As we strive towards our health improvement, one of the key factors is nutrition. Although it is not the only factor for health improvement, however, it is vital portion of our wellbeing because that is how we survive. Yet, it is somewhat confusing because information tends to change frequently and difficult to figure out what we should be following. The questions I want to address in this article is "why there is so much complication and ambiguity in nutritional guideline?", "Why are studies contradicting to one another?".
From Sugar Does Not Cause Diabetes to Limiting Sugar
Let's compare Dietary Guideline for Americans from 1980 to 2018.
Despite the trend of diabetes been increasing (about 5.53 million) in 1980, Dietary Guideline concluded that over consumption of sugar does not lead to diabetes where population was already consuming about 130 lb. of sugar per year per person. They've also stated that there is no evidence that sugar caused heart attack or blood vessel disorder.
In 2018 they are advising the population to not consume more than 10% of calorie consumption from sugar. In other words, if you are following 2000 calorie diet, you are allowed to consume 200 calories or 50 g of sugar per day or 40 lb per year.
Huge step to better health but took more than 20 years to get here with 23.35 million people as of 2015 are being diabetic where US population is over 330 million. Most likely this number will keep on rising.
Why did it took this long and why are information still unclear? To understand this, we need to go through research history of salt and sugar.
Two White Crystal
When looking back in history, like back before we were evolved, four-limbed creature, tetrapod learn to live between sea and land by adapting their kidney to be able to filter and retain sodium.
After tetrapod evolving to amphibians, reptiles, and mammals, we have consumed food sources that were rich in sodium mainly from marine prey. Obviously, there were no dietary guideline so they were relying mainly on their biological sensor, which we also have called homeostasis. So if you think about it, their kidney must have capacity to excrete huge amount of salt. In fact, research has shown that with normal blood pressure and kidney function, we can easily excrete 10 times as much salt as we currently consume on regular basis.
When you look into history, almost every major Roman cities were located close to some sources of salt source. According to Salt: World History by Mark Kurlansky, Romans have consumed average of 25 grams of salt per day!
In sixteenth century Europeans were estimated to consume around 40 grams of salt per day and increased to 70 grams per day in eighteenth century.
Salt Causing Hypertension Myth
Although there were no blood pressure assessing tool in 1800s, however, we do know that case of hypertension in the US was 5-10 percent in 1900s. In 1939 hypertension in adults was 11-13 percent. However, hypertension gradually increased in 1975, 25 percent and in 2004, 31 percent of population was monitored as hypertension.
If salt was main cause of hypertension and heart disease, shouldn't we have hundred cases, if not thousands, in Europe for consuming well over 40 grams per day?
High salt intake was there for centuries, not just to flavor the food but also to preserve them. Yet when you look at Dietary Guideline it is still suggesting us to limit our sodium intake to 2300 milligram (2.3g). The question comes why?
Salt was viewed as caused of high blood pressure in 1920s by a medical doctor in New York. Him and his coworkers published papers to advise medical professionals that restricting salt has potential of lowering blood pressure. He also hypothesized that consumption of salt was irritating the kidney to cause overwork. However, there was enough publications to oppose with this theory.
Rice Diet and Salt Sensitive Rat
Then a doctor by the name Walter Kempner invented a diet called Rice Diet in 1939. Diet is low in salt and mainly consumed with rice and fruits. No meat of course, but also no nuts canned or dried fruits were allowed. No vegetable juice but was allowed to add more sugar.
Kempner's theory was salt is waste product of the kidney and reducing salt can relieve kidney from overwork. Kempner reported that Rice Diet has been successfully used for people with hypertension, kidney disease, and even diabetes. Case reports have pull the attention of you know who, media. Was the diet successful? Blood pressure did drop on some of his patients but majority of his patients were excessively high in blood pressure and one study showed there were 83% of patients showed no effectiveness in Rice Diet. However, Kempner reported his diet to be 64% successful.
Regardless of the fact, Rice Diet was recognized as successful diet and low-salt was effective in treating hypertension.
Then in 1950's Dr. Lewis Dahl proven the high salt consumption lead to hypertension by using what we now know as "Salt-sensitive rat". That's right. He used salt-sensitive rat and gave salt and showed that the blood pressure of rat has elevated.
Sugar Is Harmless
Interesting thing is until 2002, thought of obesity can elevate blood pressure and cause hypertension was not popular theory. However, sugar consumption in 1700 in England was 4 lb per person per year. In 1950, that number skyrocketed to 100 lb per year. In the US, this number was reached by 1920. Yes the same time the salt was thought as a cause of hypertension.
In 1950's American scientist promoted the idea that dietary fat was cause of heart disease but England researcher, at the same time, thought that sugar was to be blamed. Yet in 1960's American Heart Association claimed saturated fat was cause of heart failure and advised all Americans to reduce intake of animal fat and increase their intake of vegetable oil.
Problem with vegetable based oil is not only because of its process of creation, however, also it oxidize faster than animal fat. When you look at the store, vegetable oil, canola, and corn oils are all in clear container sitting on the shelves of several days under a light before it is purchased. When you look at oil such as butter or olive oil they are using darker container or wrapper to avoid light exposure and usually stored in cooler environment.
Going back to sugar. Sugar industry also played role in sugar is harmless concept by sponsoring popular events like Olympics to provide positive image of sugar. Even in 1977, obesity was caused by inactivity. This is where true mis-direction started from "harmed calorie" to "total calorie", which majority of current fitness industry still follow today.
From 1975, there has been number of studies that were published and funded by sugar industry. So not only media played role in advertising that the sugar is healthier than fat, but because of food industry started to fund the studies, the research articles are also biased towards favoring sugar as healthier energy source.
Confusion of Information
So the example above is between sugar, salt and fat, however, there are other nutrients such as protein, that was not properly informed about it's importance. The confusing part is this. There are studies that are available that are well designed and properly informed. However, because of biased studies and articles are also present, that is where the conflict of information occurs and confusion rises.
One of the challenging nutrition studies is questionnaire studies. Although you can acquire more participants, however, remembering what you ate from few days ago is not easy. Can you recall what you ate 3-4 days ago? Our memory of what we have eaten is not that great. Also when question like "how is your diet?" or "how do you feel after the meal?" comes around what would you answer? Even when it is not good, many may answer good.
Another issue is how can we test causality of the food, supplements, and so on to our health? What if it does cause a health problem? What university or scientists want to risk people's lives on their studies on something that is uncertain? In other words, it is difficult to perform human studies to test causation where we have to consume over period time to see the effect.
Last issue is fixed data. This probably is the biggest issue. There has been number of studies adjusted the outcome and publicized as an results. Why would they do that? Sponsor, peer pressure, money, and fame. This is not just in nutrition but can be seen in other profession as well.
Confusion happens because there is a basic knowledge of how our body works and information by professionals concluding the studies by stating otherwise. Even before 1980s, we knew how insulin worked and possible cause of obesity, diabetes, and other metabolic illnesses.
What is Happening Now?
Little by little, science and common sense has started to be realized by the public and we can obtain number of well educated information through media. However, many of the information you may currently have and hearing from health professionals including fitness professionals, nutritionist, dietitian, and so on may still be biased and manipulated. I must address that it is not their fault for educational materials they have learned from may have been already biased.
Keep in mind that for nutrition, there is no one right answer. Depending on your current condition, your up bringing, and your genetics, you may need to be following completely different nutritional guideline then suggested. If you are struggling to get healthier, you have to educate yourself so that you can create plan that is suited for you.
If you are serious about pursuing optimum health, what I suggest is to get your facts about basic nutrition and physiology straight. When you have basic understanding of how our body works then you'll have better understanding of how your nutrition should be like. We are all unique, however, baseline of how our body operate is about the same. Once the basics is down, then adjust it according to what works for you. If it is not working, change it.
If anybody is talking about nutrition without conversing about how body works (metabolism, homeostasis, hormones, lipid profile and etc.), they are most likely reciting what they have learned in their certification courses or social media that they are following. This may mean that the information is not designed for you.
I hope that I have made you curious and start doubting the information you currently have. Every scientific studies start with curiosity and doubt. It is ok to doubt the information that you have learned. Do your own research and studies.
Happy Learning,
Kota Shimada
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