Wednesday, June 27, 2012

Nuts and Seeds

Here is my understanding of what our cadre of mostly plant-based, whole foods diet doctors (BarnardCampbellEsselstynFuhrmanMcDougall, and Ornish) recommend (note, Campbell is a Ph.D., not an M.D., for what it's worth).

  • They all consider oils to be harmful.  I've heard two reasons quoted for this:  1), they are empty calories, at about 120 calories per tablespoon.  2), perhaps more significantly, most are very high in omega-6 fatty acids (more on this below).
  • Whole foods fat sources are good for you, in limited quantities.  These include nuts and seeds, avocado and relatively unprocessed soy products (soy milk, tofu, edamame, tempeh).  (NOT isolated soy products used to make tofu hotdogs and sausages and protein supplements).
As far as I know, the only differences in their recommendations are
  • Fuhrman has a lower limit to the amount of nuts and seeds that should be consumed by everyone, which is 1 oz.  I think the other doctors do not. 
  • Fuhrman recommends an omega-3 supplement (DHA), and none of the others do as far as I know.  In fact, some are adamant in their opposition to this.
These differences may be minor, but this became an important question for me lately as I considered transitioning to a lower-fat diet.  Some people have very low calorie needs (e.g., older women) and 1 oz of nuts and seeds, along with modest quantities of avocado and soy products, can easily put the fat percentage above 25%.  

I highly recommend Jeff Novick's DVDs on nuts and oils.  (I also recommend his DVDs on calorie density and lightening up).  This is the best summary that I know of on the topic.  Here I learned about the important of the omega-6 to omega-3 ratio in your diet.  The standard American diet has a very high ratio of omega-6 to omega-3 fatty acids.  We all need a very small amount of omega-3 fats.  Most of us ingest a sufficient amount if we eat a whole foods, mostly plant-based diet with lots of vegetables.  However, we only have so many enzymes available to digest these fatty acids.  If our intake is dominated by omega-6 fatty acids, the enzymes will get used up digesting those.  I hadn't appreciated that fine point until I watched Novick's DVDs.  It might explain something I've been curious about.  I've noticed that some people on the Standard American Diet, who are obviously ingesting large amounts of fat, sometimes appear to have dry, scaly skin and brittle hair.  I suspect they have an omega-3 deficiency--or are unable to digest what they ingest of omega-3, because of the omega-6 imbalance.  I'm just speculating.  Anyway, back to Novick.  He says, as long as we avoid the oils, and excessive consumption of healthy fats, which also mostly have high ratios of omega-6 to omega-3 fats, then we will ingest a sufficient amount of both in proper ratios.  McDougall says the body gets very good at converting the ALAs in foods to omega-3s when it needs them.   The foods with high ALAs, or alpha-linolenic Acids, are flaxseeds and walnuts (hemp too I think).   Novick says if you really want the assurance you are getting enough omega-3s, eat a tablespoon of flaxseed per day.  

Campbell is adamantly opposed to omega-3 supplements.  This surprised me.  I heard him speak about this at the food revolution summit.  He cited studies that show the supplements did not behave as we thought they would.  Here is a quote from the transcript:

"I have in mind particularly a review which was done of a total of 59 different kinds of studies of omega three fats that was published in 2006. This is 6 years ago. It came to the conclusion they simply don't work for reducing heart disease, cancer and diabetes." 
Another study showed that it can increase the incidence of type II diabetes.  what?   He also argues that it's the ratio of omega-6 to omega-3 that matters.

I'm still digesting some other articles sent to me by Kristi (thanks!).  

I decided to follow Novick's advice for now.  I'm not setting a lower limit to my nuts and seed intake (eek!).  I am not taking DHA (Dr. Fuhrman's omega-3 supplement) anymore (eek!), I'm eating 1 T of flaxseed most days.  This is a big change for me as I have been following the Fuhrman advice for about 5 years.  eek!

1 comment:

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