Food and nutrition for kids: An evidence-based guide

© 2009 Gwen Dewar, Ph.D., all rights reserved

New research offers important insights about nutrition for kids. Some examples:

Iron. Laboratory analyses confirm which foods are the best sources of iron. And experimental research helps us understand how we can improve iron absorption.

Picky eaters. Are you having trouble getting your child to try new foods? Or to eat his vegetables? Some kids are predisposed to be picky eaters. But research suggests several good strategies for coping with picky eaters, such as pairing new foods with sweet flavors. To learn more, see these evidence-based tips for dealing with picky eaters.



Probiotics and Prebiotics. Food and supplement manufacturers are pushing prebiotics and probiotics. Are the claims overblown? Perhaps. But studies suggest that probiotic supplements can be an effective treatment for diarrhea, and the daily consumption of prebiotics may bolster the immune system.

Milk

For instance, modern science confirms the many benefits of breast milk. Baby formula has greatly improved since the 20th century, but it’s still second best.

By the same token, it appears that modern agricultural diets—-the diets associated with affluent, industrial nations—-are in some ways inferior to the diets of our Stone Age ancestors.

In part, this is because agricultural diets are relatively new.

For hundreds of thousands of years, humans ate only wild plant and animal foods. Then, around 10,000 years ago, people began the shift to agriculture and animal husbandry. Humans began eating food types they’d never eaten before. The human body, adapted to digest a Paleolithic diet, was suddenly challenged with an agricultural diet.

Four hundred generations later, descendants of the first farmers have evolved new adaptations for coping with new foods (Patin and Quintana-Murci 2008). For instance, some people retain the ability to digest milk sugars after infancy.

Others possess genes that produce extra amylase--an enzyme that breaks down dietary starch (Perry et al 2007). Indeed, there is evidence that our ancestors began eating starchy roots and tubers long before the advent of agriculture (e.g., Gibbons 2009; or, better yet, read anthropologist Richard Wrangham's delightful and absorbing book, Catching Fire: How Cooking Made Us Human).

But humans haven’t had enough time to adapt completely to the new menu of saturated fats and highly refined, highly processed cereals. Some anthropologists argue that 21st century diets are responsible for many chronic diseases, including cardiovascular disease, hypertension, and diabetes (Cordain et al 2005).

So I think it’s worth a review. What can Stone Age menu teach us about nutrition for kids? Perhaps that the traditional food pyramid-—which tells us to eat lots of bread and rice—-is misguided.

Paleolithic nutrition for kids?

Paleolithic people were athletic, fit, and free from the chronic diseases associated with affluent, sedentary lifestyles: obesity, hypertension, heart disease, and diabetes.

Why?

They exercised regularly—-walking an average of 8 miles a day.

And their diets were notably different.

They ate no milk products and consumed only very lean meat. As a result, their diets were low in saturated fats. 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--excessive saturated fat and insufficient omega 3 fatty acids are linked with 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

So here’s the point: The “Paleolithic” carbs trigger relatively gradual rises in blood sugar levels. And that’s a good thing, since chronically high blood sugar levels increase the risk of many ailments, including heart disease and stroke, diabetes, and kidney disease.

In addition, the high fiber intake associated with the Paleolithic diet should protect people from obesity, cancer, and diseases of the digestive system.

And people consuming a Paleolithic diet would be at little risk of vitamin and mineral deficiencies.

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 I certainly don’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

I think it quite 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. 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, such as the gene for lactase. 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, nutrition for kids may depend on individual differences, including genetics and environmental factors, like the availability of nutrients.

More information about nutrition for kids

References: The science of nutrition for kids

Eaton SB, Eaton SB III, and Konner MJ. 1999. Paleolithic nutrition revisited. In W. R. Trevathan, E.O. Smith, and J.J. McKenna (eds), Evolutionary Medicine. New York: Oxford University Press.

Foster-Powell K, Holt SH, and Brand-Miller JC. 2002. International table of glycemic index and glycemic load values. Am J Clin Nutr 76:5–56.

Gibbons A. 2009. Of tools and tubers. Science 324 (5927): 588 - 589.

Hoppe C, Mølgaard C, and Michaelsen KF. 2006. Cow's milk and linear growth in industrialized and developing countries. Annu Rev Nutr. 26:131-73.

Patin E, Quintana-Murci L. 2008. Demeter's legacy: rapid changes to our genome imposed by diet. Trends Ecol Evol. 2:56-9.

Perry GH, Dominy NJ, Claw KG, Lee AS, Fiegler H, Redon R, Werner J, Villanea FA, Mountain JL, Misra R, Carter NP, Lee C, and Stone AC. 2007. Diet and the evolution of human salivary amylase gene copy number. Nat. Genet. 39(10): 1256–1260.

Rich-Edwards JW, Ganmaa D, Pollak MN, Nakamoto EK, Kleinman K, Tserendolgor U, Willett WC, and Frazier AL. 2007. Milk consumption and the prepubertal somatotropic axis.Nutrition Journal 6: 28-35.

Sinclair A and O’Dea K. 1993. The significance of arachidonic acid in hunter-gatherer diets: Implications for the contemporary Western diet. Journal of Food Lipids 1: 143-157.

Trichopoulou A, Bamia C, and Trichopoulos D. 2009. Anatomy of health effects of Mediterranean diet: Greek EPIC prospective cohort study. BMJ. 338:b2337.

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