Category Archives: Low-Carb

Which Vegetables Are Low in Carbohydrate Content?

Laura Dolson over at About.com has a helpful list of low-carb veggies.  Helpful if you experience excessive

blood sugar spikes from high-carb items, or if you’re restricting carbs for weight management.

-Steve

Are Ketogenic Diets Crazy?

You get it?

Ketogenic diets don’t have anything to do with the paleo diet usually.  However, I think they may play a legitimate role in weight loss for overweight type 2 diabetics.  They could also be helpful in rapid control of blood sugars in out-of-control diabetics (excluding diabetic ketoacidosis).

Has anyone devised a ketogenic paleo diet yet?  I don’t recall one off the top of my head.

Registered Dietitian Franziska Spritzler recently reviewed the concept of low-carb ketogenic diets.  She thinks they are a valid approach to certain clinical situations.  Among dietitians, this puts her in a small but growing minority.

I hesitate to mention this, but I will anyway.  Many, if not most, dietitians too easily just go along with the standard party line on low-carb eating: it’s rarely necessary and quite possibly unhealthy.  Going along is much easier than doing independent literature review and analysis.  I see the same mindset among physicians.

Franziska breaks the mold.

Steve Parker, M.D.

Nephrologist and Type 1 Diabetic Keith Runyan Tried the Paleo Diet

Jimmy posted a recent interview with type 1 diabetic Dr. Keith R. Runyan, who is a nephrologist and internist.

Dr. Runyan is training for the Great Floridian Triathlon this coming October so he naturally has a great interest in high level athleticism as it intersects with diabetes.  He fuels his workouts with dietary fats and proteins rather than the standard carbohydrates.

Dr. Runyan’s current carb consumption level didn’t come up specifically in the interview, but his website indicates he’s on a ketogenic diet heavily influenced by Dr. Richard Bernstein.  I figure he’s eating under 50 grams of digestible carbohydrate daily.  He also tried Loren Cordain’s paleo diet; my sense is that it didn’t help much with his diabetes, but perhaps some.  My sense is that he incorporates at least a few paleo features into his current eating plan.

People with type 2 diabetes can probably tolerate a higher level of carbohydrates, compared to type 1’s, generally speaking.  This didn’t come up in the podcast interview.

Overall, the interview strongly supports carbohydrate-restricted eating for folks with diabetes.  Definitely worth a listen for anyone with diabetes who’s not sold on a very-low-carb diet.  If you’re sitting on the fence, at least check out Dr. Runyan’s “About Me” page.

Steve Parker, M.D.

Triathlon: run, swim, bike

The Carbohydrate and Chronic Disease Connection

Simple dinner roll, or a future HEART ATTACK?

Adherents of the paleo diet and low-carb diets will love this post; it supports their choices.

Dentists are considering a return to an old theory that dietary carbohydrates first cause dental diseases, then certain systemic chronic diseases, according to a review in the June 1, 2009, Journal of Dental Research.  It’s written by Dr. Philippe P. Hujoel, who has been active in dental research for decades and is affiliated with the University of Washington (Seattle). He is no bomb-throwing, crazed, radical.

We’ve known for years that some dental and systemic diseases are associated with each other, both for individuals and populations. For example, gingivitis and periodontal disease are associated with type 2 diabetes and coronary heart disease. The exact nature of that association is not clear. In the 1990s it seemed that infections – chlamydia, for example – might be the unifying link, but this has not been supported by subsequent research.

The “old theory” to which I referred earlier is the Cleave-Yudkin idea from the 1960s and ’70s that excessive intake of digestible carbohydrates, in the absence of good dental care, leads both to certain dental diseases – caries (cavities), periodontal disease, certain oral cancers, and leukoplakia – and to some common systemic chronic non-communicable diseases such as coronary heart disease, type 2 diabetes, some cancers, and dementia. In other words, dietary carbohydrates cause both dental and systemic diseases – not all cases of those diseases, of course, but some.

In the context of excessive carbohydrate intake, the article frequently mentions sugar, refined carbs, and high-glycemic-index carbs. Dental effects of excessive carb intake can appear within weeks or months, whereas the sysemtic effects may take decades.

Hujoel compares and contrasts Ancel Keys’ Diet-Heart/Lipid Hypothesis with the Cleave-Yudkin Carbohydrate Theory. In Dr. Hujoel’s view, the latest research data favor the Carbohydrate Theory as an explanation of many cases of the aforementioned dental and systemic chronic diseases. If correct, the theory has important implications for prevention of dental and systemic diseases: namely, dietary carbohydrate restriction.

I agree with Dr. Hujoel that we need a long-term prospective trial of serious low-carb eating versus the standard American high-carb diet. Take 20,000 people, randomize them to one of the two diets, follow their dental and systemic health over 15-30 years, then compare the two groups. Problem is, I’m not sure it can be done. It’s hard enough for most people to follow a low-carb diet for four months. And I’m asking for 30 years?!

Dr. Hujoel writes:

Possibly, when it comes to fermentable carbohydrates, teeth would then become to the medical and dental professionals what they have always been for paleoanthropologists: “extremely informative about age, sex, diet, health.”

Dr. Hujoel mentioned a review of six studies that showed a 30% reduction in gingivitis score by following a diet moderately reduced in carbs. He mentions the aphorism: “no carbohydrates, no caries.” Anyone prone to dental caries or ongoing periodontal disease should do further research to see if switching to low-carb eating might improve the situation.

Don’t be surprised if your dentist isn’t very familiar with the concept.

Steve Parker, M.D.

Reference: Hujoel, P. Dietary carbohydrates and dental-systemic diseasesJournal of Dental Research, 88 (2009): 490-502.

Mendosa, David. Our dental alarm bell. MyDiabetesCentral.com, July 12, 2009.

Jimmy Moore’s 2012 interview with Dr. Hujoel.

What’s Our Preferred Fuel?

Dr. Jay Wortman has been thinking about whether our bodies prefer to run on carbohydrates (as a source of glucose) or, instead, on fats. The standard American diet provides derives about half of its energy from carbs, 35% from fats, and 15% from proteins. So you might guess our bodies prefer carbohydrates as a fuel source. Dr. Wortman writes:

Now, consider the possibility that we weren’t meant to burn glucose at all as a primary fuel. Consider the possibility that fat was meant to be our primary fuel. In my current state of dietary practice, I am burning fat as my main source of energy. My liver is converting some of it to ketones which are needed to fuel the majority of my brain cells. A small fraction of the brain cells, around 15%, need glucose along with a few other tissues like the renal cortex, the lens of the eye, red blood cells and sperm. Their needs are met by glucose that my liver produces from proteins. The rest of my energy needs are met with fatty acids and these come from the fats I eat.

Dr. Wortman, who has type 2 diabetes, in the same long post also writes about oolichan grease (from fish), an ancestral food of Canandian west coast First Nations people.

Drs. Jeff Volek and Stephen Finney have done research on athletes using a low-carb, high-fat diet.

Steve Parker, M.D.

Random Thoughts On Paleo Eating For People With Diabetes

Not really pertinent, but I like buffalo

I was interviewed  yesterday by Amy Stockwell Mercer, author of Smart Woman’s Guide to Diabetes.  All I knew beforehand was that she was interested in my thoughts on the paleo diet as applied to diabetes.

In preparation, I collected some random thoughts and did a little research.

What’s the paleo diet?

Fresh, minimally processed food.  Meat (lean or not? supermarket vs yuppiefied?), poultry, eggs, fish, leafy greens and other vegetables, nuts, berries, fruit, and probably tubers.

Non-paleo: highly processed, grains, refined sugars, industrial plant/seed oils, legumes, milk, cheese, yogurt, salt, alcohol.

Is the paleo diet deficient in any nutrients?

A quick scan of Loren Cordain’s website found mention of possible calcium and vitamin D deficits.  Paleoistas will get vitamin D via sun exposure and fish (especially cold-water fatty fish).  Obtain calcium from broccoli, kale, sardines, almonds, collards.  (I wonder if the Recommended Dietary Allowance for calcium is set too high.)

What About Carbohydrates and Diabetes and the Paleo Diet?

Diabetes is a disorder of carbohydrate metabolism.  In a way, it’s an intolerance of carbohydrates.  In type 1 diabetes, there’s a total or near-total lack of insulin production on an autoimmune basis.  In type 2 diabetes, the body’s insulin just isn’t working adequately; insulin production can be high, normal or low.  In both cases, ingested carbohydrates can’t be processed in a normal healthy way, so they stack up in the bloodstream as high blood sugars.  If not addressed adequately, high blood glucose levels sooner or later will poison body tissues .  Sooner in type 1, later in type 2.  (Yes, this is a gross over-simplification.) 

Gluten-rich Neolithic food

If you’re intolerant of lactose or gluten, you avoid those.  If you’re intolerant of carbohydrates, you could avoid eating them, or take drugs to help you overcome your intolerance.  Type 1 diabetics must take insulin.  Insulin’s more optional for type 2’s.  We have 11 classes of drugs to treat type 2 diabetes; we don’t know the potential adverse effects of most of these drugs.  Already, three diabetes drugs have been taken off the U.S. market or severely restricted due to unacceptable toxicity: phenformin, troglitazone, and rosiglitazone. 

Humans need two “essential fatty acids” and nine “essential” amino acids derived from proteins.  “Essential” means we can’t be healthy and live long without them.   Our bodies can’t synthesize them.  On the other hand, there are no essential carbohydrates.  Our bodies can make all the carbohydrate (mainly glucose) we need.

Since there are no essential carbohydrates, and we know little about the long-term adverse side effects of many of the diabetes drugs, I favor carbohydrate restriction for people with carbohydrate intolerance.  (To be clear, insulin is safe, indeed life-saving, for those with type 1 diabetes.)

That being said, let’s think about the Standard American Diet (SAD) eaten by an adult.  It provides an average of 2673 calories a day (not accounting for wastage of calories in restaurants; 2250 cals/day is probably a more accurate figure for actual consumption).  Added sugars provide 459 of those calories, or 17% of the total.  Grains provide 625 calories, or 23% of the total.  Most of those sugars and grains are in processed, commercial foods.  So added sugars and grains provide 40% of the total calories in the SAD.  Remember, we need good insulin action to process these carbs, which is a problem for diabetics.  (Figures are from an April 5, 2011, infographic at Civil Eats.)

Anyone going from the SAD to pure Paleo eating will be drastically reducing intake of added sugars and grains, our current major sources of carbohydrate.  Question is, what will they replace those calories with? 

That’s why I gave a thumbnail sketch of the paleo diet above. Take a gander and you’ll see lots of low-carb and no-carb options, along with some carb options. For folks with carbohydrate intolerance, I’d favor lower-carb veggies and judicious amounts of fruits, berries, and higher-carb veggies and

Will these cause bladder cancer? Pancreatitis?

tubers.  “Judicious” depends on the individual, considering factors such as degree of residual insulin production, insulin sensitivity, the need to lose excess weight, and desire to avoid diabetes drugs.

Compared to the standard “diabetic diet” (what’s that?) and the Standard American Diet, switching to paleo should lower the glycemic index and glycemic load of the diet.  theoretically, that should help with blood sugar control.

A well-designed low-carb paleo diet would likely have at least twice as much fiber as the typical American diet, which would also tend to limit high blood sugar excursions.

In general, I favor a carbohydrate-restricted paleo diet for those with diabetes who have already decided to “go paleo.”  I’m not endorsing any paleo diet for anyone with diabetes at this point—I’m still doing my research.  But if you’re going to do it, I’d keep it lower-carb.  It has a lot of potential.

Are There Any Immediate Dangers for a Person With Diabetes Switching to the Paleo Diet?

It depends on three things: 1) current diet, and 2) current drug therapy, and 3) the particular version of paleo diet followed. 

Remember, the Standard American Diet provides 40% of total calories as added sugars and grains (nearly all highly refined).  Switching from SAD to a low-carb paleo diet will cut carb intake  and glycemic load substantially, raising the risk of hypoglycemia if the person is taking certain drugs.

Drugs with potential to cause hypoglycemia include insulin, sulfonylureas, meglitinides, pramlintide, and perhaps thiazolidinediones.

Who knows about carb content of the standard “diabetic diet”?  Contrary to popular belief, there is no monolithic “diabetic diet.”  There is no ADA diet (American Diabetes Association).  My impression, however, is that the ADA favors relatively high carbohydrate consumption, perhaps 45-60% of total calories.  Switching to low-carb paleo could definitely cause hypoglycemia in those taking the aforementioned drugs.

One way to avoid diet-induced hypoglycemia is to reduce the diabetic drug dose.

A type 2 overweight diabetic eating a Standard American Diet—and I know there are many out there—would tend to see lower glucose levels by switching to probably any of the popular paleo diets.  Be ready for hypoglycemia if you take those drugs.

Paleo diets are not necessarily low-carb.  Konner and Eaton estimate that ancestral hunter-gatherers obtained 35 to 40% of total calories from carbohydrates.  I’ve seen other estimates as low as 22%.  Reality likely falls between 22 and 65%.  When pressed for a brief answer as to how many carbohydrate calories are in the paleo diet, I say “about a third of the total.”  By comparison, the typical U.S. diet provides 50% of calories from carbohydrate.

Someone could end up with a high-carb paleo diet easily, by emphasizing tubers (e.g., potatoes), higher-carb vegetables, fruits, berries, and nuts (especially cashews). Compared with the SAD, this could cause higher or lower blood sugars, or no net change.

A diabetic on a Bernstein-style diet or Ketogenic Mediterranean Diet (both very-low-carb) but switching to paleo or low-carb paleo (50-150 g?) would see elevated blood sugars.  Perhaps very high glucoses.

Any person with diabetes making a change in diet should do it in consultation with a personal physician or other qualified healthcare professional familiar with their case.

Steve Parker, M.D.

Fun Facts!

  • A typical carbonated soda contain the equivalent of 10 tsp (50 ml) of sugar.
  • The typical U.S. adult eats 30 tsp  (150 ml) daily of added sweeteners and sugars.
  • U.S total grain product consumption was at record lows in the 1970s, at 138 pounds per person.  By 2000, grain consumption was up by 45%, to 200 pounds per person.
  • Total caloric sweetener consumption (by dry weight) was 110 pounds per person in the  1950s.  By 2000, it was up 39% to 150 pounds.
  • Between 1970 and 2003, consumption of added fats and oils rose by 63%, from 53 to 85 pounds.  [How tasty would that be without starches and sugars?  Not very.]
  • In 2008, “added fat” calories in the U.S. adult diet were 641 (24% of total calories).

Fun Facts provided by the U.S. Department of Agriculture. 

(The paleo diet is also referred to as the Paleolithic, Old Stone Age, Stone Age, Ancestral, Hunter-Gatherer, or Caveman diet.)

Dr. Andreas Eenfeldt Explains the LCHF Diet

LCHF Cheese

Dr. Eenfeldt of DietDoctor.com gave a talk at the inaugural Ancestral Health Symposium in California, on the rationale of the current low-carb, high-fat diet (LCHF) so popular in his home country of Sweden.  It’s very understandable to the general public and is a good introduction to low-carb eating.  The entire YouTube video is 55 minutes; if you’re pressed for time, skip the 10-minute Q&A at the end.

He also discusses the benefits of LCHF eating for his patients with diabetes.

If you reduce carbohydrate, you’re going to replace it with either protein, fat, or both.  Carbohydrate restriction, whether or not part of a Paleolithic eating pattern, generally improves blood sugar levels, especially in people with diabetes. 

Steve Parker, M.D.

Old Stone Age Diet Depended On Latitude

There isn’t any single Stone Age diet, according to J.A.J. Gowlett, who (whom?) I assume is an archeologist with the University of Liverpool.

(I was tempted to write “there isn’t a monolithic Stone Age diet.”  Get it?  “Lith” is Greek or Latin for “stone.”)

This is probably old new for you guys who have been interested in the paleo diet for much longer than I.

Here are a few more of Gowlett’s ideas:

  • The Stone Age is is more accurately referred to as the Old Stone Age.
  • Hominids (the family of human ancestors) branched off from ape ancestors around eight to 10 million years ago.
  • Roots and tubers have been a part of our ancestral diet for perhaps as long as three million years,  which “places starchy carbohydrate consumption as part of the deep ancestry of human beings.”
  • Meat eating assumed greater importance about two million years ago.
  • Migration to colder environments necessitated more meat consumption because plant foods were more limited.
  • Our ancestors migrated from tropical to temperate latitudes about by 1.7 million years ago.
  • Early humans began using fire for cooking between 500,000 to 1.5 million years ago.
  • Neanderthals were heavily carnivorous.
  • “Ancestors of modern humans are now believed to have evolved in the tropics, probably in Africa, from about 200,000 years ago.”  Their diet was perhaps 70% plant-based.
  • “In contrast, modern humans entering Europe 40,000 years ago would have adopted a meat-based diet by necessity, and maintained this over hundreds of generations.”
  • “Modern hunters and gatherers echo the variety of past diets, ranging from largely plant based in the tropics, to being also heavily meat based in the arctic.”
  • No ancient human population depended heavily on cereals or non-human milk.  “Fruit certainly came first of all….”

Potential Implications For a Paleo Diabetic Diet (highly speculative)

Diabetics with tropical lineage may do better with a plant-based diet.  Those with northern European ancestry may do better with meat-based.

Paleo diets likely had very high fiber contents, reflecting the degree to which they were plant-based.  We’re looking at 70+ grams of fiber daily.  That much fiber would tend to reduce the effect of carbohydrate on blood sugar levels.

Fruits and roots have a high concentration of carbohydrate, with potential adverse effects on blood sugar (raising it, of course).  Diabetics eating paleo-style may need to avoid or limit certain fruits and roots: the ones with lower fiber content and higher glycemic index.  Blood sugar responses will vary from one diabetic to another.  Monitor blood sugar levels one or two hours after carb consumption to learn your idiosyncratic response.

Steve Parker, M.D.

Reference: Gowlett, J.A.J.  What actually was the Stone Age diet?  Journal of Nutritional and Environmental Medicine, 13 (2003): 143-147.

Paleolithic Nutrition: Twenty-Five Years Later

Melvin Konner and S. Boyd Eaton wrote a review article for Nutrition in Clinical Practice that update’s their seminal New England Journal of Medicine  paleo nutrition article of 1985.  They took a fresh look at recent  data on modern hunter-gatherer societies as well as advances in anthropology. 

NEJM likely has much wider circulation, so it’s too bad the update wasn’t published there.

I’ve written previously about the history of the modern paleo movement.  I consider S. Boyd Eaton and Melvin Konner two of the founders. 

I wanted to share a few tidbits from the new article:

  • The transition from hunting/gathering to farming (about 10,000 year ago) saw a decrease in body size and robustness, plus evidence of nutritional stress
  • Modern humans migrated away from Africa between 50,000 and 100,000 years ago
  • Levels of muscular and aerobic fitness in ancestral groups are much higher than modern societies, with a concomittant higher level of calorie consumption
  • Average life expectancies in pre-industrial hunter-gatherer (H-G) groups was only 30-35 years, but much of this low number simply reflects high infant and child death rates
  • H-G deaths overwhelmingly reflect infectious diseases
  • H-G groups had a high degree of dependence on plant foods
  • Cooking has been important to humans for at least 230,000 years, if not longer
  • Fish and shellfish are more important food sources than these authors thought 25 years ago
  • Ancestral H-G groups derived 35 to 65% of diet (calories, I guess) from animal flesh
  • Game animals have more mono- and polyunsaturated fatty acids than supermarket meat
  • H-G diets are higher in fat than they once thought: the new range is 20 to 35% of calories
  • H-G diet omega-6: omega-3 ratio was 2:1, in contrast to the modern Western ratio of 10:1
  • H-G groups eat more protein than they once thought
  • Carbohydrate consumption of H-G groups varied from about 35 to 65% of calories.  (I’ve written elsewhere about the carb content of paleo diets.)
  • Nearly all H-G carbs are from vegetables and fruits, which have more favorable glycemic responses than grains and concentrated sugars
  • Uncultivated fruits and veggies have much more fiber than commercial ones (13 versus 4 g fiber per 100 g of food)
  • H-G diets have at least 70 g of fiber daily
  • Sodium in H-G diets is very low: 800 mg/day

The Diet-Heart Hypothesis is the idea that dietary total and saturated fat, and cholesterol, cause or contribute to atherosclerosis (hardening of the arteries), leading to heart attacks and strokes.  Konner and Eaton still believe the theory is valid for fats, but not cholesterol.  The latest evidence is that even total and saturated fat are minimally or unrelated to atherosclerosis

They also believe total fat, due to its caloric load, is an important contributor to obesity and type 2 diabetes.  (I agree that my be true if you eat a lot of carbs with fat.)

Konner and Eaton review the very few clinical studies—a grand total of four—that apply a paleo diet to modern humans.  Results support their theory that paleo-style eating has healthful metabolic effects.

Their conception of a paleo food pyramid is a base of high-fiber vegetables and fruits, the next tier up being meat/fish/low-fat dairy (!?) (all lean), then a possible tier for whole grain (admittedly very unusual), with a small peak of oils, fats, and refined carbohydrates.

They recommend high activity levels, including resistance exercise, flexibility, and aerobics, burning over 1,000 cals/day exclusive of resting metabolism.

They also seem to favor small amounts of alcohol—not generally considered paleo—to reduce heart disease risk, admitting that “…the HG model cannot answer all questions.”

Eaton and Konner suggest the following as the “estimated ancestral diet“:

  • Carbohydrates, % daily energy                 35-40
  • Protein, % daily energy                                 25-30
  • Fat, % daily energy                                          20-35
  • Added sugar, % daily energy                            2
  • Fiber, g/day                                                        >70
  • EPA and DHA*, g/day                                    0.7-6
  • Cholesterol, mg/day                                       500+
  • Vitamin C, mg/day                                           500
  • Vitamin D, IU/day                                4,000 (sunlight)
  • Calcium, mg/day                                       1,000-1,500
  • Sodium, mg/day                                         under 1,000
  • Potassium, mg/day                                         7,000

*Eicosapentaenoic acid and docosahexaenoic acid

Konner and Eaton call for more randomized controlled studies of the paleo diet.  These studies will need to define the paleo diet carefully.  Their definition is probably as good as any, if not the best.  Of course, the listed nutrients should come from minimally processed, natural foods.  We just need Loren Cordain‘s and Staffan Lindeberg‘s  input on a concensus definition of the paleo diet, then we’re ready to rock’n’roll.

Steve Parker, M.D.

Reference:

Konner, Melvin and Eaton, S. Boyd.  Paleolithic Nutrition: Twenty-Five Years LaterNutrition in Clinical Practice, 25 (2010): 594-602.  doi: 10.1177/0884533610385702

Eaton, S.B. and Konner, M.  Paleolithic nutrition: a consideration of its nature and current implicationsNew England Journal of Medicine, 312 (1985): 283-289.

 

Is the Paleo Diet Low-Carb?

Low-carb diet and paleo diet advocates often align themselves, even though S. Boyd Eaton’s 1988 version of the paleo diet doesn’t appear to be very low-carb at all: 46% of total calories from carbohydrate.  The standard American diet provides 50-55% of calories from carbohydrate.  Paleo proponents and low-carbers do share an affinity for natural, whole foods, and an aversion to grains, milk, and legumes. 

A 2010 article by Kuipers et al (reference below) sugggests that the East African Paleolithic diet derived, on average, 25-29% of calories from protein, 30-39% from fat, and 39-40% from carbohydrate.  That qualifies as low-carb.  Modern Western percentages for protein, fat, and carb are 15%, 33%, and 50%, respectively.

Loren Cordain and associates in 2000 suggested that Paleolithic diets may have derived about a third—22 to 40%—of calories from carbohydrate, based on modern hunter-gatherer societies. 

You can make a good argument that these paleo concepts are healthy: high physical activity, nonsmoking, consumption of natural whole foods while minimizing simple sugars and refined starches.  The paleo community is convinced that grains and legumes are harmful; many others disagree.  Also debatable are the roles of dairy, polyunsaturated to saturated fat ratio, low sodium, and high potassium.  Modern diets tend to be high-sodium and low-potassium, which may predispose to high blood pressure and heart trouble—diseases of modern civilization.

It appears that the average paleo diet may have derived about a third of calories from carbohydrate: that qualifies as low-carb.

For more on the paleo diet and lifestyle, visit Robb Wolf’s website, Mark’s Daily Apple, and Archevore

Steve Parker, M.D.

References:

Kuipers, R., Luxwolda, M., Janneke Dijck-Brouwer, D., Eaton, S., Crawford, M., Cordain, L., & Muskiet, F. (2010). Estimated macronutrient and fatty acid intakes from an East African Paleolithic diet British Journal of Nutrition, 1-22 DOI: 10.1017/S0007114510002679.  Note that one of the authors is Loren Cordain.  Good discussion of various Paleolithic diets.

Eaton, S., Konner, M., & Shostak, M. (1988). Stone Agers in the fast lane: Chronic degenerative diseases in evolutionary perspective. The American Journal of Medicine, 84 (4), 739-749 DOI: 10.1016/0002-9343(88)90113-1

Cordain, L., et al.  Plant-animal subsistance ratios and macronutrient energy estimations in worldwide hunter-gatherer dietsAmerican Journal of Clinical Nutrition, 71 (2000): 682-692.