The seminal paper by Motoo Kimura [K68] suggested that evolution is the result of random mutations of DNA at the molecular level. If the organism carrying such mutations is good/lucky enough to reproduce, these mutations are then propagated to the next generation. Gradually, the mutations that are good are accumulated over time and the organism evolves.
But what does this neutral theory of molecular evolution have to do with nutrition? As we know, over the last century, technology improved leaps and bounds. In contrast, molecular evolution is a very slow process. Our body simply can't keep up with the advance in food technology, not to mention the all-powerful marketing omnipresent in the modern world. These two forces combine together make us consume highly processed food in a high quantity. It is natural that our body can't handle this for long, becomes obese and/or suffer all kinds of chronic diseases.
In this page, I would like to show you first a simple guideline to adjust your diet to make it in tune with our current evolution state. Then I will proceed to fill in some hard nutrition data from the Institute of Medicine of the US government that allows you to fine tune the diet to become the healthiest possible under the current medical knowledge. After that I will explore other issues tangentially related to nutrion before I conclude.
Humans were hunter-gathers beginning from our appearance two million years ago. Until the invention of fire at about 800,000 years ago, basically we subsisted on fruits we gathered and raw meat we hunt. From then on, until about 12,000 years ago, because of fire, we started consuming lightly processed food. The introduction of argriculture 12,000 years ago gave us access to grains and therefore exposure to high GI food. The high rate of technogical devleopment right after World War II revolutionized our food culture and gave us the highly processed food that causes chronic diseases.
It is obvious that our history of consuming highly processed food is just a blip over the two million years long human history. It is not likely that majority of us can evolve this fast to adapt to this relatively new environment. Actually, I would venture to say that we might never naturally evolve out of this because the chronic diseases developed usually only kill us after we reproduce. Therefore we have to live with the fact that our bodies are not ready for the highly processed food now and possibly forever. To live well under the cloud of this fact, we need to avoid consumption of highly processed food.
There are many varieties of processed food. It is like a wide spectrum with various degree of processing. Some are almost completely artificial, for example, the soft drinks. Some are from natural source but then after processing, the new nutriton profile is not necessarily healthy, for example high concentration fruit juice (unhealthy for its high concentration of sugar). On the other end of the spectrum, we have the natural fruits you can pick in the wild or sashimi (raw fish) you get at a Japanese restaurant.
In general, the highly processed food are made to be more sweet, umami (the taste of MSG), oily and/or salty than unprocessed food. This is because these characteristics make them more pleasant to our taste buds. Some also contain caffeine or similar chemicals to keep us addicted.
More sweet means more refined (ie high GI) carbohydrates which will disrupt our insulin level, make us fat (thru the mechanism of prevent us from burning fat, see the Diet page) and increase the chance of diabetes. Salt and MSG contribute to higher blood pressure and also higher probability of developing gastrointestinal (ie the digestive system that consists of esophagus, stomach, intestine and colon) cancer. Deep fried food like potato chips contain a lot of calories from oil and carb without making us satisfied.
It is safe to say that in general the more processed the food is, the more unhealthy it is. But we should treat this as a rough guideline because first of all, degree of processing can't be properly defined; second, there are always exceptions to the rule. The most accurate way to decide whether a food is healthy is to examine its nutrition profile. We will discuss this in the Hard Nutriton Data section.
One good news for us health conscious people is that processed food in developed countries now usually comes with a Food Label that shows the content of major nutrients. A good practice is to always read the food label to separate the good food from the bad food. Some basic terms you should look carefully are: Sodium (from salty or umami food), carbohydrate (wreck our insulin balance). Fat per se is ok for our body but a combination of it with carbodydrate in deep-fried fashion is very bad.
Another advantage of relatively natural food is that they are more likely to be "tested" for a longer much longer time. Therefore, there is a lower risk that natural food can cause chronic diseases. For example, the coca cola zero has been available since 2005, so it is only widely "tested" for 3 years as of 2008. While the possibility is low, it is no guarantee that it can't cause chronic diseases. On the other hand, juice of oranges was "tested" for perhaps as long as humans existed, so it is far safer to say that it is not bad for health.
One big class of processed food is preserved ethnic food, for example, Salted Cod in Scandinavian food, Salami in Italian food, Kimchi in Korean food, Tsukemono in Japanese food, Jinhua Ham in Chinese food and so on. These food were developed before the age of refrigerator because that was the only way to preserve food. Techniques like drying, curing (ie salting), smoking are used. These techniques usually involve the use of carcinogenic additives.
While these food are usually quite delicious, they are obviously bad for your health. Unless you want to have a life expectancy below 50 like people 100 years ago, I would recommend you avoid these preserved food as much as you can.
Having said all the bad words about processed food, some of them are not that bad. Diet coke is a good example. The diet coke since 2005 replaces the sugar with zero calories sugar substitutes sucralose and acesulfame potassium. Therefore compare to the normal coke, it should be much healthier. According to the authorities, these sugar substitutes are "safe". But there are also some research suggest they have some adverse side effects. Obviously, since they are relatively new, long term test is not available, so take it in your own risk.
From the natural food doctrine I outlined from the previous section that with few exceptions, the less we process the food, the more natural it is and therefore the more healthy it is, it follows that steaming and boiling with water are the two healthiest ways to cook. Apparently, using either method won't add more calories to the food. Grilling is generally ok but the char produced is carcinogenic. Pan fying or sauteed require oil, so it does add calories but calories from oil is not as bad as calories from refined carbs. They add Roasting is not as healthy as it requires the addition of sugar. Deep fry is the worst because it combines lots of fat and lots of refined carb in a very high temperature. While it makes the food very easy in the mouth, it is also not very satisfying for your stomach, so you will easily consume more calories than you want.
Another thing to be careful about is cooking oil. Olive oil, while generally agreed to be a healthy cooking oil can turn into carcinogenic if you heat it over its low smoke point (especially the extra virgin version). If you plan to deep-fry food, you are recommended to use an oil with high smoke point like rice bran oil or peanut oil.
Another thing that our body couldn't evolve in line with the technological advances is in the mental department. Nowadays, with the development of marketing, we are experiencing daily bombardment of food advertising in TV and other media. The mouth-watering imagery and the excitement demonstrated by actors in the advertisements create an artificial desire for food in our mind.
Note that you seldom see advertisements for unprocessed food. This is not surprising because the more processed a food is, the more profit is to be made in the expense of your health.
Now you understand the importance of eating fresh and minimally processed food. You should now have learned some easy-to-follow guidelines of healthy eating. As we know, to completely control our nutritional destiny, we do need to have a better grip of the hard nutrition data.
What follows is the lastest official nutrition guideline, ie the Dietary Reference Intake (DRI), as suggested by the Institute of Medicine of the US government. Terms are defined first and then there will be calculators that give you the specific nutriton data for your sex and age group. After that, I will further explore other nutrition issues that have not been addressed yet.
[Note: Knowledge of elementary statistics including hypothesis testing is required to understand this section.]
For nutrients with an EAR, a z-score is calculated using the following equation:
| mean observed intake - EAR | ||
| z-score | = | ---------------------------------------------------------------------------------- |
| [(SD of requirement)2 + (within-person SD)2 / number of days of intake records]1/2 |
To illustrate the above equation, let's take Vitamin C as an example. Suppose you are a young male adult (19-30yr) whose Vitamin C intake in the last 10 days are as follows: 89mg, 97mg, 139mg, 53mg, 45mg, 201mg, 123mg, 98mg, and 134mg respectively. Here, mean observed intake will be the average which is 98mg/day. EAR is 75mg/day. SD of requirement is (RDA-EAR)/2 = (90-75)/2 = 7.5mg/day. Within person SD is the population standard deviation, ie you divide the sum of squared deviations by 10 instead of 9. The "within person SD" is 43.63mg/day. The number of recorded days is 10. By plugging in the numbers, we find that the z-score is 1.4645.
For nutrients with an AI, it is not very useful to compare individual intake with it because AI is usually in excess of EAR by a very large amount. Fortunately, it is possible to determine the confidence with which one can conclude that usual intake exceeds the AI using the following equation:
| mean observed intake - AI | ||
| z-score | = | -------------------------------------------------------- |
| within-person SD / (number of days of intake records)1/2 |
For nutrients with UL, you can assess whether UL is exceeded. The equation is very simliar to the one with AI
| mean observed intake - UL | ||
| z-score | = | -------------------------------------------------------- |
| within-person SD / (number of days of intake records)1/2 |
This is the complete Dietary Reference Intakes (DRI) from [DRI05]. All data are in RDA except for the italics which are in AI. For your convenience, there is a calculator to calculate the daily requirements based on the age group you input below the next table.
| Sex | Men | Women | Pregnancy | Lactation | ||||||||||||||||||||||
| Age | 0-6m | 7-12m | 1-3y | 4-8y | 9-13y | 14-18y | 19-30y | 31-50y | 51-70y | >70y | 0-6m | 7-12m | 1-3y | 4-8y | 9-13y | 14-18y | 19-30y | 31-50y | 51-70y | >70y | 14-18y | 19-30y | 31-50y | 14-18y | 19-30y | 31-50y |
| Carbohydrates (g/day) | ||||||||||||||||||||||||||
| Fiber (g/day) | ||||||||||||||||||||||||||
| Total Fat (g/day) | ||||||||||||||||||||||||||
| Linoleic Acid (g/day) | ||||||||||||||||||||||||||
| α-Linolenic Acid (g/day) | ||||||||||||||||||||||||||
| Protein (g/kg/day) | ||||||||||||||||||||||||||
| Histidine (mg/kg/day) | ||||||||||||||||||||||||||
| Isoleucine (mg/kg/day) | ||||||||||||||||||||||||||
| Leucine (mg/kg/day) | ||||||||||||||||||||||||||
| Lysine (mg/kg/day) | ||||||||||||||||||||||||||
| Methionine + Cysteine (mg/kg/day) | ||||||||||||||||||||||||||
| Phenylalanine + Tyrosine (mg/kg/day) | ||||||||||||||||||||||||||
| Threonine (mg/kg/day) | ||||||||||||||||||||||||||
| Tryptophan (mg/kg/day) | ||||||||||||||||||||||||||
| Valine (mg/kg/day) | ||||||||||||||||||||||||||
| Water (L/day) | ||||||||||||||||||||||||||
| Vitamin A (μg RAE/day) | ||||||||||||||||||||||||||
| Vitamin B6 (mg/day) | ||||||||||||||||||||||||||
| Vitamin B12 (μg/day) | ||||||||||||||||||||||||||
| Biotin (μg/day) | ||||||||||||||||||||||||||
| Vitamin C (mg/day) | ||||||||||||||||||||||||||
| Choline (mg/day) | ||||||||||||||||||||||||||
| Vitamin D (μg/day) | ||||||||||||||||||||||||||
| Vitamin E (mg/day) | ||||||||||||||||||||||||||
| Folate (μg DFE/day) | ||||||||||||||||||||||||||
| Vitamin K (μg/day) | ||||||||||||||||||||||||||
| Niacin (mg NE/day) | ||||||||||||||||||||||||||
| Pentothenic Acid (mg/day) | ||||||||||||||||||||||||||
| Riboflavin (mg/day) | ||||||||||||||||||||||||||
| Thiamin (mg/day) | ||||||||||||||||||||||||||
| Calcium (mg/day) | ||||||||||||||||||||||||||
| Chromium (μg/day) | ||||||||||||||||||||||||||
| Copper (μg/day) | ||||||||||||||||||||||||||
| Fluoride (mg/day) | ||||||||||||||||||||||||||
| Iodine (μg/day) | ||||||||||||||||||||||||||
| Iron (mg/day) | ||||||||||||||||||||||||||
| Magnesium (mg/day) | ||||||||||||||||||||||||||
| Manganese (mg/day) | ||||||||||||||||||||||||||
| Molybdenum (μg/day) | ||||||||||||||||||||||||||
| Phosphorus (mg/day) | ||||||||||||||||||||||||||
| Potassium (g/day) | ||||||||||||||||||||||||||
| Selenium (μg/day) | ||||||||||||||||||||||||||
| Sodium (g/day) | ||||||||||||||||||||||||||
| Chloride (g/day) | ||||||||||||||||||||||||||
| Zinc (mg/day) | ||||||||||||||||||||||||||
There are just too many nutrients to keep track of to make sure that you are adequate in all of them. To simplify this process for you, I will pick a "typical" diet and then tell you which nutrients are deficient or overconsumed in this diet. Since these pages are written in English, I presume many readers have a Standard American Diet (SAD) that contains a large amount of saturated fat, trans fat, chemical additives, refined sugar, and overall calories.
Obviously, people who are on SAD will have a large amount of carbohydrates, protein and fat. So it is best to eat less of each one of them, in particularly carb (and to a lesser extent protein) because they have GI implications (check the GI control section in the Diet page) in addition to preventing your body from burning fat.
While fat makes you fat and is only essential for infants, there are two essential fatty acids that our body can't do without. They are Linoleic Acid (aka Omega-6 fatty acid) and α-Linolenic Acid (aka Omega-3 fatty acid). The people of SAD should have enough of the former but most likely they lack the latter. Major food sources for Omega-3 fatty acid are flaxseed, canola, soy bean and fatty fish. The Omega-3 from fatty fish like salmon and tuna is particularly well absorbed by our body. If you don't like fish or flaxseed, I would recommend you taking Omega-3 supplements regularly. Omega-3 fatty acid can reduce the risk of many chronic diseases including coronary heart disease, stroke and diabetes. The traditional Japanese diet is high in Omega-3 due to high consumption of sashimi (aka raw fish). It is no wonder that the Japanese have a lower rate of chronic diseases. Indeed, a diet that mainly consists of vegetables and fish has the lowest mortality ratio (observed deaths to expected deaths) among all diets. It is even healthier than the vegetarian diet.[KFTABRBKMM99]
Cholesterol is a nutrient SAD people overconsume. High consumption of cholesterol is associated with higher risk of coronary heart disease. To reduce cholesterol consumption, eat less meat and some type of seafoods like shrimp, lobster, salmon and sardines and also full-fat diary products.
Trans fatty acid is also overconsumed for people with SAD diet because it has a heavy presence in fast food, snack food, fried food and baked food. [DRI05] says any incremental consumption of trans fatty acid increases the risk of coronary heart disease. Therefore the more you can avoid it the better.
Saturated fatty acid presents in meat, cheese, cream, chocolate, butter and so on. These items are also high in SAD diet. Again, excessive consumption can increase the risk of cardiovascular diseases.
There is no RDA or AI or UL for cholesterol, trans fatty acids and saturated fatty acids. [DRI05]'s recommendation is "as low as possible while consuming a nutritionally adequate diet".
Among the vitamins, SAD people are deficient in Vitamin C and folate. By consuming more fruits and leafy vegetables, you should be adequate in Vitamin C. Deficiency in Vitamin C can lead to scurvy. To combat folate deficiency, you can consume more dark green vegetables, beans and legumes. Deficiency in folate can lead to macrocytic anemia which has symptoms of weakness, fatigue, difficulty in concentrating, irritability, headache, palpitations, shortness of breath and atrophic glossitis.
Among the minerals, SAD people overconsume Sodium, Chloride and Phosphorus while deficient in Potassium and Calcium. Table salt is by definition a compound of Sodium and Chloride. Typical processed food like instant noodle, pre-packaged meals, canned soup, etc contain an excess amount of table salt. In addition, food at restaurants typically are heavily salted to enhance flavor and suppress unfreshness of food. It is very easy to exceed the 2.3g/day UL of Sodium and 3.6g/day UL of chloride if you have a habit of consuming highly processed food and eating out. Excess intake of table salt increase thse chance of hypertension which can lead to heart disease, stroke and kidney disease. To avoid hypertension, try eat out less and cook natural food without adding salt. Phosphorus is another ingredients food industry love to add to food to increase smoothness, improve binding and moisture retention. Phospohrus is also present in many soft drinks. Excess intake of phosphorus can cause hyperphosphatemia. Symptoms of this disorder are reduced calcium absorption and calcification of nonskeletal tissues, particularly the kidneys.
Potassium is like the antagonist of sodium. In fact, the higher the ratio of Potassium to Sodium, the more water is inside cells than in between cells. [EMP03] The water in between cells include lymph, blood plasma, urine, etc. Therefore the more Potassium we have, the less water is in blood and hence lower blood pressure and lower chance of hypertension. Severe Potassium deficiency can lead to hypokalemia which has consequences like cardiac arrhythmias, muscle weakness and glucose intolerance. To have enough potassium, you eat leafy greens and vine fruit (such as tomatoes, cucumbers, eggplants, pumpkins, etc) and root vegetables.
Calcium is important for the normal growth and maintenance of teeth and bones. Lack of it can results in rickets, poor blood clotting and osteoporosis. When you look at the AI of Calcium, you will notice that it is unusally high. A typical cup (240ml) of milk only has about 300mg of it (ie 30% of daily AI for a typical adult). Since most other non-diary food have only very little Calcium, it does appear to be very hard to meet the daily requirement unless you are an avid diary food eater. But you have to note that AI is usually much higher than the true requirement RDA. Also, excessive protein and/or phosphorus intake can reduce aborption of calcium. Therefore, by sticking to a diet very different from SAD, you should not need to actually fulfill that AI requirement. Having said that, calcium supplement is still recommended especially for elderly women.
While it appears that many major nutrients are identified and studied in details, there remains tons of nutrients (e.g. phytochemicals) that the scientists know very little about. Some of them may be essential to your health. Also, since you can't get them from fortified processed food or supplements, you should consume more food from natural source to make sure that you have these lesser known nutrients covered.
Now you should have a fairly complete picture of how to hit all the daily nutrients requirements to maintain the best health possible based on current scientific knowledge. From here on until conclusion, I will explore other issues related to our health. I will start with chewing gum first and then follow by vegetarianism.
You might have heard that some years ago Singaporean government banned the sale of chewing gum, possibly because it is hard to clean up the gums that stick to the ground. Interestingly, recently they started to allow the selling of gums that have medical benefits. So what are these chewing gums with medical benefits?
They are gums that contain a type of sugar alcohol called Xylitol. In addition to carb, protein and fat, sugar alcohol is also a source of energy to our body. For Xylitol, it is about 2kcal/g. As is implied by its name, sugar alcohol is sweet. So it can act as a natural sugar substitute. Unfortunately, its sweetness is nowhere comparable to the artificial sweetener, so it is typically not used to replace sugar. Unlike carb, sugar alcohol has no effect on your insulin.
Among various sugar alcohol, Xylitol stands out with its capability to kill germs that cause cavity. Since such germs can only feast on carb (hence the stories of sweety teeth), it is recommended that if you just had a meal with high amount of refined carb, you should blush your teeth immediately. But as you know doing that might not be convenient in many circumstances. Chewing the Xylitol gum does appear to be a very good compromise.
In addition to preventing cavities, chewing gums can also play a role in dieting. While you are dieting, sometimes you might just find that you eat too little for a meal and feel a bit hungry before the next meal. What to do? A good solution is to chew sugar alcohol gums. Usually it takes you ten or more minutes to chew a gum. This prevents you from consuming other food uncontrollably during that time. It is also a good exercise for your jaw muscles. (albeit I personally had strained my jaw muscles several times by chewing gums too frequently. I guess as an old saying goes, "Too much of anything is a bad thing." :-P)
Combine this with the germ killing capabilities, chewing Xylitol gums can kill two birds with one stone. Isn't that wonderful?
In general, being a vegetarian is a healthy choice. Vegetables, especially the leafy ones, has a very high amount of various nutrients as well as fiber. Also, there aren't many highly processed vegetables in the SAD diet.
Some vegetarians don't consume animal products (e.g. eggs, milk) at all. This group of vegetarians are called vegans. But being a strict vegan who only consumes natural plant will cause Vitamin B12 deficiency. Vitamin B12 deficiency can cause irreversible damage of the nervous system and hence clinical depression and other mental illness. It will also increase chances of stroke and heart diseases. Vitmain B12 deficiency combines with non-excessive consumption of folate can also cause megaloblastic anemia (ie failure to create functional red blood cell).
Therefore to prevent Vitamin B12 deficiency, it is recommended that you either eat Vitamin B12 fortified food or take Vitamin B12 supplements. Hardcore vegans are recommended to take Vitamin B12 supplements made from Chinese herb dong quai (angelica sinensis), one of the few plants that is a good source of Vitamin B12.
Another less important health problem facing vegetarians is that plant proteins are incomplete proteins. This means that each plant species does not have all the eight essential amino acids needed by humans. It is recommended that you eat a wide variety of vegetables such that you get all the essential amino acids you need.
Thanks for reading this far. I hope I have covered almost everything related to nutrition. It is quite sad that the evolution of our species can't keep up with food revolution. Fortunately, in the foreseeable future, the DNA manipulation technology might be mature enough to allow us to take control of our evolution destiny. When that happens, we might no longer need to worry about what food to eat. But then, I am sure there will be other new problems....
To sum up this page in four words: Eat Natural Eat Smart! Eat Natural gives you a guideline to establish a healthy diet. Eat Smart by studying the various nutrients, reading food labels and plan accordingly should give you the healthiest diet possible. I hope you find this page useful such that you can outlive your evolutionary destiny and have a long and healthy life!