Recently, researchers from the United States published a review in the magazine "Nutrition" and made a comprehensive evaluation of ketogenic diet. After weighing the advantages and disadvantages of this diet strategy and chronic diseases, they think that ketogenic diet may cause long-term damage to health.
According to the previous articles, this study analyzed the possible effects of ketogenic diet on epilepsy, obesity, diabetes, fatty liver, cancer and Alzheimer's disease.
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"Ketogenic diet" generally refers to a diet with extremely low carbohydrate content, moderate protein content and high fat content. According to the weight, the ratio of dietary fat to the combination of dietary protein and carbohydrate is 4: 1 or 3: 1(2). Its principle is to replace carbohydrates with fat. After the body consumes glucose, it starts to burn fat to provide energy, and the body slowly enters the ketogenic state.
Worldwide, the lifetime prevalence of epilepsy is 7.6 per 65,438+0,000 people. Most people can get rid of seizures through drug treatment, but about 30% people are not sensitive to drug treatment. Fortunately, 30-50% of patients with drug-resistant epilepsy can reduce the frequency of seizures by at least 50% through ketogenic diet.
Epilepsy occurs because the brain is too active and discharges frequently. Brain cells like glucose as an energy source. Ketogenic diet can use ketone body instead of glucose as energy source. At this time, brain cells will be inhibited and the frequency of attacks will be reduced.
In addition, ketogenic strategy can also reduce the content of glutamate in the brain of epileptic patients and enhance the synthesis process of GABA, which may be of great significance for maintaining the normal activity of neural network in the brain of epileptic patients. It can be said that it is a good method for epileptic patients to adhere to ketogenic diet.
Ketogenic diet can indeed lose weight in a short time, but the weight loss mainly comes from fat-free parts, such as body water, glycogen, protein and gastrointestinal contents, rather than fat. Ketogenic diet is also very easy to gain weight, and may bring the potential consequence of increasing the content of low density lipoprotein and total cholesterol-weight loss, but high blood lipid. In addition, look at other dietary therapies, such as a low-fat vegan diet (10% energy comes from fat), which can suppress appetite more effectively than a ketogenic diet.
1 type diabetes …
For children with 1 diabetes, ketogenic diet can improve blood sugar, but there are risks such as malnutrition, growth retardation, decreased bone density, hyperlipidemia, poor sleep, amenorrhea and hypoglycemia in this therapy, so ketogenic diet is generally not used for children.
For adults with 1 type diabetes, the benefit of ketogenic diet is naturally to improve blood sugar. However, ketogenic diet increases the risk of hypoglycemia, dyslipidemia and cardiovascular events. In addition, hyperketonemia may also lead to oxidative stress, inflammation, nonalcoholic fatty liver disease and insulin resistance.
Type 2 diabetes mellitus ...
Because of the extremely low carbohydrate intake, ketogenic diet is often considered to be able to maintain blood sugar level well, which is of great benefit to improve the sensitivity of type 2 diabetes, especially glycosylated hemoglobin, fasting blood sugar and insulin. But the above effect was only a flash in the pan, and it returned to the original level after a while.
In addition, compared with other diets, long-term use of ketogenic diet will increase the risk of diabetes in men by 37%, while the prevalence of diabetes in people who drink low-carbon water and emphasize plant protein and fat has not increased, even among men under 65, the risk of diabetes has decreased by 22%.
Why does the risk of diabetes increase? This may be because ketogenic diet makes people consume a lot of animal protein containing saturated fatty acids, pro-oxidant (such as heme iron) and inflammatory compounds, but lacks the intake of fruits, vegetables and whole grain foods, and the vitamins (such as vitamin B6 and B 12), minerals (such as calcium and magnesium) and active ingredients (such as linolenic acid) needed by the body cannot be supplemented, so the incidence of diabetes increases.
It is also worth noting that the expression of human C-reactive protein (a marker of inflammation) increased significantly in ketogenic diet. In other words, long-term adherence to the ketogenic diet has improved the level of inflammation in the body and accelerated aging. Instead of improving diabetes, it increases the risk of illness.
Nonalcoholic fatty liver disease is a serious disease. Too much fat is stored in liver cells, leading to steatosis, which can develop into nonalcoholic steatohepatitis and increase the risk of hepatocellular carcinoma. Ketogenic diet will increase the intake of saturated fat, cholesterol and animal protein, which are related to insulin resistance, oxidative stress and increasing the flow of free fatty acids to hepatocytes.
Lifestyle changes, special changes in diet, weight loss and exercise can be used to treat NAFLD. It is found that lifestyle intervention to promote weight loss can reduce liver fat, improve transaminase concentration and insulin sensitivity. Some people suggest that ketosis may be beneficial to improve fatty liver, but the research supporting this point is limited, which usually limits energy intake. Long-term safety and specific clinical results have not yet been determined.
When it comes to cancer, it is necessary to say the "Warburg effect", that is, cancer cells have a feature that even in the presence of oxygen, they will increase glucose intake and up-regulate glycolysis, giving priority to fermenting glucose into lactic acid. By eliminating the glucose available to cancer cells, the ketogenic diet will theoretically put pressure on cancer cells and starve them to death.
There are not many existing clinical trials. In 2020, a systematic review analyzed 13 studies on ketogenic diet as a complementary therapy for various cancers, and beneficial effects were observed in four of them. However, in vitro experiments show that the use of ketone in cancer cells will increase the expression of related genes that promote cancer cell metastasis. Next, large-scale and well-designed randomized clinical trials are needed to determine the safety and effectiveness of ketogenic diet in cancer treatment.
It has become a disease that seriously affects people's old age. In view of the fact that the brains of patients with Alzheimer's disease can't effectively use glucose, some scientists suggest that ketone bodies should be used as the energy source for patients with AD.
On the one hand, a team of 20 19 found that increasing blood ketone by supplementing medium-chain triglycerides can really improve some cognitive function indexes of AD patients. In the review of short-term ketogenic diet and ketogenic supplements for the elderly (including those with no functional impairment, mild cognitive impairment and AD) in 2020, six of the nine controlled trials with clinical endpoints found that the cognition of the intervention group was significantly improved, while other trials did not. However, due to the lack of long-term follow-up, it is still unknown whether cognitive gain can be maintained after stopping diet/supplementation.
However, on the other hand, ketogenic diet will increase the intake of saturated fat, and high saturated fat intake is related to the risk of AD events increased by 2 to 3 times. 20 16 Review of international data found that eating high-fat dairy products such as meat, eggs, butter, cheese and candy is related to the increased risk of developing AD.
In a word, ketogenic diet can improve symptoms in a short time by providing ketones that neurons in AD can metabolize, but the nutritional status of diet may increase the long-term risk of healthy individuals.
For people without chronic kidney disease (CKD), one of the potential risks of ketogenic diet is kidney calculi, because the intake of animal protein in diet is recognized as a promoting factor of kidney calculi. Ketogenic diet can also promote the formation of stones by reducing citrate and pH value in urine, and at the same time increase the calcium content in urine.
The second potential risk is the development of chronic kidney disease. In the observational study of western dieters, the high animal fat consumption in ketogenic diet is related to the increased risk of proteinuria. In a 23-year prospective study of nearly 65,438+02,000 people, high animal protein intake was associated with a 23% increase in the risk of chronic kidney disease.
If a low-carbohydrate diet is adopted before or during pregnancy, the risk of fetal defects and gestational diabetes will be greatly increased. The National Birth Defect Prevention Study in the United States found that 30% of the fetuses of women who ate a low-carbohydrate diet one year before conception were accompanied by neural tube defects, especially anencephaly and spina bifida. Even the use of folic acid supplements can not reduce the risk of a low-carbohydrate diet.
To sum up, this paper mainly talks about the following points:
1. ketogenic diet can reduce the seizure frequency of some drug-resistant epilepsy patients;
2. In the field of weight loss, this method can also lose weight, but it is not more effective than other dietary methods in the long run, and it is easy to rebound;
3. In diabetes, ketogenic diet can also reduce blood sugar, but the effect is short-term;
4. In terms of kidney health, ketogenic diet increases the risk of kidney calculi and CDK;
5. For pregnant women, even in the case of folic acid supplementation, people who use ketogenic diet are more likely to give birth to children with neural tube defects;
6. The increased food and dietary components in ketogenic diet (such as red meat, processed meat and saturated fat) are related to the increased risk of CKD, cardiovascular disease, cancer, diabetes and Alzheimer's disease, while the intake of protective foods (such as vegetables, fruits, beans and whole grains) is usually reduced.
The current evidence shows that for most people, the ketogenic diet does more harm than good, and it is more like a "devil", so you need to think twice before you act. Of course, with the development of various studies, we also see the great potential of dietotherapy, and look forward to more surprises from ketogenic diet.
Text/Sheng Jie
Editor/Jane
Literature source
Crosby L, Davis B, Joshi S, Jardine M, Paul J, Neola M, Barnard ND. Ketogenic diet and chronic diseases: weighing the pros and cons. Positive nutrition. 202 1 Jul 16； 8:702802.