Twin Study - Vegan vs. Omnivore

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Last year, Mike (my identical twin brother) and I, along with 21 other pairs of identical twins participated in a medical study through the Stanford School of Medicine comparing vegan and omnivore diets. Last month, the first study results were published, and in just a few days, the Netflix documentary series about the study, You Are What You Eat: A Twin Experiment, premieres.

Mike and I arrive at Stanford for our first lab appointment before the study starts. March 31, 2022

To be eligible, twins needed to live near one another, have similar lifestyles, be willing to eat a controlled diet (either vegan or omnivore, chosen at random by the study - one twin for each) for eight weeks, visit the Stanford campus a few times for tests, and collect regular blood and stool samples at home (my guess is that this was a deal breaker for some twins).

For the first four weeks, each participant was provided all their meals from a company called Trifecta. I received a week’s worth of meals at a time, 21 individual meals delivered to my doorstep - seven breakfasts, lunches, and dinners. Except for what I would eat that day, they all went in the freezer (an additional requirement of the study was that participants had access to a freezer that could hold the rest of the week’s meals).

My first week’s worth of meals!

Since I was selected to be in the vegan group, I was a little nervous about what my meals would consist of. But after the first day I didn’t worry; the meals were great! Not only was I on a vegan diet for the first time in my life, it also cut out all added sugar and processed or refined foods. We were also required to track all everything we ate in an app and give very detailed accounts of everything we ate during regular phone check-ins with the study team.

I didn’t have much time to worry about how this new, short-term diet would impact my fitness. I am a cyclist and a runner, and Mike is an ultra-marathon runner and cyclist. The team at Stanford assured us that there were other athletes in the group and that the team would help us come up with ways to augment our calorie intake on high activity weeks. For me, even though I’m light years away from his fitness level, Tyler Pearce, The Vegan Cyclist was definitely an inspiration - he is banana sandwich intense on the bike!!!

I had a 100-mile bike ride scheduled on the fifth day of the study. Normally, I eat a high carb meal the day before a long bike ride, but since I wasn’t eating anything other than what were in the meals that were shipped to me, I couldn’t do that. And normally I bring Clif bars for the ride but also eat at the rest stops (usually peanut butter sandwiches, trail mix, blueberry muffins). And near the end of the ride, I love when the rest stops have Lays potato chips and cold cans of Coke. Well, the Delta Century did not disappoint in that regard. But I stuck to eating what I brought… not nearly enough boiled small potatoes and apples. While my riding buddy, Mike took fun in describing everything he ate in detail, it was a great ride and I survived it without that bag of Lays and can of Coke.

For the second half of the eight-week study, I still had to stick to a vegan diet (again, with no added sugar and no processed or refined foods). I did have the four previous week’s worth of meals to get a good sense of what I liked and how to prepare different dishes. We also had terrific access to the nutrition team at Stanford Medical who helped me come up with what to make.

At the end of the final day of our eight weeks, Mike and I drove to Stanford for our final lab work appointment and talked joyfully about what we couldn’t wait to eat later that day.

Once I got home, I made the greatest peanut butter and jelly sandwich I have ever had! That night, Dawn and I went to The Oxford Kitchen in Lodi. We ordered Scotch eggs as an appetizer, and I had fish and chips for dinner. I also sampled the Beef Wellington that one of our friends had ordered.

The question I often get these days is if I stuck with the vegan diet after the study. We didn’t get the results of the study for several months, but, as you read my first post-study meal, I did not. I did, however, learn more about how to put more vegetables in my meals, and still make a couple of the vegan dishes pretty regularly.

Earlier this year, Mike and I returned to Stanford with most of the other pairs of twins for the study wrap party. The organizers asked the vegan cohort members to wear green and the omnivore cohort members wear red which made it great to immediately see who was in which group. It was the first time Mike and I had ever been around so many other twins! The results did not surprise me. Suffice it to say, all my key health metrics improved. Most notably, my cholesterol dropped more in eight weeks than at any other time in my adult life.

Big thanks my bro, Mike, for agreeing to be a part of this study! And thank you to Dr. Christopher Gardner, a professor in the Stanford Prevention Research Center and leader of this research team, and the rest of his team. They were first class from start to finish. It has also been awesome getting to know some of the other twins more.

If you are a twin, or know a twin, I highly encourage you to register at the Stanford Twin Registry. Mike and I registered many years ago which is what led us to this study. Since last year, we have participated in a couple of other shorter studies. All in the name of science. I can’t help thinking how incredibly proud Mom would have been.

Watch the Netflix doc! And let me know what you think!