The Official Newsletter of
updated: November 10, 2011
The Optimal Diet
 for Humans

by Ron Brown, Ph.D., author of The Body Fat Guide 

"Ron Brown is a certified fitness trainer who doesn't have an inch of flab on his body. He'll tell you what you can do to become fit and trim too." 
Washington DC

AN OPTIMAL DIET for humans maximizes health, prolongs life, and prevents chronic diseases, such as coronary heart disease, cancer, and diabetes (Nestle, 1998). An optimal diet may even be used therapeutically to reverse some chronic diseases (Campbell, II & Campbell, 2008). However, the medical healthcare system places little emphasis on an optimal diet in treatment, and has not been able to prevent or reverse the current global epidemic of chronic diseases (National Center for Chronic Disease Prevention and Health Promotion, 2008). As healthcare costs rise, national rankings in life expectancy at birth are plummeting in advanced countries like the United States (United Nations, 2007). The declining health of the population due to chronic disease indicates that the Western diet is far from optimal for health. How did we get here, and how do we get back on track?

When humans first appeared on earth, what was their original optimal diet? Researchers do not know the answer to this question, but they can infer some ideas. Homo Sapiens first appeared in the historical record about 200,000 years ago. There are two concepts that describe how early humans acquired food around that time. They hunted animals, and they gathered plant substances. 

Researchers have estimated that the composition of a hunter-gatherer diet consumed by early humans adequately met the biological needs of the human genome (Cordain et al., 2005). There are several nutritional characteristics of this diet that are strikingly different from our modern diet. In addition to a high amount of soluble fiber, the diet of early humans provided little starch, and no refined sugar, salt, or oil (the ingredients in a donut). However, although humans may have included the consumption of some animal food out of convenience and for survival due to scarcity of plant foods, there is no evidence that the general population of early humans ate very large quantities of animal foods (Nestle, 1998). Among those few people who could afford to include ducks, cattle, geese, and fish in their diet, such as the elite class of ancient Egyptians 3,500 years ago, Allam et al. (2009) found that their mummified remains showed signs of atherosclerosis, arthritis, and dental decay, similar to diseases prevalent in today's population.

Walker (1981) studied tooth and jaw wear patterns in hominids that preceded early humans, such as Australopithecus, which indicated these species ate a plant-based diet. Other researchers speculated that Homo Erectus killed animals for food (Nova, 2009). A severe jaw abscess in a discovered Homo Erectus skeleton named “Turkana Boy” provides supporting evidence that a high-protein meat diet may not have been optimal for the health of the species. The larger-brained, cave-dwelling Neanderthals of Northern Europe ate a meat diet, and died at young ages until the species became extinct.

In modern humans, epidemiological, clinical, and experimental evidence has revealed that the consumption of animal food, including lean animal protein, is a significant risk factor for developing chronic disease (Campbell & Campbell, II, 2006). This evidence rules out animal foods as an optimal diet for humans, and places the focus on a plant-based diet. 

Because fire may not have been discovered until many years after the first appearance of humans, it is likely that the early human diet was uncooked, which supports the concept that humans ate mainly a plant-based diet of uncooked fruit, nuts, and vegetables. In addition, this diet contained an abundance of alkaline-forming minerals from plant foods that provided bases to buffer acids generated within the body, which is necessary to preserve bone, muscle, and other tissue (Sebastian et al., 2002). 

Why did early humans eventually move away from an optimal diet? Most likely, climate change reduced the amount of food available to humans, and forced humans to search for new food sources. There is evidence that an eruption of a super volcano with a 100-km wide crater at Lake Toba, Indonesia, covered the earth's atmosphere with sulfuric acid 75,000 years ago, killing plant and animal life, and plunged the earth into a volcanic winter. In any event, by the time of the Agricultural Revolution, 10,000 years ago, the human diet had changed significantly, even though the biological needs of the human genome did not change. Animal husbandry introduced dairy and meat products, and farmers cultivated grains and starchy vegetables, which required cooking for consumption. Although the abundance of the food supply was increased, the nutritional effects of this diet on the biological needs of humans were no longer optimal. The de-optimization of the human diet accelerated with the introduction of food processing during the Industrial Revolution, 200 years ago, and continued up to the development of modern fast-foods, which began about 50 years ago. 

A return to the preagricultural, plant-based diet of early humans appears to be the optimal diet for modern humans (Jenkins & Kendall, 2006). Raw fruits, nuts, and green leafy vegetables, as early humans consumed them, provide the balanced nutrients required for an optimal diet to meet the biological needs of modern humans. See Bananas, Coconuts, and Green Smoothies: Nature's Perfect Foods. Some researchers have suggested that the balance between an optimal diet’s acid-forming components, such as protein in nuts, and the alkaline-forming minerals, such as potassium in fruit, prevents chronic low-grade metabolic acidosis, which compromises the health of modern humans who eat a predominately acid-forming diet (Frassetto et al., 1998). In addition, leafy green vegetables have an excellent balance of protein and potassium, as well as chlorophyll, calcium, phosphorus and other nutrients, and are included in an optimal diet to ensure the proper balance of nutrients.

Balancing an Optimal Diet

There is disagreement among advocates of a raw fruit, nut, and green leafy vegetable diet about the proper proportions of each of these food groups that should be included in the diet. Although individuals have slightly different nutritional needs, the overall balance of nutrients in a raw diet probably should not vary significantly from the balance recommended by conventional nutrition authorities, which is approximately 10% calories from protein, 30% calories from fat, and 60% calories from carbohydrates. Note, however, that actual protein needs are as low as 5%. The recommended amount is increased for safety, largely because of different efficiencies among people in digesting and absorbing protein. For example, some cooked proteins are less usable by the body.

Fruits are high in the nutrients lacking in nuts, and nuts are high in the nutrients lacking in fruit. Green vegetables are high in nutrients found in lower amounts in both fruit and nuts, such as calcium, and are an essential addition to the raw diet. Some advocates of a raw fruit, nut, and vegetable diet recommend very high amounts of fat from nuts, avocados, and other fats, while other advocates recommend hardly any fat from these foods. For example, David Wolfe's Sunfood Diet recommends approximately 44% of calories from fat, while Doug Graham's 80-10-10 raw diet recommends only 10% of calories from fat. See my reviews of these books at Some advocates recommend high amounts of green vegetables, and others recommend high amounts of fruit. 

What are the problems with these unbalanced combinations? Let's look at the following unbalanced diet combinations: fruit alone, nuts alone, green vegetables alone, fruit and vegetables alone, and nuts and vegetables alone. A diet of fruit alone, although rich in vitamins and minerals, is low in protein, deficient in fat, and too high in sugar. Green vegetables alone are deficient in carbohydrates and fat. Although the protein content of green vegetables is high, it is impossible to eat green vegetables in sufficient quantity to derive adequate amounts of energy. Fruit and vegetables alone are low in protein and deficient in fat. On this diet, all of the calories are supplied by carbohydrates, which can lead to cravings from lack of fat.

Nuts alone are deficient in carbohydrates, with the exception of some nuts like coconuts, which are lower in protein. Many nuts are high in protein and phosphorus, and are acid-forming. Green vegetables together with high-protein nuts are low in carbohydrate content. Although potassium and other alkaline minerals are well supplied in green vegetables, the percentage of calories from acid-forming protein in a meal of high-protein nuts and green vegetables remains high. 



Fruit is generally an alkaline-forming food, but assessing the potential acid-load of a food by the total amount of alkaline-forming minerals it contains ignores important independent relationships between several minerals, such as calcium and phosphorus. Although a high fruit intake may have a low overall potential acid-load due to high levels of potassium, most fruit contains more phosphorus than calcium and may lead to disturbances in calcium balance if eaten excessively. This explains why eating excessive amounts of some types of sweet fruit appears to have an acidic effect and demineralizes bone and teeth. For example, fruit farmer workers consuming excessive amounts of apples and grapes suffer higher rates of tooth loss (Grobler & Blignaut, 1989). Unlike oranges, apples and grapes contain twice as much phosphorus as calcium, and their excessive consumption may disturb the body's normal calcium-phosphorus balance, even though the overall mineral content of apples and grapes is alkaline due to high potassium levels. This does not mean to avoid apples and grapes; it just means that these foods should be part of a well-balanced diet that includes plenty of leafy green vegetables.

The body requires equal amounts of phosphorus and calcium by molecular weight to build bone. Phosphorus has twice the absorption rate of calcium in the intestines. This implies that the optimal diet for humans should be twice as high in calcium than phosphorus. The foods that best meet this requirement are raw dark green leafy vegetables like kale, collards, bok choy, etc., and some citrus fruits. Animal studies show that bone mineral density is highest when the calcium: phosphorus ratio of the diet fed is 2:1.

Although mono-diets of fruit have been used therapeutically to help patients recover health, the small amount of fruit fed is intended to keep the daily intake of sugar, starch, fat, and protein as low as possible. Similarly, 2700 calories worth of almonds provides over 1200 milligrams of calcium, but also includes an excessive amount of acidic protein and phosphorus that results in bone and teeth demineralization. Even excessive fat intake is acidic and results in demineralization as the excess fat is combined with alkaline minerals and eliminated in the feces. 

Note that a raw diet that supplies 10% or more calories as protein from nuts and from other raw foods may be too acid forming for health, even when including high amounts of fruit and vegetables. It may be safer to reduce dietary protein to 5–6% of calories. In his book, The China Study, Dr. Campbell says, 

"Relative to total calorie intake, only 5–6% dietary protein is required to replace the protein regularly excreted by the body...increasing dietary protein within the range of about 10-20% is associated with a broad array of health problems, especially when most of the protein is from animal sources."

Dr. Campbell recommends 8–12% calories from protein (Cordain & Campbell, 2008), but his recommendation includes cooked protein, which has a lower level of bio-availability. This recommended amount also is calculated to exceed the needs of 98% of the general population, while ensuring the higher protein needs for the remaining 2% of people. 

To summarize, on an optimal diet of raw fruits, nuts, and green vegetables, each component of the diet contributes essential nutrients, and should be properly balanced with the other dietary components. My personal recommendation is to balance an optimal raw diet with approximately 5–10% calories from protein, 30–45% calories from fat, and 45–60% calories from carbohydrates. The Food & Nutrition Board of the National Academies, Institute of Medicine, recommends 45–65% carbohydrate. If you feel 65% carbohydrate on a raw diet provides too much sugar and acid from fruit, reduce the percentage of calories from carbohydrates and increase the percentage from fat. It is not unusual to consume equal percentages of fat and carbohydrates, such as 45% of each, which is about what the average American eats.  Leafy green intake should amount to between one and two pounds. If there is a need for extra protein for growth purposes, as in pregnancy and bodybuilding, or more energy is required from both fat and carbohydrates for physical activity, this may be supplied by increasing the overall caloric intake of an optimally balanced diet.


Allam, A. H., Thompson, R. C., Wann, L. S., Miyamoto, M. I. & Thomas, G. S. (2009). Computed tomographic assessment of atherosclerosis in ancient Egyptian mummies. Journal of the American Medical Association, 302, 2091–2094.

Campbell, T. C., & Campbell, II, T. M. (2006). The China study: Startling implications for diet, weight loss, and long-term health. Dallas , TX : BenBella.

Campbell, T. M., II, & Campbell, T. C. (2008). The benefits of integrating nutrition into clinical medicine. The Israel Medical Association Journal, 10, 730–732.

Cordain, L., & Campbell, T. C. (2008). The protein debate. Performance Menu: Journal of Nutrition & Athletic Excellence. Downloaded December 16, 2009 from

Cordain, L., Eaton, S. B., Sebastian, A., Mann, N., Lindeberg, S., Watkins, B. A., et al. (2005). Origins and evolution of the Western diet: Health implications for the 21st century. American Journal of Clinical Nutrition, 81, 341–354.

Frassetto, L. A., Todd, K. M., Morris, Jr., C., & Sebastian, A. (1998). Estimation of net endogenous noncarbonic acid production in humans from diet potassium and protein contents. American Journal of Clinical Nutrition, 68, 576–583.

Grobler, S. R., & Blignaut, J.B. (1989) The effect of a high consumption of apples or grapes on dental caries and periodontal disease in humans. Clinical Preventive Dentistry, 11, 8–12.

Jenkins, D. J. A., & Kendall, C. W. C. (2006). The Garden of Eden: Plant-based diets, the genetic drive to store fat and conserve cholesterol, and implication for epidemiology in the 21st century. Epidemiology, 17, 128–130.

National Center for Chronic Disease Prevention and Health Promotion. (2008). Chronic disease overview. Retrieved November 20, 2008 from

Nestle, M. (1998). Animal v. plant foods in human diets and health: Is the historical record unequivocal? Proceedings of the Nutrition Society, 58, 211–218. 

Nova. (2009). Becoming human: Part II & Part III. PBS.

Sebastian, A., Frassetto, L. A., Sellmeyer, D. E., Merriam, R. L., & Morris Jr., R. C. (2002). Estimation of the net acid load of the diet of ancestral preagricultural Homo sapiens and their hominid ancestors. American Journal of Clinical Nutrition, 76, 1308–1316.

United Nations. (2007). World population prospects: The 2006 revision. Retrieved October 23, 2008 from

Walker, A. (1981). Dietary hypotheses and human evolution. Philosophical Transactions of the Royal Society of London, 292, 57-64.

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