Should public health guidelines recommend reducing saturated fat consumption as much as possible? Nutrition experts are tackling that controversial question head-on in a new series of papers outlining key points of agreement--and disagreement--in how to interpret the evidence and inform health guidelines.
Ronald Krauss, MD, of Children's Hospital Oakland Research Institute, and Penny Kris-Etherton, PhD, of Pennsylvania State University, present their positions in the premiere of Great Debates in Nutrition, a new section edited by David S. Ludwig in the American Journal of Clinical Nutrition. Krauss and Kris-Etherton will also debate the topic in a live interactive session as part of NUTRITION 2020 LIVE ONLINE, a virtual conference hosted by the American Society for Nutrition.
"The debate format enabled us to identify and refine points of agreement, as well as issues that remained in dispute," the authors wrote in a paper summarizing their viewpoints. "While these proceedings represent our personal perspectives, we hope that they provide a framework for discussion of dietary saturated fat recommendations among health professionals and for improved understanding by the general public of the controversies that have surrounded this topic."
Saturated fats are those that are solid at room temperature, such as bacon grease and butter. The Dietary Guidelines for Americans 2015-2020 recommends limiting saturated fats intake to less than 10% of calories per day. A majority of Americans currently exceed this level, with saturated fat representing about 11-12% of daily calories, on average.
Animal products are the main source of saturated fats in Americans' diets, with mixed dishes such as burgers, sandwiches, tacos and pizza contributing a little over a third of this daily intake. Snacks and sweets contribute about 18% of total saturated fat intake, protein foods contribute 15% and dairy products provide 13%. Tropical plant products, like coconut butter, also have high saturated fat content.
The debate centers around the evidence linking saturated fat with heart disease and the potential consequences--intended and unintended--of a public health guideline to reduce consumption as much as possible.
Both experts agree that a person's overall dietary pattern matters more than any single food component, and that dietary patterns associated with lower rates of heart disease are not high in saturated fat. In addition, both agree that low-density lipoproteins (LDLs) increase the risk of heart disease and that consuming saturated fats in place of unsaturated fats and carbohydrates increases LDL cholesterol levels.
However, they disagree about the strength of the evidence that a recommendation to limit saturated fat as much as possible would actually reduce rates of heart disease by helping to keep cholesterol in check. One set of questions revolves around the specific role of LDL cholesterol and the extent to which other mechanisms may come into play. Another question is whether the effect of dietary saturated fat on LDL cholesterol levels could be influenced by other factors, particularly the amount and types of carbohydrates a person consumes.
Both experts point to uncertainty with regard to how different sources of saturated fats affect health, as well as how the body's response to these fats may differ from person to person. While both call for additional research to help resolve the questions that remain, they come to different conclusions regarding what to make of the evidence as it stands.
"Though it is possible that dietary intake of saturated fatty acids has a causal role in cardiovascular disease, the evidence to support this contention is inconclusive," Krauss wrote. "Collectively, neither randomized clinical trials nor observational studies have conclusively established a benefit on cardiovascular disease outcomes and mortality [that can be specifically attributed to] reducing dietary saturated fatty acids." Krauss also questions the scientific basis for implementing a numerical target for the population as a whole, given that the effects of saturated fats may vary by source or by person.
Despite the outstanding questions, Kris-Etherton argues that the available evidence is strong enough to justify a recommendation to decrease intake of saturated fats. "We still have a large body of convincing and consistent evidence from different types of studies for making population-wide dietary recommendations to lower saturated fatty acids," said Kris-Etherton. "To wait until all questions are answered before any recommendations are made to limit saturated fatty acids further ignores the evidence base we have which when implemented can prevent cardiovascular disease (and other diseases) in many people."
Both experts caution that any guidance on this topic should avoid inadvertently encouraging people to replace foods high in saturated fat with foods high in added sugars and refined or processed carbohydrates, which they agree would pose substantial health risks.
For the study, investigators analyzed residential outdoor light at night estimated from satellite imagery in 1996 and assessed rates of breast cancer over 16 years of follow-up in 186,981 postmenopausal women.
Compared with the lowest level of exposure to outdoor light at night, the highest exposure was associated with a 10% higher risk of developing breast cancer during follow-up, after controlling for confounding factors.
"The small number of studies to investigate this question have often relied on subjective exposure data and yielded inconsistent results. We utilized an objective exposure measure--estimated outdoor light at night from satellite data," said senior author Rena Jones, PhD, MS, of the National Cancer Institute, part of the National Institutes of Health. "It will be important for future studies to accurately measure light at night exposure for individuals using a combination of objective measures, carefully designed questionnaires, and personal measurement devices."
Large study looks at which types of carbohydrates affect risk of developing type 2 diabetes
A new analysis of more than 200,000 people found that eating high-quality carbohydrates, such as whole grains, was associated with a lower risk for type 2 diabetes.
"High intake of carbohydrates has been suggested to be associated with a higher risk of type 2 diabetes," said research team leader Kim Braun, PhD, from Erasmus University Medical Center and Harvard T.H. Chan School of Public Health. "We looked at whether this effect is different for high-quality carbohydrates and low-quality carbohydrates, which include refined grains, sugary foods and potatoes."
Braun will present the new findings as part of NUTRITION 2020 LIVE ONLINE, a virtual conference hosted by the American Society for Nutrition (ASN).
Braun and colleagues analyzed data from three studies that followed health professionals in the U.S. over time. These included 69,949 women from the Nurses' Health Study, 90,239 women from the Nurses' Health Study 2 and 40,539 men from the Health Professionals Follow-up Study. Collectively, the studies represented over 4 million years of follow-up, during which almost 12,000 cases of type 2 diabetes cases were documented.
The researchers observed a lower risk of type 2 diabetes when high-quality carbohydrates replaced calories from saturated fatty acids, monounsaturated fats, polyunsaturated fats, animal protein and vegetable protein. They also found that replacing low-quality carbohydrates with saturated fats, but not with other nutrients, was associated with a lower risk of type 2 diabetes.
"These results highlight the importance of distinguishing between carbohydrates from high- and low- quality sources when examining diabetes risk," said Braun. "Conducting similar studies in people with various socio-economic backgrounds, ethnicities and age will provide insight into how applicable these findings are for other groups."
Due to the cancellation of the Nutrition 2020 meeting, which was to be held in Seattle, this abstractwill be presented as part of ASN's virtual meeting, NUTRITION 2020 LIVE ONLINE, which will be held from June 1-4, 2020. Contact the media team for more information or register to access the virtual content.
Rockville, MD (June 1, 2020) - A new study of children and teens found that more than 25% of the calories they consume were considered empty - those from added sugars and solid fats. The top sources of these empty calories were soft drinks, fruit drinks, cookies and brownies, pizza, and ice cream.
"Our findings suggest a need for continued research into what children and adolescents are eating," said Edwina Wambogo, PhD, who was a recent postdoctoral Cancer Research Training Award Fellow with the National Cancer Institute. "Examining the whole landscape of available foods and beverages for children and adolescents can help inform new ways to promote healthier eating."
Wambogo, the primary investigator for the study, will present the research as part of NUTRITION 2020 LIVE ONLINE, a virtual conference hosted by the American Society for Nutrition (ASN).
The researchers used data from the 2007-2008 through 2015-2016 National Health and Nutrition Examination Survey to analyze diet trends for children and adolescents ages 2 to 18 years old.
"Over the time period studied, we observed a downward trend in the percent of calories coming from empty calories without any associated decrease in total calorie intake," said Wambogo. "This trend was mostly driven by declines in added sugars intake, including those from soft drinks and fruit drinks."
Despite this positive trend, the analysis revealed that for all age groups studied more than 25% of their caloric intake came from empty calories, with the percentage of empty calories increasing with age. The top food sources for these calories remained almost the same from 2007-2008 to 2015-2016. However, with increasing age, the sources shifted from beverages such as fruit drinks and flavored milks to foods such as pizza and sweet bakery products. In terms of drinks, older children and teens also tended to consume more calories from soft drinks rather than fruits drinks, flavored milks and whole milk.
Based on their findings, the researchers suggest several strategies that might be used to help children and teens consume healthier foods:
Designing interventions that target top sources of energy and empty calories.
Nutrition education that addresses hidden sources of empty calories from frequently consumed foods.
Increased marketing that promotes healthier foods to children and teens and limited marketing of less healthy foods.
Product reformulation such as reducing added sugars in beverages.
Changing the food environment to ensure availability of healthy foods and limit access to less healthy foods.
The researchers are planning a follow-up study to examine how the top sources of energy and calories consumed by this age group vary by family income. They also want to study further how added solid fats and sugars in beverages may impact intake of calories among children and adolescents.
Virtual conference presents progress and pitfalls in understanding the best way to lose excess weight
Many of us are eating differently during the COVID-19 pandemic, and some are taking the stay-at-home lifestyle as an opportunity to work on weight loss goals. Get the latest research findings on fad diets, losing weight and healthful eating at NUTRITION 2020 LIVE ONLINE, a virtual conference featuring leading nutrition experts from around the world.
NUTRITION 2020 LIVE ONLINE is hosted by the American Society for Nutrition (ASN), the preeminent professional organization for nutrition research scientists and clinicians. ASN's flagship meeting, Nutrition 2020, was canceled due to the impacts of COVID-19. Attend the meeting for free online or contact the media team for more information.
Is your weight loss diet giving you enough nutrients?
Micronutrients are important for keeping your body healthy and warding off disease. In a year-long randomized controlled trial, researchers found that 54 people following one of two diets--a low-carbohydrate diet or a high-fiber, bean-rich diet--showed similar results in terms of weight loss but were deficient in some micronutrients. While nutrient content varied between the two diets, participants in both groups consumed less than the recommended daily amount of vitamin D, vitamin E, calcium, magnesium and copper.
Neal G. Malik, California State University, is the presenting author. This research will be presented as a virtual abstract presentation beginning June 1 at 12 p.m. EDT.
When healthy eating becomes an obsession
A new study suggests weight-loss diets may go hand-in-hand with orthorexia nervosa, a potentially damaging obsession with healthy eating. An internet survey of more than 400 college students found more than three-quarters of respondents who reported following a weight loss diet also showed signs of orthorexia, compared to less than 40% among those who were not dieting. Those following a weight loss diet also showed a much higher risk for other eating disorders.
Zhiping Yu, University of North Carolina at Chapel Hill, is the presenting author. This research will be presented as a virtual abstract presentation beginning June 1 at 12 p.m. EDT.
Looking beyond food
Can gut microbes help--or hinder--weight loss?
While the microbes living in and on our bodies play a big role in our health, little is known about how they influence weight loss efforts. New research suggests that the type of bacteria in a person's gut may help predict their likelihood of weight-loss success. Out of 36 people participating in a six-month weight loss program, the 12 participants who succeeded in losing the targeted amount of weight (5% weight loss) showed lower concentrations of certain bacteria and higher concentrations of others at baseline compared to participants who did not lose weight. The findings suggest gut microbes may influence weight loss by affecting how the body processes food, researchers say.
Moira K. Differding, Johns Hopkins Bloomberg School of Public Health, is the presenting author. This research will be presented as a virtual abstract presentation beginning June 1 at 12 p.m. EDT.
Exercise brings no weight loss boost compared to diet alone
A study involving 383 overweight adults found that following a calorie-restricted diet resulted in roughly the same amount of weight loss regardless of a person's level of physical activity. After one year of limiting their intake to 1,200-1,800 calories per day, participants lost just over 20 pounds on average, but the amount of weight lost was not significantly different among participants who exercised an average of 1.5 hours per week compared to those exercising nearly 4 hours per week. The researchers also found that participants' level of physical activity did not affect their ability to keep their calorie and fat consumption within bounds.
Carli A. Ligouri, University of Pittsburgh, is the presenting author. This research will be presented as a virtual abstract presentation beginning June 1 at 12 p.m. EDT.
How reliable are commercial nutrition apps?
Researchers examined how calories and nutrients are calculated in two commercial nutrition apps--CalorieKing and MyFitnessPal--compared to a reference database used by scientists, the University of Minnesota Nutrition Coordinating Center Nutrition Data System for Research (NDSR). Overall, the apps were similar to the NDSR in counting calories and nutrients for the 50 most commonly consumed foods, with a few exceptions. MyFitnessPal was less reliable in its assessment of total fat and fiber intake for all foods, and was especially unreliable when it came to calculating calories, carbohydrates and fiber content of fruits. This variability underscores the need to compare nutrition apps with validated data sources if they are to be used in research and practice, researchers say.
Annie W. Lin, Northwestern University, is the presenting author. This research will be presented as a virtual abstract presentation beginning June 1 at 12 p.m. EDT.
Personalized weight loss program does not bring added confidence
Researchers are exploring whether a weight loss diet can be made more effective by accounting for how a person's body responds to specific foods. Early results from the three-month data involving 75 participants suggest this personalized approach has no effect on how people perceive their ability to resist overeating compared to a one-size-fits-all diet. The researchers plan to continue the study to examine how a personalized diet might affect participants' confidence or actual weight loss in the longer term.
Lu Hu, New York University, is the presenting author. This research will be presented as a virtual abstract presentation beginning June 1 at 12 p.m. EDT.
Researchers at the University of Copenhagen's Department of Nutrition, Exercise and Sports have demonstrated that physical activity prompts a clean-up of muscles as the protein Ubiquitin tags onto worn-out proteins, causing them to be degraded
Researchers at the University of Copenhagen's Department of Nutrition, Exercise and Sports have demonstrated that physical activity prompts a clean-up of muscles as the protein Ubiquitin tags onto worn-out proteins, causing them to be degraded. This prevents the accumulation of damaged proteins and helps keep muscles healthy.
Physical activity benefits health in many ways, including the building and maintenance of healthy muscles, which are important for our ability to move about normally, as well as to fulfill the vital role of regulating metabolism. As most of the carbohydrate that we eat is stored in muscle, our muscles are extremely important for regulating metabolism.
An intense bike ride boosts Ubiquitin activity
Maintaining muscular function is essential. Part of our ability to do so depends upon proteins - the building blocks of muscles - being degraded when worn-out and eliminated in a kind of clean up process that allows them to be replaced by freshly synthesized proteins.
Now, Danish researchers - in collaboration with research colleagues at the University of Sydney, Australia - have demonstrated that a single, intense, roughly 10-minute bicycle ride results in a significant increase in the activity of Ubiquitin, the 'death marker protein' and a subsequent intensification of the targeting and removal of worn-out proteins in muscles. This paves the way for an eventual build-up of new proteins:
"Muscles eliminate worn-out proteins in several ways," explains Professor Erik Richter of the Section for Molecular Physiology at UCPH's Department of Nutrition, Exercise and Sports. He continues:
"One of these methods is when Ubiquitin, "the death-marker", tags a protein in question. Ubiquitin itself is a small protein. It attaches itself to the amino acid Lysine on worn-out proteins, after which the protein is transported to a Proteasome, which is a structure that gobbles up proteins and spits them out as amino acids. These amino acids can then be reused in the synthesis of new proteins. As such, Ubiquitin contributes to a very sustainable circulation of the body's proteins."
Why physical activity is healthy
While extensive knowledge has been accumulated about how muscles regulate the build-up of new proteins during physical training, much less is known about how muscle contractions and exercise serve to significantly clean-up worn-out proteins. According to Professor Bente Kiens, another project participant: "The important role of Ubiquitin for 'cleaning-up' worn-out proteins in connection with muscular activity was not fully appreciated. Now we know that physical activity increases Ubiquitin tagging on worn-out proteins."
Professor Jørgen Wojtaszewski, a third Danish project participant, explains that their findings serve to strengthen the entire foundation for the effect of physical activity: "Basically, it explains part of the reason why physical activity is healthy. The beauty is that muscle use, in and of itself , is what initiates the processes that keep muscles 'up to date', healthy and functional."
There remains a great amount of knowledge that would be interesting to delve deeper into, as very little is known about how different training regimens, gender, diet and genetic background impact the process and thus, the possibility of influencing optimal muscle function.
Some men benefit from an earlier cancer diagnosis; however, more men are at risk of overdiagnosis and treatment-related complications; studies have yet to show whether a risk-adapted approach will affect this conclusion
INSTITUTE FOR QUALITY AND EFFICIENCY IN HEALTH CARE
The benefit of population-based PSA screening for men with an average risk of prostate cancer does not outweigh the harm caused. This is the conclusion drawn by the Institute for Quality and Efficiency in Health Care (IQWiG) in its final report after evaluating the worldwide evidence from studies on the topic. While screening using a PSA test benefits some men by preventing or delaying metastatic prostate cancer, at the same time, however, considerably more men are at risk to become permanently incontinent or impotent due to overdiagnosis and subsequent overtreatment - and this at a relatively young age.
At the hearing on the preliminary report, IQWiG discussed in detail with participants whether and how the harm from PSA screening could be reduced using risk-adapted screening strategies without simultaneously reducing the benefit. IQWiG's Director Jürgen Windeler emphasizes "Measures such as restricting biopsies to men at high risk of progression or using new biopsy methods are promising approaches to improve the benefit-harm ratio of PSA screening in the long term. However, there are currently no studies to prove this." Therefore, the overall assessment of PSA screening remained unchanged in IQWiG's final report.
The most common type of cancer in men
Prostate cancer is the most common cancer in men in Germany, accounting for 23 percent of all new cancer cases and causing approximately 14,000 deaths per year.
The aim of screening is to detect prostate cancer with a high risk of progression at an early stage in order to cure the disease. Two screening tests are currently used: the digital-rectal examination and the test for prostate-specific antigen (PSA). The former is part of the screening programme offered by statutory health insurance for men aged 45 and older, the PSA test is not.
The IQWiG benefit assessment now available is based on the analysis of 11 randomized controlled trials with more than 400,000 participants worldwide. All of these studies compare prostate cancer screening using the PSA test with no screening for prostate cancer.
More harm than benefit in the overall balance
After evaluating the evidence, IQWiG concludes that prostate cancer screening using a PSA test benefits some men with prostate cancer by delaying or preventing metastatic cancer. This advantage only occurs after several years. Moreover, it is unclear whether screening leads to an increase in overall life expectancy in these men.
At the same time, PSA screening harms overdiagnosed men (men with prostate cancer not requiring treatment) and men with a false-positive screening test result (men without prostate cancer). The overdiagnosed men are at risk of treatment-related complications such as incontinence and impotence. Men with a false-positive result may experience harm in the form of a worrying test result that is followed by a prostate biopsy.
Overall, prostate cancer screening using a PSA test harms considerably more men through overdiagnosis than it benefits men through earlier diagnosis of the cancer. In summary, on the basis of the available studies IQWiG therefore concludes that the benefit of PSA screening does not outweigh the harm. The Institute is in good company with this careful consideration: worldwide, almost all national health authorities and professional societies recommend against population-based PSA screening.