The Starvation Rainbow

Most animals for most of their life live not too far from the edge of starvation. Simple ecological processes mean that if potential food resources are in abundance and under-utilised then populations will increase until production balances consumption. At that balance point any fluctuation in production can stress the population and the weaker individuals will succumb. True starvation is pretty rare in nature, usually reserved for apex predators. Other animals become easy meals for their predators when they become even moderately weakened. Likewise in humans true starvation is rare since disease and conflict usually compound the difficult situations that tend to interrupt food supplies. While settled agricultural societies have an intimate history with famine, with successive crop failures coming about once a generation in many cultures, hunter gatherers by contrast have a very different outlook. The Khoi-San of southern Africa have a deep belief that nature will always provide food for them. They function in a hierarchy of edibility, with their energy going toward the most rewarding food gathering activities during good times, but leaving less profitable food sources for difficult seasons. The ability to simply move to another location is also extremely valuable for dealing with variable food production, a trick that most settled farming people have lost. Those peasants though often still utilized a hierarchy edibility where possible, abandoning their fields during crop failures to gather less rewarding foods like wild chestnuts that were barely worth bothering with when their granaries were full. Food sources with the highest return on investment were always preferred, since using them left ample time to do activities other than growing and processing food.

With the recent coronavirus pandemic and economic chaos people have been revisiting the forgotten cultural connection to famine. Few modern people living in industrial cities have a clear idea about how much food a person actually needs to live. Starvation comes in many different forms, with different consequences. The most obvious of these is lack of energy (measured in calories or kilojoules), a type of starvation also known as marasmus. This usually translates as a lack of carbohydrate or fat in the diet. A typical human requires about 10 000 kJ of energy per day, which translates to 625 of pure starch if this was a person’s only food intake. Carbohydrates normally make up about 50 % of the diet, so about 300 g starch would be more typical. Flour is about 70% starch so that would translate into 430 g per person per day, while cooked rice is 30 % starch so a person would need 1000 g per day, and finally potatoes which contain even more water and fibre are about 20 % starch so a person would need 1500 g per day. A typical diet also gets about 40 % of its energy from fat, with the final 10 % coming from protein. Fat is more energy dense than carbohydrate so this amount can be provided by about 100 g of pure fat per day. This could be provided directly by a bit under half a cup of pure vegetable oil or animal fat, or via a cup of oily nuts which are about 50 % fat. With prolonged energy starvation the body first depletes its carbohydrate stores in the liver and muscles, then depletes fat stores in various places, then finally starts to break down protein in non-essential tissues in order to continue supplying energy to the brain and vital organs. Without sufficient energy most people can survive with decreasing strength and functioning for 8-12 weeks. General energy deprivation reduces the ability of the body to produce mucus, an essential protective barrier against microbes that can cause disease.

Another major form of starvation occurs due to lack of protein, an essential ingredient for the growth and repair of structures in your body. Severe protein starvation is called kwashiorkor, familiar to people as the sight of skeletal infants with swollen bellies in commercials for aid organisations. Societies that are proficient at growing starchy staples but lack sources of cultivated or domesticated protein often experience widespread protein malnutrition, such as is endemic in Papua New Guinea. Protein deficiency manifests in different ways, with the body’s ability to maintain immune function being severely impacted. For example the ability to produce antibodies is reduced in the case of protein deficiency, leading to dormant tuberculosis in the lungs becoming active. The fatality rate for measles in protein deficient children is over 200 times higher than in those with an adequate diet. Even normally benign gut microbes can turn pathogenic when a person experiences prolonged protein deficiency. The protein requirement of the body can increase significantly when fighting infectious illness. The common tradition of providing meat based broth to people fighting an illness may be based on this requirement. Chicken soup for the white blood cells and not just the soul. Adult humans require about 50 g of protein per day, translating to 200 g of meat or 600 g of cooked legumes.

Apart from these macronutrients humans also require a reliable intake of a wide range of other nutrients. These micronutrients are usually called vitamins and minerals and insufficient intake is called a deficiency, but to me they are just another band on the starvation rainbow. Most people know about vitamin C and the dreadful disease of scurvy caused by prolonged deficiency. Vitamin C helps the body make collagen, the tough material that holds skin together. Without vitamin C your body disintegrates. Humans need about 0.1 g per day, provided by about 300 g of leafy greens or 200 mL of citrus. Other common fruit aren’t a particularly rich source, though some smaller potent fruit like acerola can provide a day’s intake from a mere 6 g, just one or two fruit. Cooking destroys vitamin C so these sources must be eaten fresh.

The multiple B group vitamins also can cause their own types of starvation when diets are inadequate. The disease pellagra swept southern Europe after corn was introduced from the New World. The crop was so much more productive than wheat that it completely replaced it. Unfortunately the European peasants did not know the techniques of the native Americans needed to release its B3 vitamin content, leading to plagues of psychological disturbances (light sensitivity, pain sensitivity, odour intolerance causing nausea, dizziness, restlessness and anxiety) plus physical symptoms (dermatitis, hair loss, insomnia, paralysis and death). They assumed the newly introduced corn was poisonous but its greater productivity led to increased population sizes so it was not possible to revert to wheat without calorie based starvation. In this way the most productive crops trap us in growing them and suffering. Humans only need about 16 mg of B3 per day, and it is found in a wide variety of meat and seeds, especially seafood and peanuts. Usually only the most meagre and unbalanced diets lead to deficiency. A similar story played out in the great beriberi epidemics in Asia. Traditionally peasants ate brown rice, while rice that was further processed to remove the bran to make white rice was only affordable for the wealthy. When industrialisation spread into Asia the processing of white rice became more common (partly because white rice is easier to store and transport) so peasants moving to live in cities started relying on inadequate diets composed primarily of white rice. These poor people experienced emotional and sensory disturbances, weakness and pain, and eventual heart failure and death. The condition was eventually traced to a B1 deficiency. Humans need a minute 1 mg per day, readily provided by a wide range of seeds, meat and fresh fruit and vegetables. Deficiencies of B and C vitamins are also linked to less effective white blood cells, lower levels of antibody production, leading to weaker immune systems.

Other nutrients are also essential for good health. Vitamin A is necessary to maintain eye function, and is readily supplied by yellow or orange vegetables such as carrots and pumpkin. Vitamin A is also essential for production of lysozyme proteins found in secretions such as tears, where they provide a powerful antibacterial effect. Vitamin D can be provided by fatty fish or fortified dairy intake and is necessary to ensure bone development and immune function. Individuals with low vitamin D levels have been found to be far more likely to experience severe symptoms from novel coronavirus. Vitamin D is mostly produced within the body with exposure to ultraviolet light, best acquired by exposing the body to sunlight during the morning and afternoon while light intensity is moderate in order to balance the benefit of vitamin D against the risks of excessive UV exposure. Older individuals and those with darker skin can have more difficulty producing sufficient vitamin D. Urbanisation coupled with constant air pollution blocking the sun led to children in early industrial cities developing bent bones, a horrible condition known as rickets. A wide variety of electrolytes (sodium and potassium), macro-minerals (calcium, phosphorus, sulfur and magnesium) and trace minerals (iron, copper, zinc, manganese, iodine, selenium, cobalt) each have their own minimum requirements, useful dietary sources and associated health impacts from deficiency. The less diverse the diet, and the greater the amount of processing and refinement, the more likely any one of these will become an issue that impacts overall health.

Putting all this together one can construct a model diet for one human for a year. It would consist of 550 kg of potatoes for carbohydrates, 36 L of vegetable oil, 70 kg of meat (or 220 kg of cooked legumes, about 55 kg of dried legumes), and about 110 kg of fresh fruit and vegetables to supply vitamin C and some other vitamins. You will notice the outsized importance of carbohydrates, fats and protein relative to fruit and vegetables. For city dwellers with limited incomes that can afford white rice, vegetable oil and beans produced by distant mechanised farms the ability to produce the final piece of the nutritional puzzle and grow their own expensive fruit and vegetables is extremely valuable. But they should keep in mind that the machines will not run forever and at some point they will need to leave the cities. In a future companion post to this article I will outline the amount of space this amount of food requires to grow, both under our modern industrial agricultural systems and in the less productive pre-industrial models in order to help people get a mental picture of the scale required to support one person.

People rarely starve the way we imagine due to outright energy deficiency. When they do it is usually due to unusual political and economic factors. What is far more common during times of chaos is for other less dramatic forms of nutritional insufficiency to slowly creep up on a population. In the supposedly richest and most powerful nation on earth about 7 % of people live in food deserts, without access to supermarkets, and 31 % of the population is at risk of at least one micronutrient deficiency. Inadequate diets then usually lead to spread of pandemic diseases where the weakest among us succumb first and spread the disease further. Conflict often follows. Among the dead caused by wars the majority usually succumb to disease, which again is usually tied back to inadequate nutrition. In these uncertain times it is useful to firmly grasp the reality of what the human animal needs in order to survive the challenges ahead.

A historic photograph from the 1915 Lebanon famine.