Updated August 31, 2015
The golden age of nutrition bloomed in the twentieth century with discoveries of proteins, fats, carbohydrates, minerals, vitamins, and other plant (phyto)-derived chemicals required for human health. Accepted wisdom about these nutrients became, “if some is necessary, then more is better.” The search for ways to “supercharge nutrition” began with supplements: pills filled with isolated, concentrated substances, such as vitamins and minerals.
Unfortunately, extensive research over the past century has consistently found that these expensive treatments offer few benefits and much harm to people. Consuming antioxidants, including beta-carotene and vitamin E, increases a person’s risk of suffering from earlier death, heart disease, and many forms of cancer. Jim Watson, co-discoverer of genetic DNA, wrote about the shortcomings of consuming too many micronutrients, even incriminating so-called superfoods with “Blueberries best be eaten because they taste good, not because their consumption will lead to less cancer.”
Besides taking pill-like supplements, the micronutrient content of a person’s diet can be enhanced by choosing foods with the highest concentrations of these substances. Colorful vegetables, especially those from the cruciferous genus, which include cabbage, collard greens, broccoli, cauliflower, kale, Brussels sprouts, turnips, and mustards, are known for their high nutrient density. Some of their disease-preventing properties come packaged with bitter tasting chemicals that the plants produce.
The July 2015 issue of Scientific American provided a scientifically supported argument for why many people dislike eating vegetables. The bitter tastes are from the noxious chemicals produced by plants. The authors explain, “The health benefits of fruits and vegetables are an inadvertent offshoot of eons-long wars waged by plants against critters, mostly insects, that are intent on eating them.” In small amounts these phyto-chemicals seem to be beneficial to humans; stimulating our immune/disease-fighting systems to ward off cancers, diabetes, and heart disease.
So far, except for a few allergies, consuming “typical portion sizes” of cruciferous plants is found to be safe in humans. Even concerns about plant-derived goitrogens, substances that suppress thyroid function, are largely rumor, with very few actual cases reported. But do consider that in her grand scheme, Mother Nature rarely makes mistakes: bad tastes suggest toxicity, and this may be especially important with higher consumptions.
Many people seeking a micronutrient-dense diet struggle to attain nutritional balance. A diet based on foods that are especially high in micronutrients, mainly non-starchy vegetables, is naturally very low in calories. People who eat this way find it a challenge to feel full, even after consuming uncomfortably large volumes of food. Consider that to meet daily energy needs of 1500 calories, 11 pounds of kale, for example, must be swallowed every 24 hours. (Cooked cabbage requires 14 pounds and broccoli 10 pounds for 1500 calories, whereas potatoes are 4 pounds and rice is 3 pounds of food.) Compounding this energy insufficiency (by relying too heavily on these green vegetables) is the overload of certain nutrients, like protein.
Our daily nutritional protein requirement is no more than 5% of our total calories; the liver and kidneys will dispose of any excesses. Metabolic burdens placed on these organs by consuming excess protein include the loss of calcium from the body and the accumulation of nitrogenous waste products in the body. In terms of excess, cabbage provides 4 times, kale 5 times, and broccoli 7 times more protein than is required.
These superfoods can also be contaminated with poisonous heavy metals. Kale, cabbage, broccoli, cauliflower, and collard greens are “hyper-accumulators” of thallium and cesium. Headlines about “arsenic in rice” must be shared with news that nickel, lead, cadmium, aluminum, and arsenic are commonly found in both organically and commercially produced greens.
A diet made up mostly of starchy vegetables and grains provides the abundant energy and balanced nutrition humans require. (As most readers of the McDougall philosophy already know:) All large populations of trim, healthy, athletic-competing, war-fighting people throughout verifiable human history have obtained the bulk of their calories from high-carbohydrate foods (starches). Examples of thriving populations include the Japanese, Chinese, and other Asians, who eat sweet potatoes, buckwheat, and/or rice; Incas in South America who eat potatoes; Mayans and Aztecs in Central America who eat corn; and Egyptians in the Middle East who eat wheat.
A diet of mostly nutrient-dense superfoods is unrealistic for both humans and the Planet. The financial cost difference between choosing calories from starchy and non-starchy sources is budget-breaking. The raw ingredients for a 1000-calorie meal plan based on beans, corn, potatoes, and/or rice is about 20 cents (US dollars). A “1000-calorie meal plan” as broccoli or kale is about 3 dollars. (People typically eat 1500 to 3000 calories daily.) In the global sense, calories from non-starchy vegetables are also too difficult and expensive to grow. Broccoli and kale could not feed seven billion people, either directly or through livestock. Furthermore, these green vegetables are highly perishable, failing again to provide a reliable and sustainable food source for humankind.
Starches, like beans, corn, potatoes, and rice are high-yield, inexpensive to produce, and can be stored for decades for later use. Thus, these conventional foods, not greens, are the bulk of the natural human diet. Dieters should not forgo bread and potatoes for platefuls of kale, nor should they force down Brussels sprouts rather than enjoy rice and beans. Make micronutrient-dense “green vegetables” side dishes rather than main dishes, as they provide color and flavor, and their various repugnant chemicals boost our defenses against common diseases.