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The Fourth Macronutrient
For decades now our ability to grasp the rapid rise in obesity and type-2 diabetes has been hampered by an illusion, our belief in a principle seemingly so basic that we’ve taken it for granted, much like we once took for granted that the earth was the center of the universe. It’s the illusion of the three energy-yielding macronutrients.

We use the term macronutrient to denote nutrients we consume in greatest quantities and from which we obtain calories. Protein, fat, and carbohydrate are these three pillars of nutrition. What could be more obvious? We teach the principle of the three macronutrients in nutrition classes and treat it as a given whenever the topic turns to diet in casual conversation. We promote it as truth when we sell food and accept its certainty when considering every explanation of how diet impacts disease. But in reality, it’s false. In fact, routinely, in practical everyday life, it reveals itself to be false. We’re just not paying attention, and we continue to pay a high price for this lack of attention. 

The illusion of the three macronutrients is based on the simple observation that protein, fat, and carbohydrate serve as combustible fuels and at the same time perform distinctly different functions. The apparent truth of this observation is seemingly confirmed by our instincts, our natural desire to satisfy our need for protein, fat, and carbohydrate. On a daily basis we seek out these three macronutrients, and we assume that in doing so, the more subtle nutrients, the micronutrients (vitamins and minerals), will be covered and for the most part they are.

But it’s in this daily seeking out of proteins, fats, and, carbohydrates that the flaw in this well-accepted paradigm reveals itself. In fact, once in a while it becomes so obvious that it’s shocking to think that we’ve allowed this well-accepted notion to pass unchallenged for so long. What’s the observation we should be making? There aren’t three macronutrients, there are four: protein, fat, sugar, and starch. While both sugars and starches are indeed carbohydrates, the former acting as the subunit of the latter, they perform very different jobs, different enough to be separated as distinct macronutrients. Sugars provide glucose to cells. All digestible carbohydrates ultimately are converted to glucose, though when eaten to excess are converted to fat, just like protein and fat.

Starches are chains of glucose sugars that also provide glucose to cells, but the distinct and irreplaceable job of starch is to make muscle cells more responsive to insulin, and thus pull more glucose out of the blood, more so than would be possible if sugars alone were sources of glucose. Insulin is the hormone that controls the entrance of glucose into cells, particularly muscle cells. Since most of what muscle cells do with the glucose they draw from blood is to make glycogen, and since glycogen is the storage form of glucose that muscles tap into for explosive and sustaining movement, starch is critical to energy and endurance. Try to find a successful athlete who doesn’t rely on starch for stamina. Try to find a civilization that does not rely on starch as a staple. It’s only when the climate is severe and farming is impossible that humans are forced to abandon this critical food. So why haven’t we heard this before?

Whenever you hear a discussion of starch and what starch is and where you find starch, the discussion is always in regards to starch in the plant. But starch in the plant is useless unless it’s cooked. We don’t efficiently digest raw starch. Starchy foods must be cooked in water to reach the gelatinization point, usually a temperature slightly below the boiling point of water. It’s here where starch granules absorb water and burst into the soft and fluffy texture that our digestive system can handle. This is starch on the plate (or in the bowl) where it has its effect. However, drive off the water with the high temperatures and dry conditions of baking or frying, and starch loses its unique function. Baked and fried starches are effectively sugars in that they supply glucose to blood but fail to enhance the response of muscle cells to insulin. The reason is simple. Starch-digesting enzymes work only from the end of the starch chain, disassembling the chain in packman-like fashion, signaling the muscles to absorb more glucose from the blood in response to insulin. Baking and frying temperatures shatter the chain, disrupting this signal. Glucose is still provided but without the direction to increase its utilization by muscles. So in reality, the fourth macronutrient is the one we as a species created and adapted to--boiled starch. Only in this form can starch perform its critical function.

The reason we have not noticed this flaw in the three-macronutrient paradigm is that boiled starch has been so embedded in all cultural cuisines there was no reason to separate them as a distinct class of carbohydrates. Their value was understood intuitively, but rarely commented on. For example, few people know that in China, gruel made of steamed rice as a base along with some beans and vegetables is traditionally a highly valued and distinctive food. There is an art to making gruel, a food defined by method of cooking, considered food for health and longevity, and critical for the elderly and the infirm. Of course cultural cuisines long preceded the advent of modern nutrition, where such observations carry little weight.

Modern nutritional science reduces foods to components, which is critical in order to establish the basic biochemistry of nutrients and their role in metabolism. But there is at the same time a failure of perspective that subverts our ability to put together a coherent picture of carbohydrates. We’ve failed to step back and consider why so much of what we say about carbohydrates is inconsistent and often downright contradictory. We ignore the contradictions for one simple reason; we don’t think we can make fundamental errors anymore when it comes to nutrition, of at least when it comes to carbohydrates. We know glycemic index has little value because of the many variables that affect this vague measure, but we like the story we can tell with it and put up with the contradictions. We know the concept of good and bad carbs is childlike and simplistic because there is no good definition of a good or bad carb that holds up to scrutiny, but it’s familiar terminology, so we put up with the contradictions. We bought the idea that carbs are fattening, irrespective of the contradictions and now look for any excuse to justify that purchase.  

It’s easier to buy a trendy idea based on weak to non-existent evidence than to rethink a fundamental error in our approach to carbohydrate nutrition. How else can you explain our willingness to accept the scapegoating of carbohydrates by writers like Gary Taubes and Walter Willet as the reason for obesity and type 2 diabetes? Taubes reinvents biochemistry and misrepresents studies in order to sell us on the ridiculous notions that fat can’t pack on any weight, and that our only reason for eating carbohydrates results from addiction. Willet heads a relentless attack (from the Harvard School of Public Health, mind you) on foods like rice and potatoes, equating them with jellybeans based only on epidemiological associations that can’t separate method of preparation and can see no distinction between fast-food (French-fries) and traditional cuisine (potato soup).

Rice has fed populations for thousands of years without causing obesity and diabetes, and potatoes show no association with obesity and diabetes unless turned into fast-food icons laden with fat. But they have to be demonized to retain the illusion of the three macronutrients, one of which is highly flawed and under suspicion. They have to be demonized in order to cover up the sloppily reasoned indictments of carbohydrates that see sugar as toxic and starch as inherently fattening. It’s time to call out the contradictions. It’s a contradiction to call starch fattening and then push whole grains ignoring the fact that the source of energy in whole grains is starch. It’s a contradiction to talk about instincts with respect to nutrition and then ignore that there are times when our hunger for carbohydrates varies from the desire for something sweet to the need for something starchy, satisfying, and soothing. Carbohydrates aren’t the problem. The acceptance of a poorly thought-out paradigm that there are three macronutrients is the problem. We won’t emerge from the present epidemic of obesity until we come to grips with this simple fundamental error.

There is a light at the end of the tunnel!