Welcome to Straight Talk on Health. I’m your host Dr. Chet Zelasko. Straight Talk on Health is recorded in conjunction with WGVU in Grand Rapids MI. I examine the world of health. Whether it’s research that makes the news, another miracle diet, or a new food fad, I look at the science behind them, and let you know whether it’s real or not. You can check out other things that I do on my website Drchet.com and sign up for my free emails.
Two recently published articles on oily cold water fish and two conditions warrant closer examination. Let’s begin with a study on fish consumption and chronic kidney disease (CKD). By definition, CKD is the loss of kidney function over time. The kidneys are the major blood filtering system, so the continued decline can impact the entire body in a very negative way.
Researchers selected 19 studies from 12 countries to perform a meta-analysis. The key variables were blood levels of omega-3 fatty acid levels and types—EPA, DHA, and DPA from seafood plus ALA from plant sources. They also measured the estimated Glomerular (gluh-mehr-yuh-lr) Filtration Rate (eGFR). The researchers identified 25,570 participants that met the criteria and were included in the analysis.
Over a median of 11.3 years of follow-up, 4944 (19.3%) developed CKD. Higher levels of total seafood omega-3s were associated with a lower CKD risk. In comparing categories of omega-3 levels, subjects with total seafood omega-3 level in the highest quintile had a 13% lower risk of developing CKD compared with those in the lowest quintile. The association appeared consistent across subgroups by age, eGFR, and prior diagnosis of hypertension, diabetes, and coronary heart disease at baseline.
While this was an observational study, there appeared to be an inverse relationship between blood levels of omega-3s from seafood sources and the development of CKD. Omega-3s from plant sources had no effect. Do we know if this included supplementation with omega-3s? That was not tested in this study. Is it surprising? Not at all.
About 12 years ago, a woman contacted me who had genetically caused CKD. All her family had died from it by age 50. She was approaching 60 years. She had decided to do all she could with her lifestyle to live as long and as well as she could. She asked me if there might be any type of diet or dietary supplements that might help her condition. I couldn’t comment on her diet because she had already done everything I could have recommended.
One thing about the kidneys. There is really nothing in nutrients such as vitamins, minerals, or other supplements that are specific to kidney health with the exception of water and reducing sodium. In my background research, I came across a rodent study that caught my attention. Several groups were testing fish oil to see if could be beneficial for kidney disease. One particular study stood out. They fed the rats corn oil as a control, plain fish oil, high-EPA fish oil, and high-DHA fish oil. Then, they chemically damaged their kidneys while continuing the diets. When they sacrificed the animals and examined their kidneys, the high-DHA group had recovered kidney function.
Humans are not rodents but if something won’t do any harm, and there is nothing left to try except dialysis and a kidney transplant, it’s worth a try. The equivalent amount given to the animals adjusted for human size would have been 9 g of high-DHA fish oil. The upper limit was 5 g per day so she took 5 g high-DHA per day. Her kidney function improved to the extent that she had another 5 years without having to have a kidney transplant. As happens, we lost touch after that. When this latest study was published, it didn’t surprise me that recent research is supporting DHA for kidney health.
Let’s turn to the study on sea food and lung health. Lung function declines as we age; depending on how we treat our lungs, our habits can determine the rate of decline. Working in toxic situations (or even worse, smoking cigarettes) can accelerate the decline. That’s why a recent study that examined blood levels of omega-3 fatty acids and measures of lung function found that our diet has an impact on lung function. Let’s take a look.
There were two studies reported in the paper, I’ll stick to the longitudinal study, although both demonstrated the positive impact of omega-3s on lung function. A couple definitions first.
Forced expiratory volume 1 (FEV1) is the amount of air that one can forcefully breathe out in one second. The normal range is 2,500 to 3,250 milliliters.
Forced vital capacity (FVC) is the amount breathed out after a normal exhalation. The normal range is 3,700 ml to 4,800 ml.
One more thing: in this study, the mean rate of lung function decline was 36.8 mL per year for FEV1 and 35.8 mL per year for FVC. That’s about 1% per year if left unchecked.
Researchers examined a pooled group of studies that were part of the National Heart, Lung, and Blood Institute Pooled Cohorts Study. Studies were chosen because of the repeated measurements of both lung function and plasma phospholipid omega-3 fatty acids. The study found that higher omega-3 fatty acid levels were associated with less decline in lung function for 15,063 participants. The omega-3 that provided the most benefit was the omega-3 fatty acid DHA. No Surprise there. In plain English, the more the DHA levels increased over time, the more the decline in lung function was prevented. I know that sounds funny to say it “prevented decline” but to say that it improved lung function would be incorrect.
In both studies, nutritional information wasn’t collected, or if it was collected, it wasn’t used in the statistical analyses performed. The assumption seems to be that seafood were the primary sources of omega-3 fatty acids, and that may be true. But it raises a question about the potential for using omega-3s in dietary supplements. Would the same response occur in reducing the risk of chronic kidney disease and preventing the loss of lung function? We just don’t know.
It also raises another question. Many studies on the benefits of omega-3 supplements on heart health and other organs are often less than overwhelming. Could it be that there is a nutrient or nutrients in fish that, together with omega-3s, could contribute to benefits? Or could it be there’s a factor that helps with digestion, absorption, and utilization in the actual form of omega-3s used as supplements? We don’t know at this time.
While the benefits of omega-3s, specifically DHA, were small, the fact that they prevented decline over years contributes to aging with a vengeance. I think having a diet that includes the regular intake of fatty fish is the key to a healthy lifestyle, and I still think regular use of fish oil supplements may prove to be beneficial once they get some of the other questions answered as to source and form of omega-3s that’s the best. As the research continues. I’ll keep you posted. Until next time, this is Dr. Chet Zelasko saying health is a choice. Choose wisely today and every day.
References:
1. Am J Respir Crit Care Med. 2023 Jul 20. doi: 10.1164/rccm.202301-0074OC
2. BMJ 2023;380:e072909. doi: 10.1136/bmj-2022-0729092
3. Renal Failure, 33(1): 66–71, (2011) DOI: 10.3109/0886022X.2010.541584
