Daily Carbohydrate Requirement: Are Carbs Essential or Not?
Let’s play a little game I call “spot what isn’t.” I want you to scan through the following list of essential nutrients (elements in your diet that are necessary for survival) and tell me if you see anything conspicuous by its absence.
Essential fatty acids (EFAs):
- Linoleic acid (omega-6)
- Linolenic acid (omega-3)
Essential amino acids:
- A (retinol)
- B1 (thiamine)
- B2 (riboflavin)
- B3 (niacin)
- B5 (panthothenic acid)
- B6 (pyridoxine)
- B12 (cyanocobalamine)
- C (ascorbic acid)
- D (ergocalciferol, or cholecalcierol)
- E (tocopherol)
- K (naphthoquinods)
- Biotin (vitamin B7, vitamin H)
- Folate (folic acid, vitamin B9, vitamin M)
- Choline (vitamin Bp)
Essential dietary minerals:
Come up with an answer yet? If not, keep looking: sometimes it’s not readily apparent. Still can’t tell? Well here’s a hint: you’ve been told for years to make this “non-essential” nutrient the central part of your diet.
Time’s up! If you’ve figured out the correct answer is “carbohydrates” then give yourself a reward!
Just don’t make it carbohydrate-based 😉
Now hold on just a minute, don’t we “need” carbohydrates for energy? Shouldn’t 50-60% of total calories be in the form of carbohydrates? Don’t we need 6-8 servings of grains/day?
Good questions, as I’m sure you’ve heard one or all the above statements at one point or another in your life. But when it comes to the “need” for carbohydrate in one’s diet, the reality is quite different.
Let’s look at the data.
Although I spend the majority of my days teaching people about nutrition and helping them get into the best shape of their lives, I do make time to stay current with nutritional science. For all you nutritional science geeks out there, I suggest you give the Dietary Reference Intake (DRI) reports a read (freely available online through the National Academies Press). This isn’t to suggest their information is the be-all and end-all of nutrition, far from it. However, after reading these documents you develop an understanding of the assumptions, both accurate and faulty, that form the basis of our current nutritional guidelines.
Any dietitian will happily inform you the minimum daily requirement for glucose is 130 grams. In fact, that’s the number quoted on page 265 of the Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). According to the DRI report, adults require this amount of glucose to allow the brain and central nervous system to operate.
Being scientifically inclined, I love the fact we have a concrete number to tell people. The obsession with prescribing nutrition based on ratios is truly idiotic. What good is telling someone that 50% of their energy should come from carbohydrates?
What happen when this person eats 1000 calories one day, then consumes 4000 calories the next? Does keeping their carbohydrate intake at 50% of total calories make any sense? Absolutely not.
Anyone worth their nutritional salt should shun lame ratios and use concrete numbers. Better yet, let’s counsel people using g/kg (or g/lbs) values to account for differences in body size. Oh look, a simple but effective approach to teach people about individualizing their nutrition – how novel!
Back to the 130 g of carbohydrate/day recommendation. Remember, this was labeled the minimum amount adults require to function. Except if you continue reading the DRI report, a mere 10 pages later (on page 275), our dear Academy writes:
“The lower limit of dietary carbohydrate compatible with life apparently is zero (my emphasis), 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).”
Hold on, I was just told I need at least 130 g of carbohydrate per day to ensure my minimum function. But then I’m told that if I consume zero grams of carbohydrates a day for up to a year and potentially my entire life time – I’ll be fine!??!? What kind of sketchy science is this?
Continuing to read the carbohydrate chapter a little further we get this nugget:
“In the absence of dietary carbohydrate, de novo synthesis of glucose requires amino acids derived from the hydrolysis of endogenous or dietary protein or glycerol derived from fat. Therefore, the marginal amount of carbohydrate required in the diet in an energy-balanced state is conditional and dependent upon the remaining composition of the diet.”
In other words, when you aren’t consuming a ton of dietary carbohydrate, your liver makes whatever glucose your system needs from dietary fats and protein. Furthermore, despite claims that your brain “exclusively” runs off carbohydrates, it can derive up to 80% of its energy requirement from ketone bodies, by-products of fat metabolism, dropping its absolute carbohydrate needs to around 25 g/day (Cahill et al., 1973) – or the equivalent of 1 banana.
Obviously, this is an extreme example and I’m not about to suggest you cut any and all carbohydrates from your diet. However, science clearly shows that anyone wanting to follow an essentially carbohydrate-free diet will not endanger their health.
In fact, assuming you get a few carbohydrates from vegetable matter, they’ll quite likely do just fine.
Score one for Dr. Atkins!
Although life can happily hum along with you eating only 25 g of carbohydrate a day, this strategy is not in most people’s best interest.
Truth be told, carbohydrates are one of the most important tools for active people to help them build a “drop ‘em dead” physique due to their effects on insulin, leptin and thyroid hormones (not to mention they contain fibre, vitamins, minerals and a host of antioxidants).
But when over-consumed without rhyme or reason, carbohydrates promote fat storage, elevate triglycerides, promote inflammation, cause fatigue and accelerate aging.
Clearly, carbohydrates are not something to play around with!
To get you started figuring when you need carbohydrates, let’s review a brilliant study completed over 15 years ago by Romijin et al. These researchers took a group of men and exercised them for 30 minutes at various exercise intensities, to determine how fuel use differs with exercise intensity.
The three intensities they investigated were 25% of VO2 max (the intensity of walking), 65% of VO2 max (intensity of a slow jog) and 85% of VO2 max (intensity of a fast jog).
Romijn et al. 1993
What they found is that during low intensity activities, the vast majority of energy needs are met through fat oxidation (burning of plasma free fatty acids). At moderate intensity exercise, fat still forms the greatest percentage of energy provision (plasma FFA + muscle triglyceride), but carbohydrate oxidation (plasma glucose + muscle glycogen) becomes significant.
The fact that fat forms a greater percentage of energy burned in moderate intensity activity is where the flawed concept of “fat-burning zone” training comes from, but I’ll address that topic in a future article. Finally, during higher intensity exercise, the major source of energy comes from carbohydrate stored in the muscle.
Incidentally, these same researchers completed a very similar study 7 years later using females and basically found the exact same pattern.
Ok – two really critical points to take away from this study.
- If you are using exercise to help you lose weight, you need to train at a greater intensity – not in some lazy-ass “fat-burning zone”. Burning more calories/minute of exercise is what is important
- During low intensity activity, almost all your energy needs are met through burning fat.
Read that last sentence again. Now one more time. Good.
Reality check: what percentage of your day is spent performing low-intensity activity? You know the stuff I’m referring to: sitting at a desk, sleeping, driving your car, eating… you get the idea.
Would it be a fair assumption on my part to say you probably spend most, if not all, of your 24 hours each day in low-intensity activity. If that’s the case… why the hell are you making carbohydrates the centerpiece of your diet?!?!
Really makes you wonder why our food guides recommend we get 50-60% of total energy from carbohydrates or stress that you need 8 servings of grains/day. These recommendation clearly have nothing to do with physiological reality.
Admittedly, some people require, and thrive, on a higher carbohydrate diet. Active growth and intense physical activity are two scenarios that merit a substantial amount of energy, energy requirements that can be satisfied with starchy carbohydrate. Therefore if you fall in one of the following categories:
- growing child
- pregnant female
- chronically lean person who struggles to maintain body weight
- avid exerciser looking to increase muscle mass
- elite athlete
Then feel free to make starchy carbohydrates the centerpiece of your diet. However, these people are the exception, not the rule.
Not only are most North Americans too sedentary, but few are genetically blessed with being able to handle repeated high glucose loads over a lifetime. The standard North American diet (high in simple sugars, grains, omega 6 fats, HFCS, unnatural levels of saturated fats and chemical additives) has crippled our ability to properly regulate insulin and carbohydrates metabolism.
It is therefore unsurprisingly that we’ve seen a dramatic increase in the rates of type II diabetes and obesity, even in children! With obesity rates having doubled over the past 30 years in North America, the situation is grave indeed.
Unfortunately, the majority of the North Americans (remember, 67% of North Americans are over-fat) don’t need the quick energy that comes from a predominantly grain- and sugar-based diet.
In fact, they need the direct opposite.
The typical North American needs foods that produce energy very slowly: protein, healthy fats, high fibre vegetables and fruits, legumes and a small amount of grain.
What advice should nutritionists be giving people in regards to carbohydrate intake? The singular best piece of advice I’ve ever heard comes by way of Dr. John Berardi. One of his favourite sayings is, “earn your starchy carbohydrates.” In other words, starchy carbohydrates like breads, pastas, rices and potato are best to eat AFTER an intense workout.
Remember, during intense physical activity we deplete a significant amount of muscle glycogen, giving us a place to store new carbohydrates. However, on days we haven’t performed any intense physical activity, we don’t have room to store excess carbohydrates in our muscle, so we tend to store high-carbohydrate meals as fat!
“Earn your carbohydrates” – the simplest diet advice ever dreamed up, but probably the most powerful in terms of helping turn your body into an efficient far-burning machine.
Keep in mind this “carbs post-workout” mantra applies to starchy and sugary carbohydrates. The rest of our daily carbohydrates should consist of vegetables, berries, nuts and fruit(in that order) and possibly dairy depending your tolerance for it.
For all you number crunches who want a starchy carbohydrate goal post-workout, start with
0.8 g -1 g of carbohydrate/kg of body weight
As an example, if you weigh 90 kg like I do, you could eat 72-90 g of carbohydrates in a post-workout meal. In real-world numbers, this works out to be 2 cups of cooked rice or pasta.
Nothing more complicated than that.
Couple those carbs with some protein (a meal containing 2-3x more carbohydrates than protein typically yields the best results), and you’ll be well on your way to transforming your health.
Instead of having that bowl of cereal for breakfast, a sandwich for lunch and pasta for dinner, think about “earning your carbohydrates” and see if that one small change in thinking doesn’t help you reel in your expanding waistline.
Remember, when it comes to your body and your health, “good enough”, isn’t.
Cahill GF, Aoki TT, Ruderman NB. (1973). Ketosis. Trans Am Clin Climatol Assoc 84:184–202.
National Academy of Sciences. (2005). Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (Macronutrients). National Academies Press.
Romijn JA et al. (1993). Regulation of endogenous fat and carbohydrate metabolism in relation to exercise intensity and duration. American Journal of Physiology: Endocrinology and Metabolism, 265, E380-391.