Protein restriction can be effective in combating obesity and diabetes

 Cutting protein intake can help control metabolic syndrome and some of its main symptoms, such as obesity, diabetes and high blood pressure (hypertension), according to a study conducted by researchers in Brazil and Denmark to compare the effects of protein and calorie restriction diets in humans. An article reporting the study is published in the journal Nutrients.

Metabolic syndrome is a cluster of conditions that heighten the risk of cardiovascular disease, stroke and diabetes, including hypertension, high blood sugar, excess body fat around the waist and abnormal cholesterol levels.

“The study showed that cutting protein intake to 0.8 g per kg of body weight was sufficient to achieve almost the same clinical results as restricting calories, but without the need to reduce calorie intake. The results suggest that protein restriction may be one of the key factors leading to the known benefits of dietary restriction. Protein restriction dieting may therefore be a more attractive nutritional strategy and easier to follow for people with metabolic syndrome,” said Rafael Ferraz-Bannitz, first author of the article and currently a postdoctoral researcher at the Joslin Diabetes Center in Harvard Medical School in the United States. 

The study was funded by FAPESP via a PhD scholarship awarded to Ferraz-Bannitz while he was attending the University of São Paulo’s Ribeirão Preto Medical School (FMRP-USP) in Brazil. The study also benefited from a FAPESP Thematic Project on strategies for mimicking the effects of dietary restriction, led by Marcelo Mori, a professor at the State University of Campinas (UNICAMP), also in Brazil. 

A multidisciplinary team of scientists conducted the study, including researchers affiliated with the University of Copenhagen in Denmark, and the University of São Paulo and the National Cancer Institute (INCA) in Brazil, as well as the Obesity and Comorbidities Research Center (OCRC), a Research, Innovation and Dissemination Center (RIDC) funded by FAPESP and hosted by UNICAMP.

Controlled diet

In the study, 21 volunteers with metabolic syndrome were analyzed for a period of 27 days during which their diet was monitored. Throughout the period, they were inpatients at FMRP-USP's teaching hospital (Hospital das Clínicas in Ribeirão Preto).

Each volunteer’s daily calorie intake was calculated as a function of baseline metabolism (energy expenditure at rest). One group was fed what the authors call a standard Western diet (50% carbohydrate, 20% protein and 30% fat) but with 25% fewer calories.

For the second group, protein intake was reduced to 10%. Calorie intake was tailored to each volunteer’s baseline energy expenditure. Both groups consumed 4 g of salt per day.

The results showed that both the calorie and protein restriction groups lost weight owing to a decrease in body fat and that the symptoms of metabolic syndrome improved. Decreased body fat is known to be associated with reduced blood sugar and more normal levels of lipids and blood pressure.

“After 27 days of monitoring, both groups had similar results in terms of lower blood sugar, weight loss, controlled blood pressure, and lower levels of triglycerides and cholesterol. Both diets improved insulin sensitivity after treatment. Body fat decreased, as did waist and hip circumference, but without loss of muscle mass,” said Maria Cristina Foss de Freitas, last author of the article and a professor at FMRP-USP.

The findings confirmed those of previous studies involving experiments on mice. “Here, however, we succeeded in conducting a fully controlled randomized clinical trial lasting 27 days, with a personalized menu designed to meet each patient’s needs,” Foss de Freitas said.

Manipulation of dietary macronutrients – protein, carbohydrate and fat – is sufficient to obtain the beneficial effects of dietary restriction. “We demonstrated that protein restriction reduces body fat while maintaining muscle mass. That’s important since the weight loss resulting from restrictive diets is often associated with loss of muscle mass,” Ferraz-Bannitz said.

The study did not investigate the molecular mechanisms that could explain the beneficial effects of protein restriction diets, but the researchers believe low protein intake triggered a change in the metabolism or enhanced the organism’s energy management by leading it to burn fat in order to produce energy for cells. “We only have hypotheses so far. One is that molecular pathways are activated to interpret the reduction in essential amino acids as being a signal to reduce food intake while leading to the production of hormones that typically increase when we’re fasting,” Mori said. “Studies in animal models have shown the involvement of such pathways in the effects of both protein and calorie restriction, both of which lead to fat loss.”

Despite the promising results of their studies, the researchers point out that the diets involved were personalized. Mori also stressed that they focused on a specific population of patients with metabolic syndrome (obesity, diabetes, hypertension and abnormal levels of cholesterol).

“Nevertheless, it’s tempting to extrapolate the results. We know research has shown vegan diets to be positive for cases of metabolic syndrome. It’s also been found that the excessive protein intake common in the standard Western diet can be a problem. Every case should be analyzed on its own merits. We shouldn’t forget protein deficiency can lead to severe health problems, as has been well-described in pregnant women, for example,” he added.

Statin use not justified for healthy people with high cholesterol

  About 40 million adults in the United States regularly take statins to lower their cholesterol levels and reduce their risk of heart disease and stroke, according to American Heart Association data from 2020.

However, many of them don’t stand to benefit from these drugs based on new research from David Diamond, a neuroscientist and cardiovascular disease researcher in the Department of Psychology at the University of South Florida.

Diamond and his co-authors reviewed literature from medical trials involving patients taking either a statin or placebo. They then narrowed their review to look at study participants with elevated levels of low-density lipoprotein-cholesterol (LDL), the so-called “bad cholesterol,” which can be reduced with a statin. Some individuals with high LDL also had high triglycerides (fat in the blood) and low high-density lipoprotein (HDL), the “good cholesterol,” which put them at the highest risk of having a heart attack.

But others with high LDL were very different. They had low triglycerides and high HDL, which meant they were healthier. People with optimal triglycerides and HDL levels typically exercise, have low blood pressure and low blood sugar, and are at a low risk of a heart attack.

Diamond and his co-authors asked two questions: If people are at a low risk of a heart attack based on having optimal triglycerides and HDL, but they also have high LDL, does that raise their risk? Further, would these people benefit from lowering their LDL with a statin?

Their findings, published in the journal Current Opinion in Endocrinology, Diabetes and Obesity, showed LDL alone has “a very weak association” with heart disease and stroke. Their review went further, showing that when people with high LDL and optimal triglycerides and HDL were given a statin, there was no benefit.

Diamond put the findings into a diet and lifestyle context.

“People who are not overweight, have low blood sugar, exercise and are on a low-carb diet typically have optimal triglycerides and HDL, and sometimes they have high LDL,” he said. “Our findings show that the people who have this healthy combination of diet and lifestyle, as well as high LDL, showed no benefit from taking a statin.”

The authors say their review also challenges the long-held contention that low-carb diets, which are often high in saturated (animal) fat, contribute to heart disease. That contention has persisted for nearly 50 years, dating to when cardiologist Robert Atkins was challenged about the potential dangers of his high-fat Atkins diet before a U.S. Senate Subcommittee on Nutrition and Human Needs in 1973.

“High blood pressure, obesity, smoking and high blood sugar are the primary drivers of heart disease,” Diamond said. “Cholesterol is an innocent bystander, and saturated fat in the diet has been undeservedly demonized.”

Dairy products in moderate amounts may protect against type 2 diabetes – but red and processed meat raise risk

 

New research being presented at the annual meeting of the European Association for the Study of Diabetes in Stockholm, Sweden (19-23 Sept) shows that dairy products, especially low-fat ones and yogurt, are associated with a lower risk of developing type 2 diabetes (T2D). 

Red and processed meat were linked to a higher risk of T2D but moderate amounts of fish and eggs could be eaten in their place, say the Italian researchers.

T2D is the most common form of diabetes and it occurs when the pancreas can’t make enough insulin (the hormone which promotes the absorption of glucose from blood into the body’s cells, maintaining normal blood sugar levels) and/or the insulin it makes doesn’t work properly (low insulin sensitivity).

Overweight and obesity are the main risk factors and incidence of T2D is projected to increase.  Common complications include heart disease, kidney disease, vision loss and circulatory problems which can lead to foot amputation. 

Existing dietary guidelines1 for the prevention of T2D recommend eating specific plant-based foods such as whole grains, vegetables, fruits, legumes, olive oil and typically advise limiting consumption of most animal products.

However, not all sources of animal protein are nutritionally equal. Knowing how different animal products are associated with T2D would allow the guidelines to be updated, making it easier for people to choose the best foods to cut their risk of diabetes.

To do this, Dr Annalisa Giosuè, of the Department of Clinical Medicine and Surgery, University of Naples Federico II, Naples, Italy, and colleagues carried out a review of existing meta-analyses into links between different animal-based foods and diabetes.  This type of “review of reviews” provides one of the highest levels of evidence available in medicine.

The PubMed, Web of Science, Scopus and Embase databases were searched for dose-response meta-analyses of studies into the relationship between different foods and T2D.

The 13 meta-analyses that were suitable contained 175 estimates of how much 12 different animal products (total meat, red meat, white meat, processed meat, fish, total dairy, full-fat dairy, low-fat dairy, milk, cheese, yogurt and eggs) may increase or reduce the risk of developing T2D.  (Red meat includes beef, lamb and pork, while white meat includes chicken and turkey.  Processed meat includes bacon, sausages, and deli meat.)

There was a substantial increase in T2D risk with the consumption of 100 g/day of total meat (20% increase in risk) and 100g/day of red meat (22% increase) and with 50g/day of processed meats (30% increase). The quality of evidence was moderate.

50g/day of white meat was associated with a smaller increase in T2D risk (4%).

Dr Giosuè says: “There are several potential reasons for this.  For example, red and processed meat are important sources of components like saturated fatty acids, cholesterol and haem iron, all known to promote chronic low-level inflammation and oxidative stress, which, in turn, can reduce the sensitivity of the cells to insulin.

“Processed meats also contain nitrates, nitrites and sodium which, among other adverse effects, can damage the insulin-producing cells of the pancreas.

“White meat, in comparison, has a lower fat content, a more favourable fatty acid profile and a lower amount of haem iron.”

Dairy foods, in contrast, appeared to protect against T2D or had a neutral relationship with the development of the condition.

Milk (200g/day) was associated with a 10% reduction in risk, total dairy (200g/day) with a 5% reduction in risk and low-fat dairy (200g/day) with a 3% reduction. Yogurt (100g/day) was associated with a 6% reduction in risk.

Cheese (30g/day) and full-fat dairy (200g/day) were found to have no effect on the risk of T2D. The quality of evidence was moderate to low.

Dr Giosuè says: “Dairy products are rich in nutrients, vitamins and other bioactive compounds which may favourably influence glucose metabolism – the processing of sugar by the body.

“For example, whey proteins in milk are known to modulate the rise of blood sugar levels after eating.

“Probiotics are also known to exert beneficial effects on glucose metabolism, which may explain why we found that a regular consumption of yogurt is associated with a reduced risk of type 2 diabetes.”

She adds that although the results suggest that low-fat dairy products are more beneficial than full-fat dairy products, the finding should be treated cautiously, due to the small size of the reduction in risk and the low quality of the evidence.

100 g/day of fish and one egg/day also had neutral association with T2D risk, with low quality of evidence.

Dr Giosuè says: “Type 2 diabetes is one of the major causes of diet-related death worldwide.  Learning more about how different dietary components increase or decrease the risk of type 2 diabetes is key to its prevention.

“Although more well-conducted research is needed to achieve high quality of evidence required to give solid recommendations, our extensive review of the scientific evidence shows that regular consumption of dairy foods in moderate amounts, especially low-fat products, milk and yoghurt, may help reduce the risk of type 2 diabetes.

“It is also clear that while red and processed meat should be eaten sparingly, moderate amounts of fish and eggs could be good substitutes.”

High intake of whole grains, fiber, fish and omega-3 fatty acids linked to lower risk of death in adults with type 2 diabetes

 Eating a diet high in whole grains, fibre, fish and n-3 polyunsaturated fatty acids (PUFAs) may reduce the risk of dying from all causes in adults with type 2 diabetes (T2D), according to a systematic review and meta-analysis synthesising all the available evidence, being presented at this year’s European Association for the Study of Diabetes (EASD) Annual Meeting in Stockholm, Sweden (19-23 Sept).

“There are some dietary recommendations and guidelines for people with type 2 diabetes, but most are not evidence-based or are derived from studies of the general population”, says author Dr Janett Barbaresko from the German Diabetes Center in Düsseldorf, Germany. “Our rigorous assessment of the best currently available evidence indicates with reasonable certainty that eating a diet rich in whole grains, fibre, fish and PUFAs as well as consuming more vegetables and plant proteins may help people with type 2 diabetes live longer.”

However, the researchers stress that the limited evidence about other dietary factors, including dietary patterns, foods such as dairy, meat, and tea, and micronutrients such as caffeine and vitamin D, underscores the need for more robust and comprehensive studies to better understand the impact of different dietary factors on the progression of T2D.

People with T2D are more prone to circulatory diseases, dementia, cancer, and bone fractures. And despite an increasing number of effective drugs, lifestyle modifications - such as exercise and diet - remain a cornerstone of treatment.

However, little is known about diet and the prevention of illness and death in people living with T2D. A few studies have assessed the association between specific dietary factors such as the Mediterranean diet or intake of vegetables on all-cause mortality in T2D, but the relation with different dietary factors has not been comprehensively summarised.

To find out more, German researchers did a systematic review of 107 prospective observational studies investigating any dietary factors (i.e., dietary patterns, foods and food groups, macronutrients [carbohydrates, fats, protein] and micronutrients [minerals and vitamins] secondary plant compounds [e.g., polyphenols], and supplements [e.g., vitamin E, magnesium]) and the risk of death from all causes in adults (aged 18 or older) with T2D, up to June 2022.

Overall, 72 studies were included in 45 meta-analyses comparing the effects of high versus low intake and to evaluate the dose-response relationship between dietary factors and death from any cause, over an average of 10 years. The number of participants included in the meta-analyses ranged from 1,073 to 84,816. The certainty of evidence was evaluated to determine the confidence in the meta-findings [1].

The analyses found that there was moderate-certainty of evidence of a protective association between the intake of whole grain, fibre, fish, n-3 PUFAs and death from all causes. Adding one serving (20 g/day) of whole grain from foods such as brown bread and rice or breakfast cereals was associated with about a 16% reduction. Each serving per week increase in fish consumption was associated with a 5% lower risk of death.

Similarly, an additional 5 g per day intake of dietary fibre (equivalent to a medium pear or two shredded wheat) and 0.1 g per day increase in n-3 PUFAs was associated with a reduced risk of death from all causes—14% and 13% lower, respectively. The body does not produce n-3 fatty acids naturally, so good sources include fish, vegetable oil, nuts (especially walnuts), flax seeds and flaxseed oil, and leafy vegetables.

Evidence of lower certainty also suggests that eating large amounts of vegetables and plant protein may be beneficial. A daily increase of 100 g of vegetables and 10 g of plant proteins such as nuts, tofu, beans, lentils and peas was associated with a 12% and 9% lower risk of death, respectively.

Possible beneficial effects of these foods include their link with favourable changes in blood pressure, cholesterol, blood sugar levels and anti-inflammatory effects, which might help to lower the risk of comorbidities such as cardiovascular diseases and cancer. 

In contrast, higher intake of eggs and dietary cholesterol was associated with an increased risk of death from any cause—with a 10 g per day increase in egg intake (equivalent to two medium eggs per week) was associated with a 5% greater risk of death, while adding 300 mg of dietary cholesterol per day was linked with a 19% increase.

For other dietary factors, no association was found and/or the evidence was very uncertain, including: dietary patterns such as the Mediterranean diet and low-carbohydrate high-protein diet; foods including nuts, dairy, meat, sugar and sweets; macronutrients including carbohydrates and micronutrients such as caffeine and vitamin D.

“More research is needed to provide more robust and comprehensive evidence on different dietary factors and the progression of diabetes,” says Dr Sabrina Schlesinger at the German Diabetes Center in Düsseldorf and the German Center for Diabetes Research (DZD) in Munich-Neuherberg (partner in Düsseldorf), who led the study. “But if individuals with type 2 diabetes are able to add a few servings of whole grains, fibre, fish, plant oils and vegetables to their weekly diets, our results suggest it may be an easy and low-risk way to possibly improve their outcome.”

The authors note that the study is observational and therefore does not prove that people with T2D who eat a diet rich in whole grains, fibre, fish and n-3 PUFAs will live longer. Rather, it shows an association. They also note that the small number of studies in many meta-analyses may limit the conclusions that can be drawn.

Added phosphorus in food bad for you

 The International Food Additives Council (IFAC), a global association representing manufacturers and end-users of food ingredients, has released its findings on a study that examined dietary phosphorus intake over time and correlations with health and physiology.

The two-part study was conducted by researchers Kristin Fulgoni, Victor Fulgoni and Taylor Wallace and found between 1988-1994 and 2015-2016, Americans’ daily intake of natural phosphorus increased by 12% while their daily intake of added phosphorus decreased by 13%.

The study also found a higher total of phosphorus intake is associated with increased bone mineral content and bone density, a decreased risk of high blood pressure by 3%, and an increased risk of lowering levels of HDL-cholesterol (or “good” cholesterol) by 21% for every 100 milligrams of added phosphorus consumed.

Phosphorus is an essential mineral that’s naturally present in many foods. The body uses this mineral to build strong bones and teeth, maintain a normal pH balance, deliver oxygen to tissues, convert food into energy, and much more. The top five food sources of natural phosphorus include cheese, pizza, chicken, reduced-fat milk and eggs.

Currently, the average total dietary phosphorus intake for adult Americans is 1,400 milligrams per day, which is well below the Tolerable Upper Intake Level (UL) of 3,000 - 4,000 milligrams per day. Added phosphorus accounts for about 11.6% of total phosphorus intake among American adults ages 19 and over. The main contributors for added phosphorus are cheese, soft drinks, cakes, pies, cookies, and brownies.

Both parts of the study can be found below:

• Trends in Total, Added, and Natural Phosphorus Intake in Adult Americans
• Association of Total, Added, and Natural Phosphorus Intakes with Biomarkers of Health Status and Mortality in Healthy Adults in the United States

Seven healthy lifestyle habits may reduce dementia risk for people with diabetes

 A combination of seven healthy lifestyle habits including sleeping seven to nine hours daily, exercising regularly and having frequent social contact was associated with a lower risk of dementia in people with type 2 diabetes, according to a study published in the September 14, 2022, online issue of Neurology®, the medical journal of the American Academy of Neurology.

“Type 2 diabetes is a worldwide epidemic that affects one in 10 adults, and having diabetes is known to increase a person’s risk of developing dementia,” said study author Yingli Lu, MD, PhD, of Shanghai Jiao Tong University School of Medicine in China. “We investigated whether a broad combination of healthy lifestyle habits could offset that dementia risk and found that people with diabetes who incorporated seven healthy lifestyle habits into their lives had a lower risk of dementia than people with diabetes who did not lead healthy lives.”

For the study, researchers looked at a health care database in the United Kingdom and identified 167,946 people 60 or older with and without diabetes who did not have dementia at the start of the study. Participants completed health questionnaires, provided physical measurements and gave blood samples.

For each participant, researchers calculated a healthy lifestyle score of zero to seven, with one point for each of seven healthy habits. Habits included no current smoking, moderate alcohol consumption of up to one drink a day for women and up to two a day for men, regular weekly physical activity of at least 2.5 hours of moderate exercise or 75 minutes of vigorous exercise, and seven to nine hours of sleep daily. Another factor was a healthy diet including more fruits, vegetables, whole grains and fish and fewer refined grains, processed and unprocessed meats. The final habits were being less sedentary, which was defined as watching television less than four hours a day, and frequent social contact, which was defined as living with others, gathering with friends or family at least once a month and participating in social activities at least once a week or more often.

Researchers followed participants for an average of 12 years. During that time, 4,351 people developed dementia. A total of 4% of the people followed only zero to two of the healthy habits, 11% followed three, 22% followed four, 30% followed five, 24% followed six and 9% followed all seven.

People with diabetes who followed two or fewer of the seven healthy habits were four times more likely to develop dementia than people without diabetes who followed all seven healthy habits. People with diabetes who followed all of the habits were 74% more likely to develop dementia than those without diabetes who followed all the habits.

For people with diabetes who followed all the habits, there were 21 cases of dementia for 7,474 person years or 0.28%. Person-years represent both the number of people in the study and the amount of time each person spends in the study. For people with diabetes who followed only two or fewer habits, there were 72 cases of dementia for 10,380 person years or 0.69%. After adjusting for factors like age, education and ethnicity, people who followed all the habits had a 54% lower risk of dementia than those who followed two or fewer. Each additional healthy habit people followed was associated with an 11% decreased risk of dementia. The association between healthy lifestyle score and dementia risk was not affected by medications people took or how well they controlled their blood sugar.

“Our research shows that for people with type 2 diabetes, the risk of dementia may be greatly reduced by living a healthier lifestyle,” Lu said. “Doctors and other medical professionals who treat people with diabetes should consider recommending lifestyle changes to their patients. Such changes may not only improve overall health, but also contribute to prevention or delayed onset of dementia in people with diabetes.”

A limitation of the study was that people reported on their lifestyle habits and may not have remembered all details accurately. Lifestyle changes over time were also not captured.

Adult ADHD linked to elevated risk of cardiovascular diseases

 

Adults with ADHD are at greater risk of developing a range of cardiovascular diseases than those without the condition, according to a large observational study led by researchers at Karolinska Institutet and Örebro University in Sweden. The researchers say the findings, published in the journal World Psychiatry, underscore the need to monitor cardiovascular health in people with ADHD.

Attention deficit/hyperactivity disorder (ADHD) is one of the most common neurodevelopmental disorders, with a global prevalence of around 2.5 percent in adults. It often exists in parallel with other psychiatric and physical conditions, some of which have been linked to an increased risk of cardiovascular disease (CVD). But whether ADHD is independently associated with overall and specific cardiovascular diseases has not received as much attention.

In the current study, the researchers sought to unmask the correlation between ADHD and some 20 different cardiovascular diseases when separated from other known risk factors such as type 2 diabetes, obesity, smoking, sleep problems and mental disorders.

“We found that adults with ADHD were more than twice as likely to develop at least one cardiovascular disease, compared with those without ADHD,” says the study’s first author Lin Li, postdoctoral researcher at the Department of Medical Epidemiology and Biostatistics, Karolinska Institutet. “When we accounted for other well-established risk factors for CVDs, the association weakened but still remained significant, which indicates that ADHD is an independent risk factor for a wide range of cardiovascular diseases.”

The findings build on national registry data of more than five million Swedish adults, including some 37,000 people with ADHD. After an average 11.8 years of follow-up, 38 percent of individuals with ADHD had at least one diagnosis of cardiovascular disease, compared with 24 percent of those without ADHD.

Risks were elevated for all types of cardiovascular diseases and especially high for cardiac arrest, hemorrhagic stroke and peripheral vascular diseases. The association was somewhat stronger in men than in women. Some psychiatric comorbidities, especially eating and substance use disorders, significantly increased the risk of cardiovascular disease in people with ADHD. Treatment with stimulants and other psychiatric drugs, such as antidepressants and anxiety-reducing medication, did not materially affect the association between ADHD and cardiovascular disease.

The researchers note that due to the observational nature of the study, the findings cannot establish a causal relationship.

“Clinicians needs to carefully consider psychiatric comorbidity and lifestyle factors to help reduce the CVD risk in individuals with ADHD, but we also need more research to explore plausible biological mechanisms, such as shared genetic components for ADHD and cardiovascular disease,” says the study’s last author Henrik Larsson, professor at the School of Medical Sciences, Örebro University, and affiliated researcher at Karolinska Institutet.

The researchers note the study has some limitations, including a lack of data on some lifestyle related factors, such as diet and physical activity, that could impact the association.

This project has received funding from the European Union’s Horizon 2020 research and innovation programme, the Swedish Research Council, the Swedish Brain Foundation, the Swedish Council for Health, Working Life and Welfare and the Swedish Society for Medical Research.

Publication: “Attention-deficit/hyperactivity disorder as a risk factor for cardiovascular diseases: a nationwide population-based cohort study.” Lin Li, Zheng Chang, Jiangwei Sun, Miguel Garcia-Argibay, Ebba Du Rietz, Maja Dobrosavljevic, Isabell Brikell, Tomas Jernberg, Marco Solmi, Samuele Cortese, Henrik Larsson, World Psychiatry, online September 8, 2022, doi: 10.1002/wps.21020