Walnuts Improve Cholesterol but Fail to Increase DHA in Vegetarians

Summary

3.0 g of ALA per day via one daily ounce of walnuts for 8 weeks did not increase DHA levels in lacto-ovo vegetarians, but did improve cholesterol ratios.

Previous research has shown that it takes at least 3.7 g of the short-chain omega-3 fatty acid, ALA, to increase DHA levels in vegetarians in the short term, with the longest trial lasting 6 weeks.

A new study from Loma Linda University (1) put a group of lacto-ovo vegetarians, average age of 38, on three different daily regimens for 8 weeks each:

– 1 oz of walnuts (3.0 g of ALA)
– 1 regular egg (110 mg DHA)
– 1 fortified egg (~500 mg DHA, 40 mg EPA, 1 g ALA)

The ratio of omega-6 to omega-3 was 6 to 1 in the walnut phase, which is relatively low for a vegetarian diet, but DHA levels did not increase. The ratio of total cholesterol to HDL was lower in the walnut treatment compared to both egg treatments and there were no significant differences for any inflammatory markers.

In conclusion, 8 weeks of 1 oz walnuts daily improved cholesterol markers but did not increase DHA levels.

I have updated Omega-3 Fatty Acid Recommendations for Vegetarians with this information.

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References

1. Burns-Whitmore B, Haddad E, Sabaté J, Rajaram S. Effects of supplementing n-3 fatty acid enriched eggs and walnuts on cardiovascular disease risk markers in healthy free-living lacto-ovo-vegetarians: a randomized, crossover, free-living intervention study. Nutr J. 2014 Mar 27;13(1):29. | link

10 Responses to “Walnuts Improve Cholesterol but Fail to Increase DHA in Vegetarians”

  1. MacSmiley Says:

    Were the subjects male or female, Jack? If they were categorized by gender, was there a difference? Flaxseeds alone put me over reference in 6 weeks time.

  2. Dan Says:

    So high-dose ALA is not enough to convert through to DHA in lacto-ovo-vegetarians, even with a very decent n6:n3 ratio (6:1). Interesting. What about in strict vegans who don’t eat dairy or eggs?

    I guess the real question is whether we even need DHA in adulthood? I still think despite all the observational evidence (and some of it is conflicting), that it’s still an open question….

  3. Jack Norris RD Says:

    MacSmiley,

    16 women, 4 men. Impressive re: flaxseeds. If you don’t mind saying, how old are you?

  4. Jack Norris RD Says:

    Dan,

    I haven’t seen a similar study for 8 weeks on vegans. I agree that whether we need DHA is still an open question.

  5. unethical_vegan Says:

    Jack, did you notice that the walnut baseline DHA is almost as high as the n-3 pufa supplemented egg end point. It’s kind of hard to claim significance at an end point when a baseline number is about as high.

    My take: small “n” noise.

  6. Jack Norris RD Says:

    unethical_vegan,

    I noticed differences in the various baselines, but since it’s a crossover study, those differences could be due to the washout period not being long enough to return all the participants’ levels to the very first baseline in between each treatment.

  7. Dan Says:

    unethical_vegan,

    It may be hard to claim significance but the authors did in fact show that the high-dose DHA-enriched eggs increased DHA compared with baseline, whereas the other two groups did not.

    Interesting “handle” – I like it!

  8. Brandon Becker Says:

    If DHA levels did not increase with the added ALA, how do we know that DHA should be increased in the first place? Is it possible that the conversion is low due to the body not needing levels of DHA to be higher?

  9. MacSmiley Says:

    @Brandon

    One would know by blood tests.

  10. Brandon Becker Says:

    I could get a blood test to see my DHA levels, but if science hasn’t yet discovered what the optimal DHA levels are then I wouldn’t know what to do with the information.

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