Could there possibly be a more controversial topic than how many carbs we should be eating?! One of the perks of following a Paleo framework is that when we maximize nutrient density (see The Importance of Nutrient Density) and eat high-quality foods from both the plant and animal kingdom, other elements of diet, like macronutrient ratios, tend to fall into place without us needing to obsessively count fat or carb grams. Still, considering how much bad press carbohydrates tend to get (as well as the tendency for the media—and even some leaders within the Paleo movement itself—to mis-portray Paleo as being low carb), a great deal of confusion exists surrounding optimal carb intake. What’s the scoop?
The short answer is… it depends! It depends on what our goals are, how far away we are from those goals, how active our lifestyles are, how well we sleep, how well-managed our stress is, and what health issues we might be dealing with. All of these factors can influence the healthiest level of carbs for our specific situation.
But, while there’s no one-size-fits-all recommendation we can all safely shoot for, we can definitely pull together some guidelines based on available evidence.
Let’s start with hunter-gatherers! According to Loren Cordain’s 2000 publication, “Plant-animal subsistence ratios and macronutrient energy estimations in worldwide hunter-gatherer diets” (which analyzed ethnographic data for 229 hunter-gatherer societies), the majority of hunter-gatherer populations ate between 22 and 40% of their diets as carbohydrates. That translates to 110 to 200 grams of carbohydrates per day on a 2000-calorie diet. There were a handful of societies falling outside that range, such as the lower-carb Inuit (3% calories as carbs) and some groups eating as high as 50% carbohydrates, but those were by far the exception rather than the rule. In general, hunter-gatherers living close to the equator had higher carbohydrate (and total plant food) intakes than populations living closer to polar regions, and virtually every group residing between 11 and 40 degrees north or south of the equator (equivalent to the range between the northern part of Colombia and New York City) ate between 30 to 35% carbohydrates as a percent of total calories. On a 2000-calorie diet, that comes out to 150 to 175 grams per day. (See “Carbs Vs. Protein Vs. Fat: Insight from Hunter-Gatherers” for more on macronutrient ratios in hunter-gatherer societies.) Some critics of the data (such as Katharine Milton) have pointed out that these carb levels could also be underestimated, due to a tendency for ethnographers to interact more with male hunters than female gatherers and consequently under-document the contribution of gathered plant foods. But, we can say with confidence that most hunter-gatherer groups eat about a third of their diet as carbohydrates, give or take!
Another way to frame the carbohydrate issue is to look at the bare minimum intake we’d need to get adequate daily fiber. (For a way more detailed rundown on why fiber is awesome, and why we need plenty of it in our diet, check out The Fiber Manifesto Part 1, Part 2, Part 3, Part 4, and Part 5, as well as Resistant Starch: It’s Not All Sunshine and Roses.) In short, fiber (especially antioxidant rich vegetable fiber) is critical for supporting gut health, promoting normal bowel movements, creating a healthy and diverse gut microbiome, protecting against many gut pathologies, regulating blood sugar, reducing inflammation, reducing the risk of certain cancers, and potentially even reducing the risk of heart disease and diabetes. It’s definitely not a nutrient we want to skimp on!
Current mainstream fiber recommendations are 25 grams per day for women and 30 to 38 grams per day for men. This is definitely less than what most Paleolithic and modern hunter-gatherers consumed (Boyd Eaton and Melvin Konner estimate 45.7 grams per day for a typical hunter-gatherer diet of 65% plant foods and Dr. Jeff Leach estimates that some hunter-gatherers eat as much as 200g of fiber per day), but we’ll use these numbers for the sake of illustration. If we look at non-starchy vegetables with the highest ratio of fiber to non-fiber carbohydrates, we see that spinach comes out near the top, with roughly half of its carbohydrates coming from fiber. In order to get 25 grams of fiber per day from spinach, our minimum carbohydrate intake would be 50 grams. (And for the record, using spinach, we’d need to eat about 45 cups of it (almost 3 pounds) to reach that level. That’s pretty ambitious, even for those of us who love veggies!)
Using this logic, carbohydrate intakes of less than 50 grams per day are almost guaranteed to shortchange us on fiber. And that’s assuming we eat nothing but the highest-fiber carbohydrate sources out there! When our diet includes starchier or more sugary carbohydrate sources like tubers and fruit, which have a lower ratio of fiber to non-fiber carbs (while also being denser fiber sources), the minimum total carbohydrates we need to eat to meet our fiber needs rises even higher. For example, you’d only need about 3.5 cups of baked sweet potato to get your 25 grams of fiber, but then of course, you’re looking at nearly 150g of total carbs.
Provided that your carbohydrates are coming from whole fruits and vegetables, the 100-200g range is probably adequate from a fiber consumption standpoint. Of course, if we’re keen to emulate hunter-gatherer fiber intake, it would be incredibly challenging to do so without total carbohydrate intake creeping up towards 300g or more!
Another consideration with optimizing carbohydrate intake is ensuring we avoid the effects of eating too much or too little of each macronutrient (not just carbohydrates, but also fat and protein). On one hand, an extremely high carbohydrate intake (more than 70% of calories) leaves less room for fat and protein in our diet, which creates its own set of problems. Inadequate fat can decrease our absorption of vitamins A, D, E, and K (which ultimately affect every system in our bodies), as well as deprive us of essential fatty acids (omega-3 and omega-6). Inadequate protein can reduce the preservation of lean muscle tissue, reduce our immune function, negatively affect our bone mineral density, and cause a host of other problems related to insufficient intakes of essential amino acids.
On the other hand, too little carbohydrate (with lots of protein and fat) could mean an insufficiency of not only fiber, but also of certain nutrients and phytochemicals found most abundantly in carbohydrate-rich foods (including vitamin C, polyphenols, chlorophyll, carotenoids, isothiocyanates, and organosulfur compounds, all of which play various roles in disease prevention). (See “The Amazing World of Plant Phytochemicals” for more on why plant foods rock!)The solution? We can balance our macronutrients by eating moderate amounts of carbohydrate, fat, and protein, rather than excessive or extremely limited levels of any single one. Returning to hunter-gatherers for a minute, Cordain’s analysis found that most populations consumed between 19 and 35% protein and 28 and 58% fat. Eating about a third of our diet as carbohydrates (about a third as protein and about a third as fat) fits in nicely with the patterns we’ve observed among healthy hunter-gatherers, and seems to be the sweet spot for optimizing vitamin, mineral, phytonutrient, fiber, essential amino acid, and essential fatty acid intake!
What About Ketogenic Diets?
Extremely low-carb ketogenic diets have gained quite a bit of popularity lately. This type of diet has long been used to manage epilepsy (and to a lesser extent, other neurological pathologies, though the research is more limited), and there’s some evidence that ketogenic diets could improve the outcome of certain cancers (although, importantly, not as a treatment for cancer categorically: some tumors become more aggressive when starved of glucose!). It’s definitely true that restricting carbohydrate intake to very low levels could have therapeutic benefits in some situations.
For most of us, though, extremely low-carb diets are neither necessary nor beneficial. Previously, I’ve written about the documented adverse effects of ketosis (see “Adverse Reactions to Ketogenic Diets: Caution Advised”). Along with reported gastrointestinal disturbances, impaired mood, hypoglycemia, kidney stones, increased susceptibility to infection, long QT intervals, hair loss, muscle cramps or weakness, impaired concentration, disordered mineral metabolism, increased fracture risk, and a shift towards atherogenic lipid profiles in some people, some potential issues require much more research than we currently have available before we fully understand the long-term effects of ketogenic diets. In particular, the impact on the gut microbiome (our gut health is strongly supported by fiber intake from carbohydrate-containing foods) and fertility in women without PCOS (the hormonal shifts seen in very low-carb diets can be beneficial for women with PCOS but problematic for those whose hormone levels are normal or low to begin with) are potential red flags.
Quantity vs. Quality
One of the biggest changes to Western diets over the last 50 years is the replacement of whole foods sources of carbohydrates with refined carbohydrates.
When you compare average carbohydrate consumption in the United States now to 100 years ago (when chronic disease rates were only a fraction of what they are now), it’s not that different, averaging about 500g per day. What is different is the percentage of those carbohydrates that come from fiber, an indicator of how refined these carbohydrate sources are: the more refined a food is, the more carbohydrate grams per fiber grams it typically has. And, right when the percentage of carbohydrate coming from fiber starts to dip is right when we start seeing exponential increases in cardiovascular disease, diabetes, and obesity.
When foods are refined, it’s not just the fiber that’s stripped out. Vitamins, minerals, and phytochemicals are also lost in the refinement process, and nutrient deficiencies themselves increase risk of disease. Combined with a large body of scientific evidence showing that low-carb high-fat diets do not provide a metabolic advantage, and in fact, low-fat high-carb diets perform equally as well from a weight loss standpoint (see Portion Control: The Weight Loss Magic Bullet and New Scientific Study: Calories Matter), we’re seeing a picture where quality of carbohydrate, meaning that we’re getting them from whole-food sources like root vegetables and fruit, if far more important than total intake.
So, How Many Carbs Should We Eat?
So, what’s the take-home message as far as carbohydrate recommendations go? For most people, going below 50 grams of carbohydrate per day for extended periods isn’t a good idea (unless a ketogenic diet is being used therapeutically for a specific condition and while under close medical supervision). A range of 100 to 200 grams per day is generally the most sustainable, but people can thrive on intakes up to even 300 grams (especially individuals with high calorie needs or very active lifestyles). These ranges are supported by evidence from healthy hunter-gatherer societies and help ensure our diets are nutrient-dense and have a diverse mix of plant and animal foods!
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