Dispelling nutrition myths, ranting, and occasionally, raving


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More fish, less oil 

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Smoking fish by werehare used under a Creative Commons Licence.

In the past I’ve blogged about fish oil supplements and taken the stance that at best they’re good for you and at worst they’re of no benefit. My belief was that if you’re not eating the recommended two servings of fatty fish per week (as most of us aren’t) that you may as well go for fish oil to try to at least get some of the benefits. Some new research has given me pause to think.

According to an exposé by CBC’s Marketplace and The Fifth Estate, some fish oil supplements may be rancid. In one brand of fish oil supplements that they tested it showed twice the Health Canada allowable level of oxidation. This was well before the expiry date on the bottle.

Unfortunately, when fish oil capsules, or even many liquid supplements, go rancid it’s not so easy to tell without access to a lab. This is because many manufacturers add flavours to mask the fishy taste. Your fish oil might even be rancid before you get it home so your best efforts to store it in a cool dark place may be for naught.

The harm caused by consuming rancid fish oil supplements likely exceeds any potential benefits you might obtain from them. While there is limited research in humans, oxidized fish oils (or any oxidized oils for that matter) contain free radicals which could potentially cause damage to your cells and contribute to the development and progression of some chronic diseases.

As a dietitian I’m generally always preaching that we should aim to obtain the majority of our nutrients from whole foods, as opposed to supplements. It’s beginning to look like fish is another case where this may be true. Until more conclusive research is conducted I’ll be hedging my bets, clearing the fish oil capsules from the fridge, and aiming to eat fish more regularly.


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5 ways fish oil supplements (probably won’t) help fat loss

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A friend recently suggested that I blog about this post touting the five ways that fish oil supplements help fat loss. Of course, the post contains no references for any of the claims so I had to do a little digging and guess at what the existing research supporting them might be. Here’s what I came up with:

  1. “They stimulate secretion of leptin, one of the hormones that decreases our appetite and promotes fat burning.”

The majority of studies I can find regarding fish oil and leptin involve mice, rats, or patients suffering from pancreatic cancer cachexia. Not exactly the general population. Off to examine.com where they reviewed two studies involving fish oil supplementation for women who were over weight. Neither study showed a significant influence of supplementation on serum leptin.

2. “They help us burn fat by activating the fat burning metabolic pathways in our liver.”

Back to examine.com (why do the work of slogging through google scholar when they’ve done it for me?). They found one study that showed no effect on metabolic rate as a result of fish oil metabolism.

3. “Fish oils encourage storage of carbs as glycogen (an energy source in our liver and muscles) rather than fat.”

Examine.com found one study that showed a very slight increase in fat oxidation with fish oil supplementation. Before you get too excited though, the study (the same as was noted in the response to “reason” number two above) participants were six lean and healthy young men. Probably not the population who is interested in taking fish oil for weight loss.

4. “They are natural anti-inflammatory agents. Inflammation causes weight gain and can prevent fat loss by interfering with our fat burning pathways in the liver and muscle cells.”

There were a lot more studies (17 to be precise) looking at this topic that were reviewed on examine.com. The results were a mixed bag. A few found a very small reduction in inflammatory markers in subjects taking fish oil supplements. However, most of the studies found no effect on inflammatory cytokines and it’s important to note that even if fish oil supplements do reduce inflammation in some individuals, we can’t be certain that this will lead to weight loss.

5. “They possess documented insulin-sensitizing effects.”

Examine.com looked at 12 studies and stated that the scientific consensus is 100% that fish oil supplementation has no effect on insulin sensitivity. There are, however, a few studies that have shown an increase in insulin sensitivity but also a few that have shown a decrease in insulin sensitivity.

Overall, there is no evidence to support the use of fish oil supplementation to lose weight. Of course, Dr. Natasha would want you to believe otherwise as the purchase of her fish oil supplements is an “essential component” of her “Hormone Diet”. Remember, it’s a red flag when someone is trying to sell you a quick fix.

Don’t forget, the best way you can get fish oil is to eat fish.


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Throwing the fish out with the oil

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For the most part I love Fooducate; however, I was a little surprised by this recent blog post on their site. The post referenced a recently published study that suggested our touting fish oil supplements (or even the recommendation to consume fatty fish twice a week) is faulty. They did not offer any thoughts or critique on the new “study”.

The study was actually an analysis of previously published research. They claimed that our recommendation to consume fish (or fish oil) was based solely on a research study of Icelandic Eskimos conducted in the 1970s. They assert that the findings of this study were misinterpreted and that the researchers did not even look at the prevalence of cardiovascular disease in the population they studied. They then looked at the other research on diet and CVD in Eskimo and Inuit populations. They only found one study that performed direct measurements on the Greenland Eskimo
population for assessing the presence of CAD or CAD risk factors”
. They state that this study, conducted before the Eskimo population had adopted a Western diet, found no difference between incidence of CAD in the Inuit population in comparison to American and European populations. Interestingly, I took a look at the original research study and the researchers actually found a lower risk of CVD in the Inuit population as compared to the Western population. Essentially the opposite of what the current researchers are claiming.

So… “What the heck does this all mean??” you may be wondering. Should you be eating fish twice a week? Should you be taking fish oil supplements? Well, unless you are a Greenlandic Inuit then this research may not apply to you at all. We can’t say that what’s healthy for the Inuit population is healthy for other populations. We also can’t be certain that it’s the consumption of fatty fish that reduced their risk of heart disease. It may be any of  number of other lifestyle factors that placed them at lower risk for CVD. Recent research into the benefits of fish oil has yielded mixed results. Some studies show benefits of fish oil consumption, others show negative effects of its consumption. As always, the best advice is that variety is the spice of life and it’s best to obtain your nutrients from whole foods. Yes, eat fish (limit the larger saltwater fish you consume though as it can be high in mercury), choose a variety. If you don’t eat fish, you might want to consider consuming a fish oil supplement. There may be benefits other than lower CVD risk associated with consuming omega-3s from fish/fish oil (such as mental and cognitive well-being, bone and joint health). Research is ongoing and you might want to wait before you turf your fish oil supplement or grilled salmon.


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Krill oil vs fish oil

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I get a lot of questions about omega-3 supplements. Generally these are from fish oil. However, there’s been more interest in the less common krill oil expressed recently.

Krill are tiny little crustaceans. Fish obtain their omega-3s from eating plankton, as do krill. I’d heard that krill oil may be a superior source of omega-3s in comparison to traditional fish oil.

Krill oil actually contains less EPA and DHA (the essential omega-3 fatty acids we aim to obtain from supplements) than fish oils. 1, 000 mg of krill oil generally contains 230-300 mg of omega-3s; 140-160 mg EPA, and 80-90 mg DHA. Compare that to a 1, 000 mg fish oil supplement: 500 mg EPA and 333 mg DHA. However, amounts tend to vary widely between brands and varieties and it’s important to ensure you’re looking at the dose you’ll be taking (many will advise you to take multiple capsules each day which is unnecessary). Advocates for krill oil will tell you that the omega-3s in it are better absorbed than the omega-3s in fish oil. However, there’s not yet any evidence to support this (1).

There may be other benefits to krill oil, such as antioxidant properties. However, as with the previous claim, there is insufficient research to make any claims at this time (2).

One benefit of krill oil that is likely true is that it won’t give you the “fishy burps” that other omega-3 supplements may. If this is a concern to you it’s still avoidable when taking fish oil supplements. Look for supplements that have “enteric coating”. This means that they’ll survive your stomach acid intact and dissolve in your intestine so that they won’t be able to come back to haunt you. You should also take your supplement before your meal, or on an empty stomach, to decrease the transit time.

I had thought that fish oil supplements might be at greater risk of mercury contamination as the fish are considerably larger than the krill. A study showed that fish oil supplements range from no contamination to negligible contamination, rendering that an useless theory.

Other differences between krill oil and fish oil supplements: krill oil tends to be pricier. Also, as krill are crustaceans, krill oil supplements are not safe for sufferers of shellfish allergies.

Bottom line: krill oil may be equally beneficial to fish oil as an omega-3 supplement. It may even have additional benefits. However, the research is not there to support any additional claims. You may want to try krill oil if you’re willing to take a gamble on those additional benefits and if you’re not budget conscious. If you’d rather save your pennies, stick with a high-quality fish oil supplement. And, as always, check with your doctor or pharmacist before taking any supplements, especially if you’re taking any other kind of medication.