For my first review of nutrition guidelines, I grade the Institute of Medicine of the National Academies based on its carbohydrate Recommended Daily Allowance (RDA), the Academy of Nutrition and Dietetics (formerly the American Dietetic Association), and the American Diabetes Association (ADA).
The AND says everyone should eat a minimum 130 grams of carbohydrate a day. The American Diabetes Association cites the IoM carbohydrate RDA of 130 g a day and has no position on the maximum amount of carbs diabetics should eat. Isn’t diabetes a disease of carbohydrate metabolism? Isn’t this like telling lung cancer patients to eat a minimum number of cigarettes a day, and no maximum?
It turns out that AND and the ADA both rely on the carbohydrate RDA “set” by the august Institute of Medicine (IoM) of the National Academies, a U.S. government body, as the source for their 130 grams/day minimum carbohydrate requirement. In rocket science parlance, we call this a root cause – everyone relies on the same source for how much carbohydrate we should eat.
Institute of Medicine
The carbohydrate RDA came from IoM. So how did IoM come up with it? Is there some essential nutrient that we can get only if we eat this much carbohydrate? Was the consequences of eating this much carbohydrate weighed against whatever benefit there might be? I would have thought that these would have been carefully considered.
IoM explains how it “set” its carbohydrate RDA in its Dietary Reference Intakes (the DRI), Chapter 6, “Dietary Carbohydrates: Sugars and Starches”. The quotes below are taken directly from this chapter. My irreverent comments are in blue.
From the summary:
“The primary role of carbohydrates (sugars and starches) is to provide energy to cells in the body, particularly the brain, which is the only carbohydrate-dependent organ in the body.”
The DRI later points out that the brain does not require ANY ingested (exogenous) carbohydrate – it can get ALL the carbohydrate it needs from conversion of ingested fat and protein (endogenous carbohydrate).
“Gluconeogenesis. Glucose can be synthesized via gluconeogenesis, a metabolic pathway that requires energy. Gluconeogenesis in the liver and renal cortex is inhibited via insulin following the consumption of carbohydrates and is activated during fasting, allowing the liver to continue to release glucose to maintain adequate blood glucose concentrations.”
Glucose is formed from protein and fat through gluconeogenesis.
“Clinical Effects of Inadequate Intake”
“The lower limit of dietary carbohydrate compatible with life apparently is zero, provided that adequate amounts of protein and fat are consumed. However, the amount of dietary carbohydrate that provides for optimal health in humans is unknown. There are traditional populations that ingested a high fat, high protein diet containing only a minimal amount of carbohydrate for extended periods of time (Masai), and in some cases for a lifetime after infancy (Alaska and Greenland Natives, Inuits, and Pampas indigenous people) (Du Bois, 1928; Heinbecker, 1928). There was no apparent effect on health or longevity. Caucasians eating an essentially carbohydrate-free diet, resembling that of Greenland natives, for a year tolerated the diet quite well (Du Bois, 1928). However, a detailed modern comparison with populations ingesting the majority of food energy as carbohydrate has never been done.”
I’m not making this up. The report everyone relies on for the requirement of eating 130 grams of carbohydrate says we can live with NO carbohydrates. In fact, when the indigenous peoples referred to above start eating Western high carb, low fat diets, they inevitably start coming down with the many diseases of Western civilization they didn’t have before, like diabetes, heart disease, cancer, strokes, Alzheimer’s, etc. The optimal amount of carbohydrate is UNKNOWN according to the DRI – which goes on to say everyone should eat 130g/day!
“It has been shown that rats and chickens grow and mature successfully on a carbohydrate-free diet (Brito et al., 1992; Renner and Elcombe, 1964), but only if adequate protein and glycerol from triacylglycerols are provided in the diet as substrates for gluconeogenesis. It has also been shown that rats grow and thrive on a 70 percent protein, carbohydrate-free diet (Gannon et al., 1985). Azar and Bloom (1963) also reported that nitrogen balance in adults ingesting a carbohydrate-free diet required the ingestion of 100 to 150 g of protein daily. This, plus the glycerol obtained from triacylglycerol in the diet, presumably supplied adequate substrate for gluconeogenesis and thus provided at least a minimal amount of completely oxidizable glucose. The ability of humans to starve for weeks after endogenous glycogen supplies are essentially exhausted is also indicative of the ability of humans to survive without an exogenous supply of glucose or monosaccharides convertible to glucose in the liver (fructose and galactose). However, adaptation to a fat and protein fuel requires considerable metabolic adjustments.”
So why do we need to eat ANY carbs?
The minimal amount of carbohydrate required, either from endogenous [made inside the body from fat and protein] or exogenous [from what we eat] sources, is determined by the brain’s requirement for glucose. The brain is the only true carbohydrate-dependent organ in that it oxidizes glucose completely to carbon dioxide and water. Normally, the brain uses glucose almost exclusively for its energy needs. … The requirement for glucose has been reported to be approximately 110 to 140 g/d in adults (Cahill et al., 1968). Nevertheless, even the brain can adapt to a carbohydrate-free, energy-sufficient diet, or to starvation, by utilizing ketoacids for part of its fuel requirements. When glucose production or availability decreases below that required for the complete energy requirements for the brain, there is a rise in ketoacid production in the liver in order to provide the brain with an alternative fuel. This has been referred to as “ketosis.”
“The required amount of glucose could be derived easily from ingested protein alone if the individual was ingesting a carbohydrate-free, but energy-adequate diet containing protein sufficient for nitrogen balance.”
In other words, we don’t need to eat any carbs, PERIOD.
Now we get to the section where the minimum daily carbohydrate requirement is “set” by our government. An interesting word they use – they don’t “determine” what it should be, they “set” it!
“Glucose Utilization by the Brain. Long-term data in Westernized populations, which could determine the minimal amount of carbohydrate compatible with metabolic requirements and for optimization of health, are not available. Therefore, it is provisionally suggested that an EAR [Estimated Average Requirement] for carbohydrate ingestion in the context of overall food energy sufficiency be based on an amount of digestible carbohydrate that would provide the brain (i.e., central nervous system) with an adequate supply of glucose fuel without the requirement for additional glucose production from ingested protein or triacylglycerols.”
WHOA! Here’s the disconnect! They acknowledge that NO digestible carbohydrates are necessary for brain function – this is widely known and not in contention. The body can manufacture all the carbohydrate the brain needs from ingested fat and protein. Then they say there’s no long term data. Next we have the “Therefore”. Normally what follows “Therefore” is some consequence of what precedes the word “Therefore.” Not in this case. They ARBITRARILY base required exogenous carbohydrate (what we need to eat) on the total amount of carbohydrate required by the brain, which can use both exogenous and endogenous (created from fat and protein) carbohydrate. Amazing. Let’s see what happens to “provisionally suggested”.
“In summary, the EAR [Estimated Average Requirement] for total carbohydrate is set at 100 g/d. This amount should be sufficient to fuel central nervous system cells without having to rely on a partial replacement of glucose by ketoacids. Although the latter are used by the brain in a concentration-dependent fashion (Sokoloff, 1973), their utilization only becomes quantitatively significant when the supply of glucose is considerably reduced and their circulating concentration has increased several-fold over that present after an overnight fast.”
“The RDA [Recommended Daily Allowance] for carbohydrate is set by using a CV [coefficient variation] of 15 percent based on the variation in brain glucose utilization. The RDA is defined as equal to the EAR plus twice the CV to cover the needs of 97 to 98 percent of the individuals in the group (therefore, for carbohydrate the RDA is 130 percent of the EAR).”
A “provisionally suggested” requirement that was arbitrarily selected has been “set” as a real requirement for Americans, regardless of their individual ability to metabolize carbs!
This is Totally Bogus (TB). Note there was no reference AT ANY POINT to populations with serious carbohydrate metabolism problems, namely diabetics and those with metabolic syndrome (as much as half the population of the US).
So what does the American Diabetes Association do with this TB RDA? They imply diabetics should have AT LEAST 130 grams of carbs a day based on it. One would think they would balance any real need for carbs (of course, it has not been demonstrated there is any need for carbs at all – quite the contrary) against the cost of drugs to control blood glucose, the cost of medical care to monitor these increased drugs, and the increased risk of diabetes complications from out-of-control blood glucose and from hyperinsulinemia (excessively high levels of insulin). But no – ADA just repeats the TB IoM RDA. ADA dieticians are out pushing carbs and ADA is pushing drugs to control the problems caused by the carbs. I suppose we shouldn’t be surprised – ADA gets lots of money from drug companies.
Some of the consequences of this TB RDA: ADA dietitians use it as an excuse to tell diabetics to eat loads of carbs. AND puts starchy foods on top of its list of food for diabetics. Abott Laboratories puts maltodextrin, a rapidly digestible carb, into Glucerna shakes “designed for diabetics.”
My grade to IoM for its carbohydrate RDA: F
American Diabetes Association
The ADA recently made two major changes in its guidelines. In 2008, it removed its statement that low carbohydrate diets should not be used by diabetics. Its 2012 Standards of Care say that for weight loss, either low carbohydrate, low-fat calorie restricted, or Mediterranean diets are effective in the short-term (up to two years).It is now officially agnostic about diet, though there are inconsistencies with this policy on its web site and in recent position statements. The ADA is moving, albeit at glacial speed.
ADA Grade: F+ (shows improvement, but much more progress needed)
Academy of Nutrition and Dietetics
“Starchy foods” are at the top of the AND list of what diabetics SHOULD eat. ‘Nuff said.
AND Grade: F-
Last updated March 14, 2013