Dr. Anthony Gustin is one of the most influential advocates of the Paleo diet, which calls for eating unprocessed food that only existed before the advent of agriculture. That means no grains, even supposedly healthy ones like heirloom and ancient varieties of wheat. Dr. Gustin and other Paleo dieters also avoid soy, corn, dairy, and nothing with added sugars or synthetic ingredients.
But one natural food that some Paleo proponents avoid, Dr. Gustin included, is fruit. That’s because fruit contains fructose. And fructose raises blood glucose levels. This logic is simple enough to understand—yet flawed.
As Miracle Noodle founder, Dr. Jonathan Carp, M.D. points out in his blog post, “Is Fructose In Fruit Bad For You,” studies showing liver toxicity of fructose and high blood pressure associated with fructose in diabetes is because of industrial fructose (high corn fructose syrup); fructose from fruit is not implicated.
Furthermore, Dr. Carp adds that because fructose gets converted into fat in the liver, this feature of fructose metabolism results in fruit sugar having a low glycemic value. This means that it does not elevate blood sugar. In fact, in comparison to table sugar’s 65 score on the glycemic index, fructose scores only 19.
Are Blood Sugar Spikes From Fruit Bad?
But what if you’re an obsessive biohacker like Gustin who certainly knows how eating fruit can lead to blood sugar elevations. If you’re trying to keep blood sugar levels rock steady and insulin secretion low, shouldn’t you really keep fruit consumption to the bare minimum? Just enough to get some antioxidants and other phytonutrients, but not so much that it causes blood glucose to spike.
Recently, Gustin travelled to Tanzania, spending five days with what very well could be one of the last indigenous hunter/gatherer tribes in Africa: the Hadza tribe. It’s estimated that only a few hundred Hadza people (‘Hadzabe’ as they are also known) have maintained their traditional ways of foraging and hunting. As hunters, the Hadza eat virtually every part of the animal from nose to tail, except the entrails, which the tribe feeds to its hunting dogs.
Besides wild game, the Hadza people subsist on honey, some tubers and fruit. So while he was in Africa, Gustin, being the biohacker he is, wore a continuous glucose monitor. In one of his most recent newsletters, Gustin describes that he usually avoids fruit because of how it spikes his blood sugar. Like the saying, “When in Rome…,” Gustin decided to consume copious amounts of fresh tropical fruit during his visit.
Blood Sugar Reductions After Eating Fruit?
“Sure enough my blood sugar spiked every time,” after eating fruit, Gustin says. But then something unexpected happened to him. After a few days of eating the typical meat and fruit diet he was exposed to, Gustin says, “My fasting blood glucose actually decreased by about 15-20 mg/dl. Yes, my blood sugar was still spiking to about 120 mg/dl, but within 45-60 minutes it would be back at baseline, which was actually much lower than when I was eating no carbs.”
This caused Gustin, who is a fierce advocate for regenerative farming and the real food movement to reconsider his repulsion to fruit—not because of the taste but because of the blood sugar spikes.
“I start[ed] thinking... is a blood sugar elevation as bad as I've really thought?” Gustin asks in his newsletter.
After Gustin returned to the States after his Africa trip, he stayed in Miami for a week and a half. Miami, Gustin points out, is a location that should have a copious amount of fresh, locally-grown fruit. However, he purchased store-bought fruit that was imported from all over the world. (Blueberries from Chile, tomatoes from Mexico, etc.)
“I felt terrible and my blood sugar was all over the place,” he says, adding that he experienced energy crashes and insatiable hunger.
But was it really the fact that Gustin was eating imported fruit that caused his blood sugar fluctuations and imbalanced energy? Or was it the fact that Gustin admits to having contracted Covid-19, which he attributes to the stress of intense international travel? Did Covid-19 destroy Gustin’s glucose tolerance, he wondered?
After quarantining in Miami, Gustin revitalized himself in Costa Rica for a few weeks, eating even more local fruit than he did in Tanzania. Consequently, Gustin says he went back to “feeling amazing.” He adds, “I was also outside nearly the entire day, in an environment where the food actually grew.”
Lessons Learned From A Paleo Thought Leader On Fruit Consumption
These experiences caused Gustin to reexamine the dreaded "glucose spike" exposed by the zealous Paleo movement (my words, not Gustin’s). Maybe the glucose spike “isn't actually as bad as we've been led to believe,” Gustin says in his email.
Gustin theorizes that in healthy people, if there’s a rapid uptick in blood glucose levels, it’s not a problem as long as blood glucose returns to normal.
However, as Gustin points out, approximately 90% of people in the USA are “metabolically broken.” And for this population, having a blood sugar spike of 80 points or higher that takes several hours to return to baseline is a huge problem.
To address these metabolic disorders, along with lifestyle changes, Gustin recommends a low-carb diet to normalize metabolism. And for some people with chronic metabolic disorders, Gustin suggests “local real food carbohydrates” [like fruit], can be included in a healthy diet.
Gustin offers this suggestion to his followers: “In general, it's probably a good idea in life to avoid zealots that lack nuance in thought.”
Dr. Gustin fails to mention if he includes himself in the disclaimer. But in Gustin’s defense, he rights the wrong by saying, “Be wary of extreme keto or carnivore advocates that demonize all carbohydrates equating real food to guzzling a 64-ounce Coke.”
One final food for thought courtesy of Gustin is to pay attention to how you feel after eating a specific food. Moreover, how you feel after eating a specific food can change from week to week.
Of course, even though he is a doctor (chiropractor), Gustin’s advice is not intended to be substituted as medical advice. This is especially true if you have type 2 diabetes, which requires vigilant, persistent continuous glucose monitoring; consult a dietician to see if eating fruit is safe for you. But Gustin’s advice to eat unprocessed, local food is words of wisdom for everybody.