fish Archives - First Washington News

January 25, 2023

Omega-3 fatty acids from fish may reduce kidney disease risk

A bird's eye view of wooden baskets full of fish as a person wearing a nón lá (leaf hat) goes to stack one on top of another — Omega-3s from seafood could improve kidney health, research shows. Pham Hung/Getty Images

Chronic kidney disease affects 1 in 10 people worldwide, and if left untreated, it can lead to kidney failure.
Diet, exercise, and maintaining a healthy weight can all help to prevent or manage the condition.
A new study suggests that by including fish-rich omega-3 fatty acids in their diet, people can reduce their risk of chronic kidney disease.

Chronic kidney disease (CKD) affects more than 10{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} of the global population at around 850 million people. It is more common in older people, and risk factors include diabetes, high blood pressure, heart disease, and a family history of kidney failure.

According to the National Institutes of Health, more than 37 million adults in the United States may have chronic kidney disease.

Damage to the kidneys can happen over a long period of time, often causing no symptoms at first. Eventually, the kidneys cannot filter blood properly, leading to edema, or fluid retention, because the kidneys cannot get rid of extra fluid and salt.

People with CKD are at higher risk of cardiovascular disease and death.

Managing blood pressure and blood sugar levels is key to keeping your kidneys healthy. Being active, maintaining a healthy body weight, and eating a healthful diet are also important in both preventing and managing CKD.

Animal studies have suggested that omega-3 fatty acids may benefit kidney function.

Now, researchers from the University of New South Wales in Sydney have found that omega-3 from seafood is associated with a moderately lower risk of chronic kidney disease and a slower decline in kidney function.

The study was published in the BMJ.

The study was a part of the Fatty Acids and Outcomes Research (FORCE) consortium of studies. FORCE was set up to understand the relationships between fatty acids from our diet and metabolic processes, using data from multiple studies.

“This is an interesting study of diet potentially having a direct effect on disease progression. […] The methodology of this pooled analysis is good—more precise and avoids measurement errors related to self-report.”

— Dr. Eamon Laird, visiting research fellow, Trinity College, Dublin, who was not involved in the study.

The researchers analyzed data from 19 studies from 12 countries to assess the association between long-chain omega-3 polyunsaturated fatty acids (n-3 PUFAs) and CKD.

They estimated glomerular filtration rate (eGFR) at baseline and follow-up visits and defined incident CKD as eGFR that decreased to below 60ml/min/1.73 m2. eGFR measures how well the kidneys are removing waste from the body. The healthy range is 90-120 ml/min/1.73 m2.

The 25,570 participants were ages 49–77 years at the beginning of the study. Overall, 4,944 (19.3{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809}) developed incident CKD during the follow-up period of, on average, 11 years.

People who had higher levels of seafood-derived omega-3 in their diet had an 8{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} lower risk of incident CKD. Those with total seafood n-3 PUFA levels in the highest fifth had a 13{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} lower risk of CKD compared with those in the lowest fifth.

The researchers found this protective association with three individual omega-3s from seafood, including eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), and docosapentaenoic acid (DPA).

Dr. Shree Mulay, CEO and nephrologist at The Kidney Experts, PLLC, who was not involved in the study, welcomed the study, but urged some caution, especially in people who already have CKD.

“It’s exciting to explore if eating fattier seafood could lead to increased PUFA intake and slower CKD progression. However, it’s essential to be wary as many of these fish are packed with phosphorus — a mineral that nephrologists work hard to keep low in dialysis patients and those with advanced CKD,” she told Medical News Today.

Plant-derived omega-3s, such as alpha-linolenic acid (ALA), which is found mainly in nuts and seeds, had no effect on CKD risk.

Corresponding author, Dr. Kwok Leung Ong, senior research fellow at the School of Biomedical Sciences, University of New South Wales (UNSW), Australia, told MNT:

“For plant-derived ALA, the finding was not too surprising although still interesting to observe, since ALA generally shows weaker effect on metabolic risk factors such as lipid, glucose and inflammatory markers in clinical trials, when compared to EPA and DHA.”

“The important implication from our study is that adequate consumption of seafood and oily fish (where most such blood omega-3 fatty acids come from) may help to prevent or delay the development of chronic kidney disease.”

— Dr. Kwok Leung Ong

And Dr. Laird agreed: “The seafood-derived omega-3 is in a ‘ready to use’ form by the body already, and it makes scientific sense it would be associated with a health outcome such as CKD.”

Although the findings from the study are promising, the results do not indicate a causal relationship.

“It should be noted that our findings do not prove a causal relationship between seafood n-3 PUFA and CKD risk as the findings were observational, but they are supportive and consistent with current clinical guidelines that recommend adequate intake of seafood as part of healthy dietary patterns, especially when seafood replaces the intake of less healthy foods,” Dr. Ong said.

Dr. Laird, meanwhile, called the findings “controversial,” and said many other compounds could have had a similar effect.

“[T]he authors did not take into account other dietary factors (including other vitamins (e.g., vitamin D) and minerals found in fish) which also have anti-inflammatory benefits which the EPA and DHA levels are just tracking against,” he noted.

“Direct mechanisms could have included anti-inflammatory, direct effects on the immune system and dampening ‘inflamaging’. In addition, higher DHA and EPA may have reno-protective properties in kidney diseases, with attenuation of fibrosis.”

— Dr. Eamon Laird

“An earlier analysis of trials in 2017 found that there was no reduction in markers of inflammation (CRP, IL-6, TNF-alpha) in patients with CVD supplemented with omega-3. However, the effects could be localized to the kidney and not show up in body system-wide inflammatory measures,” Dr. Laird added.

The Dietary Guidelines for Americans recommend that adults eat 8-10 ounces (225-280g), or 2-3 portions, of seafood each week. Children should eat 2-3 ounces weekly to limit methylmercury exposure. The American Heart Association advises a similar intake. On average, Americans eat less than half of that.

Most seafood contains some n-3 PUFAs, but the highest levels are found in cold-water oily fish such as:

salmon
anchovies
herring
mackerel (Atlantic and Pacific)
tuna (bluefin and albacore)
sardines

People can also get their seafood-derived omega-3s from fish oil supplements. For people on a vegetarian diet, chia seeds, flax seeds, and walnuts are high in ALA, some of which the body converts to EPA and DHA.

DHA and EPA are both thought to reduce inflammation, which has been linked to a range of chronic conditions, such as type 2 diabetes, heart disease, and other autoimmune disorders.

So, although this study does not prove conclusively that including seafood in your diet will reduce your risk of CKD, for most people, increasing the intake of seafood, particularly oily fish, is likely to benefit overall health.

November 5, 2021

Can fish help protect our brains as we age?

Fish in a fishmongers — Could fish consumption protect against vascular brain disease? luoman/Getty Images

Cerebrovascular disease — or vascular brain disease — which impacts the blood vessels in the brain, is the fifth leading cause of death in the United States.
Health experts associate fish consumption with a lower risk of cerebrovascular disease and the accompanying decline in cognitive function.
A recent cross-sectional study found a link between higher fish intake and lower levels of markers for vascular brain damage in healthy older adults, especially those aged 65–74 years.
The effect of consuming fish two–three times per week on cerebrovascular disease-associated brain markers was similar in magnitude to the effect of high blood pressure, which was associated with increased vascular brain damage.

Cerebrovascular disease, or vascular brain disease, refers to multiple conditions that affect the blood vessels and blood circulation in the brain, such as stroke and vascular malformation.

Cerebrovascular disease is the second leading cause of death in the world. It is also the fifth leading cause of death in the U.S. and was responsible for 37.6 deaths per 100,000 individuals in the U.S. in 2017.

In addition to causing physical disability, cerebrovascular diseases can result in the development and progression of cognitive impairment and dementia.

Moreover, health experts also associate subclinical cerebrovascular damage — that is, brain abnormalities observed in the early stages of the cerebrovascular disease before its symptoms become evident — with an increased risk of dementia.

Healthy lifestyle modifications, including making dietary changes, increasing physical activity levels, and quitting smoking, can reduce the risk of cerebrovascular disease.

For instance, there is a relation between higher intake of fish and a lower risk of stroke. Fish are an excellent source of omega-3 polyunsaturated fatty acids, which may mediate these benefits on cerebrovascular health.

However, the evidence that fish consumption reduces vascular brain damage before the onset of the cerebrovascular disease is mixed.

A recent cross-sectional study investigated the link between fish consumption and vascular brain damage in healthy older adults before cerebrovascular disease onset.

The study reports an association between eating fish two or more times per week and lower levels of brain abnormalities related to vascular brain damage, especially in individuals under the age of 75 years.

The study’s senior author, Dr. Cecilia Samieri, a senior researcher at the University of Bordeaux in France, explains: “Our results are exciting because they show something as simple as eating two or more servings of fish each week is associated with fewer brain lesions and other markers of vascular brain damage, long before obvious signs of dementia appear. However, eating that much fish did not have a protective effect in people 75 years of age and older.”

The study appears in the journal Neurology.

The present study analyzed data collected between March 1999 and March 2001 as part of the Three-City Study, which aims to understand the relationship between vascular diseases and dementia in people aged 65 years and older.

The analysis involved 1,623 people with an average age of 72.3 years and residing in Dijon, France. Individuals were excluded from the study if they had a dementia diagnosis, a history of stroke, or hospitalization for cardiovascular diseases.

The researchers evaluated the extent of subclinical cerebrovascular damage using brain MRI scans.

They analyzed the MRI scans for the presence of three markers associated with subclinical cerebrovascular damage:

White matter consists of nerve fibers, or axons, that relay messages between brain regions. Cerebrovascular disease can result in nerve fiber degeneration and cause damage to the myelin sheath that surrounds the nerve fibers. This leads to white matter abnormalities.

Infarcts are regions of dead tissue resulting from inadequate blood supply. This is often due to a blood clot in a blood vessel.

Perivascular spaces are fluid-filled spaces surrounding blood vessels. When enlarged, they are associated with cerebral small vessel disease.

Each of these markers predicts the extent of cognitive decline related to cerebrovascular disease. However, previous studies have shown that a single measure obtained by combining multiple cerebrovascular disease markers can be a better predictor of cognitive decline than any single marker.

Scientists refer to a combined measure of multiple cerebrovascular disease markers as the global cerebrovascular disease burden.

At inclusion, the researchers assessed the participants’ weekly intake of various food items, including meat, fish, fruits and vegetables, legumes, and cereals, with the help of a brief questionnaire.

They assessed the relation between the global cerebrovascular disease burden and the frequency of fish intake. They noted a link between a higher frequency of fish intake and lower cerebrovascular disease marker levels.

The participants consuming fish two or more times per week had lower combined levels of cerebrovascular disease markers than those who consumed fish less frequently.

Moreover, the strength of the association between lower cerebrovascular disease marker levels and frequency of fish intake was influenced by age. This association was strongest in younger participants aged 65–69 years, but it was not statistically significant in individuals aged over 75 years.

The researchers observed similar results after adjusting for multiple variables, such as age, sex, physical activity levels, education levels, brain volume, and the intake of food items.

Health experts associate high blood pressure with an increased risk of cerebrovascular disease. The authors of the current study observed a similar association between cerebrovascular disease marker levels and high blood pressure, regardless of age of the participants.

To further contextualize the results, the researchers compared the impact of high blood pressure on cerebrovascular disease markers with the frequency of fish intake.

In the participants aged 65–69 years, consuming fish twice per week had a similar effect on cerebrovascular disease marker levels as high blood pressure, but in the opposite direction.

Moreover, the magnitude of the effect of consuming fish four or more times per week on levels of vascular brain damage markers was twice that of high blood pressure.

Dr. Jyrki Virtanen, an associate professor at the University of Eastern Finland, who was not involved in the study, spoke with Medical News Today.

He said, “This is an interesting and potentially important study, as it showed that fish intake can be beneficial for the brain and that it is possible to detect benefits even before overt signs or symptoms appear.”

“The magnitude of the association was also quite significant, as it was about similar to hypertension (a major risk factor for cerebrovascular disease), but in the opposite direction.”

– Dr. Jyrki Virtanen

“An interesting finding was also that the beneficial association was mainly observed among the younger participants,” he explained. “This may mean that for getting the benefits of fish intake on brain health, one should regularly consume fish in younger ages.”

The strengths of the study include the use of high-resolution MRI scans to evaluate three different markers and derive a more comprehensive measure of overall cerebrovascular health.

The researchers also analyzed the data after controlling for numerous variables, such as lifestyle choices, education levels, age, and more, which could have impacted the analysis.

There were, however, a few limitations to the study. Dr. Virtanen noted, “A major limitation of the study is that it is a cross-sectional observational study, so it cannot establish causality between fish intake and better brain health., i.e., that higher fish intake leads to better brain health.”

“However,” he continued, “in nutrition research, well-conducted observational studies can provide good evidence for diet-disease relationships.”

The authors also note that they administered the food frequency questionnaire only once during the study and that the survey may not represent long-term dietary patterns.

Magda Gamba, a nutritionist and doctorate researcher at the Institute of Social and Preventive Medicine at the University of Bern in Switzerland, who was not involved in the study, told MNT:

“This is an observational study associating fish intake measured at only one point in time with image indicators of cardiovascular disease burden. This means that we cannot make any direct conclusions on fish as a food that prevents brain damage.”

“More studies are warranted in order to really establish if fish is the real determinant of the observed MRI markers results in this study,” Gamba concluded.

“More research is needed to help us understand the mechanism of how eating fish may preserve brain vascular health,” says senior author Dr. Samieri, “because diet is a factor people can modify to possibly decrease their risk of cognitive decline and even dementia later in life.”

Gamba similarly noted, “This article contributes to the knowledge about the relationship existing between fish intake and brain health; younger adults seem to benefit more, but in general, a healthy diet as a part of a healthy lifestyle is recommended for all persons to keep the brain healthy and functional regardless of their age.”