunter-gatherers living in the wild, this may restrict the diet to the point of unsustainability. Eating totally raw is not necessarily realistic even under more "natural" conditions of living off the land when's one life is dependent on using what is available in one's immediate environment.
- Cooking in the context of other "simple," "natural" processing techniques. Finally, to put cooking in a broader perspective, many other processing techniques have been used by humans to improve digestibility, such as soaking, sprouting, fermentation, aging, leaching of toxins and antinutrients, acid or alkaline treatment, etc. Cooking is sometimes helpful--overdoing it isn't. Obviously, whenever a food can be eaten raw with better results, it is preferable to do so and to be recommended.
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