Do Flaxseeds Offer Sufficient Omega-3’s for Our Heart?

According to two of perhaps the most credible nutrition authorities, the World Health Organization and the European Food Safety Authority, we should get at least half of a percent of our calories from the essential omega-3 fat ALA. That’s easy: Just have about one tablespoon a day of chia seeds or ground flaxseeds and you’re all set.

Our body can then take the short-chain ALA from our diet and elongate it into the long-chain omega-3s, EPA and DHA. The question, however, has long been whether our bodies can make enough EPA and DHA for optimal health. How would one determine that? Take fiber, for example. “A convincing body of literature showed an increased [heart disease] risk when diets were low in fiber,” so the Institute of Medicine came up with a recommendation for about 30 grams a day, which is an intake observed to protect against coronary heart disease and to reduce constipation. “Thus, just as [cardiovascular disease] was used to help establish an [adequate intake] for dietary fiber,” it was also used as a way to develop a recommendation for EPA and DHA, as I discuss in my video Should We Take EPA and DHA Omega-3 for Our Heart?.

With reviews published as late as 2009 suggesting fish oil capsules may help with heart disease, nutrition authorities recommended an additional 250 mg per day of preformed EPA and DHA, since, evidently, we were not making enough on our own if taking more helped. So, in addition to the one or two grams of ALA, it was suggested we should take 250 mg of preformed DHA/EPA, which can be gotten from fish or algae.

Fish is a tough one. On one hand, fish has preformed DHA and EPA, but, on the other hand, our oceans have become so polluted that seafood may also contain various pollutants, including dioxins, PCBs, pesticides like DDT, flame-retardant chemicals, and heavy metals, including mercury, lead, and cadmium, all of which can negatively affect human health. Dietary exposure to PCBs, for example, is associated with increased risk of stroke in general and an almost three times higher risk of hemorrhagic stroke. Unless you live next to a toxic waste dump, the major  source of exposure to PCBs is fish consumption. Salmon may be the worst.

This may explain why studies in the United States have shown that just a single serving of fish a week may significantly increase one’s risk of diabetes, emphasizing that even levels of these pollutants once considered safe may “completely counteract the potential benefits of [the omega-3] fatty acids and other nutrients present in fish,” and lead to the type of metabolic disturbances that often precede type 2 diabetes. Now, one could get their daily 250 mg of preformed DHA/EPA from algae oil rather than fish oil. Algae oil is free of toxic contaminants because it is manufactured without pollutant exposure. 

Then, one could get the best of both worlds: the beneficial nutrients without the harmful contaminants. However, it was demonstrated recently that these long-chain omega-3s don’t seem to help with preventing or treating heart disease after all. Since that was the main reason we thought people should get that extra 250 mg of preformed EPA and DHA, why do I still recommend following the guidelines in my Optimum Nutrition Recommendations? Because the recommendations were not just based on heart health, but brain health, as well. See my video Should We Take DHA Supplements to Boost Brain Function?.


Other omega-3 videos include:

If the no-heart-benefit surprised you, check out Is Fish Oil Just Snake Oil?.

Surprised by the link with diabetes and want to learn more? See:

Food Sources of PCB Chemical Pollutants has more on PCBs, and here are additional videos on other pollutants:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations:

Chlorella May Help Preserve Immune Function During High Intensity Athletic Training

Sedentary women who start walking briskly on a treadmill for 45 minutes a day for a few months may cut their risk of upper respiratory tract infections in half. How exactly does exercise improve our immune system?

Approximately 95 percent of all infections are initiated at the mucosal surfaces—the moist surfaces, like our eyes, nose, and mouth. These are protected by antibodies like IgA, which provide “an immunological barrier by neutralizing and preventing viral pathogens from penetrating the body through the mucosal surfaces.” The IgA in our saliva, for example, is “the first line of defense against respiratory tract infections such as pneumonia and influenza.” As you can see in my video Preserving Athlete Immunity with Chlorella, moderate aerobic exercise—even just 30 minutes in the gym three times a week—may be all it takes to significantly boost IgA levels and significantly decrease the risk of coming down with flu-like symptoms.

We’ve known for a long time that prolonged heavy exercise, though, may reduce resistance to infectious disease, manifested by an apparent two- to six-fold increase in upper respiratory tract infection symptoms for several weeks following marathon running.

Sport coaches are advised to monitor immune function, since illness could ultimately lead to a decrease in performance. Therefore, it may be necessary to take protective actions to minimize contact with cold viruses, for example. Athletes can’t get away with just washing their hands and wearing a mask, though, because upper respiratory tract infections are often triggered by reactivations of latent viruses already inside our bodies, such as Epstein-Barr virus (EBV). As soon as our immune function dips, the virus becomes reactivated. Researchers found that IgA levels drop the day before EBV comes out of hiding and causes a spike in symptoms. “These results suggest that the appearance of [upper respiratory symptoms] is associated with reactivation of EBV and reduction of [salivary] IgA during training.”

How can we preserve immunity in athletes? In Preserving Immune Function in Athletes with Nutritional Yeast, I discussed the efficacy of using a one-celled fungi—nutritional yeast—to boost the immune systems of athletes. What about a one-celled plant?

Researchers in Japan found that IgA concentrations in breast milk could be increased by giving mothers chlorella, a unicellular, freshwater, green algae sold as powder or compressed into tablets. What about other parts of the body? Thirty tablets of chlorella a day for a month increased IgA secretion in the mouth, too. But does that actually help in a clinically meaningful way? Researchers in Canada tried to see if they could boost the efficacy of flu shots, but a chlorella-derived dietary supplement did not appear to have any effect. They were using some purified extract of chlorella, though, not the real thing.

What about giving it to athletes during training camp? High-intensity physical activity and group living create an environment ripe for infection, and, indeed, the training was so intense IgA levels significantly dropped—but not in those given chlorella each day. So, chlorella intake may attenuate the reduced IgA secretion during athletic training.


There is a caveat to the use of chlorella. See Treating Hepatitis C with Chlorella and Is Chlorella Good for You? to make up your own mind about whether the benefits outweigh the risks.

Interested in some other ways to decrease your risk of upper respiratory tract infections? See:

For the cuddliest way to protect your immune function, see my Are Cats or Dogs More Protective For Children’s Health? video.

What else can exercise do? See:

In health,
Michael Greger, M.D.

PS: If you haven’t yet, you can subscribe to my free videos here and watch my live, year-in-review presentations: