Are omega-3 food supplements useless in old age?

Dubious effect of omega-3 fatty acids on cognitive decline.

Dubious effect of omega-3 supplements on cognitive decline in old age.

There goes my last hope for a food supplement that actually works in old age. The omega-3 fatty acid docosahexaenoic acid is essential for the growth and functional development of the brain in infants and is present in mother’s milk. It has also been proposed  that a diet high in omega-3 fatty acids can protect brain health and slow cognitive decline in older persons.

Omega-3 fatty acids are made by marine algae and are concentrated in fish oils. They are believed to be responsible for the health benefits associated with regularly eating fish, such as salmon, tuna, and halibut. Other omega-3 fatty acids are found in plant foods such as flaxseed, walnuts, soy products, and canola and soybean oils. And of course the food supplement industry markets omega-3 supplements.

Studies show no effect of omega-3 supplements on cognitive decline

Now researchers at the National Institutes of Health has concluded that omega-3 supplements do not slow cognitive decline in older persons. In a large double-masked randomised clinical trial they followed 4,000 patients over a five-year period. The patients were divided into four groups with one given a placebo capsule, one given an omega-3 capsule (with 350 mg docosahexaenoic acid and 650 mg eicosapentaenoic acid), one given a capsule with lutein and zeaxanthin and finally one given a capsule with omega-3, lutein and zeaxanthin. The reason for this complex design was to also establish the impact on age-related macular degeneration.

Participants were given cognitive function tests at the beginning of the study to establish a baseline, then at two and four years later. The tests, all validated and used in previous cognitive function studies, included eight parts designed to test immediate and delayed recall, attention and memory, and processing speed. The cognition scores of each subgroup decreased to a similar extent over time, indicating that no combination of nutritional supplements made a difference.

So unfortunately, contrary to popular belief, the researchers didn’t see any benefit of omega-3 supplements in delaying cognitive decline. This is similar to results from a large 2011 study that found that omega-3 supplements did not improve brain health of older patients with preexisting heart disease. However, other studies surveying people’s dietary habits and health have found that regular consumption of fish with omega-3 fatty acids in their ‘natural’ form has benefits for eye, brain and heart health. It may be that the timing of nutrients, or consuming them in a certain dietary pattern, is important.

So a big, black mark against omega-3 food supplements for old age health.

Maybe not the final word

But maybe not so clearcut. Consider that chronic inflammation plays an important role in the development of colorectal cancer, a leading cause of cancer-related death worldwide. Accumulating evidence from animal and in vitro studies indicates that omega-3 fatty acids have potent anti-inflammatory activity and inhibit colorectal carcinogenesis. However, epidemiologic findings on the association between omega-3 fatty acids and colorectal cancer are inconsistent, with even an increased incidence of cancer associated with high omega-3 fatty acid intake reported in some prospective studies.

Now researchers at Harvard have shown that omega-3 fatty acids can have a protective effect against the development of one particular subtype of colorectal cancer. This type of cancer is called microsatellite instable and comprise about 10% to 15% of all colorectal cancers. Complicating the findings, participants with higher intakes of omega-3 fatty acids were more likely to be active, to be regularly taking multivitamins and fish oil supplements, to undergo lower gastrointestinal endoscopy, and to have more frequent consumption of poultry, fruits, and vegetables and less consumption of unprocessed and processed red meat.

Robust conclusions are thus evasive but maybe some glimmer of hope.

And there is more

Fish is the best food source of omega-3 fatty acids (Photo: Johan Munk Wolfhage).

Fish is the best food source of omega-3 fatty acids (Photo: Johan Munk Wolfhage).

We have covered the microbiome before. It includes commensal gut bacteria that are generally considered to be friendly, since they can help their host in numerous ways. They can actually help to regulate the immune system, amongst many other beneficial functions that support the host’s health. Remember that inflammation can play a role in colorectal cancer.

In lab-based work on human gut cells, researchers tested whether gut cells respond differently to a commensal bacterium (Lactobacillus gasseri) and two pathogenic bacteria (Escherichia coli and Staphylococcus aureus), and also whether the responses could be altered with omega-3 fatty acids. They found that the lactobacilli increased the secretion of the immune signalling protein TGF-β1 (Transforming Growth Factor β1), but the pathogenic bacteria didn’t.  TGF-β1 has an important role in promoting tolerance towards commensal bacteria and also in dampening immune responses following inflammation. When the omega-3 fatty acid eicosapentaenoic acid was added to the cell culture model along with L. gasseri, there was a greater increase in TGF-β1 gene expression.

The results may suggest that there is an interaction between eicosapentaenoic acid and colorectal cell response to a commensal bacterial strain that could possibly be important in cancerogenesis.

Life is complicated

All I can say at this stage is that science can be complicated as is life itself. There is clearly no harm in increasing fish consumption, but you might give omega-3 fatty acid supplements a miss until more convincing results are presented.

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Pill popping danger

Dangers lurking in dietary supplements (photo: Steven Depolo)

Dangers lurking in dietary supplements (Photo: Steven Depolo)

We have previously warned about the lurking dangers of herbal supplements. International trade in herbal supplements is a profitable market with increasing demand in both developing and developed nations. There are currently more than 1,000 companies producing a bewildering 29,000 different medicinal plant products with annual revenues in excess of US$60 billion.

We have reported about Canadian results of testing 44 bottles of popular supplements sold by 12 companies. They showed that pills labelled as popular herbs were often diluted by cheap fillers or included herbs other than what was claimed on the label. Some herbal supplements were adulterated with potentially toxic ingredients that could pose serious health risks to consumers. Product substitution occurred in 30 of the 44 products tested and only 2 of the 12 companies had products without any substitution, contamination or fillers. Quite a bad situation.

Now similar alarming findings have been reported in an American study. The U.S. Food and Drug Administration (FDA) is responsible for looking after the dietary supplement legislation. Between January 2009 and December 2012 the FDA recalled 274 dietary supplements under the class 1 recall legislation for adulteration with pharmaceutical ingredients. Earlier research had found that even after an FDA recall, the dietary supplement remained available on store shelves. However, it was not known if the supplements on sale after FDA recalls were free of the adulterants.

In the new survey, 27 of the 274 recalled supplements met inclusion criteria for the study and were analysed using the same methods at the FDA’s laboratories. Of the 27 products, 20 were produced by U.S. manufacturers and the rest fully imported. About two-thirds of the recalled dietary supplements analysed still contained banned drugs at least 6 months after being recalled, according to the survey, irrespective of their origin. Most still contained the same adulterant identified by the FDA. Six supplements contained one or more additional banned ingredients not previously identified by the FDA. Some supplements contained both the previously identified adulterant as well as additional pharmaceutical ingredients.

Promises of herbal supplements might be more than you asked for

Herbal supplement effects might be more than you asked for

Illegal substances identified in recalled supplements included:

  • sibutramine and sibutramine analogs (oral anorexiants prescribed as an adjunct in the treatment of obesity but have been associated with increased cardiovascular events and strokes and have been withdrawn from the market in many countries),
  • sildenafil (trade name Viagra, is a drug used to treat erectile dysfunction and pulmonary arterial hypertension),
  • fluoxetine (trade name Prozac, is an antidepressant),
  • phenolphthalein (has been used for over a century as a laxative, but is now being removed from over-the-counter laxatives because of concerns over carcinogenicity),
  • aromatase inhibitor (a class of drugs used in the treatment of breast cancer and ovarian cancer in postmenopausal women), and
  • various anabolic steroids (increase protein in skeletal muscles with androgenic and virilizing properties, including growth of the vocal cords, testicles and body hair).

A revered previous Prime Minister of Australia, Gough Whitlam, passed away on 21 October 2014. His slogan in winning the election was “It’s time”. I think it is high time that someone takes some serious action in preventing the sale of potentially harmful herbal supplements worldwide.