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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.

December 10, 2022

Study finds heart health benefits for Omega-3, curcumin, and CoQ10

Three hands holding a supplement in three diferent forms (powder capsule, pill, and liquigel) between their index finger and thumb on a blank colored surface — Not all supplements are safe or effective for everyone. Javier Díez/Stocksy

Researchers assessed the effects of various micronutrients on cardiovascular and type 2 diabetes risk.
They found that some micronutrients such as omega-3 fatty acids, curcumin, and coenzyme Q10 decreased cardiovascular risk but not others.
They also found that beta-carotene supplements are linked to increased cardiovascular risk and cardiovascular mortality.
Experts say that further research is needed to understand how these results may apply to dietary recommendations.

Diet and nutrition are important drivers of cardiovascular disease (CVDs) and type 2 diabetes (T2D).

The American Heart Association recommends diets high in antioxidants, vitamins, and minerals and low in saturated fat and sodium to reduce CVD and T2D risk.

Further research into micronutrients is crucial for personalizing preventive strategies for CVDs and T2D.

In a recent study, researchers reviewed 884 randomized controlled trials to assess the link between micronutrients and cardiometabolic risk.

While some micronutrients reduced cardiometabolic risk, others had a neutral effect. Beta-carotene, however, increased CVD risk.

The study was published in the Journal of the American College of Cardiology.

For the study, the researchers analyzed 884 studies with a total of 883,627 participants.

Data included micronutrient supplementation; nine measures of cardiometabolic risk factors covering blood pressure, blood lipids, and blood sugar levels, and a range of outcome measures including cardiovascular events, diagnosis of T2D, and mortality from stroke, heart disease, and all-cause mortality.

From their analysis, they found that several micronutrients improved at least two of the nine CVD risk factor measures based on moderate to high quality studies. These included:

omega-3 fatty acid
omega-6 fatty acid
L-arginine
L-citrulline
folic acid
magnesium
zinc
alpha lipoic acid
coenzyme Q10
Anthocyanin
curcumin
genistein
quercetin

They noted that omega-3 fatty acid supplements decreased CVD mortality, heart attacks, and other heart diseases, while folic acid reduced strokes.

Meanwhile, vitamin C, vitamin D, vitamin E, and selenium had no effect on CVD events such as heart attack, arrhythmia or stroke, or diagnosis of T2D and had no impact on longer-term outcomes such as cardiovascular mortality.

They further found that while omega-3 fatty acids, omega-6 fatty acids, vitamin E, and beta carotene were not linked to T2D incidence, an analysis of 10 polyphenols found moderate quality evidence for a reduction in HbA1c (a measure of longer-term blood sugar levels) for coenzyme Q10 and reduction in fasting blood insulin levels for flavanol, genistein, and quercetin. There was high quality evidence for similar reductions in insulin levels for curcumin.

Beta-carotene supplements, however, were linked to an increased risk of all-cause mortality, CVD mortality, and a reduction in the number of strokes.

To understand how the different micronutrients studied may affect cardiometabolic health, Medical News Today spoke with Dr. Debbie Fetter, assistant professor in teaching nutrition at the University of California Davis, who was not involved in the study.

“[Nutrients like vitamin C, vitamin E, and beta carotene] function as antioxidants, which helps protect body cells from oxidative damage. […] Antioxidants help prevent the cell membrane from weakening so that carcinogens or rogue compounds can’t get inside. We can think of antioxidants as [molecules] that protect us from oxidative damage that may lead indirectly to diet-related chronic disease, like CVD.”
— Dr. Debbie Fetter

Dr. Fetter explained that omega-3 fatty acids play an important role in the brain, heart, and immune system, as well as metabolism. She noted that research indicates omega-3 intake may lower CVD risk via an anti-inflammatory effect.

She further noted that vitamin D reduces oxidative stress, which improves cardiometabolic outcomes, but that research is still inconclusive as to whether it helps prevent CVD.

“Magnesium is another essential nutrient that plays a role in muscle and nerve function. Our heart is a muscle, so adequate magnesium is needed to keep our heart properly functioning (i.e. contractions and rhythm),” she added.

Beta-carotene is a plant pigment that gives vegetables and fruits their red, orange, and yellow colors.

To understand what might explain the observed effects of beta-carotene on cardiometabolic risk, MNT spoke with Dr. Ronald Grifka, Chief Medical Officer at the University of Michigan Health-West, not involved in the study. He noted that several factors might be involved:

“One factor may be the patients did not have a deficiency, and the excessive intake of beta-carotene resulted in the higher mortality. Also, beta-carotene may have a different effect on male and female patients and on those who are smokers or drinkers. Combining data from multiple studies do not control for these variables, making it difficult to interpret the results.”

Dr. Fetter stressed that beta-carotene can be beneficial when consumed as a part of food. However, she added that research has shown it is often harmful when a part of a supplement.

She noted that one study found that beta-carotene supplements increased the risk of lung cancer and overall mortality in smokers.

“This is a classic example of where we see benefits from getting the nutrient from the whole food, but when we isolate the nutrient and put it into supplement form, we see adverse consequences,” she said.

Dr. Nurgul Fitzgerald, associate professor in nutrition and public health at Rutgers University, who was not involved in the study, told MNT:

“A potential mechanism might have to do with the antioxidant properties of beta-carotene. Under certain conditions, antioxidants can become pro-oxidant – creating the opposite, harmful effect.”

“Beta-carotene supplementation is linked to increased risk of lung cancer, especially among high risk segments of the population such as smokers. If you consider that smoking is also a cardiovascular disease risk by itself, the supplementation might be compounding the risk there.”
— Dr. Nurgul Fitzgerald

The researchers concluded that some but not all micronutrients might benefit cardiometabolic health.

When asked about the study’s limitations, Dr. Fitzgerald noted that it is difficult to directly transfer these results to everyday lives due to the variety of dietary combinations.

“Some nutrients work better or worse when we consume them in certain amounts or consume them with other nutrients. Nutrients can have synergistic effects on one another, and other components in our foods can hinder the absorption of some of the nutrients.”

She added that the United States and other countries regularly add vitamins or minerals to certain foods meaning that the effects of supplementation might vary among different countries.

Dr. Grifka added that the studies assessed different doses of various micronutrients over varying periods of time, which could have resulted in ‘markedly’ different effects.

“If several micronutrients are included in a patient’s daily consumption, one micronutrient may offset the effect of the other or amplify the effect of another, further confusing the clinical results,” he continued.

“It would be important to identify the specific dosages and individual participants’ characteristics to better understand the findings,” Dr. Fetter concluded.

October 24, 2021

Can omega-3 help undo memory damage from processed foods?

Two omega-3 capsules next to a glass of water — A recent animal study looks at the effect of processed foods on memory and asks whether omega-3 might reverse the deficit. Elena Popova/Getty Images

Researchers investigated the effects of a diet high in processed foods on rats’ memory and whether omega-3 supplementation could stave off negative effects.
They found that omega-3 supplementation reduced some, but not all, neuroinflammatory markers.
The researchers note that their results do not mean that omega-3 supplements offset the negative health effects of processed foods and that people should ensure they consume adequate amounts of complex carbohydrates to improve their health.

Carbohydrates are an essential source of energy for the body. There are two groups of carbohydrates: simple and complex.

Complex carbohydrates take longer to digest and have many nutritional benefits that help regulate blood sugar levels.

By contrast, refined carbohydrates take less time to digest, have fewer nutritional benefits, and can increase blood sugar levels and increase the risk of health conditions such as type 2 diabetes and heart disease.

Health experts also link diets containing high levels of refined carbohydrates to learning and memory difficulties, as well as weight gain in rodents, primates, and humans.

Previous research has shown that aged, but not young, rats eating a short-term high fat diet had impaired memory and increased levels of inflammation in various parts of the brain. The researchers found, however, that a dietary intervention can reduce this.

Other research has observed that an omega-3 called docosahexaenoic acid (DHA) can reduce inflammation in the brain relating to traumatic brain injury, stroke, and age-related cognitive decline.

Scientists do not know whether DHA protects against carbohydrate-related effects on cognition and neuroinflammation.

Little is also known on how a diet high in processed foods with high levels of refined carbohydrates and saturated fats and a lack of fiber affects the aging brain.

Recently, researchers from Ohio State University (OSU) and Inotiv Inc. conducted a study to understand the mechanisms behind the neurologic effects of processed diets and whether omega-3 supplementation could improve these effects.

They found that processed food diets impaired memory function among aged, but not young, rats and that this occurred alongside increased signs of inflammation. Omega-3 supplementation, however, improved these effects.

When asked whether these results were surprising, Dr. Ruth Barrientos, Ph.D., lead author of this research and associate professor at OSU, told Medical News Today:

“Yes, many studies, including our own, have focused on high fat and high sugar diets being detrimental to memory function, but few have examined the short-term effects of a highly processed diet. Given that many processed diets are low in fat, we had our doubts that we’d see any significant results. Not only did we observe very significant memory impairments, [but] we also saw significant weight gain with this diet.”

MNT also spoke with Dr. Andile Khathi, academic leader of Human Body and Function at the University of KwaZulu-Natal in South Africa, who was not involved in the present study. He said,

“I think we’ve known for a while that prolonged consumption of highly processed foods can be detrimental to the body, but this study shows just how bad this can be for the brains of [older adults].”

“Other studies have shown how beneficial omega-3 can be, but this study has gone a step further to show how its consumption can be good for mental health,” he added.

The research appears in the journal Brain, Behavior, and Immunity.

The researchers obtained 3- and 24-month old rats for the research. As female rats were not available in the older age category at the time of the study, the researchers exclusively used male rats.

At the beginning of the research, the younger rats weighed around 300 grams (g) on average, whereas the older rats weighed around 550 g.

The rats were housed two to a cage and randomly assigned to continue eating either a regular diet including 54{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} complex carbohydrates, a processed food diet including 63.3{cfdf3f5372635aeb15fd3e2aecc7cb5d7150695e02bd72e0a44f1581164ad809} refined carbohydrates, or a processed food diet and DHA supplements for 28 days.

After this period, the scientists placed the rats separately in a conditioning chamber, where the rats heard a tone for 15 seconds and then received a 2-second footshock. Four days later, the scientists reintroduced the rats to the cage and the sound to assess their fear response.

While there were no differences in freezing behavior between the different groups of rats during the conditioning phase, the researchers observed that older rats exclusively fed a processed diet froze significantly less in both fear experiments than older animals on other diet plans.

The researchers also found that both groups of rats that ate a processed food diet experienced weight gain similar to that of the rats on the alternative diet. Moreover, older animals were more affected than younger ones.

After these experiments, the researchers isolated different areas of the rats’ brains to analyze their RNA.

These analyses revealed that the rats that ate a processed food diet alone had significantly higher inflammatory gene expression than those that consumed the alternative diet, or a processed food diet with DHA supplementation.

The authors found, however, that DHA supplementation did not impact all genes that the study investigated.

According to the researchers, this means that DHA supplements do not necessarily offset the negative effects of highly refined foods and that people should focus on overall diet improvement by increasing complex carbohydrate and fiber intake.

“Processed and refined foods are unfamiliar to our gut microbiome, which has evolved over thousands of years, so these foods can provoke an inflammatory immune response, almost as if the processed food was a pathogen,” Dr. Barrientos explained.

“This peripheral immune response can easily trigger inflammation in the brain, and due to some brain immune cells in the aging brain being sensitized, this neuroinflammation can become exaggerated. Exaggerated neuroinflammation in turn is known to impair various memory-forming and maintenance mechanisms,” she added.

“The omega-3 fatty acid DHA and its metabolites are known to resolve inflammation, and we believe that explains the protective effects.”

– Dr. Ruth Barrientos

“Many studies have shown how the chronic consumption of refined carbohydrates and saturated fats can lead to various metabolic aberrations underpinned by inflammation,” Dr. Khathi explained. “The hippocampus, which is responsible for memory, is quite sensitive to metabolic changes, especially in [older adults].”

“This could explain why the consumption of these highly processed foods has such negative effects on memory. The consumption of unsaturated/polyunsaturated fats has been found to be good for various parts of the body, so it stands to reason that it could be good for the protection of brain structures such as the hippocampus,” he added.

The researchers conclude that a processed food diet with refined carbohydrates impairs cognitive function, increases neuroinflammatory gene expression, and increases weight gain in aged rats. They also found that DHA supplementation can reduce this effect.

One limitation of the study is that the researchers do not know exactly how much food each rat ate, as the rats were housed two to a cage.

“While intriguing, this research needs to be replicated in humans to determine if the same effect is seen,” Dr. Claire Sexton, D.Phil., director of Scientific Programs and Outreach at the Alzheimer’s Association, who was not involved in the study, told MNT. She continued,

“To date, there isn’t a single food, ingredient, or supplement that — through rigorous scientific research — has been shown to prevent, treat, or cure Alzheimer’s or other dementia in humans.”

Dr. Sara Imarisio, head of research at Alzheimer’s Research UK, who was not involved in the study, also spoke with MNT. She said, “What is not clear from the study is whether DHA could have similar effects in people or whether it acts against biological mechanisms that cause dementia.”

“A small number of studies have specifically linked omega-3 to better heart health and circulation, but research has so far not conclusively shown that taking omega-3 can reduce memory and thinking problems.”

Dr. Imarisio continued, “This early stage study can’t tell us whether DHA may have an impact on diseases like Alzheimer’s, and further work is needed to explore any possible link.”

In future studies, the researchers aim to examine and define the effects of processed food diets on the gut and to include female rats in their research.