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Cat limit (CR) can extend lifespan, which has always been a strong opinion that many people believe, including me.
However, a new study found that calorie limits are good for monkeys' health, but does not extend their lifespan .
This research is not done casually by an amateur medical institution, but a professional experiment of National Institute of Aging (NIA) .
Have you always believed in it wrong? Can calorie limit CR really not extend life?
So far, the most convincing thing is the University of Wisconsin (UW) study, which is also their prove that CR can prolong life.
So, why do we draw different conclusions?
When we carefully compare these two studies, we will find that they prove the same thing, just to see how we understand it.
Wall Street Journal : Caloric limit cannot extend life
The Wall Street Journal reported this NIA study and reviewed previous experiments that proved that CR can extend lifespan, and believed that the conclusions of previous research were not clear. What conclusions have been drawn to the
→NIA research? The experimental subjects of the
NIA and UW studies are both rhesus monkeys . On the one hand, it is because rhesus monkeys have about 93% sequence identity with the human genome, and anatomy and physiology are also very similar.
On the other hand, caloric limiting and control experiments in humans not only involve moral ethics, but it takes about 80 years to track natural death, while the average life span of rhesus monkeys is 30 years.
In fact, both experiments followed the natural death of rhesus monkeys, so the time lasted for a long time; and there were control groups.
NIA experiment is as follows:
1. The researchers divided female and male monkeys into three age groups: juvenile (1-2 years old), teenagers (3-5 years old) or elderly (16-23 years old);
2. Each group of monkeys was divided into control group (CON) and restriction group (CR). The feeding amount in the CR group was 30% less than usual, while the CON group could be at will;
3. Comparison of survival data and mortality rates of monkeys in the control group that were fed closer to normal diets with the control group.
For the analysis of monkey survival data, the researchers also adopted two methods: all-cause mortality rate and age-related deaths, and exclude age-related deaths such as acute diseases.
It can be said that NIA's experiments are very scientific and objective, and exclude the influence of variables such as age, gender, disease , and the conclusion is that caloric limit CR monkeys are not longer than those of CON monkeys in the control group.
Is CR really useless? Let’s take a closer look at
UW Research: Caloric limit extends the median life span
See the previous University of Wisconsin (UW) research was conducted almost at the same time as NIA, and the end time was similar. It was also a rhesus monkey experiment, and the CR group and the control group were set up.
→UW Conclusions drawn by the study
UW is a professional scientific research institution. In their experimental conclusions, it was not concluded that CR extended the lifespan of rhesus monkeys, but said that CR reduced the mortality and morbidity .
Maybe it was because the media had different understandings, or CR-related research was more eye-catching and quickly became headlines in the media. What’s interesting is that it was also a report by at that time in the Wall Street Journal . There is no need to repeat the experiment of
UW. The biggest difference between them and NIA is the monkey's age (all adults) and food . Other processes and monitoring results are similar.
Finally, they concluded that caloric limit delayed the onset and mortality rate of in rhesus monkeys, and the disease risk increased by 2.9 times and the risk of death increased by 3.0 times.
At the time when monkeys died naturally due to aging, 50% of the controls survived, while the survival rate of CR animals was 80%.
At the same time, CR delayed the onset of age-related pathology, including the incidence of diabetes , cancer, cardiovascular disease and brain atrophy . Why do
UW and NIA have different conclusions?
So, why does it become CR to extend the lifespan of rhesus monkeys in media reports and popular science in self-media? In fact, this is related to the different understanding of , which extends lifespan, and understands .
→Different concepts of extending lifespan
It can be said that both UW and NIA studies have proved that CR extends the lifespan of monkeys, but to be precise, median lifespan .
Median lifespan or median lifespan refers to the average lifespan of the monkeys in this group when 50% of all monkeys in this group die.
For easy understanding, we can look at an exaggerated example, for example, the normal median life span of monkeys is 30 years, while the CR group is 25 years, and the CON group is 20 years. In this case, it can be said that CR extends the median lifespan than CON, but both are shorter than normal.
Of course, this is just an exaggeration. The average age of rhesus monkeys is about 27 years. The median lifespans of CR and CON monkeys in the UW experiment were 8 and 26, respectively. The median lifespan of monkeys in
NIA experiments were CR females 27.8 years and males 35.4 years, both exceeding the median lifespan of captive monkeys 27 years, but the control group CON reached 9 years .
Then a new problem arises, that is, why does the uncontrolled control group have a longer median lifespan than normal monkeys? Even more than the CR group of UW experiments?
→The food composition of different
Many scholars are also puzzled by NIA and have also put forward various different inferences. There are currently three more reasonable ones:
One is the of the two experimental monkeys, there are big differences in the diet of .
UW The foods given to the two groups of monkeys are closer to human diet, and they are fast food restaurant foods such as hamburgers, fries, and happy water .
However, the monkeys in NIA experiment ate more natural , mainly including wheat, corn, soybeans, tuna and alfalfa powder , etc., and some oil will be added to both groups.
The natural diet of rhesus monkeys includes roots, fruits, seeds and bark, as well as insects and small animals. There is no doubt that NIA monkeys eat foods that are closer to naturally fed.
→The feeding amount is different
The second important difference is Feed amount is .Although both experiments planned to feed the CON group at will, the total amount of food in the NIA experimental monkeys was actually a prescribed upper limit.
There is one evidence to prove, that is, the monkey's average weight .
The two studies not only had significant differences in body weight between the control group, but the weight of NIA monkeys was also lower than that of naturally-captive monkeys.
(above picture: UW and NIA male and female monkey weight ↑)
So one generally accepted explanation is that the control animals studied in NIA are actually restricted, and although they are further restricted in the CR group, they have little advantage.
80% of the elderly individuals living to over 40 years old in NIA are from the CR group, which shows that CR has certain effects, but is not enough to exceed the advantage of CON's mild limit.
(above picture: mortality curves of the University of Wisconsin and NIA monkeys↑)
Finally, the two selected objects are different in age . The UW experiment only selected adult and elderly monkeys, while the NIA experiment also selected young monkeys.
According to the prediction of the delayed aging model, the effect of CR on all-cause survival is only obvious when is old. Moreover, the number of CR monkeys currently surviving is twice that of the CON group, and their effects may not have stopped. What inspiration does
study give us?
compares the differences between these studies, and then see if the researchers have found common conclusions.
→What are the common conclusions of the two studies? Both
UW and NIA studies have found that various aging-related diseases will occur later in the CR group, and many indicators of metabolic health and overall function have improved.
First of all, weight . Both the male and female CR groups were lower than the CON group. Of course, this is more obvious in UW research, and their CON group weight is far beyond the natural level.
followed by health-related indicators all of the CR group. For example, triglyceride , cholesterol and glucose levels, which means that CR group is more and is less likely to suffer from cardiovascular diseases.
(above picture: fasting serum triglycerides of CR and CON monkeys ↑)
In addition, males in the CR group significantly reduced plasma free prostaglandins, which is an indicator of oxidative stress . This shows that the oxidative stress level of in the CR group is obviously reduced.
But the same sentence is still the case, these effects are more obvious in UW research. For example, the mortality rate caused by age-related reasons is 24% lower than that of CON-37%.
→The real effect of limiting calorie CR
The comparison between these two studies may provide a truly effective usage of calorie limit.
First, calorie limit is beneficial to health.
has clear evidence in various biological studies as well as in human studies, and CR can increase healthy lifespan.
The second and most important point is that calorie limit is not just enough to limit calories.
If does not control the dietary structure, even limiting the total calories will not be able to remedy .
NIA The monkeys studied had few corn and sugars in their diet, while protein and fat were high. UW research is the opposite, basically how it is unhealthy.
The result is that the NIA control group has a longer median lifespan than the restricted group studied by the UW.
The key Shoulong said
Some students may have been dizzy when they saw it. The results of these two experiments are indeed a bit confusing. I'll try to summarize it for you.
summarized in two ways: First, we misunderstood the lifespan of CR before. UW research actually proved that the median lifespan of was extended . There is no problem in studying from this perspective.
The second is NIA research. The reason for the abnormal results may be related to the control group not really feeding at will. The control group actually used a kind of unstricted calorie restriction CR.
Both studies were fine, but it was interesting to compare: NIA research is much healthier than the monkeys studied by UW, but it was just adjusted to diet structure is that different?
The answer is OK. The monkeys studied by UW eat junk food every day. Although the CR group has controlled to eat less, their lifespan has been shortened compared to those of a healthy diet.
Everyone hopes that there is a way to improve health and prolong life, but the facts tell us that no matter how good the method is, we can't stand it and eat high sugar every day.
Last sentence:
controls calories, and will definitely reduce the risk of chronic diseases and other diseases.
But the premise is to eat enough nutrition and stick to a healthy diet instead of eating junk food every day.
