Category: Diet and Nutrition

Study: Intermittent Fasting Positively Affects Female Hormones in PCOS 

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Polycystic ovary syndrome, or PCOS, affects as many as 18% of all childbearing-age women. The condition occurs when a woman’s body produces too androgens, chiefly testosterone. Menstrual irregularity, obesity and even infertility can result.

The first line of treatment is typically hormonal birth control, said UIC professor of nutrition Krista Varady. But there can be negative side effects to mood, libido and metabolism, plus an increased stroke risk in some people, Varady said.

“We’re looking for other ways of lowering testosterone levels in these women,” she said. “One way is through weight loss. If someone loses around 5% of their body weight, they can actually help lower testosterone levels and sidestep any kind of drug intervention.”

A new study led by Varady tested how one weight-loss method — intermittent fasting — affects hormones and symptoms in patients with PCOS. Published in Nature Medicine, the research shows that restricting eating to a six-hour daily window decreased testosterone without negatively affecting female hormones. The study also showed that weight loss through calorie counting decreased testosterone. 

However, some critics of intermittent fasting have posited that the diet disrupts female hormones, Varady said.

“There’s a particular sentiment that intermittent fasting is really bad for women.” This is untrue, she said. “This study and several other studies published by our lab and others show that intermittent fasting can actually improve female hormone levels, particularly in women with PCOS.” 

Varady and her colleagues studied a type of intermittent fasting called time-restricted eating. In this method, you eat only during a set six- or eight-hour period each day. During the remaining 18 or 16 hours, you fast with calorie-free beverages and water until the next day. 

Simply put, the strategy helps people eat less, Varady said. So does counting calories, a method Varady and her colleagues tested alongside intermittent fasting in the study. But intermittent fasting had some additional benefits.

“It’s a way of reducing energy intake without having to do really complicated calorie counting,” she said about intermittent fasting. Varady and others have shown in previous work that eating only during an eight-hour window can cut around 300 to 500 calories a day.

In addition to obesity and insulin resistance, which raise risks of diabetes and heart disease, PCOS can cause ovarian cysts, acne and facial hair growth.

In a group of 76 pre-menopausal women with PCOS, the researchers tested how outcomes differed after six months between time-restricted eating between 1 and 7 p.m. daily and calorie counting. Both diet schemes ended up cutting participants’ intake by about 200 calories per day, the team found, leading to average weight loss of about 10 pounds over the six months.

Both groups also experienced a decrease in testosterone concentrations. But only time-restricted eating reduced free androgen index, the ratio between testosterone and the protein that transports it through the blood, which is a marker of how much active testosterone is reaching a body’s tissues. It also improved A1C levels, a risk marker for diabetes, Varady said.

Though intermittent fasting did not lessen other PCOS symptoms, like menstrual period irregularity, Varady suggested those symptoms might improve with longer time on the diet and greater weight loss.

About 80% of the participants in the time-restricted eating group said they were going to continue the diet, Varady said.

Story by Tess Joosse

Source: EurekAlert!

Trace Levels of Food Pathogen Aren’t Always a Health Risk, Study Finds

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Ultra-sensitive food safety tests may drive food waste and unavailability with limited public health benefit, according to a Frontiers in Science study.

These food safety measures and ultra-sensitive tests may drive edible food being thrown away, excessive packaging, and extra costs for consumers.

The international team of researchers make it clear that food safety is an important concern, as foodborne pathogens account for approximately 420 000 deaths and 600 million cases of illness each year. However, the authors argue that food systems will be more sustainable, while continuing to protect public health, if “zero-detection” expectations are replaced with evidence-based targets for “sufficiently safe” food.

Their new article sets out how regulators might find trade-offs with other important factors, such as food supply security, sustainability, and nutritional health.

“Although the public expects food to be completely safe, there will always be some risk of foodborne illness. Zero risk doesn’t exist, and we shouldn’t be aiming for that either. Just as we don’t limit highway speeds to 10 miles per hour to minimize road deaths, we need to take a balanced approach that considers possible negative consequences of extreme food safety measures,” said lead author Prof Martin Wiedmann from Cornell University.


Read and download the article


Impact of aiming for zero risk

The study’s authors highlight several situations where excessive caution can cause harm.

Many rules and purchasing standards rely heavily on detecting a pathogen, sometimes treating any detection as unacceptable without fully considering dose, exposure, the food’s ability to support microbial growth, or who is most at risk.

For example, a food product might be considered contaminated if it tests positive for the bacterium Listeria monocytogenes, regardless of levels.

These alarms can result from ultra-sensitive tests detecting small amounts of microbes unlikely to cause disease in humans. In some cases, the concerns may come from bacteria that are not harmful themselves, but are an indirect indicator of contamination.

Throwing away such food reduces the available food supply and wastes resources. Similarly, recalling food products from consumers can damage consumer trust, pushing people away from otherwise healthy products.

Other protective measures, such as storage temperatures, packaging, and heat treatment, can waste energy, increase costs, and reduce nutritional content. While these are all important safety measures, they should only be applied if needed and associated trade-offs should be considered.

“A tremendous amount of food is wasted that would have been sufficiently safe to eat. Too often, trade-offs such as environmental or economic costs are only considered after a traditional microbial risk assessment. We cannot afford to carry on like this at a time when we desperately need to reduce our impact on the planet and assure not only food safety but food security,” said co-author Prof Sophia Johler at Ludwig Maximilian University of Munich, Germany.

Focus on risk rather than hazard

The current situation is driven by an emphasis on hazard-based assessments, according to the authors, where regulations focus on detecting pathogens, regardless of the threat to consumers. The researchers argue that the food system should move towards more flexible risk-based approaches, which assess the probabilities of harms and adjust the safety measures accordingly.

Regulations that overemphasize stringent corrective actions (such as recalls) when swab samples from a food-processing facility test positive for an indicator, for example, could lead to undue corrective actions in areas that are unlikely to contaminate the food. The authors explain that this could be an opportunity cost that diverts resources away from more effective interventions and control strategies in high-risk areas.

“There’s well-established evidence that focusing on end-product testing is generally ineffective to ensure safety. Overemphasis on end-product testing may distract from other food safety measures (e.g., applying validated and verified process controls), which can provide greater public health benefits,” said co-author Dr Sriya Sunil at Cornell University.

Better tools to assess priorities

Computational tools that incorporate vast amounts of information across the food production system could help with establishing acceptable risks.

One challenge is how to prioritize different hazards. For example, in the US, norovirus causes thousands of times more cases than Listeria monocytogenes, yet Listeria monocytogenes causes more deaths per year.

While there are trade advantages to having consistent international food safety standards, the balance between competing interests may vary between regions. This can become even more complex when factoring in the health and environmental implications of greenhouse gas emissions.

“Specialists across social sciences, economics, and life sciences must work together to establish values that align with consumers’ priorities. Together with advanced models that build on geographic information, AI, and genomics, we can assess, manage, and communicate risks far more accurately,” said Wiedmann.

Source: Frontiers

High Meat Intake Linked to Lower Dementia Risk in APOE4

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Older people with a genetic risk of Alzheimer’s disease did not experience the expected increase in cognitive decline and dementia risk if they consumed relatively large amounts of meat. This is shown in a new study from Karolinska Institutet published in JAMA Network Open. The results may contribute to the development of more individually tailored dietary advice.

APOE is a gene that affects the risk of Alzheimer’s disease. In Sweden, approximately 30 per cent of the population are carriers of the gene combinations APOE 3/4 or APOE 4/4. Among people with Alzheimer’s disease, those with these genotypes account for nearly 70 per cent.

When the Swedish Food Agency presented an overview of research on the link between diet and dementia last year, more research was requested to assess a possible link between meat consumption and the development of dementia.

‘This study tested the hypothesis that people with APOE 3/4 and 4/4 would have a reduced risk of cognitive decline and dementia with higher meat intake, based on the fact that APOE4 is the evolutionarily oldest variant of the APOE gene and may have arisen during a period when our evolutionary ancestors ate a more animal-based diet,’ says first author Jakob Norgren, researcher at the Department of Neurobiology, Care Sciences and Society, Karolinska Institutet.

The study followed more than 2100 participants in the Swedish National Study on Aging and Care, Kungsholmen (SNAC-K) for up to 15 years. All were aged 60 or older and had no diagnosis of dementia at the start of the study. The association between self-reported diet and cognitive health measures was analysed, adjusting for age, sex, education and lifestyle factors.

Twice the risk of dementia

At lower meat intake, the group with APOE 3/4 and 4/4 had more than twice the risk of dementia than people without these gene variants. However, the increased risk of cognitive decline and dementia in the risk groups was not seen in the fifth of participants who consumed the most meat. Their median consumption is estimated at approximately 870 grams of meat per week, standardised to a daily energy intake of 2,000 calories.

‘Those who ate more meat overall had significantly slower cognitive decline and a lower risk of dementia, but only if they had the APOE 3/4 or 4/4 gene variants,’ says Jakob Norgren. He continues: 

‘There is a lack of dietary research into brain health, and our findings suggest that conventional dietary advice may be unfavourable to a genetically defined subgroup of the population. For those who are aware that they belong to this genetic risk group, the findings offer hope; the risk may be modifiable through lifestyle changes. ‘

The study also shows that the type of meat is important.

‘A lower proportion of processed meat in total meat consumption was associated with a lower risk of dementia regardless of APOE genotype,’ says Sara Garcia-Ptacek, assistant professor at the same department, who together with senior lecturer Erika J Laukka is the study’s last author.

The findings also extend beyond brain health. In a follow-up analysis, the researchers observed a significant reduction in all-cause-mortality in carriers of APOE 3/4 and 4/4 with higher consumption of unprocessed meat.

However, the study is observational and needs to be followed up with intervention studies that can better demonstrate causal relationships.

‘Clinical trials are now needed to develop dietary recommendations tailored to APOE genotype,’ says Jakob Norgren. He continues:

‘Since the prevalence of APOE4 is about twice as high in the Nordic countries as in the Mediterranean countries, we are particularly well suited to conduct research on tailored dietary recommendations for this risk group.’

The research was funded by, among others, the Swedish Alzheimer’s Foundation, the Swedish Dementia Foundation, the Emil and Wera Cornell Foundation, the Leif Lundblad family and other philanthropists, the Swedish Research Council and FORTE. The researchers state that they have no related conflicts of interest.

APOE Gene Facts:

Apolipoprotein E plays a central role in the transport of cholesterol and fats in the brain and blood. The protein is encoded by the APOE gene, which exists in three main variants: epsilon 2, 3 and 4. These variants affect the risk of developing Alzheimer’s disease and cardiovascular disease. Each person inherits two APOE genes, one from each parent, giving six possible combinations (genotypes): 2/2, 2/3, 2/4, 3/3, 3/4 and 4/4.

Compared to the most common genotype 3/3, one 4 variant increases the risk of Alzheimer’s disease by about three to four times and two 4 variants by about ten to fifteen times, while the 2 variant is associated with a lower risk. However, the increase in risk varies between different ethnic groups.

Source: Belloy et al., JAMA Neurology, 2023

Source: Karolinska Institutet

Reducing Sodium in Everyday Foods may Yield Heart-health Benefits Across Populations

Credit: Pixabay CC0

Lowering sodium in packaged and prepared foods could significantly improve cardiovascular health and prevent many cases of heart disease, stroke and deaths in the general population in France and the U.K., according to two new research studies published in Hypertension, an American Heart Association journal.

Consuming too much sodium is a major risk factor for hypertension, also known as high blood pressure, which can lead to health complications such as heart attack, stroke, chronic kidney disease, dementia and other forms of cardiovascular disease, according to the American Heart Association.

To address the global concern about excessive sodium consumption many countries have implemented salt-reduction strategies to improve public health and reduce health costs.

Two studies – one in France involving salt-reduction targets for baguettes and other bread products in 2025, and the other in the United Kingdom focusing on 2024 goals for takeaway and packaged foods – estimated the potential impact on the general population if those salt-reduction targets were met. The projections calculated in these two studies indicate that minor adjustments in sodium content to some of the most common prepared foods in each country would require no effort from people to change their eating habits, yet may produce significant public health benefits.

“This approach is particularly powerful because it does not rely on individual behaviour change, which is often difficult to achieve and sustain. Instead, it creates a healthier food environment by default,” said Clémence Grave, M.D., lead author of the study from France and epidemiologist and public health physician at the French National Public Health Agency, headquartered in Saint-Maurice near Paris.

The World Health Organization recommends adults should consume less than 2,000 milligrams (mg) of sodium per day, however, global intake is much higher. The American Heart Association recommends daily intake of no more than 2300mg of sodium a day – equal to about 1 teaspoon of table salt; but also says the ideal limit is no higher than 1500 mg per day for most adults, especially for those with high blood pressure.

Sodium reduction in bread (France)

In 2019, France set a national public health goal to reduce salt consumption by 30%. In 2022, a voluntary agreement was signed between the government and bread producers to lower salt content by 2025. Bread, especially the baguette, is a culturally and nutritionally central food in France, yet it can be high in salt– traditionally contain about 25% of total daily recommended intake of salt. By 2023, most breads made in France already met the new sodium standards.

To understand the potential impact of the agreement on public health, researchers used national data and a mathematical model to estimate how many cases of cardio-cerebrovascular disease (conditions and diseases that affect both the heart and the brain’s blood vessels), kidney disease and dementia could be prevented if the salt-reduction targets met full compliance.

The analysis found that with bread consumption remaining the same and sodium-reduction targets fully met, less salt in baguettes and bread would decrease daily intake by 0.35 g per person, leading to slightly lower blood pressure across the population.

“This salt-reduction measure went completely unnoticed by the French population – no one realised that bread contained less salt,” Grave said. “Our findings show that reformulating food products, even with small, invisible changes, can have a significant impact on public health.”

Sodium reduction in packaged foods and take-out meals (United Kingdom)

For the study in the U.K., researchers used national survey data to estimate the amount of salt people consumed from pre-prepared packaged and take-out meals. They then estimated daily sodium intake if all relevant food categories met the 2024 sodium-reduction targets.

Sales-weighted average and maximum salt content targets were set for 84 grocery food categories – including bread, cheeses, meats, and snacks – and, for the first time, 24 out-of-home categories such as burgers, curries, and pizza. The modelling also covered how these changes could affect heart disease, stroke, quality of life and health care costs.

The research found that fully meeting the sodium reduction goals could have reduced average salt intake from about 6.1 g to 4.9g per day – translating to an estimated average of 17.5% less salt consumed per person per day. Men would experience slightly larger reductions than women because they tend to consume more salt in general.

Even this small, daily reduction in salt would lower blood pressure modestly across the population, and the improvements could add up.

Source: American Heart Association

Trial Results Show Daily Multivitamin Use May Slow Biological Ageing

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An analysis led by Mass General Brigham investigators found slower aging in older adults after two years of a daily multivitamin, with greater benefits for those who began the trial with accelerated biological age.

‘Biological age’, age on a cellular level, can differ from chronological age. Using data from a large randomised clinical trial of older adults, researchers at Mass General Brigham evaluated the effects of taking a daily multivitamin over the course of two years on five measures of biological ageing and found a slowing equivalent to about four months of ageing. The benefits were increased in those who were biologically older than their actual age at the start of the trial. Their results are published in Nature Medicine.

“There is a lot of interest today in identifying ways to not just live longer, but to live better,” said senior author Howard Sesso, ScD, MPH, associate director of the Division of Preventive Medicine in the Mass General Brigham Department of Medicine. “It was exciting to see the benefits of a multivitamin linked with markers of biological ageing. This study opens the door to learning more about accessible, safe interventions that contribute to healthier, higher-quality ageing.”

Epigenetic clocks estimate biological ageing based specific sites in our DNA that regulate gene expression (known as DNA methylation) and change naturally as we get older, helping track mortality and the pace of ageing. This study, which uses data from the well-established COcoa Supplement Multivitamins Outcomes Study (COSMOS), analysed DNA methylation data from blood samples of 958 randomly selected healthy participants with an average chronological age of 70.

The study participants were randomised to take a daily cocoa extract and multivitamin; daily cocoa extract and placebo; placebo and multivitamin; or placebos only. Samples were analysed for changes in five epigenetic clocks from the start of the trial and at the end of the first and second years. Compared to the placebo only group, people in the multivitamin group had slowing in all five epigenetic clocks, including statistically significant slowing seen in the two clocks that are predictive of mortality. The changes equated to about four months less biological ageing over the course of two years. Additionally, people who were biologically older than their actual age at the start of the trial benefited the most.

“We plan to do follow-up research to determine if the slowing of biological ageing – observed through these five epigenetic clocks, and additional or new ones – persists after the trial ends,” said co-author and collaborator Yanbin Dong, MD, PhD, director of Georgia Prention Institute, Medical College of Georgia at Augusta Univeristy.

Further studies are also needed to determine how improvements in biological aging may explain reductions in clinical outcomes. The COSMOS team plans to investigate how the effects of a daily multivitamin on biological aging may extend to different outcomes they have seen evidence of benefits for, such as improvements in cognition and reductions in cancer and cataracts.

“A lot of people take a multivitamin without necessarily knowing any benefits from taking it, so the more we can learn about its potential health benefits, the better,” said Sesso. “Within COSMOS, we are fortunate and excited to build upon a rich resource of biomarker data to test how two interventions may improve biological aging and reduce age-related clinical outcomes.”

Source: Mass General Brigham

Honey from Australian Wildflowers has Potent Power to Kill Bacteria

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Kenya Fernandes, University of Sydney

Before antibiotics and antiseptics, healers across ancient Egypt, Greece, and China reached for honey to treat wounds. Archaeological evidence shows humans have been harvesting and collecting honey for thousands of years – and for much of that time, we understood it to be more than just food.

Today, honey sits in most kitchen cupboards as a perfectly ordinary pantry staple. But honey has never entirely shed its medicinal reputation. And modern research shows us why: it possesses genuine antimicrobial properties, capable of killing or inhibiting a wide range of bacteria, including drug-resistant strains.

This matters now more than ever. Antimicrobial resistance – where bacteria evolve to survive drugs designed to kill them – is one of the defining public health crises of our time. Infections caused by these resistant microbes are becoming harder and more expensive to treat, creating an urgent need for alternative therapies.

Our new study, published in the journal MicrobiologyOpen, shows honeys from Australia’s native flora might be a big part of the solution.

What did we do?

We analysed 56 honey samples collected from more than 35 apiaries across New South Wales. Many samples came from landscapes recovering from the 2019–2020 bushfires. Most were derived from native Australian plants such as eucalyptus, leptospermum and melaleuca.

We tested the honeys against two common bacterial pathogens: Staphylococcus aureus (golden staph) and E. coli – both among the six leading causes of deaths associated with antibiotic resistance. For each sample we measured the minimum concentration needed to stop bacterial growth. The lower the concentration, the more potent the honey.

We also carried out comprehensive chemical profiling, measuring sugars, organic acids, amino acids, enzymes and a wide range of plant-derived compounds. Statistical and machine-learning analyses helped us identify which chemical features best explained antibacterial strength.

What did we find?

More than three-quarters of the honey samples stopped bacterial growth even when the honeys were diluted to 10% or less. This places Australian native flora honeys alongside some of the world’s most potent varieties.

The most striking factor was floral diversity.

Honeys from mixed floral sources – where bees foraged across multiple native plant species rather than a single species – were consistently the most antimicrobial.

This potency wasn’t due to any single compound but to a chemically rich combination.

Multiple bioactive factors – substances that have a measurable effect on living cells or tissues – worked together to inhibit bacteria. These included naturally produced hydrogen peroxide, plant-derived phenolic compounds (naturally occurring chemicals that plants produce as part of their own defence systems), and antioxidants.

When bacteria encounter honey, this combination acts on several fronts at once. The low moisture content draws water out of bacterial cells, while the acidity disrupts their metabolism. Hydrogen peroxide damages their cellular structures, and phenolic and antioxidant compounds interfere with their ability to function and reproduce.

The strength of mixed floral honeys may also reflect the health of the bees themselves.

Access to diverse forage keeps colonies well nourished. And healthier bees produce more biologically active honey as their enzymes help integrate and activate the plant compounds into a complex antimicrobial mixture.

What does this mean for antimicrobial resistance?

Honey won’t replace antibiotics for serious or systemic infections.

But for topical applications – chronic wounds, burns, or surgical site infections – it is a genuinely promising option. Because honey attacks bacteria through multiple simultaneous mechanisms, resistance is far less likely to emerge than with single-target drugs. Our team is now exploring these applications in more detail.

Australia is particularly well-placed to lead in bioactive honey production. Around 70% of Australian honey comes from native plants. These plants are found not only in forests but also across farmland, regional landscapes, and urban green spaces.

Our findings show that prioritising floral diversity over monoculture isn’t just good for ecosystems – it produces more potent honey. With the beekeeping industry under serious pressure from bushfires, floods, and now the varroa mite, protecting and restoring florally-rich landscapes is critical: for bee health, for industry resilience, and for expanding our natural antimicrobial toolkit.

In the meantime, the next jar of Australian honey you buy may just be doing more good than you realise.

Kenya Fernandes, Research Fellow, Faculty of Science, University of Sydney

This article is republished from The Conversation under a Creative Commons license. Read the original article.

Three-quarters not Meeting Recommended Intakes of Omega-3, Study Shows

More than three-quarters of the global population are not getting enough omega-3, according to new research

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A review by the University of Southampton found that 76% of people worldwide are not meeting recommended intakes of the omega-3s EPA and DHA. The peer-reviewed paper, published in Nutrition Research Reviews, was a collaboration with scientists at the University of East Anglia and Holland & Barrett.

It is the first global review of national and international omega-3 intake recommendations across all life stages for generally healthy people.

Professor of Nutritional Immunology Philip Calder from Southampton, who was part of the study, said: “The omega-3s EPA and DHA are essential for health throughout the life course. But to benefit from these nutrients, people first need to understand how much they should be consuming.

“In this review, we brought together all the recommendations for EPA and DHA intake in healthy populations from authorities around the world to help answer the important question: ‘how much do I need?’ What is clear is that most people are not meeting these recommendations.”

Omega-3 consumption supports a healthy lifestyle throughout all stages of life.

The new review found that the most frequently recommended intake for adults is 250mg per day of combined EPA and DHA, with an additional 100–200mg of DHA advised for pregnant women.

Prof Calder said these targets can be achieved by eating more oily fish, such as salmon, sardines or mackerel, or through supplementation where needed.

The paper also identified challenges that different populations have in achieving current omega-3 recommendations.

These include difficulties in meeting oily fish recommendations due to low seafood consumption, or sustainability concerns, as well as some populations having limited access to supplementation advice.

Dr Abbie Cawood , Science Director at Holland & Barrett and Visiting Research Fellow at the University of Southampton, led the study.

She said: “Omega-3s play such a vital role in health, ensuring people can meet their needs either through diet or with the support of supplementation is essential at every life stage.

In fact, our review highlights that supplementation is often required to meet recommended intakes especially in pregnancy and in those with low fish intakes. We are hopeful that this publication can act as an enabler to inform omega-3 dietary guidelines and shape future nutrition policy and public health strategies.”

The full paper can be viewed at pubmed.ncbi.nlm.nih.gov/41277237 .

Source: University of Southampton

Vegan Diet Helps People With Type 1 Diabetes Cut Insulin Costs by 27%

Novolog insulin pen. Photo by Dennis Klicker on Unsplash

A low-fat vegan diet that doesn’t limit calories or carbohydrates could help people with type 1 diabetes reduce insulin use and insulin costs, according to new research by the Physicians Committee for Responsible Medicine published in BMC Nutrition.

The new research, which is a secondary analysis of a 2024 Physicians Committee study, compared the effect of a low-fat vegan diet to a portion-controlled diet on insulin use and insulin costs in people with type 1 diabetes. The analysis found that the total dose of insulin decreased by 28%, or 12.1 units, per day in the vegan group, compared to no significant change in the portion-controlled group. The reductions in insulin use in the vegan group likely reflect improved insulin sensitivity, or how well the body responds to insulin. Total insulin costs decreased by 27%, or $1.08 per day, in the vegan group, compared to no significant change in the portion-controlled group.

The 2024 study found that a vegan diet also led to an average weight loss of 11 pounds, improved insulin sensitivity and glycaemic control, and improved cholesterol levels and kidney function in people with type 1 diabetes.

The new research comes as insulin prices in the United States continue to rise. Spending on insulin in the United States tripled in the past 10 years, reaching $22.3 billion in 2022, due to the increased usage and higher price of insulin, according to the American Diabetes Association. The inflation-adjusted cost of insulin increased by 24% from 2017 to 2022.

“As insulin prices continue to rise, people with type 1 diabetes should consider a low-fat vegan diet, which can help improve their insulin sensitivity and reduce the amount of insulin they need, potentially saving them hundreds of dollars a year,” says Hana Kahleova, MD, PhD, the lead author of the study and director of clinical research at the Physicians Committee for Responsible Medicine.

Source: Physicians Committee for Responsible Medicine

Too Many Saturated Fats may be More Harmful than Too Many Refined Carbohydrates

Mice who consumed high-fat diets, especially the ketogenic diet, experienced more weight gain, liver damage and other negative health effects than those who ate a high-carbohydrate diet

Photo by Mariana Kurnyk

In recent years, many media reports and social media influencers have emphasised the dangers of eating too many carbohydrates. Though a carbohydrate-heavy diet can be harmful, consuming too many fats may cause more health problems, according to a study in mice led by researchers in the Penn State Department of Nutritional Sciences.

In a study published in the February issue of Journal of Nutrition, the researchers analysed how diets containing different ratios of fats and carbohydrates affected metabolic health and liver function in mice over time. They found, overall, higher-fat diets were more harmful than high-carbohydrate diets, but that fibre supplementation might be able to reduce harm in specific conditions.

Mice consumed one of four diets: high carbohydrate, high fat, ketogenic or a standard chow that was rich in whole grains and served as the experiment’s control group. In mice of normal weight, the keto diet led to weight gain, impaired the use of glucose, disrupted the balance of lipids in the body and increased inflammation and fat deposits in the liver. The high-fat diet also led to weight gain and other health problems not seen in mice who consumed the high-carbohydrate diet. Overall, mice who consumed the standard chow displayed the best markers of health.

“Human beings and mice have very different metabolisms, but there are relevant lessons in this study for people,” said Vishal Singh, associate professor of nutritional sciences and senior author of the study. “Most people are aware that a balanced diet is important, but some people are attracted to diets with very high fat content – like the keto diet – for weight loss. This research points to very real harm to the liver that can occur when these diets are not used appropriately.”

Fats versus carbohydrates

In each experimental diet in the study, the protein level of the food was always 18% of the total calories, so only the fat-to-carbohydrate ratios differed. The high-fat diet contained 42% carbohydrates and 40% fats, the high-carbohydrate diet contained 70% carbohydrates and 11% fat and the ketogenic diet contained 1% carbohydrates and 81% fats.

The fats in these diets were largely saturated fats, which are a group of fats that are typically solid at room temperature. The American Heart Association recommends that saturated fats make up 6% or less of the total calories in a person’s diet.

The carbohydrates in these diets were largely refined, which are processed foods including white flour and added sugars. Scientific research has frequently connected refined carbohydrates to metabolic dysfunction and other harmful physical and mental health outcomes.

These diets were compared to a whole-grain rich chow that is a standard diet for laboratory mice. It contained 29% proteins, 57.5% carbohydrates and 13.5% fats.

The researchers measured blood sugar and a broad array of markers of liver function and health at regular intervals during the 16-week study. Other measurements were gathered after the experimental diets concluded.

“We wanted to understand how altering the balance of carbohydrates and fats would affect health when the diet was maintained for 16 weeks,” said Umesh Goand, postdoctoral researcher in the Penn State Department of Nutritional Sciences and first author of the study.

Keto and high-fat diets harmed liver and increased weight

In the ketogenic or ‘keto’ diet carbohydrate consumption is nearly eliminated. This induces a metabolic state called ketosis, where the body burns fat for fuel instead of glucose, the typical source of energy.

Results from the study demonstrated that the high-fat and keto diets promoted obesity, with the weight of mice on these diets doubling over the 16 weeks of the study. Mice on the control diet increased weight by around 10% – a normal rate for mice of that age – despite all mice in the study consuming roughly the same number of calories. In addition, the high-fat and keto diets impaired glucose tolerance and compromised liver function. Liver damage and elevated levels of blood sugar were observed after only two weeks of both diets.

Mice on the keto diet also developed elevated levels of triglycerides and showed increased levels of systemic inflammation. Additionally, they developed fat deposits in the liver and expressed genes associated with inflammation and liver scarring.

“The keto diet was very damaging to the livers and overall health of mice with regular weights,” Singh said, explaining that the body can utilise fat for energy, but there are metabolic consequences associated with the increase in fat processing. “People who hear about the keto diet’s reputation for weight reduction may be tempted to try it themselves. What this research says is – don’t! This diet should only be considered when properly supervised by a physician and/or dietician.”

Whole grains and carbohydrates

In comparison, mice on the high-carbohydrate diet did not continuously gain weight nor experience liver damage like those on the high-fat diets. Singh emphasized that a highly processed, carbohydrate-heavy diet is not inherently healthy, but it did less damage to the liver than the high-fat diets.

Mice on the whole-grain rich chow diet gained the least weight and demonstrated the best health indicators.

“A whole-grain-based diet is always a win – for mice or people,” Singh said.

The potential of fibre

In a separate experiment in the study involving mice with obesity, the high-fat and keto diets also led to further weight gain. However, when the keto diet was supplemented with fibre – a condition not tested in mice with normal weights – mice with obesity maintained more stable weight and better health indicators in several areas compared to mice on the high-fat diet or the keto diet without extra fibre.

The researchers also found that fibre supplementation did not hinder ketogenesis in mice who ate the keto diet. This is important, Singh said, because the keto diet is used for managing specific medical conditions, like epilepsy.

“Incorporating dietary fibres into the keto diet may reduce gastrointestinal complications associated with very high-fat diets while maintaining the therapeutic benefits of ketogenesis for patients,” Singh said.

Dietary choices are complex, but that does not make them equivalent

The important thing to remember, Singh said, is that diet is complex, and there is no one-size-fits-all solution.

“Over time, researchers have learned a lot about what is healthy or unhealthy based on an individual’s health status, but there is no single dietary magic bullet for weight loss or any other metabolic health concern,” Singh said. “Anyone who experiences health problems or is concerned about their diet should talk to their physician or a registered dietician to develop a plan, based on research, that fits their specific needs and life circumstances.”

Source: Penn State University

Evidence Behind Intermittent Fasting for Weight Loss Fails to Match Hype

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Intermittent fasting is unlikely to lead to greater weight loss in overweight or obese adults than traditional dietary advice or doing nothing, a new Cochrane review finds. 

Obesity is a significant public health problem that has become a leading cause of death in high-income countries. Worldwide adult obesity has more than tripled since 1975, according to the WHO. In 2022, 2.5 billion adults were overweight. Of these, 890 million were living with obesity.

Intermittent fasting has surged in popularity in recent years, fuelled by social media, lifestyle influencers, and claims of rapid weight loss and metabolic benefits.

No meaningful difference in weight loss

Researchers analysed evidence from 22 randomised clinical trials involving 1995 adults across North America, Europe, China, Australia, and South America. Trials examined multiple forms of intermittent fasting, including alternate-day fasting, periodic fasting, and time-restricted feeding. Most studies followed participants for up to 12 months.

The review compared intermittent fasting with traditional dietary advice and with no intervention. Intermittent fasting did not appear to have a clinically meaningful effect on weight loss compared to standard dietary advice or doing nothing. 

Reporting of side effects was inconsistent across trials, making it difficult to draw firm conclusions. The evidence base remains limited, with only 22 trials, many with small sample sizes and inconsistent reporting. 

Hype outpaces the evidence

First author Luis Garegnani also cautioned against the hype surrounding fasting online. 

Intermittent fasting just doesn’t seem to work for overweight or obese adults trying to lose weight. It may be a reasonable option for some people, but the current evidence doesn’t justify the enthusiasm we see on social media.

 Luis Garegnani, Universidad Hospital Italiano de Buenos Aires Cochrane Associate Centre. 


Few trials have looked at the long-term results of intermittent fasting. The authors stressed that obesity is a chronic condition, and short-term trials make it difficult to guide long-term decision-making for patients and clinicians. 
 
The majority of the included studies enrolled predominantly white populations in high-income countries. As obesity is a rapidly growing crisis in low- and middle-income countries, further research is needed in these populations.

The authors therefore warn that these results may provide clues, but cannot be extrapolated to the entire population, as they may vary depending on sex, age, ethnic origin, disease status, or underlying eating disorders or behaviours.
 

With the current evidence available, it’s hard to make a general recommendation. Doctors will need to take a case-by-case approach when advising an overweight adult on losing weight.

 Eva Madrid, Cochrane Evidence Synthesis Unit Iberoamerica. 

By Mia Parkinson

Source: Cochrane Review