Low-income countries could lose 30% of nutrients like protein and omega-3 from seafood due to climate change

The nutrients available from seafood could drop by 30 per cent for low-income countries by the end of the century due to climate change, suggests new UBC research.

That's in a high carbon emissions and low mitigation scenario, according to the study published today in Nature Climate Change. This could be reduced to a roughly 10 per cent decline if the world were to meet the Paris Agreement targets of limiting global warming to 1.5 to 2 degrees Celsius -- which recent reports have shown we're not on track to achieve.

"Low-income countries and the global south, where seafood is central to diets and has the potential to help address malnutrition, are the hardest hit by the effects of climate change," said first author Dr. William Cheung, professor and director of the UBC Institute for the Oceans and Fisheries (IOF). "For many, seafood is an irreplaceable and affordable source of nutrients."

The researchers examined historical fisheries and seafood farming, or mariculture, databases including data from UBC's Sea Around Us to find out quantities of key nutrients that were available through fisheries and seafood farming in the past, and used predictive climate models to project these into the future. They focused on four nutrients that are plentiful in seafood and important to human health: calcium, iron, protein and omega-3 fatty acids, the latter of which is not readily available in other food sources.

They found that the availability of these nutrients peaked in the 1990s and stagnated to the 2010s, despite increases provided by farming seafood, and from fishing for invertebrates such as shrimp and oysters.

Calcium sees biggest decline

Looking to the future, the availability of all four nutrients from catches is projected to decrease, with calcium the hardest hit at a projected decline of about 15 to 40 per cent by 2100 under a low and high emissions scenario, respectively. Omega-3 would see an approximately five to 25 per cent decrease. These declines are largely driven by decreases in the amounts of pelagic fish available for catch.

"Small pelagic fish are really rich in calcium so in areas of the world where people have intolerances to milk or where other animal-sourced foods, like meat and dairy, are much more expensive, fish is really key to people's diets," said senior author Dr. Christina Hicks, professor at Lancaster University. "In many parts of the world, particularly low-income countries across the tropics, fish supply nutrients that are lacking in people's diets."

While seafood farming will contribute more nutrients in the future compared with current levels, the researchers projected these increases would not be able to compensate for the loss from fisheries. Under a high emissions scenario, any gains in the availability of nutrients from seafood farming before 2050 would be lost by 2100.

"The primary reason for this is climate change, which is also a significant threat to seafood farming, leaving us with a growing nutritional deficit," said co-author Dr. Muhammed Oyinlola, a postdoctoral fellow in the UBC department of zoology and the Institut national de la recherche scientifique. "Seafood farming alone cannot provide a comprehensive solution to this complex issue."

The availability of all four nutrients from tropical waters of generally lower income nations, such as Indonesia, the Solomon Islands and Sierra Leone, is projected to decline steeply by the end of the century under a high emissions scenario, compared with minimal declines in higher income, non-tropical waters, such as those of Canada, the U.S. and the U.K.

Globally, the researchers projected that seafood-sourced nutrient availability would decrease by about four to seven per cent per degree Celsius warming. For lower-income countries across the tropics including Nigeria, Sierra Leone, and the Solomon Islands, the projected decline was two to three times this global average at nearly 10 to 12 per cent per unit of warming.

"This research highlights the impact of every degree of warming," said Dr. Cheung. "The more we can reduce warming, the fewer risks to marine and human life."

Using all of a fish

Certain types of fish such as anchovies and herring are packed with nutrients but often used for fish meal and fish oil because these nutrients also promote fish growth. Similarly, many countries retain only select parts of a fish for sale. The researchers highlighted potential adaptations to increase nutrient availability from seafood, by retaining more of these nutritious fish for local human consumption, as well as reducing food waste in fisheries production and consumption by using all parts of a fish including the head and fins.

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Researchers develop model for how the brain acquires essential omega-3 fatty acids

Researchers at the UCLA David Geffen School of Medicine, the Howard Hughes Medical Institute at UCLA and the National Institutes of Health have developed a zebrafish model that provides new insight into how the brain acquires essential omega-3 fatty acids, including docosahexaenoic acid (DHA) and linolenic acid (ALA). Their findings, published in Nature Communications,have the potential to improve understanding of lipid transport across the blood-brain barrier and of disruptions in this process that can lead to birth defects or neurological conditions. The model may also enable researchers to design drug molecules that are capable of directly reaching the brain.

Omega-3 fatty acids are considered essential because the body cannot make them and must obtain them through foods, such as fish, nuts and seeds. DHA levels are especially high in the brain and important for a healthy nervous system. Infants obtain DHA from breastmilk or formula, and deficiencies of this fatty acid have been linked to problems with learning and memory. To get to the brain, omega-3 fatty acids must pass through the blood-brain barrier via the lipid transporter Mfsd2a, which is essential for normal brain development. Despite its importance, scientists did not know precisely how Mfsd2a transports DHA and other omega-3 fatty acids.

In the study, the research team provides images of the structure of zebrafish Mfsd2a, which is similar to its human counterpart. The snapshots are the first to detail precisely how fatty acids move across the cell membrane. The study team also identified three compartments in Mfsd2a that suggest distinct steps required to move and flip fatty acids through the transporter, as opposed to movement through a linear tunnel or along the surface of the protein complex. The findings provide key information on how Mfsd2a transports omega-3 fatty acids into the brain and may enable researchers to optimize drug delivery via this route. The study also provides foundational knowledge on how other members of this transporter family, called the major facilitator superfamily (MFS), regulate important cellular functions.

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Vitamin D benefits and metabolism may depend on body weight

Researchers from Brigham and Women's Hospital, a founding member of the Mass General Brigham healthcare system, have found new evidence that vitamin D may be metabolized differently in people with an elevated body mass index (BMI). The study, appearing in JAMA Network Open, is a new analysis of data from the VITAL trial, a large nationwide clinical trial led by Brigham researchers that investigated whether taking vitamin D or marine omega-3 supplements could reduce the risk of developing cancer, heart disease, or stroke.

"The analysis of the original VITAL data found that vitamin D supplementation correlated with positive effects on several health outcomes, but only among people with a BMI under 25," said first author Deirdre K. Tobias, ScD, an associate epidemiologist in Brigham's Division of Preventive Medicine. "There seems to be something different happening with vitamin D metabolism at higher body weights, and this study may help explain diminished outcomes of supplementation for individuals with an elevated BMI."

Vitamin D is an essential nutrient involved in many biological processes, most notably helping our body absorb minerals, such as calcium and magnesium. While some of the vitamin D we need is made in the body from sunlight, vitamin D deficiencies are often treated with supplementation. Evidence from laboratory studies, epidemiologic research and clinical research has also suggested that vitamin D may play a role in the incidence and progression of cancer and cardiovascular disease, and it was this evidence that prompted the original VITAL trial.

The VITAL trial was a randomized, double-blind, placebo-controlled trial in 25,871 U.S. participants, which included men over the age of 50 and women over the age of 55. All participants were free of cancer and cardiovascular disease at the time of enrollment. While the trial found little benefit of vitamin D supplementation for preventing cancer, heart attack, or stroke in the overall cohort, there was a statistical correlation between BMI and cancer incidence, cancer mortality, and autoimmune disease incidence. Other studies suggest similar results for type 2 diabetes.

The new study aimed to investigate this correlation. The researchers analyzed data from 16,515 participants from the original trial who provided blood samples at baseline (before randomization to vitamin D), as well as 2,742 with a follow-up blood sample taken after two years. The researchers measured the levels of total and free vitamin D, as well as many other novel biomarkers for vitamin D, such as its metabolites, calcium, and parathyroid hormone, which helps the body utilize vitamin D.

"Most studies like this focus on the total vitamin D blood level," said senior author JoAnn E. Manson, MD, DrPH, chief of the Division of Preventive Medicine at the Brigham and principal investigator of VITAL. "The fact that we were able to look at this expanded profile of vitamin D metabolites and novel biomarkers gave us unique insights into vitamin D availability and activity, and whether vitamin D metabolism might be disrupted in some people but not in others."

The researchers found that vitamin D supplementation increased most of the biomarkers associated with vitamin D metabolism in people, regardless of their weight. However, these increases were significantly smaller in people with elevated BMIs.

"We observed striking differences after two years, indicating a blunted response to vitamin D supplementation with higher BMI," Tobias said. "This may have implications clinically and potentially explain some of the observed differences in the effectiveness of vitamin D supplementation by obesity status."

"This study sheds light on why we're seeing 30-40 percent reductions in cancer deaths, autoimmune diseases, and other outcomes with vitamin D supplementation among those with lower BMIs but minimal benefit in those with higher BMIs, suggesting it may be possible to achieve benefits across the population with more personalized dosing of vitamin D," said Manson. "These nuances make it clear that there's more to the vitamin D story."

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About 3 grams a day of omega-3 fatty acids may lower blood pressure, more research needed

About 3 grams daily of omega-3 fatty acids, consumed in foods or supplements, appears to be the optimal daily dose to help lower blood pressure, according to a research review published today in the Journal of the American Heart Association, an open access, peer-reviewed journal of the American Heart Association.

Omega-3 fatty acids docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) are typically found in fatty fish, such as salmon, tuna, sardines, trout, herring and oysters. Some people also take combined DHA and EPA in supplements. While some studies suggest that consumption of omega-3 fatty acids may lower blood pressure, the optimal dosage needed to lower blood pressure has not been clear. The National Institutes of Health has established an adequate intake of omega-3 fatty acids for healthy people at 1.1- 1.6 grams daily, depending on age and sex.

"According to our research, the average adult may have a modest blood pressure reduction from consuming about 3 grams a day of these fatty acids," said study author Xinzhi Li, M.D., Ph.D., assistant professor and program director of the School of Pharmacy at Macau University of Science and Technology in Macau, China.

Researchers analyzed the results of 71 clinical trials from around the world published from 1987 to 2020. The studies examined the relationship between blood pressure and the omega-3 fatty acids DHA and EPA (either individually or combined) in people aged 18 and older with or without high blood pressure or cholesterol disorders. There were nearly 5,000 participants combined, ranging in age from 22 to 86 years. Participants took dietary and/or prescription supplement sources of fatty acids for an average of 10 weeks.

The analysis found:
 

• Compared to adults who did not consume EPA and DHA, those who consumed between 2 and 3 grams daily of combined DHA and EPA omega-3 fatty acids (in supplements, food or both) had reduced systolic (top number) and diastolic (bottom number) blood pressure by an average 2 mm Hg.
• Consuming more than 3 grams of omega-3 fatty acids daily may have added blood pressure-lowering benefit for adults with high blood pressure or high blood lipids:
• At 3g a day of omega-3s, systolic blood pressure (SBP) decreased an average of 4.5 mm Hg for those with hypertension, and about 2 mm Hg on average for those without.
• At 5g a day of omega-3s, SBP declined an average of nearly 4 mm Hg for those with hypertension and less than 1 mm Hg on average for those without.
• Similar differences were seen in people with high blood lipids and among those older than age 45.

About 4-5 ounces of Atlantic salmon provide 3 grams of omega 3 fatty acids. A typical fish oil supplement contains about 300 mg of omega-3s per pill, but doses vary widely.

"Most of the studies reported on fish oil supplements rather than on EPA and DHA omega-3's consumed in food, which suggests supplements may be an alternative for those who cannot eat fatty fish such as salmon regularly," Li said. "Algae supplements with EPA and DHA fatty acids are also an option for people who do not consume fish or other animal products."

The U.S. Food and Drug Administration (FDA) announced in June 2019 that it did not object to the use of certain health claims that consuming EPA and DHA omega-3 fatty acids in food or dietary supplements may reduce the risk of hypertension and coronary heart disease. However, they noted that the evidence was inconclusive and highly inconsistent.

"Our study supports the FDA guidance that EPA and DHA omega-3 fatty acids may reduce the risk of coronary heart disease by lowering high blood pressure, especially among people already diagnosed with hypertension," he said. "However, while our study may add a layer of credible evidence, it does not meet the threshold to make an authorized health claim for omega-3 fatty acids in compliance with FDA regulations."

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Meta-analysis finds that omega-3 fatty acids improved cardiovascular outcomes

For decades, there has been great interest in whether omega-3 fatty acids can lower rates of cardiovascular events. In 2018, results from the Reduction of Cardiovascular Events with Icosapent Ethyl-Intervention Trial (REDUCE-IT) were published in the New England Journal of Medicine and showed that a high dose of a purified ethyl ester of eicosapentaenoic acid (EPA) in patients at elevated cardiac risk significantly reduced cardiovascular events. Results from the trial led to US. Food and Drug Administration, Health Canada, and European Medicines Agency approval of the prescription drug icosapent ethyl for reducing cardiovascular risk in patients with elevated triglycerides, as well as updates to worldwide guidelines. But prior and subsequent studies of omega-3 fatty acid supplements that combine EPA and docosahexaenoic acid (DHA) have had mixed results.

Investigators from Brigham and Women's Hospital and elsewhere conducted a systematic review and meta-analysis of 38 randomized controlled trials of omega-3 fatty acids. Overall, they found that omega-3 fatty acids improved cardiovascular outcomes. Results, now published in eClinical Medicine, showed a significantly greater reduction in cardiovascular risk in studies of EPA alone rather than EPA+DHA supplements.

"REDUCE-IT has ushered in a new era in cardiovascular prevention," said senior author Deepak L. Bhatt, MD, MPH, the executive director of Interventional Cardiovascular Programs at the Brigham and lead investigator of the REDUCE-IT trial. "REDUCE-IT was the largest and most rigorous contemporary trial of EPA, but there have been other ones as well. Now, we can see that the totality of evidence supports a robust and consistent benefit of EPA."

Bhatt and colleagues performed a meta-analysis of 38 randomized clinical trials of omega-3 fatty acids, including trials of EPA monotherapy and EPA+DHA therapy. In total, these trials included more than 149,000 participants. They evaluated key cardiovascular outcomes, including cardiovascular mortality, non-fatal cardiovascular outcomes, bleeding, and atrial fibrillation. Overall, omega-3 fatty acids reduced cardiovascular mortality and improved cardiovascular outcomes. The trials of EPA showed higher relative reductions in cardiovascular outcomes compared to those of EPA+DHA.

The researchers note that there are crucial biological differences between EPA and DHA -- while both are considered omega-3 fatty acids, they have different chemical properties that influence their stability and strength of the effect that they can have on cholesterol molecules and cell membranes. No trials to date have studied the effects of DHA alone on cardiovascular outcomes.

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Consuming a diet with more fish fats, less vegetable oils can reduce migraine headaches, study finds

A diet higher in fatty fish helped frequent migraine sufferers reduce their monthly number of headaches and intensity of pain compared to participants on a diet higher in vegetable-based fats and oils, according to a new study. The findings by a team of researchers from the National Institute on Aging (NIA) and the National Institute on Alcohol Abuse and Alcoholism (NIAAA), parts of the National Institutes of Health; and the University of North Carolina (UNC) at Chapel Hill, were published in the July 3 issue of The BMJ.

This study of 182 adults with frequent migraines expanded on the team's previous work on the impact of linoleic acid and chronic pain. Linoleic acid is a polyunsaturated fatty acid commonly derived in the American diet from corn, soybean, and other similar oils, as well as some nuts and seeds. The team's previous smaller studies explored if linoleic acid inflamed migraine-related pain processing tissues and pathways in the trigeminal nerve, the largest and most complex of the body's 12 cranial nerves. They found that a diet lower in linoleic acid and higher in levels of omega-3 fatty acids (like those found in fish and shellfish) could soothe this pain pathway inflammation.

In a 16-week dietary intervention, participants were randomly assigned to one of three healthy diet plans. Participants all received meal kits that included fish, vegetables, hummus, salads, and breakfast items. One group received meals that had high levels of fatty fish or oils from fatty fish and lowered linoleic acid. A second group received meals that had high levels of fatty fish and higher linoleic acid. The third group received meals with high linoleic acid and lower levels of fatty fish to mimic average U.S. intakes.

During the intervention period, participants monitored their number of migraine days, duration, and intensity, along with how their headaches affected their abilities to function at work, school, and in their social lives, and how often they needed to take pain medications. When the study began, participants averaged more than 16 headache days per month, over five hours of migraine pain per headache day, and had baseline scores showing a severe impact on quality of life despite using multiple headache medications.

The diet lower in vegetable oil and higher in fatty fish produced between 30% and 40% reductions in total headache hours per day, severe headache hours per day, and overall headache days per month compared to the control group. Blood samples from this group of participants also had lower levels of pain-related lipids. Despite the reduction in headache frequency and pain, these same participants reported only minor improvements in migraine-related overall quality of life compared to other groups in the study.

Migraine, a neurological disease, ranks among the most common causes of chronic pain, lost work time, and lowered quality of life. More than 4 million people worldwide have chronic migraine (at least 15 migraine days per month) and over 90% of sufferers are unable to work or function normally during an attack, which can last anywhere from four hours to three days. Women between the ages of 18 and 44 are especially prone to migraines, and an estimated 18% of all American women are affected. Current medications for migraine usually offer only partial relief and can have negative side effects including sedation, and the possibility of dependence or addiction.

"This research found intriguing evidence that dietary changes have potential for improving a very debilitating chronic pain condition like migraine without the related downsides of often prescribed medications," said Luigi Ferrucci, M.D., Ph.D., scientific director of NIA.

The NIH team was led by Chris Ramsden, a clinical investigator in the NIA and NIAAA intramural research programs, and UNC adjunct faculty member. Ramsden and his team specialize in the study of lipids -- fatty acid compounds found in many natural oils -- and their role in aging, especially chronic pain and neurodegenerative conditions. The UNC team was led by Doug Mann, M.D., of the Department of Neurology, and Kim Faurot, Ph.D., of the Program on Integrative Medicine. Meal plans were designed by Beth MacIntosh, M.P.H., of UNC Healthcare's Department of Nutrition and Food Services.

"Changes in diet could offer some relief for the millions of Americans who suffer from migraine pain," said Ramsden. "It's further evidence that the foods we eat can influence pain pathways."

The researchers noted that these findings serve as validation that diet-based interventions increasing omega-3 fats while reducing linoleic acid sources show better promise for helping people with migraines reduce the number and impact of headache days than fish-oil based supplements, while reducing the need for pain medications. They hope to continue to expand this work to study effects of diet on other chronic pain conditions.

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An omega-3 that's poison for tumors

So-called "good fatty acids" are essential for human health and much sought after by those who try to eat healthily. Among the Omega-3 fatty acids, DHA or docosahexaenoic acid is crucial to brain function, vision and the regulation of inflammatory phenomena.

In addition to these virtues, DHA is also associated with a reduction in the incidence of cancer. How it works is the subject of a major discovery by a multidisciplinary team of University of Louvain (UCLouvain) researchers, who have just elucidated the biochemical mechanism that allows DHA and other related fatty acids to slow the development of tumours. This is a major advance that has recently been published in the journal Cell Metabolism.

Key to the discovery: interdisciplinarity

In 2016, Olivier Feron's UCLouvain team, which specialises in oncology, discovered that cells in an acidic microenvironment (acidosis) within tumours replace glucose with lipids as an energy source in order to multiply. In collaboration with UCLouvain's Cyril Corbet, Prof. Feron demonstrated in 2020 that these same cells are the most aggressive and acquire the ability to leave the original tumour to generate metastases. Meanwhile, Yvan Larondelle, a professor in the UCLouvain Faculty of Bioengineering, whose team is developing improved dietary lipid sources, proposed to Prof. Feron that they combine their skills in a research project, led by PhD candidate Emeline Dierge, to evaluate the behaviour of tumour cells in the presence of different fatty acids.

Thanks to the support of the Fondation Louvain, the Belgian Cancer Foundation and the Télévie telethon, the team quickly identified that these acidotic tumour cells responded in diametrically opposite ways depending on the fatty acid they were absorbing. Within a few weeks, the results were both impressive and surprising. "We soon found that certain fatty acids stimulated the tumour cells while others killed them," the researchers explained. DHA literally poisons them.

A fatal overload

The poison acts on tumour cells via a phenomenon called ferroptosis, a type of cell death linked to the peroxidation of certain fatty acids. The greater the amount of unsaturated fatty acids in the cell, the greater the risk of their oxidation. Normally, in the acidic compartment within tumours, cells store these fatty acids in lipid droplets, a kind of bundle in which fatty acids are protected from oxidation. But in the presence of a large amount of DHA, the tumour cell is overwhelmed and cannot store the DHA, which oxidises and leads to cell death. By using a lipid metabolism inhibitor that prevents the formation of lipid droplets, researchers were able to observe that this phenomenon is further amplified, which confirms the identified mechanism and opens the door to combined treatment possibilities.

For their study, UCLouvain researchers used a 3D tumour cell culture system, called spheroids. In the presence of DHA, spheroids first grow and then implode. The team also administered a DHA-enriched diet to mice with tumours. The result: tumour development was significantly slowed compared to that in mice on a conventional diet.

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