Putting nutrition for kids in an evolutionary context
It’s become a cliché.
Paleolithic people were athletic, fit, and free from the chronic diseases associated with modern, affluent, sedentary lifestyles: obesity, hypertension, heart disease, and diabetes.
They exercised regularly, walking an average of 8 miles a day. That must have counted for a lot. But their diets were also notably different.
They ate no milk products and consumed very lean meat. They ate fish and shellfish. As a result, their diets were low in saturated fats. They consumed virtually no trans fats (Eaton et al 2007).
In addition, a relatively high proportion of their fat intake was in the form of healthy omega-3 fatty acids (Sinclair and O’Dea 1993).
These differences were very important. A diet of excessive saturated fat and insufficient omega-3 fatty acids is linked with impaired cognitive development, cardiovascular disease, autoimmune diseases, and cancer.
But I’d like to focus on another aspect of the Paleolithic diet: The plant foods.
Studies of contemporary foragers reveal a remarkable breadth of foods, including an average of more than 100 different plant species.
These plant foods accounted for a carbohydrate intake that is similar to that of people living in affluent industrialized countries--about 45-50% of daily energy (Eaton et al 1999).
But there was an important difference. Modern, affluent diets feature carbohydrates that rapidly raise blood sugar levels. Carbs like refined sugars, highly-processed grains, and starchy potatoes. In addition to raising blood sugar, these foods are also relatively poor sources of fiber, vitamins, and minerals.
By contrast, foragers got their carbs from vitamin-and mineral-rich, high-fiber vegetables and fruits.
Big difference? Oh yes. Nutritionists evaluate a food’s potential for raising blood glucose levels by measuring it’s “glycemic index,” or GI.
Glucose has a glycemic index of 100. Anything under 55 is considered to be low. You can check the GI of various foods by checking the International Table of Glycemic Index and Glycemic Load Values (Foster-Powell et al 2002).
Consider how these agricultural staples score:
• Baked russet potatoes, GI approximately 86.
• Corn tortillas (from a Western supermarket), GI approx. 74.
• Breakfast cereals (like corn flakes), GI over 70.
• Wheat flour breads vary. Coarse wheat breads (with uncracked kernels) have GIs in the 50s. White breads have GIs in the 70s.
• Rice varies. Jasmine rice (my favorite) has a GI of approximately 109. Basmati rice has a GI in the range of 58.
By contrast, many of the starchy roots and tubers eaten by non-Western peoples have GIs less than 50. Most green vegetables have GIs far below 50.
And even sweet fruits sold in Western supermarkets have GIs under 55:
• Apples, GI approximately 38
• Bananas, GI approx. 52
• Oranges, GI approx. 42
• Mangos, GI approx. 51
• Peaches, GI approx. 42
Which may explain why researchers have observed an important difference between artificially sweetened fruit juice, and fruit juice that contains no added sugar. Whereas the intake of sugar-sweetened fruit juice has been linked with the development of type 2 diabetes, the consumption of 100% natural fruit juice has not (Xi et al 2014).
So here's the point: The “Paleolithic” carbs trigger relatively gradual rises in blood sugar levels, which may protect children from a variety of ailments, including diabetes, heart disease, stroke, and kidney disease.
Moreover, the high fiber content in fruits and vegetables may independently lower a child's risk of obesity, cancer, and diseases of the digestive system.
And there are interesting theoretical speculations about the consequences of rejecting paleo-carbs in favor of processed, starchy foods. As Ian Spreadbury has argued, a diet of highly-processed carbohydrates promote the growth of gut bacteria that blunt our feelings of satiety, encouraging us to overeat (Spreadbury 2012).
In addition, there is evidence hinting that high-starch diets pose a particular risk of obesity for people who possess fewer copies of the AMY1 gene (Falchi et al 2014). Perhaps individuals who carry many copies of this gene (discussed below) are less likely to develop insulin resistance, a condition that contribute to the accumulation of body fat.
And what about vitamins and minerals? Studies of hunter-gatherer diets reveal dramatic differences between Paleolithic intakes and what's typical for people living in modern agricultural societies.
Vitamins and Minerals
According to an analysis by S. Boyd Eaton and his colleagues, contemporary foragers consume higher levels of vitamins and minerals than are currently recommended by the US RDA (Eaton et al 1999). For instance, foragers average
• 0.357 mg of folate
• 6.49 mg of riboflavin
• 3.91 mg of thiamin
• 600 mg of vitamin C
• 1950 mg of calcium
• 10,500 mg of potassium
• 43.4 mg of zinc.
These aren’t megadoses, and Eaton’s group doesn’t advocate megadoses. Taking supplements of vitamins and minerals in megadoses can be dangerous—especially for children.
But the Paleolithic example helps put modern agricultural diets in perspective. According to data collected in the 1990s, most Americans aren’t getting the recommended amounts of magnesium, calcium, or zinc.
Almost one third of Americans aren’t getting enough folate, riboflavin, or thiamin, and 37% fail to get even 60 grams of daily vitamin C.
Implications: What the hunter-gatherers teach us about nutrition for kids
Is the traditional “food pyramid” wrong?
It seems likely that the traditional food pyramids--those graphics suggesting that people should consume high quantities of highly refined cereals--are wrongheaded. Parents interested in improving nutrition for kids should place a stronger emphasis on high-fiber, nutrient-rich vegetables and fruits.
Other research supports this idea. A new study suggests that the high consumption of fruits and vegetables is one of the key reasons that that the classic Mediterranean diet is so healthful (Trichopoulou et al 2009).
Researchers tracked thousands of Greek men and women for more than 8 years. Then they compared diets and mortality. The results suggested that high intake of vegetables and fruits was a strong predictor of survival. By contrast, the effects of high cereal intake (e.g., bread consumption) were small.
But we needn't avoid all the cereal-based foods. When cereals are less thoroughly refined and processed, they have much lower glycemic indices. According to the International Table of Glycemic Index and Glycemic Load Values, corn tortillas made by the Pima indians have a GI of only 38.
Nor should we assume that the Stone Age menu is ideal, or that any deviations from it are automatically bad.
Evidence that humans have evolved to cope with more “modern” diets
I’ve heard people attack milk or wheat or soy merely because they are evolutionary “new” foods. That objection is insufficient.
Humans have evolved significant, new adaptations since the rise of agriculture.
For instance, the gene AMY1 codes for salivary amylase, the enzyme that breaks down dietary starch. The more copies you possess of this gene, the more salivary amylase you can make. People who live in populations with high-starch diets carry more copies of the AMY1 gene, presumably because natural selection favored it (Perry et al 2007).
Or consider the more familiar case
of the gene for lactase, the enzyme that helps the body break down milk
sugars. Most human adults don’t produce lactase. The gene is turned
off when childhood ends. But among certain populations—such as
those in the Europe, the Middle East, and North Africa—most people possess the ability to digest milk throughout adulthood.
Should lactose-tolerant people give up milk?
Research suggests that there are both
costs and benefits associated with milk consumption.
For instance, studies suggest that milk increases insulin resistance. But milk also enhances growth (Hoppe et al 2006; Rich-Edwards et al 2007). And for some people--including those who are vegetarians by choice or necessity--milk may provide a crucial source of calcium and animal proteins.
So I think we need to avoid sweeping generalizations. When it comes down to it, there isn’t anything magical about Paleolithic nutrition. What’s best for kids may depend on individual differences, including genetics and environmental factors, like the availability of different nutrients.
And in case you were wondering about life spans...
When many people hear about the low incidence of chronic, degenerative disease amongst hunter-gatherers, they voice the obvious question: “But isn’t that because hunter-gatherers don’t live long enough to die of these conditions?”
Of course people are less likely to die of heart disease if accidents, warfare, infectious disease, or famine kills them first.
And it would be silly to compare a group of geriatric Americans with a group of young hunter-gatherers!
But that’s not what anthropologists like S. Boyd Eaton do.
Rather, they examine the health status of younger people. They look for the early warning signs of chronic disease--biomarkers like increased platelet aggregatability, clinical hypertension, high cholesterol, and insulin resistance.
When you compare hunter-gatherers with their similarly-aged counterparts in affluent, industrial countries, the hunter-gatherers have much healthier-looking profiles (e.g., Eaton et al 1988; Joffe et al 1971).
Researchers also examine the health status of older hunter-gatherers. About 20% of hunter-gatherers live to age 60 or beyond, and these individuals are remarkably free of symptoms of chronic, degenerative diseases (Eaton et al 2002).
Does this mean that we’d all be better off as hunter-gatherers, or that the Paleolithic was a Garden of Eden? Certainly not. Life in the Paleolithic wasn’t just shorter. It was undoubtedly much less pleasant than many sentimentalists realize (Bogin 2011).
But the point here is that eating lots of high-fiber, nutrient-rich plant foods--and trading saturated fats for the “good” fats--has probably played a key role in lowering the risk of chronic, degenerative disease.
More information about nutrition for kids
If you'd like to consult the International Table of Glycemic Index and Glycemic Load Values, you can do so
If you'd like more evidence-based information about food in general, see these Parenting Science articles about nutrition for kids
And are you wondering about other diets purported to be "natural" and good for kids?
Not every claim made about the Paleolithic diet is supported by the evidence. And many diets being marketed as "natural" are of questionable value for kids. In fact, some are dangerous.
For more information, check out this critical look at some
popular, "natural" diets and their effects on kids.
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Content of "Paleolithic nutrition for kids" last modified 4/14