25 years of research in the United States reveals: How to eat carbohydrates to be healthy?

Recently, a friend asked me that since he started to follow the intermittent fasting calorie restriction diet that I advocate, he has developed a state of "low desire" and he feels that his reaction speed to external stimuli is slower than before. He asked me if this is normal. When I heard him ask this, I knew that he must be following the calorie restriction and eating too little carbohydrates.

Whether it is the currently popular 5:2, 16:8, or alternate-day fasting method, when the calorie intake is less than 500 calories per day, it will cause insufficient energy supply to the body and have adverse effects on health. Therefore, it is not recommended to follow a calorie-restricted diet for a long time. Even if it is to be implemented, a nutritionist must be consulted regularly to assess the health status.

So, do we need to eat carbohydrates? How much should we eat to achieve health and longevity?

In 2018, The Lancet Public Health, a subsidiary of the famous medical journal The Lancet, published a study, which concluded that a low-carbohydrate diet can shorten life expectancy by up to 4 years. The study was conducted by Dr. Scott D Solomon and his research team at Brigham and Women's Hospital in Boston, USA. It lasted for 25 years and involved more than 430,000 people in the follow-up, so it is highly credible.

The researchers enrolled 15,428 adults aged 45-64 from different socioeconomic backgrounds in four communities in the United States into the Atherosclerosis Risk in Communities (ARIC) cohort study and asked them to fill out questionnaires about the food and beverages they consumed and followed them for 25 years. The scientists assessed the proportion of calories they got from carbohydrates, fats and proteins. The researchers then conducted a meta-analysis combining data from eight prospective cohort studies with data from 432,179 people in countries in North America, Europe and Asia.

The results of the analysis showed that after an average of 25 years of tracking, the risk of death was significantly lower in the moderate-dose carbohydrate diet compared with the low-dose diet, and slightly lower than the high-carbohydrate group. The moderate-carbohydrate group refers to people who get 50-55% of their energy from carbohydrates. The moderate-carbohydrate group also meets the recommendations of the Chinese Dietary Guidelines. In other words, there is a U-shaped association between overall carbohydrate intake and life expectancy.

The researchers estimated that people in the moderate carbohydrate group could expect to live an average of 33 years from age 50. However, people who consumed less than 30% of their total energy intake from carbohydrates could expect to lose four years. People who consumed 30%-40% of their energy from carbohydrates could expect to lose two to three years. People who consumed more than 65% of their energy from carbohydrates could expect to lose one year.

Then, the researchers compared a low-carb diet rich in animal protein and fat with a low-carb diet containing a lot of plant protein and fat. The results showed that eating more animal protein, such as beef, lamb, pork, chicken and cheese instead of carbohydrates, was associated with an increased risk of death; on the contrary, eating plant protein from foods such as vegetables, beans and nuts instead of carbohydrates was associated with a lower risk of death. From the conclusion of this article, it is important to eat carbohydrates, eat them appropriately, and the source should be healthy.

The picture comes from Tuchong.com

Let's analyze the limitations of this article. First, the analysis results only show observational associations rather than causal associations. At the same time, the data on the proportion of carbohydrate intake by people is based on self-reported data, which may not be accurate. However, the conclusions of the article are still worthy of attention.

Before we decide whether or not to eat carbohydrates and how to eat carbohydrates, let us first understand a few important concepts to help us understand the significance of carbohydrates to us.

First of all, what are carbohydrates?

When it comes to carbohydrates, many people will first think of the rice and flour we often eat. In fact, there are more types of carbohydrates. Almost all the foods we eat that contain sugar contain carbohydrates. Even fruits contain some carbohydrates, because there are many types of sugars. For example, fruits also contain a lot of fructose, and processed foods also contain a lot of white sugar or sucrose. We can simply understand carbohydrates as foods that mainly provide carbohydrate nutrition. And sugar can be divided into many types, which are not listed here one by one.

When talking about carbohydrates, we have to talk about insulin. Insulin is a hormone secreted by the pancreas to lower blood sugar. Insulin works hard to keep our blood sugar in a suitable range. When we eat food, insulin will be secreted to lower blood sugar, and when we eat high-glycemic index high-carbohydrate food, a large amount of insulin will be secreted to maintain our blood sugar level. People with insulin secretion defects or insulin action defects may suffer from diabetes. When we eat too much carbohydrates, the blood sugar that cannot be consumed by insulin will be converted into fat, which is our belly and fat.

Just now we talked about the glycemic index (GI) as one of the important indicators for us to choose food. If the glycemic index value of food is relatively high, it means that this food will increase your blood sugar. If the blood sugar rises and cannot be consumed, sorry, fat synthesis will be activated, and getting fat is inevitable. Refined foods, such as rice and white flour, have a too high glycemic index, which will quickly cause blood sugar to rise. If insulin is not secreted in large quantities to consume these sugars, the body will start fat production. This type of refined carbon water is also called "bad carbon water" by many nutritionists. However, some unrefined foods, such as brown rice and buckwheat, have not been refined and retain a lot of dietary fiber and other ingredients that help us digest. Therefore, even if the intake is large, it will not increase our blood sugar like refined foods such as rice and white flour. This type of carbon water is called "good carbon water".

In nutrition, carbohydrates are the most important way to provide us with energy. Our brain, nervous system, and various cells need carbohydrates as energy. When carbon water enters the human body, it will be converted into glycogen, which is generally stored in the body for 24 hours. Therefore, we must have a certain amount of food that is carbon water every day, that is to say, carbon water is a nutrient that must be consumed every day. The impact of obesity caused by a long-term high-carbon water diet on health and life expectancy is obvious, so I won’t explain it here. Reducing carbon water will only bring about a short-term and obvious weight loss, but in the long run, this method is not only not conducive to our physical health, but also will cause loss of muscle and energy, and shorten life.

Since carbs are essential, how should we choose carbs? Here are a few suggestions for your reference:

1. First of all, we should choose whole grain foods, which are "good carbon water", instead of finely processed foods, which are "bad carbon water". For example, we should try not to eat rice and white flour as much as possible. Because these foods not only do not give us a strong sense of fullness, but also have high calories, which accelerates the rise of blood sugar and easily makes us obese;

2. To go further, choose rich unprocessed carbohydrates, such as brown rice, oats, whole wheat, quinoa, buckwheat or beans. This kind of natural unprocessed carbohydrates contains a lot of bran, which can provide dietary fiber, vitamins and minerals. In fact, brown rice is the unprocessed version of the refined rice we usually eat. This kind of healthy food can slow down our digestion and make us feel full for a long time. The increase in satiety will reduce our intake, which means that we will be much fuller than ordinary food and eat less.

3. The amount of carbon water that the human body needs every day can be calculated through body indicators. There is a simple method for your reference: Generally speaking, the amount of carbon water that an adult consumes per meal is about the size of a fist.

In short, for the sake of our health, we must eat carbohydrates. The key is to master the correct way to eat them.

This article is a work supported by Science Popularization China Starry Sky Project

Author: Tiangeng

Reviewer: Zhang Na (Associate Researcher, School of Public Health, Peking University)

Produced by: China Association for Science and Technology Department of Science Popularization

Producer: China Science and Technology Press Co., Ltd., Beijing Zhongke Xinghe Culture Media Co., Ltd.