"Fasting for 2 days can restart the entire human immune system!"
"Hunger is the natural way to maintain health!"
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Similar claims have made countless "health enthusiasts" flock to it, does fasting really have so many health benefits?
Fasting to restart the immune system stems from a 2014 study by the University of Southern California published in the top journal Cell Stem Cell[1].
The study sought to explore how prolonged fasting affects chemotherapy and aging-induced immunosuppression.
Mice were used in the study.
The scientists divided the mice into two groups, A and B, group A ate freely, and group B received multiple "fasting-re-feeding" dietary cycle interventions, and the duration of a fasting ranged from 24 to 72 hours.
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Then, the researchers gave chemotherapy drugs to the mice at a fixed time point to observe their blood immunity-related indicators, including white blood cell count, lymphocyte count, etc.
The results showed that the chemotherapy drugs damaged the hematopoietic function of the mice. The immunity-related indicators of free-eating group A mice were always in a "collapse" state; the immunity-related indicators of group B mice showed significant improvement after a period of fasting.
Through subsequent cell experiments, the researchers found that such results may be attributed to the "fasting-refeeding" diet cycle pattern, which regulates certain special hormones in mice, such as insulin-like growth factor 1 (IGF-1), which inhibits the damaging effect of chemotherapy drugs on the hematopoietic system and promotes hematopoietic function reconstruction.
The researchers achieved similar results in aging mice.
The study concluded that prolonged fasting has great therapeutic potential to improve or reverse the aging-induced immune aging, as well as chemotherapy-induced immunosuppression.
The immune system is like a scavenger and a bodyguard, cleaning up the various pathogenic factors inside and outside for us, helping humans to resist disease.
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But with natural aging, or some special treatments such as chemotherapy, the immune system may have to "bow its head" - their power is suppressed or weakened, and they are unable to fight the causative factor, which is why some special people are more likely to get sick and recover after illness.
This study does provide a potentially effective dietary treatment option, but any dietary interventions and treatments cannot be based on a single piece of literature alone. There are several reasons for this:
1. Research is based on animal experiments and cell experiments, and there are essential differences between animals and humans.
Cells are cultured in an in vitro environment and are very different from the internal environment of the human body.
The results of animal and cell experiments can only be said to have some value in this idea, and further verification is needed in designated populations to confirm the true effectiveness and safety.
It is by no means like the self-media, arbitrarily applying the results directly to people.
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2. The so-called "long-term fasting" word, in this study, is to let the mice fast for 24 to 72 hours, and then refeed, and according to a certain cycle to circulate, intervention.
Ordinary people see words like "long fasting" and react completely differently, which may cause misunderstanding. Some people may let themselves be hungry for a long time, in a state of severe lack of calorie and nutrient intake, and over time evolve into malnutrition, so that the body and mind suffer. To do so is tantamount to chronic self-harm!
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3. For the elderly population and patients receiving chemotherapy, nutritional interventions should refer to the corresponding disciplinary guidelines.
These guidelines bring together many of the latest, high-level studies to guide them. A single study alone is not enough as strong evidence.
4. Blind fasting may produce many adverse reactions, even if you want to try, you should also carry out under the guidance of a doctor. We must not listen to the "popular science" of some self-media and experiment with ourselves at home.
Some self-media like to play word games. "Immune restart" gives people the illusion of "resurgence", in fact, it may only be the improvement of some indicators, whether it has clinical significance needs to be further verified.
Patients with tumors who receive chemotherapy are at high risk of malnutrition [2]. This is because chemotherapy can directly affect metabolism, or cause nausea, vomiting, loss of appetite, swallowing disorders, digestive and absorption dysfunction, etc., interfering with nutrient intake and utilization [2].
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Malnutrition itself can damage immune function, which is equivalent to adding fuel to the fire on the toxic side effects of chemotherapy.
Malnutrition also lowers plasma albumin levels and reduces the body's ability to tolerate chemotherapy [2].
Therefore, if chemotherapy patients blindly believe in the "super efficacy" of prolonged fasting, they may lead to further deterioration of their nutritional status and fall into a more dangerous vicious circle.
As for older adults, their physical functions decline in all areas, including chewing and digestion capacity, enzyme activity, and hormone levels [3]. Compared with the average adult, they are at greater risk of malnutrition, such as muscle decay and osteoporosis.
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Inadequate daily dietary intake only increases the risk of nutritional deficiencies, infectious diseases, and chronic noncommunicable diseases [3].
Therefore, the weight standard of the elderly can be appropriately raised, and it is most ideal to maintain the body mass index (BMI = weight (kg) / height square (㎡)) between 20 and 26.9 [3].
For the average person, controlling energy intake through intermittent fasting may have some benefits.
Intermittent fasting is the practice of strictly controlling eating throughout the day or week according to certain rules.
Maintaining a period of eating less or not eating can effectively control the level of calorie intake without exceeding the standard, improve metabolic status, enhance resistance, maintain health and resist disease [4].
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There are 3 modes that are most used:
1. Alternate-day fasting method: Fasting once every other day. However, on the day of fasting, it is not to eat nothing, but to ensure that the total energy intake of the day does not exceed 500 to 600 kcal, which is equivalent to eating only one meal of calories. Eat normally at other times.
2. 5+2 fasting method: It is required to choose an uninterrupted 2 days within 7 days, control energy intake in 1/4 of the daily life (about 500 kcal for women, 600 kcal for men), and eat normally for the remaining 5 days.
3. Time-limited eating method: It is required to choose a continuous 6 to 8 hours within 1 day as a time period for allowing eating, and the remaining 16 to 18 hours are not eaten.
But there is a gap between theory and reality.
Intermittent fasting is not in line with the mainstream food culture of "three meals a day", and it is difficult to stick to it when it comes to socializing or gathering with friends.
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Emotional problems (such as impatience), insomnia, and work and study inefficiencies may occur during fasting.
Ordinary people can not casually fast, but need dietitians to regularly assess and monitor to avoid nutritional imbalance.
All this makes the threshold for the implementation of fasting become very high, and even become a burden on life and spirit.
In fact, we can also maintain normal eating habits while improving dietary patterns and food choices, to achieve the same purpose as "intermittent fasting".
You can refer to the recommendations of the Dietary Guidelines for Chinese Residents 2016:
Maintain a balanced dietary pattern;
Let fresh fruits and vegetables, coarse grains, fish, eggs, milk and other roughly processed, fresh, nutritious foods always occupy the "C position" of your recipes;
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Strictly limit foods that are high in sugar, salt, fat, calories, low in dietary fiber and micronutrients (such as sugary drinks such as cola, sweets, puffed foods, etc.).
Scratch the point!
1. Nutrition and dietary interventions are not as simple as "skipping meals", but based on scientific evidence, using methods that have been shown to be safe and effective in improving your situation.
2. Extreme fasting methods that are out of control and scientific concepts, such as eating only apples or cucumbers for several consecutive days, or even drinking only water, are "crooked ways" that lead people into the pit.
3. We must rationally look at the crazy explosive articles in the network, and if we want to control diet and energy intake, we must carry out under the guidance of doctors, nutritionists, etc.
Review expert: Shi Zhengli | Nutritionist of The Department of Nutrition, Beijing Friendship Hospital
bibliography
[1] Cheng C, Adams G, Perin L et al. Prolonged Fasting Reduces IGF-1/PKA to Promote Hematopoietic-Stem-Cell-Based Regeneration and Reverse Immunosuppression. Cell Stem Cell. 2014;14(6):810-823. doi:10.1016/j.stem.2014.04.014
[2] Chinese Anti-Cancer Association, Chinese Anti-Cancer Association Tumor Nutrition and Supportive Therapy Professional Committee, etc. Nutritional Therapy Guidelines for Chemotherapy Patients. Electronic Journal of Tumor Metabolism and Nutrition. 2016; 3(3):158-161.
Chinese Nutrition Society. Dietary Guidelines for Chinese Residents 2016.
[4]de Cabo R, Mattson M. Effects of Intermittent Fasting on Health, Aging, and Disease. New England Journal of Medicine. 2019;381(26):2541-2551. doi:10.1056/nejmra1905136
*The content of this article is a popularization of health knowledge and cannot be used as a specific diagnosis and treatment recommendation, nor is it a substitute for face-to-face consultation by a practicing physician, for reference only.
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