We've been taught what a general, baseline healthy diet is: lots of plants, sweet treats rarely, healthy fats and fiber, and a few other buzzwords. But the question remains: where do animal products fit into the puzzle? Does meat and cheese belong in what we consider a "healthy" diet, or is vegan truly the only way to go when it comes to physical health? We compared blood results from our vegan and non-vegan users to see who's really healthier. Here are a few areas that show distinct differences between the two groups.
Where vegans take the crown
- Cardiovascular health
InsideTracker users who identify as vegan (reported never or rarely eating animal products) have considerably lower LDL cholesterol than those who do not (reported consuming animal products once a month or more). And this checks out – a summary of multiple trials found that vegetarian diets result in lower LDL levels than those which include meat.1
In a more general sense, massive studies of thousands of people agree that vegan diets are associated with a lower risk of cardiovascular disease than omnivorous ones.2-5 If you’re concerned with your heart health or have trouble controlling your cholesterol levels, consider reducing your animal product intake. Start with one meatless day per week!
Blood sugar levels
While the difference doesn’t appear to be huge in the chart below, vegan InsideTracker users do have significantly lower blood glucose levels than non-vegans. The same pattern has been found in multiple studies (the same goes for hemoglobin A1c, too!).1,6
This might not seem intuitive at first – glucose is a carbohydrate, and animal products mostly contain fat and protein, so where’s the overlap? Well, the specific type of iron found in animal foods (more on that in a minute) may interrupt glucose metabolism.7 So if your glucose or A1c levels are above optimal, consider reducing your red meat intake.
Where meat-eaters have a leg up
- Sex hormones
Men who follow a vegan diet have significantly high Sex Hormone Binding Globulin (SHBG) than those who eat meat. This relationship holds true for women, too; vegan women have significantly higher levels than their meat-eating ones.
SHBG safely transports sex hormones throughout the bloodstream and regulates their levels within the body. SHBG levels tend to increase in parallel with testosterone levels, given it's responsible for regulating sex hormone levels. Additionally, SHBG prevents sex hormones from being cleared from the bloodstream, acting as a pool of reserved hormones that can be tapped into when levels become low.
Since SHBG binds testosterone, high levels may create a false pretense of low testosterone levels. However, given the information above, SHBG prevents bound testosterone from leaving the body. Testosterone metabolism is complex and levels can be unoptimized for a variety of reasons, however, high SHBG is not the sole culprit.
These patterns do appear to hold true for InsideTracker users – vegans have both lower testosterone and higher SHBG levels than non-vegan users. If you follow a vegan diet but are willing to experiment, try supplementing your diet with animal products and monitor your blood levels of SHBG and testosterone over time for any changes. Otherwise, be sure to monitor your protein intake and ensure you're hitting your daily needs (which depend on things like sex, age, and activity level). Good plant-based sources of protein include tofu, lentils, and pumpkin seeds.
People who eat animal products with high concentrations of heme iron (the form of iron found in animal sources), like meat and seafood, have significantly higher levels of hemoglobin and hematocrit than those who exclusively get their iron from plant sources.13 This is because heme iron is perfectly structured for our bodies to absorb and use, directly influencing our red blood cell and iron biomarkers. Non-heme iron (the form found in plant sources), on the other hand, is in a more difficult structure for our bodies to absorb. This often results in lower iron stores and levels.
In fact, vegan InsideTracker users have significantly lower levels of ferritin than those who eat animal products regularly. If you’re vegan and your iron markers, particularly ferritin, are low, consume your iron-rich meals with a squeeze of citrus – vitamin C makes non-heme iron more bioavailable. Since ferritin is a marker of long-term iron status, it’s slow to respond to any changes we make in our diet – be sure to re-test at least 3 months after your initial results to track changes over time.
What we've learned
- Of course, it must be acknowledged that there are plenty of factors (differences in physical activity, other lifestyle habits, etc.) that may be inherently different between vegans and non-vegans, and therefore contributing to the differences we see between InsideTracker groups. But when considered alongside the numerous studies with similar findings, it seems the science does in fact add up.
When making decisions about the way you eat, there are countless factors to consider (price, environmental impact, accessibility, etc), of which health is just one. Both herbivores and omnivores can be exceptionally healthy, and you don't necessarily have to compromise on the diet pattern that makes sense for you and your values. But ultimately, understanding how your body responds to your diet at the blood level is the only way to know if your eating habits are promoting good health.
- Viguiliouk, E., et al., Effect of vegetarian dietary patterns on cardiometabolic risk factors in diabetes: A systematic review and meta-analysis of randomized controlled trials. Clin Nutr, 2019. 38(3): p. 1133-1145.
- Dinu, M., et al., Vegetarian, vegan diets and multiple health outcomes: A systematic review with meta-analysis of observational studies. Crit Rev Food Sci Nutr, 2017. 57(17): p. 3640-3649.
- Orlich, M.J., et al., Vegetarian dietary patterns and mortality in Adventist Health Study 2. JAMA Intern Med, 2013. 173(13): p. 1230-8.
- Song, M., et al., Association of Animal and Plant Protein Intake With All-Cause and Cause-Specific Mortality. JAMA Intern Med, 2016. 176(10): p. 1453-1463.
- Tharrey, M., et al., Patterns of plant and animal protein intake are strongly associated with cardiovascular mortality: the Adventist Health Study-2 cohort. Int J Epidemiol, 2018. 47(5): p. 1603-1612.
- Yokoyama, Y., et al., Vegetarian diets and glycemic control in diabetes: a systematic review and meta-analysis. Cardiovasc Diagn Ther, 2014. 4(5): p. 373-82.
- Fernandez-Real, J.M., D. McClain, and M. Manco, Mechanisms Linking Glucose Homeostasis and Iron Metabolism Toward the Onset and Progression of Type 2 Diabetes. Diabetes Care, 2015. 38(11): p. 2169-76.
- Allen, N.E., et al., Hormones and diet: low insulin-like growth factor-I but normal bioavailable androgens in vegan men. Br J Cancer, 2000. 83(1): p. 95-7.
- Belanger, A., et al., Influence of diet on plasma steroids and sex hormone-binding globulin levels in adult men. J Steroid Biochem, 1989. 32(6): p. 829-33.
- Armstrong, B.K., et al., Diet and reproductive hormones: a study of vegetarian and nonvegetarian postmenopausal women. J Natl Cancer Inst, 1981. 67(4): p. 761-7.
- Aubertin-Leheudre, M. and H. Adlercreutz, Relationship between animal protein intake and muscle mass index in healthy women. Br J Nutr, 2009. 102(12): p. 1803-10.
- Karelis, A.D., et al., Comparison of sex hormonal and metabolic profiles between omnivores and vegetarians in pre- and post-menopausal women. Br J Nutr, 2010. 104(2): p. 222-6.
- Vallianou, N.G., et al., Influence of protein intake from haem and non-haem animals and plant origin on inflammatory biomarkers among apparently-healthy adults in Greece. J Health Popul Nutr, 2013. 31(4): p. 446-54.