Our food supply has been changing for 2.5 million years...

Some people in the nutrition world feel that the in the Paleolithic era best reflects the diet our bodies evolved to handle. This hunter-gatherer, or caveman, type of diet existed about 2.5 million years ago, ending around 10,000 years ago with the introduction of agriculture and animal farming. The Paleolithic diet was composed of fruits, vegetables, wild game and small amounts of honey. Grains, dairy products, sugars, refined vegetable oils, and alcohol were relatively absent. For comparison, grains, dairy, sugars and refined vegetable oils make up about 72% of the total daily energy consumed by people in the U.S. today.

A diet centered around fruits and vegetables is naturally nutrient-rich and low in sodium. Fruits and vegetables provide vitamins, minerals, fiber and phytonutrients that have been associated with a lower risk of numerous chronic diseases. In a 2012 critical review, increased fruit and vegetable consumption was associated with a reduced risk of cardiovascular disease, stroke, high blood pressure, cancer, obesity, certain eye disease, dementia, asthma, rheumatoid arthritis and osteoporosis.

Wild game would have provided a lean source of protein. It also has a much higher level of essential omega-3 fatty acids compared to the grain-fed meat widely available in our current food supply. Higher intakes of omega-3 essential fatty acids have been associated with a reduced risk of cardiovascular disease, stroke, inflammatory disorders, and depression. It is estimated that the ratio of omega-3 to omega-6 fatty acids in hunter-gatherer diets was between 2:1 and 3:1, while modern diets have been calculated to contain 10:1.

Additionally, with a high fiber content and non-existent refined carbohydrate content, the paleolithic diet had a low glycemic load. Glycemic load is a measurement of the effect of carbohydrates in a food on blood sugar. A low-glycemic load diet results in more stable blood sugar levels and decreased insulin demands compared to a high glycemic load diet. High blood glucose levels and the accompanying insulin demands have been associated with the loss of the insulin-secreting function of the pancreatic beta-cells that leads to diabetes. Research has shown that diets with a higher glycemic load are associated with an increased risk of developing diabetes. In the Nurses’ Health Study, women with the highest dietary glycemic loads were 37% more likely to develop type 2 diabetes than women with the lowest dietary glycemic loads.

As outlined above, with its lack of grains, and emphasis on fruits, vegetables and wild game the paleolithic diet has the potential to reduce the risk of most modern diseases. For this reason, a grain-free paleolithic diet has emerged and touted as many as an optimal diet. The reasoning behind this type of diet is that the addition of grains to our food supply is a relatively new change in our evolutionary history. However, with changes to the modern food supply, it would be nearly impossible to find enough wild game to be comparable in omega-3 essential fatty acid composition to these early diets. Additionally, fruits and vegetables have decreased nutrient levels no longer bringing the high levels of calcium, magnesium and other nutrients that wild-grown and harvested plants would have had.

Following the Paleolithic era, approximately 10,000 years ago, humans entered the Neolithic era and began the practice of farming. Population increases made wild game more scarse and therefore to accommodate nutritional needs, humans began to raise animals and grow crops. Grains, legumes and dairy products were more easily accessible and became a prevalent part of the food supply. This era included whole ground grains, higher fat grass-fed meats and full fat dairy from grass-fed animals. While some point to this evolutionary shift as one that resulted in declining health, cultures thrived for many thousands of years with grain-based diets.

Ancient varieties of grains have similar macronutrient compositions compared to modern varieties, but tend to be higher in minerals. In a 2013 randomized crossover study published in the European Journal of Clinical Nutrition, 22 study participants were fed grain products made with made with ancient Kamut® brand Khorasan wheat for 8 weeks, followed by a washout period of 8 weeks, followed by 8 weeks in which all grain products were made with modern Durum wheat and soft wheat. Following the Kamut® phase of the study, subjects’ total cholesterol decreased by an average of 4%, LDL (“bad”) cholesterol decreased 7.8%, and markers of inflammation dropped 23-36%. At the same time, blood levels of potassium and magnesium rose 4.6% and 2.3% respectively. The cause of these health differences has not been determined. Analyses of the Kamut® and control wheat showed that the two grains had similar amounts of protein, fiber and resistant starch, however the Kamut variety had higher levels of potassium and magnesium. Additionally, these grains were eaten whole or stone-ground, preserving most of the nutrient profile, unlike modern milling and bleaching practices which can destroy nutrients.

There were also big differences in meat and dairy compared with modern sources. Farming allowed higher levels of fat in the diet year-round, although early breeds of cattle were much leaner than modern varieties. Additionally, these farmers raised animals that grazed on grasses rather than corn. Grass-fed meats and dairy products provide a higher ratio of omega-3 essential fatty acids than modern diets, as well as high levels of conjugated linoleic acid (CLA). CLA has been associated with a leaner body composition as well as possibly having anticancer properties. Additionally, dairy products from grass-fed cattle have higher levels of fat-soluble vitamins.

Sodium intakes also increased during the Neolithic period, as salt mining and transportation of salt became more common. However, levels did not come close to the 9.6 grams per day consumed in the typical modern U.S. Diet.

Small family farms continued to be the norm until the early 20th century, with the Industrial Revolution. At the turn of the century, 39% of the labor force lived and worked on farms, which decreased to less than 11% in 1950 and less than 2% in 1990. With people leaving small family farms, the industry began to focus on gaining larger tracts of land and increased productivity through mechanization and other technologies. This mechanization allowed for the processing of cereal grains and vegetable oils, which compose large portions of modern diets. Today, 85% of the cereal grains consumed in the U.S. are highly processed, while this type of grain was not available before the Industrial Revolution. Similarly, mechanization of the oil seed industry allowed for the increased availability of vegetable oils and hydrogenated trans fats.

In modern times, farming has become a big business, focusing on productivity rather than nutritional quality. Growing cities require increased food production and processing techniques that enable greater preservation. World War II required even greater production, leading to the Green Revolution, defined by a number of research, development, and technology initiatives dedicated to improving crop yield. The Green Revolution was the start of genetically modified seed varieties, insecticides and chemical fertilizers.

Widespread use of these techniques, however, have come at the expense of the environment and nutrient content of the crops. Differences in fertilization and soil microbiology alter the mineral uptake by the plants, while increases in atmospheric carbon dioxide decrease the protein content of our crops. Early harvesting of immature crops to allow easier transport and storage, decrease the nutrient content of the crops. Further processing for enhanced shelf-life removes vital nutrient-rich components and essential fatty acids.

Agricultural Changes

Growing Practices

While traditional agricultural practices caused very little change to the soil, modern farming and fertilization practices can be damaging to the soil make-up and ecology â€" the complex array of living organisms in the soil that help break down nutrients. Using limited NPL fertilization does not put back the various trace minerals used by the plants. Protein producing plants require numerous elements from the soil, including nitrogen, sulfur, phosphorus, calcium, magnesium, manganese, boron, copper, zinc, molybdenum and others. While some of these minerals are needed in very small amounts, it is likely that the soil may become depleted over time eventually leading to nutrient declines in our food supply. Differences in soil composition can also alter macronutrient composition of the crops, particularly the ratio of carbohydrate to protein.

Conventional versus Organic Farming

Organic farming methods limit the use of chemical fertilizers and pesticides, focusing on more natural traditional methods. While not all research comparing organic farming practices with conventional practices have shown higher levels of nutrients, organically grown crops do have decreased levels of pesticide residues. The majority of research suggests that there are some differences in the nutrient composition between organic and conventionally raised produce, however the range of differences varies considerably.

Growing region

Research has shown that nutrient levels vary depending on the region in which a crop was grown. Climate, soil type and amount of rainfall all influence the nutrients levels of a plant. While growing region has been a minimal concern due to the variety in our food supply, as small local farmers give way to large agro-businesses, the area that supplies our food becomes increasingly consolidated and growing region could become a factor in nutrient content.

Crop variety

Modern crops have been bred for pest resistance, harvest timing, plant architecture, yield, shelf-stability, processing traits and consumer preference. In order to maximize the farmer's profit, the crops must be hardy, easily harvested and pleasing to the consumer. These traits are much more important to farmers than the ability of the crops to extract or synthesize nutrients from the environment. As crop varieties become more limited and selected for yield or other characteristics related to harvest and storage, the macro and micronutrient content of our crops becomes an increasing concern. Often plant varieties with increased yields are associated with lower protein and mineral content. This results in lower levels of these critical nutrients in our bodies and a potential for less than optimal dietary intakes.

Genetic modification

While genetic modification of the food supply has occurred since Mendel first crossed yellow and green peas, new technologies allow for insertion of genetic material into plants that could never occur through even the most rigorous of plant cross-breeding. Some researchers suspect that genetic modification could be decreasing the mineral bioavailability of our food supply, or even causing foods to have detrimental effects.

Environmental Contaminants

Pollution

The past 100 years has brought a huge increase in manufacturing, motor vehicles and airplanes, all bringing with them an increase in atmospheric pollutants. Burning hydrocarbons for fuel releases large amounts of carbon dioxide, carbon monoxide, sulfur dioxide, hydrogen sulfide, nitrogen monooxide, nitrogen dioxide and ethylene. These gases are responsible for smog, ozone and peroxyacetylnitrate, which can be damaging to plants and animals.

Atmospheric CO2

Research has shown as atmospheric CO2 increases, the levels of carbohydrate in plants increases. However, the levels of nitrogen, an important component of protein, and other nutrients decrease. Nitrogen use efficiency increases, which results in a decreased nitrogen demand and therefore lower levels in the plant and grain. Research suggests that similar decreases are found for calcium, sulfur, magnesium and zinc, while the uptake of other nutrients may be increased. Additionally, within the plant a higher accumulation of water soluble carbohydrates had a diluting effect on most of the other nutrients resulting in a lower level.

Ozone

Ozone has been found to lower harvest index and reduce the of time a plant devotes to grain filling (when nutrients are transported through the plant for storage in the seed). While crop yield has been shown to decrease with increasing ozone, some reviews suggest an increased protein concentration of the crops. Studies in potatoes, wheat, rice and beans have found that increased ozone resulted in a decreased starch and sugar content, while increasing protein and vitamin C. Furthermore, ozone exposure seems to alter the expression of proteins differently. Proteins related to detoxification increase, but proteins involved in photosynthesis and carbohydrate metabolism decrease. These proteins may also have a higher likelihood of allergenicity.

Acid Rain

Acid rain is caused by high levels of air pollution dissolving into the water droplets, decreasing the pH of rain. When this rain is dropped onto the ground, the resulting soil becomes more acidic. Acidic soil then affects the dynamics of the soil composition and plant nutrient uptake limiting growth and micronutrients within the plant. Acid soils limit the availability of certain minerals, particularly phosphorus. Decreased pH increases the binding of phosphorus with aluminum and iron oxides, preventing uptake by the plants.

Toxins

Our modern lives involve thousands of chemicals. Every day we come into contact with these chemicals in the form of pesticides, dyes, colors, medicines, flavoring, perfumes, plastics and plasticizers (phthalates and bisphenol A), resins and solvents. These chemicals have been introduced into the food supply generally only within the last hundred years, so the effect remains unknown. Some researchers suspect these chemicals may be responsible for the obesity epidemic or increasing incidence in developmental diseases.

Heavy metals

The adverse effects from heavy metal exposure have been known for decades. These metals include lead, cadmium, mercury and arsenic. While use of these metals has been declining, accumulation and exposure to these metals in the environment and food supply continues. Industrial emissions and waste ends up in the soil and water leading to increased contamination. This contamination leads to increased uptake in crops and animals, making the food supply a major source of these heavy metals.

Food Processing and Post-Production

Crop Maturity

The maturity of the crop at harvest is an important factor to nutritional quality. Crops that are ripened on the vine typically have the highest nutrient content. However, ripe fruits cannot typically survive the postharvest handling and transport to get them to the store. For this reason, crops are often harvested before they are fully mature.

Harvesting

Harvesting method and conditions have an impact on the nutritional quality of our crops. The weather conditions or damage during harvest, post-harvest treatments and the time between harvest and consumption all play a part in the nutrient content of the crops. High temperatures, chilling, or low humidity all decrease the nutrient content of the crops. Every 10 degree temperature increase accelerates the deterioration and increases loss by 2 to 3-fold. Other nutrients can be damaged by heat, oxygen, alkaline conditions, or physical damage.

Storage

Delays between harvest and consumption result in nutrient loss. At temperatures of 30º and 40º, delays of 24 hours between harvest and processing resulted in 5 and 12% losses in vitamin C, respectively. Kale held at room temperature for 2 days lost 20% of its vitamin C content, compared to 10% loss over 6 days at 6 degrees. Similar results were found for carotenoid content, as well as other vegetables, including spinach, cabbage and snap beans. Potatoes stored over time lost significant vitamin C when stored for 90 days or longer compared to a 5 day storage time.

Processing

Processing is a key part of the American diet. It is used to extend shelf-life and preserve nutrients. Crops can go though any number of types of processing after harvest. Processing can include grinding grains for flour, juicing, chopping, canning, freezing or cooking fruits and vegetables. For each step that a food item is processed, chances are it is losing nutrients due to both the timing and production process.

Home cooking

Home cooking can further increase nutrient losses. In an experiment involving potatoes, cooking decreased the vitamin C content by 30% and keeping them warm 1 hour after cooking decreased vitamin C by 10% more. Changes that can occur with cooking include minerals, vitamins and amino acids leaching into the cooking water, degradation of amino acids (when heated above 100 degrees or are exposed to prolonged periods of heat or alkali), and the hydrolysis of polysaccharides (starch and fiber) to lower moleular weight sugars.