If you have been alive more than 40 years, you have experienced both the low carb and high carb diet craze. Which is right or best for you? Before deciding that it is important to understand what a carbohydrate is, why it is necessary and where things can go wrong.
While different types of carbohydrates from whole-grain bread, cereal, and potatoes to fruit, candy, and soda are digested and absorbed a little differently, they are all made of carbon and hydrogen molecules. And they are all eventually broken down into glucose, the simplest form of sugar the body can use. As soon as the liver finishes converting dietary carbohydrates into glucose, this simple fuel is either burned for immediate energy, stored in the liver or muscles as glycogen (the storage form of glucose), or converted into triglycerides and stored as fat.
The total amount of glucose found in the bloodstream of a healthy human is only a teaspoon (for the metric-minded that’s about five grams). Anything above this amount becomes toxic. If you have 1¼ teaspoons of glucose in your bloodstream, you would be considered diabetic. If the amount drops to ¾ of a teaspoon, you would pass out from severe hypoglycemia (low blood sugar).
Achieving and maintaining a healthy blood sugar level is a delicate balancing act. From an evolutionary perspective, it’s one that has been handled extremely well by the body’s internal, metabolic processes–not from the constant supply of dietary carbohydrates we have become increasingly reliant on as a primary fuel source.
In the United States, the Standard American Diet (SAD) is now dominated by carbohydrates in the form of processed grains and sugars. The massive increase in their consumption over the past 100 years has been definitively linked to the onset of most “modern,” chronic disease.
Grains were introduced to the human diet a mere 10,000 years ago–which is a few, short seconds when considered in an evolutionary context. From an ancestral standpoint, excessive carbohydrate consumption wasn’t a problem for millions of years. Until very recently, humans just didn’t have access to simple carbohydrates. It’s now widely known that an excessive carbohydrate intake can lead to obesity, diabetes, and heart disease. High blood glucose (the inevitable result of an excessive carbohydrate intake) also contributes to systemic inflammation, which will negatively impact a woman’s ability to recover from an illness or injury, even if she’s not suffering from a chronic disease.
Your specific level of activity will, of course, influence the amount of glucose your body requires. But from a health perspective, even the most active of athletes would benefit from reducing their body’s dependence on it. Ingesting carbohydrates (in any form) causes blood sugar to rise. In response, the pancreas produces insulin—a hormone that encourages the cells to absorb the sugar for either energy or storage, depending on what the body’s needs are at the time.
In many ways, Insulin functions as a high-level manager, directing the transport of myriad nutrients and hormones to their intended organs and storage depots. Its primary goal is to deplete the bloodstream of available (glucose-based) energy by making sure it goes somewhere and it gets there fast in order to prevent toxicity. It speeds glucose into the cells and targets any excess for (glycogen) storage in the liver. It shuttles amino acids into the muscles. And it locks triglycerides (the storage form of fat) into fat cells.
If insulin becomes chronically elevated, however, the cells start to “tune out” its instructions. They become insulin resistant when they lock down and stop recognizing and processing glucose entirely. When insulin resistant, the body demands an ever-increasing amount of insulin to manage its resulting glucose surplus. Part of the master plan includes encouraging the body to make more fat, which gives glucose, in the form of triglycerides, a place to go. But these new, insulin-inspired fat cells produce estrogen, a female hormone that specializes in convincing the body it should produce and store even more fat.
Unfortunately, this isn’t your ordinary, run-of-the-mill body fat–the annoying but inactive variety that takes up residence in the thighs, waist, and bottom. It’s inflammatory fat–the invisible fat that infiltrates the intestinal lining, the liver, the kidneys, and even the heart. Inflammatory fat is metabolically active; it produces signals called cytokines which create even more inflammation, further disrupting and diminishing the body’s overall capacity for health and wellness.
Clearly, high blood sugar isn’t a good thing. But what happens if your blood sugar drops too low?
The fear of “bonking” has made many athletes—both male and female—become overly reliant on carbohydrate-based fuel. But it’s important to realize that low blood sugar is a relatively easy problem for the body to solve. Even in the complete absence of dietary carbohydrates, the metabolic processes of gluconeogenesis and ketosis can adequately meet the body’s energy needs.
While the initial symptom of low blood sugar is usually hunger, some people experience fatigue, sugar cravings, lightheadedness, and/or a decrease in focus and concentration first. When the body is required to deal with frequent and ongoing bouts of hunger, it experiences system-wide stress which increases cortisol and triggers the body’s “fight or flight” response. Cortisol lowers glutathione—an antioxidant which not only aids in fat metabolism, but in muscular recovery, immunity, and cognitive function.
The repetitive rise and fall of blood sugar (and insulin) can literally wear your body down. In fact, insulin fluctuations have been shown to accelerate the rate of cellular division which leads to premature aging and a significantly reduced capacity for health, performance, and recovery.
In all fairness, it’s important to acknowledge that the brain does rely primarily on glucose to function (although it doesn’t have to). And it’s the preferred form of fuel for muscles exercising at medium to high intensity. For these reasons, conventional dietary recommendations for athletes are typically skewed toward a higher carbohydrate intake.
But the body’s ability to store glucose is extremely limited–similar to the size of a tiny coat closet in the entryway of a large house. Since it’s burned quickly, it needs to be replenished frequently. So it’s not an efficient fuel. And the repetitive intake of excess glucose (more than the body can immediately use) promotes systemic inflammation, suppressed immune function, and a general state of unwellness.
So how many carbohydrates do you need? The answer can vary greatly from one person to another. Your age and activity level are key considerations. If you are recovering from a recent illness or injury, your body’s need for “easy” energy will be greater. And after a return to regular training, specifics need for carbohydrates will likely change again.
As a very general guideline, the brain and other key organs require about 150 grams of carbohydrate a day to sustain their basic functions. But becoming a fat adapted can significantly reduce the body’s reliance on glucose as a primary source of fuel. In fact, an extremely limited carbohydrate intake (50 or fewer grams a day) will force the body into the metabolic state known as ketosis, in which it burns fat as it’s primary source of fuel.
The Glycemic Index
The more rapidly a carbohydrate is broken down, the higher its glycemic index or GI—the relative ranking of carbohydrate-based foods according to how quickly they increase blood glucose levels. Carbohydrates with a GI value of 55 or less are more slowly digested, absorbed, and metabolized. This means they cause a lower and slower rise in blood glucose and insulin levels. In general, carbohydrates that are less-processed and higher in fiber will contain a more complex carbohydrate structure and lower GI index.
A whole orange, for example, takes some time to eat and is rich in fiber (pulp) so it has a much lower GI index than a glass of orange juice which can contain the amount of carbohydrates found in two or three oranges and can be consumed in less than a minute. Steel cut oats, which require 30 minutes of stove top cooking and are rich in fiber, have a very low GI; rolled oats (which have less fiber and fewer nutrients) have a moderate index, and instant oats (which have had most of their fiber and nutrients processed away) are scored very high.
The vast majority of the time, we want to eat slower-digesting carbohydrates not only because they keep us feeling full for a longer period of time, but because they release their energy more evenly and gradually. The best sources of these complex carbohydrates are whole vegetables and fruits (but not juices). Simple carbohydrates stimulate (instead of satiate) the appetite, are digested quickly, and generally devoid of any significant nutrient value. As a result, they create rapid and unwanted fluctuations in blood sugar and insulin levels.
You may be surprised to learn that many gluten-free foods often have a very high glycemic index. While the gluten-free lifestyle has become increasingly popular for a variety of legitimate health and performance concerns, be wary of products that feature processed grains, starches, and sugars. While they may be gluten-free, they are not necessarily healthy.
You may also be surprised to learn that whole-wheat breads and pastas raise blood sugar and insulin higher than a Milky Way or Snicker’s Bar. Believe it or not, these candy bars contain enough protein and fat to slow the digestion and absorption of sugar into the bloodstream. It’s a little disconcerting to think that some seemingly well-intentioned dietary advice (eat more “healthy” whole grains) has played a major role in the decline of our society’s general health and well-being. And the pervasive presence of fructose, which is found in everything from sodas to sausages, has compounded the problem.
A century ago, the average American consumed about 15 grams of fructose a day, which came from eating fresh fruits and vegetables (along with the fiber, vitamins, minerals, enzymes, and other beneficial nutrients they contain). The average American now consumes about 75 grams of fructose a day, much of it in the form of high-fructose corn syrup. While high-fructose corn syrup doesn’t cause a large spike in blood sugar (because it has to be metabolized by the liver), it’s turned into inflammatory fat far more rapidly than any other type of sugar.
Pay close attention to the fact that large amounts of fructose can be found in more than just high-fructose corn syrup. Agave nectar, which has been successfully marketed as a “healthier” alternative to sugar, is actually 90 percent fructose. Regular corn syrup, honey, cane sugar, maple syrup, and many fruits are just 50 percent fructose by comparison.