New Perspectives Challenge the Idea that Saturated Fats Cause Heart Disease

In science, sometimes a new perspective can turn our interpretation of the data upside-down, and necessitate a paradigm shift.

There has been, and continues to be, fierce disagreements in nutrition science as to what constitutes a healthy diet. A key controversy is the role of saturated fats in health and disease. Saturated fats are known to increase blood cholesterol levels, and increased blood cholesterol is often observed in people who develop cardiovascular disease.

It has been thought for more than half a century that saturated fats in the diet promote heart disease by increasing blood cholesterol. However, a new model explains why this so-called “diet-heart hypothesis”, which has had a major influence on dietary guidelines, may have an alternative explanation.

In a new article published today in the American Journal of Clinical Nutrition, three scientists have raised a question that challenges the diet-heart-hypothesis: Why do saturated fats increase blood cholesterol, and why should this be dangerous? After all, saturated fats occur naturally in a wide variety of foods, including breast milk.

“Cholesterol is a critically important molecule for all cells in the body,” explains associate professor Marit Zinöcker, the lead author at Bjørknes University College, Oslo, Norway. “A cell is surrounded by a fluid membrane that controls cell function, and the cells depend on the ability to incorporate a certain amount of cholesterol molecules, so that their membranes don’t become too stiff or too fluid.”

“The basis of the model is that when saturated fats replace polyunsaturated fats in the diet, less cholesterol is needed in the cell membranes,” she explains. The opposite is true when eating more polyunsaturated fatty acids, which include omega-3 and omega-6 fatty acids. “This is because polyunsaturated fats from the diet enter our cell membranes and make them more fluid. The cells adjust the fluidity of their membranes by incorporating cholesterol recruited from the bloodstream. According to the model presented by the researchers, this can explain why blood cholesterol levels decrease when we eat more polyunsaturated fats.

The authors have named the model the “Homeoviscous Adaptation to Dietary Lipids” (HADL) model.

“Cells need to adjust their membrane fluidity according to changes in their environment, such as the access to different types of fat”, says co-author Simon N. Dankel, researcher at the Department of Clinical Science, University of Bergen, Norway.

“This phenomenon is called homeoviscous adaptation, and has been described in both microorganisms, vertebrates and in human skin cells. We argue that this is a critical principle in human physiology. Our cells are normally capable of adjusting their cholesterol content according to changes in dietary fats.”

“Nutrition research often focuses on what changes in the body, but the question of why something, such as the blood cholesterol, changes, is of equal importance”, says co-author Karianne Svendsen, postdoctoral fellow at the Department of Nutrition, University of Oslo, Norway.

This is where the new HADL model comes into play, providing an explanation based on adaptive human physiology. “From the perspective of the HADL model, we find logical explanations for why cells need to change their cholesterol content, and thereby the blood cholesterol, when fats in the diet change,” says Zinöcker.

In the paper, other reasons for elevated LDL-cholesterol in people with cardiovascular disease are discussed, such as low-grade inflammation and insulin resistance. This indicates that elevated blood cholesterol caused by metabolic disruptions must be uncoupled from elevated blood cholesterol caused by a major change in intake of dietary saturated fatty acids. It also questions the benefit of lowering blood cholesterol by adding polyunsaturated fatty acids to the diet, and not addressing the root cause.

“There is at best weak evidence that a high intake of saturated fat causes heart disease,” says Dankel. “The overall data are inconsistent and unconvincing, not to mention the lack of a logical biological and evolutionary explanation.”

“Also, people with metabolic disorders often do not show the expected changes in blood cholesterol when changing their fat intake, suggesting loss of the normal response.”

“The research and reasoning that the HADL model is based on indicates that the effect of dietary fats on blood cholesterol is not a pathogenic response, but rather a completely normal and even healthy adaptation to changes in diet.” Zinöcker concludes.

The authors state that although the model is based on existing knowledge of cellular mechanisms, the model still needs to be verified. The authors therefore urge researchers to discuss the HADL model using #HADLmodel and to test the model.

Source: EurekAlert!

COVID Lockdown Loneliness Linked to More Depressive Symptoms in Older Adults

Loneliness in adults aged 50 and over during the COVID-19 lockdown was linked to worsening depressive and other mental health symptoms, according to a large-scale online study.

Loneliness emerged as a key factor linked to worsening symptoms of depression and anxiety in a study of more than 3,000 people aged 50 or over led by the University of Exeter and King’s College London, and funded by The National Institute for Health Research (NIHR) Maudsley Biomedical Research Centre (BRC).

Researchers had access to data going back to 2015 for participants of the PROTECT online study. They also found that a decrease in physical activity since the start of the pandemic was associated with worsening symptoms of depression and anxiety during the pandemic. Other factors included being female and being retired.

Dr Byron Creese, of the University of Exeter Medical School, who led the study, said: “Even before the pandemic, loneliness and physical activity levels were a huge issue in society, particularly among older people. Our study enabled us to compare mental health symptoms before and after COVID-19 in a large group of people aged 50 and over. We found that during lockdown, loneliness and decreased physical activity were associated with more symptoms of poor mental health, especially depression. It’s now crucial that we build on this data to find new ways to mitigate risk of worsening mental health during the pandemic.”

The study found that before the pandemic, lonely people would report an average of two symptoms of depression for at least several days over the previous last two weeks. During lockdown, lonely people reported either an increase in frequency of depressive symptoms, to more than half the days in the two week period, or a new symptom for at least several days in that timeframe. In people who were not lonely, levels of depressive symptoms were unaffected.

PROTECT began in 2011, and has 25,000 participants signed up. Designed to understand the factors involved in healthy ageing, the innovative study combines detailed lifestyle questionnaires with cognitive tests that assess aspects of brain function including memory, judgment and reasoning over time. In May, researchers included a new questionnaire designed to assess the impact of COVID-19 on health and wellbeing. Running from May 13 to June 8, the questionnaire was completed by 3,300 people, of which 1,900 were long-standing PROTECT participants. The study is continuing to run so that longer term outcomes can be assessed.

Zunera Khan, Research Portfolio Lead at Institute of Psychiatry, Psychology & Neuroscience said “We’ve found links between loneliness and a drop in physical exercise and worsening mental health symptoms. It should be within our power to find ways of keeping people socially engaged and active. Our online PROTECT platform ultimately aims to find new ways to engage people in their homes, however, technology can only be part of the picture. We need to ensure we can find new ways to help people stay active and social, whether they are online or not.”

Professor Clive Ballard, Executive Dean and Pro-Vice Chancellor of the University of Exeter Medical School, who leads PROTECT, said: “We are only just beginning to learn the impact that COVID-19 is having on the health and wellbeing of older people. For example, the effect of any economic impact may not yet have emerged. Our largescale study will span a number of years, and will help us understand some of the longer-term effects of COVID-19 on mental health and wellbeing, and ultimately, on whether this has any knock-on effect on aspects of ageing, such as brain function and memory. “

The study plans to conduct further analysis on groups at particularly high risk, such as people with cognitive impairment and those with caring roles.

Source: University of Exeter

How Many People Need to Get a COVID-19 Vaccine in Order to Stop the Coronavirus?

Pedro Mendes wrote . . . . . . . . .

It has been clear for a while that, at least in the U.S., the only way out of the coronavirus pandemic will be through vaccination. The rapid deployment of coronavirus vaccines is underway, but how many people need to be vaccinated in order to control this pandemic?

I am a computational biologist who uses data and computer models to answer biological question at the University of Connecticut. I have been tracking my state’s COVID-19 epidemic with a computer model to help forecast the number of hospitalizations at the University of Connecticut’s John Dempsey Hospital.

This type of computer model and the underlying theory can also be used to calculate the vaccination rates needed to break the chain of transmission of the coronavirus. My estimate is that for the entire U.S., roughly 70% of the population needs to be vaccinated to stop the pandemic. But variation in how people behave in different parts of the country, as well as open questions on whether the vaccine prevents infection entirely or just prevents people from getting sick, add a degree of uncertainty.

Cutting off transmission

Clinical trials have shown that once a person gets vaccinated for the coronavirus, they won’t get sick with COVID-19. A person who doesn’t get sick can still be infected with the coronavirus. But let’s also assume that a vaccinated person can’t spread the virus to others, though researchers still don’t know if this is true.

When enough of the population is vaccinated, the virus has a hard time finding new people to infect, and the epidemic starts dying out. And not everyone needs to be vaccinated, just enough people to stop the virus from spreading out of control. The number of people who need to be vaccinated is known as the critical vaccination level. Once a population reaches that number, you get herd immunity. Herd immunity is when there are so many vaccinated people that an infected person can hardly find anyone who could get infected, and so the virus cannot propagate to other people. This is very important to protect people who cannot get vaccinated.

The critical vaccination level depends on how infectious the disease is and how effective the vaccine is. Infectiousness is measured using the basic reproduction number – R0 – which is how many people an infected person would spread the virus to on average if no protective measures were in place.

The more infectious a disease is, the larger the number of people who need to be vaccinated to reach heard immunity. The higher the effectiveness of the vaccine, the fewer people need to be vaccinated.

Not the same everywhere

R0 values differ from place to place because their populations behave differently – social interactions are not the same in rural and urban locations, nor in warm climates compared to cold ones, for example.

Using the data on positive cases, hospitalizations and deaths, my model estimates that Connecticut currently has an R0 of 2.88, meaning that, on average, every infected person would pass the virus on to 2.88 other people if no mitigation measures were in place. Estimates at the county level range from 1.44 in rural Alpine, California to 4.31 in urban Hudson, New Jersey.

But finding an R0 value for the entire U.S. is especially tricky because of the diversity of climates and because the virus has affected different areas at different times – behavior has been far from uniform. Estimates vary from 2.47 to 8.2, though most researchers place R0 for the entire U.S. around 3.

While R0 varies by location and between estimates, the effectiveness of the vaccines is constant and well known. The Pfizer-BioNTech and Moderna vaccines are 95% and 94.5% effective at preventing COVID-19, respectively.

Using values for vaccine effectiveness and the R0, we can calculate the critical vaccination level. For Connecticut, with an R0 of 2.88, 69% of the population needs to be vaccinated. For the entire U.S., with R0 of 3, this would be 70%. In New York City, with an estimated R0 of 4.26 this would be 80%.

A lot of uncertainty

While the math is relatively simple, things get complicated when you consider important questions for which epidemiologists still have no answers.

First, the formula for critical vaccination level assumes that people interact randomly. But in the real world, people interact in highly structured networks depending on work, travel and social connections. When those contact patterns are considered, some researchers found critical vaccination levels to be considerably smaller compared to assuming random interactions.

Unfortunately, other unknowns could have an opposite effect.

Vaccine trials clearly show that vaccinated people don’t get sick with COVID-19. But it is still unknown whether the vaccines prevent people from getting mild infections that they could pass on to others. If vaccinated people can still be infected and pass on the virus, then vaccination will not provide herd immunity – though it would still prevent serious disease and reduce mortality drastically.

A final question that remains to be answered is how long immunity to the coronavirus lasts after a person is vaccinated. If immunity wanes after a few months, then each individual will need repeated vaccinations.

It is hard to say with certainty how many people need to be vaccinated in order to end this pandemic. But even so, the arrival of COVID-19 vaccines has been the best news in 2020. In 2021, as a large proportion of individuals in the U.S. get the vaccine, the country will be heading toward the critical vaccination level – whatever it may be – so that life can start to return to normal.

Source : The Conversation

World-wide COVID-19 Cases Passed 100 millions Today

Enlarge image . . . . .

The chart shows the ten countries with the most COVID-19 cases. The world data cover cases in 219 countries and territories.

Source : Worldometer

Study: Exercise Doesn’t Boost Heart Health for Obese Individuals

The harmful effects of obesity on the heart can’t be undone by exercise, and it’s not possible to be “fat but healthy,” Spanish researchers warn.

“Exercise does not seem to compensate for the negative effects of excess weight,” said study author Alejandro Lucia, a professor of exercise physiology at European University in Madrid.

The study findings “refute the notion that a physically active lifestyle can completely negate the deleterious effects of overweight and obesity,” he said.

Lucia and his colleagues analyzed data from nearly 528,000 working adults in Spain. The participants’ average age was 42 and close to 7 out of 10 were men.

About 42% of these adults were normal weight; 41% were overweight, and 18% were obese. Most were inactive (63.5%); 12.3% got some but not enough exercise, and 24.2% were regularly active.

About 30% of participants had high cholesterol; 15% had high blood pressure, and 3% had diabetes.

No matter how active they were, however, overweight and obese people had a higher risk of heart disease than those whose weight was normal, according to the study, published in the European Journal of Preventive Cardiology.

Compared to active people of normal weight, active obese people were about twice as likely to have high cholesterol, four times more likely to have diabetes, and five times more likely to have high blood pressure.

“One cannot be ‘fat but healthy,’ ” Lucia warned in a journal news release.

But the researchers did not disregard the importance of exercise. In all weight categories, any physical activity was associated with a lower risk of diabetes, high blood pressure or high cholesterol, according to the findings. And the risk of diabetes and high blood pressure fell as physical activity rose.

“This tells us that everyone, irrespective of their body weight, should be physically active to safeguard their health,” Lucia said.

“More activity is better, so walking 30 minutes per day is better than walking 15 minutes a day,” he noted.

Lucia said it’s equally important to fight obesity and inactivity. “Weight loss should remain a primary target for health policies together with promoting active lifestyles,” he concluded.

Source: HealthDay