Archive for the ‘Omega-3s’ Category

VeganHealth.org Update: ALA Not Associated with Prostate Cancer

Friday, December 7th, 2012

I’m a bit late in adding this info to the Prostate Cancer section of Omega-3 Fatty Acid Recommendations for Vegetarians.

There has been a question as to whether the short-chain omega-3 fatty acid, alpha-linolenic acid (ALA), might cause prostate cancer as a few early studies suggested. But from 2004 to 2010 there were three meta-analyses not finding this to be the case. The 2010 meta-analysis I just added to the site found that subjects who consumed more than 1.5 g/day of ALA had a significantly decreased risk of prostate cancer (0.95, 0.91-0.99) compared to those who ate less.

Reference

Carayol M, Grosclaude P, Delpierre C. Prospective studies of dietary alpha-linolenic acid intake and prostate cancer risk: a meta-analysis. Cancer Causes Control. 2010 Mar;21(3):347-55. Review. (Abstract)   |   Link

2002 Study of MPV in Vegans

Monday, October 22nd, 2012

A reader asked me about a 2002 study that showed vegans to have a higher mean platelet volume (MPV) than high and moderate meat-eaters and lacto-ovo vegetarians (1). I had not previously reviewed this study and decided to do so here.

The exact measurements were not given for the four diet groups, but the chart indicates that vegans had an average MPV of about 9 fl while the other groups had an MPV of about 8 fl. A normal MPV is between 7.2 and 11.7 fl (2).

MPV is a measure of the size of platelets and a high level can indicate a state of platelet activation or increased propensity for blood-clotting.

In the 2002 study, MPV was inversely correlated with the percentage of docosapentaenoic acid (DPA) and dihomo gamma linolenic acid (DGLA). DPA is an intermediary fatty acid that can be produced from EPA and that can be turned into EPA or DHA. DPA has not been studied like EPA and DHA because it is not as prevalent in fish oil and isolated supplements have not been readily available – it is not known if it has any unique functions.

The higher MPV of the vegans is likely due to a lower intake of omega-3 fatty acids and/or a higher intake of omega-6 fatty acids. The lower omega-3 fatty acid status of vegans who do not ensure a regular source of omega-3s is not news, and the vegans’ MPV levels were well within the normal range (a fact not pointed out in Li’s paper which was supported by Meat and Livestock Australia).

In other words, there is nothing really new or surprising here.

1. Li D, Turner A, Sinclair AJ. Relationship between platelet phospholipid FA and mean platelet volume in healthy men. Lipids. 2002 Sep;37(9):901-6. | link

2. Demirin H, Ozhan H, Ucgun T, Celer A, Bulur S, Cil H, Gunes C, Yildirim HA. Normal range of mean platelet volume in healthy subjects: Insight from a large epidemiologic study. Thromb Res. 2011 Oct;128(4):358-60. Epub 2011 May 28. | link

Omega-6s: Not So Bad?

Friday, July 13th, 2012

For background on the discussion below, please see Omega-3s in Vegetarian Diets.

The July 2012 issue of the Academy of Nutrition and Dietetics (AND) contained a meta-analysis of studies examining the intake of the omega-6 polyunsaturated fat, linoleic acid (LA), and whether it increases markers of inflammation (1). The AND recommends that people get 3-10% of calories as omega-6s, most of which will be in the form of LA. There is concern that large amounts of LA will be converted to arachidonic acid (AA) and will also prevent the conversion of alpha-linolenic acid (ALA) into EPA and DHA, both of which could increase inflammation.

The meta-analysis found no evidence that intakes of LA up to 10% of calories increased markers of inflammation. Adding LA to the diet did reduce levels of EPA in the blood, but this did not increase inflammation. Adding LA to the diet did not decrease the amount of DHA in the blood, but this is probably due to the fact that so little ALA is effectively converted all the way to DHA in the first place.

In a study from 1992 (2), vegans ate 9-10% of their calories as LA and, of course, had no natural dietary source of DHA. Whether large amounts of LA harm the DHA status of vegans has yet to be determined, but this meta-analysis indicates that reducing LA, a recommendation vegan health professionals have long suggested as a way to reduce inflammation and increase the conversion of ALA to DHA, might not be effective. It also provides more evidence that a DHA supplement might be the only reliable way for vegans to increase DHA levels, since reducing (or, actually, “not increasing”) LA intake does not appear to matter.

I have not changed my recommendations to limit LA based on this meta-analysis alone, but I’m leaning in that direction. Hopefully, there will be more research to come.

References

1. Johnson GH, Fritsche K. Effect of Dietary Linoleic Acid on Markers of Inflammation in Healthy Persons: A Systematic Review of Randomized Controlled Trials. Journal of the Academy of Nutrition and Dietetics. 2012 Jul;112(7):1029-41. | linklink

German Vegetarians and Mental Disorders

Monday, June 25th, 2012

In June 2010 I blogged about a study showing that Seventh-day Adventist (SDA) vegetarians had “less negative emotions” than SDA non-vegetarians (link).

Earlier this month, a cross-sectional study from Germany was released showing that vegetarians were more likely to have had mild mental disorders. The purpose of the study had been to see if vegetarians who eat less fish (for DHA) and get less vitamin B12 were more likely than non-vegetarians to develop mental disorders. It turned out that while the vegetarians did have higher rates of mental disorders, they had, on average, developed them before becoming vegetarian.

Many of the vegetarians did eat fish, but excluding them did not change the results. It is not clear how many, if any, of the vegetarians were vegan, but definitely not more than half (the percentage who never ate fish).

The data was taken from the German National Health Interview and Examination Survey (GHS) conducted in 1998/1999, making me feel less bad that it took me two weeks to get around to writing a post about it.

They did find that the vegetarians were more likely to develop an eating disorder after they became vegetarian, whereas the rest of the disorders (depression, anxiety, somatoform (hypochondria and pain)) tended to occur before becoming vegetarian.

I originally read this study for the B12 and DHA angle. As I read it and found out that more than half of the “vegetarians” were actually semi-vegetarians, I became less enthused about reporting on it, but in the end decided I should in case it was mentioned elsewhere on the Internet.

Hopefully, things have improved for German vegetarians in the last 10 years.

Reference

Michalak J, Zhang XC, Jacobi F. Vegetarian diet and mental disorders: results from a representative community survey. Int J Behav Nutr Phys Act. 2012 Jun 7;9(1):67. (link)

Omega-3s in Vegetarian Diets

Thursday, June 7th, 2012

The article I wrote, Omega-3’s: Are You Getting Enough?, for the Made Just Right blog had to be removed due to legal concerns regarding giving health advice, so I am reprinting it here. And I added a short section on children towards the end.

Summary

There is strong evidence that omega-3 fatty acids are useful in the prevention and treatment of heart disease. There is also some evidence that they might be important for cognitive function or useful as a treatment for depression. While short-chain fatty acids are found in a variety of plant and animal foods, fish provide the main source of the long-chain omega-3s. There are also long-chain omega-3 vegan supplements made from seaweed. Especially in the case of older vegetarians, there is a concern that an omega-3 deficiency could cause cognitive problems and omega-3 supplementation is recommended.

Background on Omega-3s

There are three important omega-3 fatty acids:

1. α-linolenic acid (ALA) is a short chain fatty acid. It is found in small amounts in animal flesh, in very small amounts in a variety of plant products, and in relatively large amounts in soy, walnuts, canola oil, camelina oil, and in flax, hemp, and chia seeds and their oils. The human body cannot make its own ALA, it is an essential fatty acid that must be obtained through the diet.

2. Eicosapentaenoic acid (EPA) is a long chain fatty acid. It is found in large amounts in fatty fish, in small amounts in eggs, and in very small amounts in seaweed. Some EPA is converted into other molecules that can reduce blood clotting, inflammation, blood pressure, and cholesterol.

3. Docosahexaenoic acid (DHA) is a long chain fatty acid. Like EPA, it is found in large amounts in fatty fish, in small amounts in eggs, and in very small amounts in seaweed. It is a major component of the gray matter of the brain, and also found in the retina, testis, sperm, and cell membranes.

All three of these omega-3 fatty acids may prevent heart arrhythmias, though ALA has been studied the least in clinical trials.

The body can convert ALA into EPA, and EPA into DHA. ALA is efficiently converted to EPA, but it may require large amounts of ALA to produce optimal amounts of DHA.

Health Benefits

The American Heart Association (AHA) recommends that adults eat at least two servings of fatty fish a week. The AHA says that people with coronary artery disease may want to talk to their doctor about fish oil supplements, and, especially for people with high triglycerides, large doses of fish oil could help.

An ALA intake of about 2 g/day has been consistently associated with a modest lowering of heart disease risk.

There is evidence that EPA and/or DHA supplementation may improve depression and cognition, particularly in infants, children and older adults, although the results of clinical trials have been mixed.

Vegetarians and Omega-3 Status

Vegetarians, including vegans, have been shown in many studies to have lower levels of EPA and DHA than meat eaters. We do not know if lower blood DHA levels reflect lower levels in other tissues in vegetarians, though it is a reasonable assumption.

Because EPA reduces blood clotting, one way to figure out if vegetarians are getting enough EPA is to compare the blood clotting parameters of vegetarians to omnivores. Two studies have done this and found the differences to be minimal.

Vegetarians already have about a 24% lower risk of heart disease than regular meat-eaters and on average have lower triglyceride levels, and it is not clear that EPA or DHA supplementation will further reduce their risk.

In terms of depression and cognition, there has been no research on omega-3s and vegetarians, but Joel Fuhrman, MD, has a private practice seeing many long-term vegans and has observed some older vegan men with very low DHA levels and cognitive problems, so there is reason to be prudent regarding DHA in older vegans, especially men.

Improving Omega-3 Status in Vegetarians

The traditional way that vegetarians were encouraged to raise EPA and DHA levels was by increasing ALA and decreasing linoleic acid (LA), a short chain omega-6 fatty acid. Although the body can convert ALA into EPA, the enzymes that do this also convert LA into longer chain omega-6s. If there is too much LA in the diet, the enzymes can be saturated with LA and unable to convert omega-3s. An ideal ratio of omega-6 to omega-3 in the diet is thought be about 3 or 4. Vegans tend to have a ratio of 10 to 15 compared to a ratio of 6 to 10 for omnivores.

To deal with this problem, in the late 90s and 00s, vegetarian health professionals recommended increasing ALA intake and decreasing LA intake. Unfortunately, there are no long-term studies looking at the EPA and DHA levels in vegetarians who follow these recommendations. Research shows that 3 – 4 g of ALA per day per day can increase DHA levels; assuming intake of omega-6 is low.

Increasing ALA to 3 – 4 g/day has some concerns. Three studies looking at age-related eye damage and fatty acids, all coming from the Nurse’s Health Study, have associated modest ALA intakes with age-related eye problems. The ALA in these studies came mostly from animal products that were likely cooked (omega-3s are easily oxidized by heating). It is not clear that the association is causal or if the causation would apply to uncooked ALA (i.e., from plants).

Although ALA has been associated with prostate cancer risk in some studies, the association has been shown with a fair degree of certainty not to be causal.

If it weren’t for the (small chance) for potential eye problems, my recommendations would be either to add 3 g of ALA per day or to take a DHA supplement. Because of the chance for eye damage, that much ALA is not worth the risk when DHA supplements are available and more effective. Vegetarians should still add .5 g of ALA per day for its benefits on heart disease and to help increase EPA levels. Such small amounts of uncooked ALA should pose no risk to the eyes.

Recommendations

Following all three of these recommendations should keep vegans on par with fish eaters:

1. Take a DHA Supplement

Under 60 years old: 200 – 300 mg every 2-3 days
60+ years old: 200 – 300 mg per day

2. Do not prepare food with oils high in omega-6 such as corn, soy, safflower, sunflower, most vegetable oil blends (typically labeled “vegetable oil”) and sesame oil. Instead, use low omega-6 oils like olive, avocado, peanut, or canola.

3. On average, vegetarians meet about 50 to 60% of the daily ALA recommendations without special diet planning and should add 0.5 g of uncooked ALA daily. This would be the equivalent of:

1/5 oz *English walnuts (3 halves)
1/4 tsp of flaxseed oil
1 tsp of canola oil
1 tsp ground flaxseeds

*English walnuts are the typical walnuts for sale in grocery stores. They are distinct from black walnuts.

Too much omega-3 can result in bleeding and bruising. If you have reason to believe you have problems with easy bleeding or bruising consult a health professional before increasing your omega-3 intake.

Vegan DHA & EPA Supplements

There are now many companies offering vegan DHA supplements made from seaweed. Some of them include EPA. Some DHA can be converted into EPA and if you are supplementing your diet with .5 g of ALA, you probably do not need a DHA supplement that also contains EPA, but there’s no harm from doing so.

Vegetarian Children and DHA

There is a concern that dietary DHA may be important to developing fetuses and infants. Anthropologist John H. Langdon argues that DHA is not an essential nutrient for the brain development of infants. Pregnant women efficiently convert ALA to DHA and fetuses and infants are able to receive DHA that is released from the mother’s fat tissues and provided through the umbilical cord or breast milk. Langdon argues that in cases of very low maternal levels of DHA, infants can utilize other fatty acids for brain tissue that can later be replaced by DHA.

In a study comparing breast milk, cow’s milk formula with DHA, soy formula with DHA, and soy formula without DHA, infants who ate soy formula without DHA had indications of slower parasympathetic development, though still within the normal range.

A 1994 study measured the DHA levels in the umbilical cords of 32 infants born to vegetarian mothers compared to omnivores, and revealed no relationship between DHA and the birth weight or head circumference of the infants.

Many children have been raised vegan without supplementing with DHA, or even extra ALA, and appear to develop well. Despite this, parents of vegetarian children are encouraged to supplement their diets with DHA at 200 mg every two or three days until more is known about DHA in vegan infants.

Flax & Chia Facts

Flax

• Flaxseeds are the most concentrated source of alpha-linolenic acid (ALA), with an omega-6 to omega-3 ratio of 1:4.

• One teaspoon of flaxseed oil contains 2.5 g of ALA.

• One tablespoon of ground flaxseeds contains 1.6 g of ALA.

• If flaxseeds are not ground, they will not be digested. They can be ground in a blender or coffee grinder, and then stored in the freezer. Ground flaxseeds can be sprinkled on cereal or used in baked goods.

• Cooking flaxseed oil damages the ALA, but it can be put on warm food such as toast. Flaxseed oil should be kept in the refrigerator.

• A straight teaspoon of flaxseed oil does not taste so great. Some people use cinnamon-flavored oil, tablets, or put it on toast or salad to make it taste better.

Chia

• Chia (Salvia hispanica; also known as Salba) seed oil is a good source of ALA.

• Dried chia seeds have 5 g of ALA per ounce, with an omega-6 to omega-3 ratio of 1:3.

More Information

This article is an abridged version of Omega-3 Fatty Acid Recommendations for Vegetarians which is fully annotated.

In addition to a short article I’ve written, Fish and Cardiovascular Disease, The Linus Pauling Institute at Oregon State University provides an in-depth review of omega-3s and heart disease in Essential Fatty Acids.

Study on Omega-3s Looking for Older Vegans

Tuesday, May 29th, 2012

Research study: Age and Gender Differences in Essential Fatty Acids in Long-term Vegans

Do you follow a vegan diet? Are you interested in participating in a research study that will reveal your level of healthy omega-3 fatty acids?

Omega-3 fatty acids (EPA and DHA) are important nutrients that protect against risk for heart disease, depression, and dementia. The purpose of this study is to determine whether there are age and gender differences in blood levels of the essential fatty acids, EPA and DHA, in long-term vegans.

If you have been a vegan for at least 3 years, are a man 70 or older or a woman 80 or older (we have already filled the quota for the younger age groups) and you are not using essential fatty acid supplements, you may be eligible to participate in this study. The study involves providing information about your actual dietary intake on three separate days and a one-time finger stick blood sample you will send to a lab using a pre-paid envelope. It should take about 3 hours of your time to be in this study.

You will receive a $20.00 Target gift card and a report of your blood levels of essential fatty acids.

Please note, we are only enrolling men 70 and older and women 80 and older at this time. If you are interested, please visit Enroll in DHA Study for further information.

This study has been approved by the University of San Diego Institutional Review Board. The Principal Investigators are Barbara Sarter, PhD, APRN, FNP-C, Hahn School of Nursing and Health Sciences, University of San Diego and Joel Fuhrman, M.D., Research Director of the Nutritional Research Project.

This project is supported by the Nutritional Research Project.

Omega-3’s: Are You Getting Enough?

Tuesday, May 29th, 2012

The good people at Earth Balance’s Made Just Right blog ran an article by me on omega-3s:

Omega-3’s: Are You Getting Enough?

There’s no new information here, but it might be my most concise attempt at explaining the omega-3 conundrum.

DHA and Non-Fish-Eating Cultures

Monday, July 25th, 2011

I just got back from AR2011 where someone asked me why vegans would need to take DHA if there are cultures that have lived without eating fish. I told him I don’t know the details about the health or DHA levels of such cultures.

What we do know is that vegans tend to have very low blood levels of DHA, even if they supplement with ALA. I pointed out that blood levels of DHA do not necessarily mean that vegans have unhealthfully low levels of DHA in other tissues, such as the brain, but until we know more, most vegans should take a moderate DHA supplement just to be safe.

One thing that could explain any phenomena of ancient cultures not eating fish, yet having adequate DHA status, is that our ratio of omega-6 to omega-3 is much higher today. This higher ratio hampers conversion of ALA to DHA; people in ancient cultures were probably able to convert ALA to DHA more efficiently.

People who can get their omega-6 to omega-3 ratio down to 4:1 or less, might be able to convert DHA efficiently. But I would recommend doing this without raising ALA intake much higher than 1.5 g per day (a level that has been associated with damage to the eyes). In today’s world, getting the ratio down to this level without adding large amounts of ALA to the diet would likely mean a very low fat diet which would be difficult to maintain for many people.

DHA and Prostate Cancer

Wednesday, May 4th, 2011

On April 27, Dr. Neal Barnard of PCRM wrote about a study, the Prostate Cancer Prevention Trial (1), which found that men with a higher percentage of DHA in their blood had a higher risk of high grade prostate cancer (Omega-3 Fatty Acids Linked to Prostate Cancer Risk). Dr. Barnard’s article also suggested that eating fish (the primary source of DHA for most people) five times or more a week could cause type 2 diabetes. People have written me asking if this means they should stop taking DHA supplements.

Based on the results from the Prostate Cancer Prevention Trial (PCPT) and some other studies, it is probably safe to conclude that large amounts of DHA do not prevent prostate cancer, but I think it is too soon to say that large amounts causes it. There are many variables when comparing percentages of fatty acids and disease, and the results tend to be all over the map. For example, the report from PCPT also found that the dreaded trans fats were inversely linked to high grade prostate cancer.

The levels of DHA in the blood of the men who had a higher rate of prostate cancer in the PCPT were >3.3% (compared to the lowest category of ≤2.6%), whereas vegans tend to have much lower levels of DHA, typically about 1% (see Omega-3 Fatty Acid Recommendations for Vegetarians).

DHA (and EPA) are normally promoted for reducing heart disease, but that is only a minor reason why I promote it for vegans. Vegans have much lower levels than omnivores and my concern is getting enough DHA for nerve tissue to function optimally. The amounts I recommend are much lower than what are typically suggested for fish oil supplements (usually 500 mg per day or more). I would not recommend taking that much DHA, EPA, or a combination.

It is still a good idea for vegans to take DHA at the rate of 200 to 300 mg every 2 to 3 days. The recent research does give me some pause in continuing to recommend 200 to 300 mg per day for those over 60 years old, cutting that down to every other day might be prudent. Unfortunately, there is no research showing how much these amounts of DHA will raise blood levels of DHA in vegans, but based on related research, I do not think it is enough to raise it much above 2%, which would still put someone in the lowest category of DHA percentage from the PCPT trial.

Reference

1. Brasky TM, Till C, White E, Neuhouser ML, Song X, Goodman P, Thompson IM, King IB, Albanes D, Kristal AR. Serum Phospholipid Fatty Acids and Prostate Cancer Risk: Results From the Prostate Cancer Prevention Trial. Am J Epidemiol. 2011 Apr 24. [Epub ahead of print] (Link)

What Should I Be Tested For?

Tuesday, November 30th, 2010

I am regularly asked by vegans what they should be tested for. Here is a run down:

Vitamin B12

As I say in Should I Get My B12 Status Tested?

Vegans do not need to get their homocysteine or B12 levels checked merely because they are vegan. Rather, being vegan means that you should get a regular, reliable source of vitamin B12 from fortified foods and/or supplements. (Though if you’ve gone a month or so without a reliable source of B12, you should replenish your stores as described in Step 1 of the Recommendations.)

About 2% of people do not absorb B12 well. While this has nothing to do with being vegan, it is nice to know if you are such a person. You will not be able to tell unless you first have a reliable source of B12 for at least a few weeks before your B12 level is checked. Additionally, there are specific tests that directly measure B12 absorption.

If you get your B12 level checked, please note that eating seaweeds can falsely inflate B12 levels. Methods for determining B12 levels do not distinguish between B12 and some inactive B12 analogues. Many seaweeds contain a variety of inactive B12 analogues. Someone who is eating large amounts of seaweed may have serum B12 levels well above normal, but much of it could be inactive B12 analogues.

Vitamin D

This is probably the one nutrient that vegans really can benefit from getting tested even if they do not have any symptoms of poor health.

Calcium

The body keeps blood calcium levels relatively constant regardless of your diet, so getting calcium levels tested doesn’t tell you much of anything (other than that you are not seriously ill). Getting your bone mineral density tested is the best way to find out what shape your bones are in. I don’t necessarily recommend this, unless you have reason to believe you might have osteoporosis. I’ve said it many times before, but I’ll say it again – most vegans should drink calcium-fortified non-dairy milks (or other foods) or take a calcium supplement.

Omega-3s

If you are taking a DHA supplement, then you are probably fine. If you are not and want to see what your DHA levels are, here are some testing places.

There is a more common test that could shed some light on your EPA status – blood clotting time. Most doctors test for this routinely. If your blood is clotting too fast, you might be lacking EPA. But, I rarely hear from a vegan whose blood is clotting too fast. If blood clotting time is normal, it doesn’t necessarily mean you have enough DHA.

Iron

If a doctor is going to draw blood, getting an iron panel to see if you have enough (or too much) iron is a good idea, especially for menstruating women.

Iodine

There is no direct test for iodine. Like B12, it’s best to just make sure you’re getting enough (but not too much). Iodine deficiency (and excess) can lead to thyroid problems, so getting your thyroid tested would be an indirect indicator. Click here for more on iodine.

And that covers it for any routine nutrients to test for regarding the vegan diet.