I go through most of the material I’ve written about in my special report on essential fatty acids, fish and fish oil, but there is some additional material in the podcast that isn’t in the written series.

I’ve also answered a few of the most common questions that came up in the comments section, or were emailed to me by readers.

Topics include:

• Why flax oil isn’t an adequate source of omega-3 fats
• The importance of reducing omega-6 consumption
• How much omega-3 is enough to prevent disease and promote health
• The advantages and disadvantages of fish vs. fish oil as sources of omega-3
• Criteria for choosing a fish oil
• Is vitamin A safe in cod liver oil?
• Is EPA or DHA more important in human health?

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Related posts:

1. Essential fatty acids: not so essential after all
2. Podcast episode I: interview with Stephan Guyenet on obesity and weight loss
3. Why fish stomps flax as a source of omega-3

Finally, stay tuned for the first episode of The Healthy Skeptic audio podcast, coming up next week. I’ll be interviewing Stephan Guyenet, Ph.D, on the subject of obesity and weight regulation. Stephan is a senior fellow at the University of Washington studying the neurobiology of body fat regulation. He’s also the author of Whole Health Source, which is one of my favorite health related blogs.

Before we get into talking about the benefits of fish consumption, or how how much fish or fish oil you should eat, it’s probably a good idea to start with a basic review of the omega-3 fatty acids.

Essential Fatty Acids 101

A fatty acid is a chain of carbon, oxygen and hydrogen atoms with a carboxyl group on one end. Fatty acids are classified on the basis of how many carbon atoms are in the chain, as well as how many double bonds exist within the molecule.

Fish contain a variety of fatty acids, but the ones that are believed to confer the majority of the benefits are the long-chain omega-3 fats eicosapentanaenoic acid (EPA) and docosahexaenoic acid (DHA). These omega-3 fats are found exclusively in seafood and marine algae.

As you can see from the chart below, it is also possible for the body to synthesize EPA and DHA from the short-chain omega-3 alpha-linolenic acid (ALA). ALA is found in plant foods such as flax, hemp and pumpkin seeds and walnuts.

Click thumbnail for a larger version

However, research clearly indicates that the conversion of ALA to EPA and DHA is extremely limited. Less than 5% of ALA gets converted to EPA, and less than 0.5% (one-half of one percent) of ALA is converted to DHA.

A common misconception, especially amongst vegetarians and vegans, is that our need for EPA and DHA can be met by consuming flax oil and other plant sources of ALA. But the conversion numbers above clearly indicate that this isn’t the case.

Studies have shown that ALA supplements (like flax oil) are unable to raise plasma DHA levels in vegans, despite low DHA levels at baseline. (ref) So unless they are supplementing with an algae-derived source of DHA, it is likely that most vegetarians and vegans are deficient.

This is significant because researchers now believe that the majority of the health benefits we get from dietary omega-3 fats come from the longer chain derivatives (especially DHA, as I will explain below).

Is DHA essential?

In fact, some researchers have proposed that DHA is essential. When scientists label a nutrient as “essential”, they they’re not just saying that it’s “very important”. In the context of nutrition essential means that the nutrient cannot be synthesized in the human body, and must be derived from dietary sources.

According to today’s nutrition textbooks, there are only two essential fatty acids, omega-6 linoleic acid (LA) and omega-3 alpha-linolenic acid (ALA). It is believed that as long as these fats are present in the diet, all of the longer-chain omega-3 and omega-6 derivatives can be synthesized in the body.

As I pointed out above, while this is theoretically possible, in reality the conversion doesn’t work well. This is true even for healthy people, but it’s especially true for those with nutrient deficiencies, because the conversion of ALA to DHA depends on zinc, iron and pyridoxine.

The bioavailability of iron in plant sources is poor compared to animal sources, so iron deficiency is common in vegans and vegetarians. This is another reason why they tend to be poor converters of ALA to DHA.

Several other observations support the hypothesis that DHA is essential:

• DHA content in the tissues of all mammals is very similar despite widely varying intakes of omega-3 fatty acids. ¹
• DHA and AA, but not other omega-3 or omega-6 fatty acids, are selectively transferred across the placenta (PDF).
• 60% of the dry matter of the brain is lipid, and DHA and AA are the most abundant fatty acids of brain phospholipids (PDF)
• DHA status in newborns is much lower in those receiving formula with LA and ALA, than in those receiving milk or formula with pre-formed DHA (PDF)

It is possible that the primarily carnivorous diet of our ancestors, which ensured a consistently high dietary intake of DHA and AA, precluded the need to evolve efficient conversion mechanisms.

In other words, since we were eating a lot of meat and fish with pre-formed DHA and AA, our bodies didn’t need to be experts at converting ALA and LA in plants to DHA and AA. It is far easier for the body to assimilate pre-formed DHA and AA than it is to synthesize them from precursors.

What about EPA? Isn’t it essential too?

EPA is another long-chain omega-3 fatty acid that is conventionally believed to be responsible for the benefits of fish consumption.

EPA is often referred to as “anti-inflammatory”. However, according to this report on essential fatty acids by Masterjohn, EPA’s effect seems to be more of an interference with the metabolism of omega-6 arachidonic acid (AA) than the performance of any essential role itself.

Take a look at the chart again that I linked to in the beginning of the post. The fatty acids in blue boxes are less inflammatory, and those in pink boxes are more inflammatory. The chart shows that AA is used to synthesize prostaglandins that cause inflammation (indicated by the pink box on the chart). Because it has the same number of carbon atoms, EPA competes with AA for the enzymes that metabolize it. Since the prostaglandins made by EPA are less inflammatory than those made by AA (indicated by the blue box).

So while EPA is less inflammatory than AA, it doesn’t make sense that the body would require an essential fatty acid just to block the inflammatory effects of of another fatty acid.

By contrast, DHA is used to synthesize compounds that play an active role in resolving inflammation. EPA only makes these compounds in the presence of aspirin (PDF). EPA is thus likely to simply be a byproduct of compromised DHA synthesis.

What does this mean to you?

Putting all of this information together yields the following conclusions:

1. DHA is the most important of the omega-3 fatty acids, and is primarily responsible for the benefits we get from consuming them.
2. DHA is likely to be essential, which means that you must consume it in the diet to prevent disease and ensure optimal function.
3. The conversion of plant sources of ALA, such as flax seed oil, to DHA is poor in healthy people and even worse in people deficient in certain nutrients. Vegans and vegetarians are especially prone to be poor converters of ALA to DHA.
4. If you’ve been buying flax oil in the hopes that it will help, you’d be far better off putting that money towards some fish or fish oil capsules.

Dietary changes over the past century have lowered the DHA status to a state of subclinical deficiency in many people. Countless studies show that this deficiency is at least in part to blame for the rising incidence of cardiovascular disease, inflammatory disease, mental and psychiatric disorders and suboptimal neurodevelopment.

DHA is not the only reason to eat fish, which is also rich in selenium and vitamin D. However, DHA is likely to be the primary reason why populations that eat fish on a regular basis have consistently been shown to healthier than those that don’t. We’ll discuss this further in the next article.

Related posts:

1. Podcast episode II: essential fatty acids, fish, and fish oil
2. How too much omega-6 and not enough omega-3 is making us sick
3. Essential fatty acids: not so essential after all

Back in April I wrote an article called “Throw Away Your Sunscreen” about the protective effects of exposure to sunlight against melanoma. Despite conventional wisdom that tells us to avoid sun exposure at all costs, it turns out that the vitamin D our bodies synthesize when exposed to UV light is a first line of defense against developing melanoma.

In an article published on June 9 in Archives of Internal Medicine, scientists reported that low levels of vitamin D are associated with a higher risk of myocardial infarction (heart attack) in men. The study showed that rates of cardiovascular disease-related deaths are increased at higher latitudes and during the winter months, and are lower at lower altitudes.

In an article published in the July issue of the Journal of Cardiovascular Pharmacology, on June 12, researchers found that vitamin D directly contributes to cardiovascular fitness. In fact, University of Michigan pharmacologist Robert U. Simpson, Ph.D. thinks it’s apt to call vitamin D “the heart tranquilizer”. Simpson and his team discovered that treatments with activated vitamin D prevented heart muscle cells from hypertrophy, a condition in which the heart becomes enlarged and overworked in people with heart failure.

Finally, in a study published on June 23 in the Archives of Internal Medicine, a team of Austrian scientists revealed that low blood levels of vitamin D appear to have an increased risk of death overall and from cardiovascular causes. Harald Donbig, M.D. and his colleagues studied 25-hydroxyvitamin D and 1,25 dihydroxyvitamin D levels in 3,258 consecutive patients (average age 62 years) who were scheduled for coronary angiography testing at a single medical center between 1997 and 2000.

During 7.7 years of follow-up, death rates from any cause and from cardiovascular causes were higher among individuals in the lower one-half of 25-hydroxyvitamin D levels and the lowest one-fourth of 1,25-dihydroxyvitamin D levels. These associations remained when researchers controlled for other factors such as coronary artery disease, physical activity and co-occurring diseases.

So what does all this mean to you? A recent consensus panel estimated that about 50 – 60 percent of older individuals in North America and the rest of the world do not have satisfactory vitamin D status, and the situation is similar for younger individuals. Blood levels of vitamin D lower than 20 to 30 nanograms per milliliter have been associated with falls, fractures, cancer, autoimmune dysfunction, cardiovascular disease and hypertension.

To put it blankly, that means half of all people around the world are deficient in vitamin D and therefore at increased risk for serious and potentially fatal conditions.

Low 25-hydroxyvitamin D levels are also correlated with markers of inflammation such as C-reactive protein, as well as signs of oxidative damage to cells, Donbig’s study revealed. In a previous article, I explained that inflammation and oxidative damage (not cholesterol) are the primary causes of the worldwide heart disease epidemic. Inflammation and oxidative damage are also contributing factors to diabetes, metabolic syndrome, cancer and many other diseases.

So how does vitamin D work its magic? It acts as a potent hormone in more than a dozen types of tissues and cells in the body, regulating expression of essential genes and rapidly activating already expressed enzymes and proteins. In the heart, vitamin D binds to specific vitamin D receptors and produces its “calming”, protective effects.

There are essentially three ways to obtain vitamin D: exposure to UV light, food and supplements. The most effective of all of these methods is exposure to sunlight. Full-body exposure of pale skin to summer sunshine for 30 minutes without clothing or sunscreen can result in the synthesis of between 10,000 and 20,000 IU of vitamin D. At most latitudes outside of the tropics, however, there are substantial portions of the year during which vitamin D cannot be obtained from sunlight; additionally, environmental factors including pollution and the presence of buildings can reduce the availability of UVB light.

In northern latitudes or during winter months when the sun isn’t shining, I recommend taking 1 tsp./day of high-vitamin cod liver oil (Green Pasture or Radiant Life are two brands I recommend) to ensure adequate vitamin D (and vitamin A) intake. You can also eat vitamin D-rich foods such as herring, duck eggs, bluefin tuna, trout, eel, mackerel, sardines, chicken eggs, beef liver and pork. If you follow this approach further supplementation should not be necessary.

Before closing, I must mention (briefly) the issue of vitamin D toxicity. Vitamin D is widely considered to be the most toxic of all vitamins, and dire warnings are often issued to avoid excess sun exposure and vitamin D in the diet on that basis. The discussion of vitamin D toxicity has failed to take into account the interaction between vitamins A, D and K. Several lines of evidence suggest that vitamin D toxicity actually results from a relative deficiency of vitamins A and K.
So, the solution is not to avoid sun exposure or sources of vitamin D in the diet. Rather, it ensure adequate vitamin D intake (through sunlight and food) and to increase the intake (through diet and/or supplements) of vitamins A & K. Stay tuned for a future post on the interaction between vitamins A, D & K and their relevance to human health.

Suggested Links

• The Vitamin D Miracle: Is it For Real?
• From Seafood to Sunshine: A New Understanding of Vitamin D Safety
• Vitamin D Toxicity Redefined

Related posts:

1. Vitamin K2: The Missing Nutrient
2. Throw away the sunscreen!
3. Ten steps to preventing heart disease naturally

Today’s nutrition textbooks refer to omega-6 (linoleic) acid and omega-3 (alpha-linolenic) acid as essential components of the human diet, and cite the requirement as something between one and four percent of total caloric intake. When scientists say a nutrient is “essential”, they mean it cannot be synthesized within our bodies from other components by any known mechanism – and therefore must be obtained from the diet.

But are “essential fatty acids” truly essential?

Chris Masterjohn, a PhD candidate in Nutritional Science at the University of Connecticut, has just published a paper which directly challenges the belief that omega-6 linoleic acid and omega-3 alpha-linolenic acid are essential.

His review of the scientific research suggests that omega-6 arachidonic acid (AA) and the omega-3 docosahexaenoic acid (DHA) are the only fatty acids that are truly essential – and thus necessary in the diet – for humans. Further, the true requirement for EFA during growth and development (during childhood, pregnancy or recovery from injury and illness) is less than one-half of one percent of calories when supplied by most animal fats, and even less (0.12 percent) when supplied by liver. In healthy adults, the requirement is “infinitesimal if it exists at all.”

So why is this a concern? Excess consumption of linoleate (omega-6 fatty acid) from vegetable oil will interfere with the production of DHA , while an excess of EPA from fish oil will interfere with the production and utilization of AA. So, by consuming an abundance of the oils which are today heavily promoted as “essential” – vegetable oil and fish oil – we are actually reducing the amount of the fatty acids that are truly essential – DHA & AA.

Finally, it must be pointed out that EFAs of all types, even the health promoting DHA & AA, are polyunsaturated fatty acids (PUFAs). PUFAs are widely known to contribute to oxidative stress, and oxidative stress directly contributes to many diseases including cancer and heart disease. This is why it is important to restrict our intake of EFAs to as close to the minimum requirement as possible.
Most people are far above this requirement, since vegetable oil is pervasive in the American diet. It’s in just about all processed foods (even the “healthy” ones), fried foods and everything cooked in a restaurant. And many people cook with it at home, without knowing what the dangers are.

The best sources of EFA in the diet are liver, egg yolk and butter from grass-fed animals. Obtaining these foods from pasture-raised animals is important, as they contain significantly higher concentrations of DHA and AA (the truly essential EFAs) and fat-soluble vitamins than their commercial feedlot counterparts.

Following these recommendations, along with a nutrient-dense, whole foods based diet low in sugar and rich in essential minerals, should reduce your intake of PUFA to closer to the recommended 0.5 (one-half of one) percent of calories, and ensure adequate intake of the truly essential DHA & AA.

Women who are pregnant or lactating, and perhaps attempting to become pregnant, children, and adults recovering from injury and suffering from chronic, degenerative disease can safely consume up to one percent of calories as PUFA. Studies have suggested that a subset of patients with pre-existing cardiovascular disease also benefit from a moderate dose of fish oil (up to one gram per day); however, in those same studies people with stable angina and with no heart disease at all, fish oil actually increased their risk of heart attack.

Check back here for a future post on what the research has to say about using omega-3 fatty acids (fish oil) in the treatment of heart disease.

Make sure to visit Chris Masterjohn’s website, where you can purchase the excellent full report for $15. It’s a worthwhile investment, in my opinion, if you want to get the straight scoop about EFAs and their role in our diet.

Related posts:

1. Podcast episode II: essential fatty acids, fish, and fish oil
2. Why fish stomps flax as a source of omega-3
3. How too much omega-6 and not enough omega-3 is making us sick