Week three is almost in the books and did not disappoint. As hoped for, the Functional Health track went more in depth this week and has me excited for what’s to come. So much so that I’m going to make it the sole focus of this week’s entry.
This week’s focus was on macronutrients. We read chapters three through five of The Paleo Cure and were updated on what the science is currently saying. I was surprised and pleased to see Chris Kresser challenging assumptions that are considered gospel in the low-carb community at large. I’ll get into that in the body of this post.
Following are what I found to be the most notable pearls of information regarding the updated science on macronutrients.
There are researchers in longevity science who argue that it is best to limit protein intake. One of their arguments is that high protein intake increases the levels of the growth hormone IGF-1, which has been shown to encourage the growth of cancer cells. Chris pointed out that recent research has shown that the amino acid methionine, which is mostly found in muscle meats and eggs, is the primary driver of IGF-1 levels. However, other research has shown that glycine reduces IGF-1 levels and has the same life-extending effects as reducing protein.
The takeaway is that maintaining a healthy methionine-to-glycine ratio is an important factor in longevity and a better alternative than limiting protein. Glycine is found in gelatinous cuts of meat, like oxtail, shanks, and brisket. It’s also abundant in bone broth. Another argument for the ancestral wisdom of nose-to-tail eating. Nature has everything covered.
Chris addressed the fact that current research confirms that dietary cholesterol does not raise cholesterol in the blood for most people. Given that some of the most nutrient-dense foods contain cholesterol, this is important. We should not avoid eggs, or seafood, or fatty cuts of meat. He also stated that only 20 percent of cholesterol in the body at any given time comes from the food we eat. The remainder is manufactured by the liver.
Still, efforts to demonize meat abound. A 2013 study published by New England Journal of Medicine proposed that the choline found in liver, eggs, and other animal proteins is converted by our gut bacteria into TMAO, an amine oxide that has been correlated with heart disease. This study has been circulated by the vegan community and others with an agenda to scare people away from eating meat. Citing his own detailed critique of this theory, Chris reasoned that if foods that increase levels of TMAO do indeed cause heart disease, then we’d find fish consumption linked to heart disease, as fish increases TMAO levels by a far greater margin than eggs and other animal proteins. In actuality, the converse it true; fish consumption is inarguably associated with a decreased risk of heart disease.
Finally, Chris stated, even if animal proteins did increase TMAO levels, most people are able to efficiently clear it through the urine before it can do any harm. So, as with so many attempts to villainize animal proteins, the fuss about TMAO turns out to be much ado about nothing.
This is where it gets juicy. Chris said that, while at the time that he wrote The Paleo Cure he saw refined sugar as a toxin, he no longer views it as such. People with gut, metabolic, or blood sugar issues should avoid consuming it. And overconsumption can be problematic for anyone. Yet, small amounts of refined sugar in the context of a nutrient-dense diet will not cause problems for the average person.
Further, he said that recent research shows no evidence to support the idea that fructose as it naturally occurs in whole foods such as fruit is uniquely fattening and there is no reason for most people to avoid it. He said that most researchers now believe that de novo lipogenesis (DNL), the process by which the liver converts dietary carbohydrates to fat, is negligible in response to fructose and is not a significant source of dietary calories.
Along the same lines, Chris stated that he no longer gives much credence to the glycemic index when considering unprocessed foods. To support his position, he explained the difference between cellular carbohydrates and acellular carbohydrates. In layman’s terms, cellular carbohydrates, found in whole foods, are stored within a shell, or sheath, of living fiber that limits the density of fructose to 25% by mass, in turn limiting the speed at which they are absorbed by the body. Acellular carbohydrates, on the other hand (think processed carbs such as flour and refined sugar), are naked and non-fibrous and can be packed into processed foods with much greater density than is typically found in nature, speeding up absorption.
The short of this is that foods such as ripe bananas and white potatoes, both of which score high on the glycemic index, have limited fructose density and contain enough fiber to slow down their absorption, making them unproblematic for the average person. Meaning they should not cause weight gain or metabolic issues. I can hear the heads of low-carb fanatics exploding as I write this now.
The caveat is that people suffering from obesity, blood sugar regulation, or other metabolic issues, would do well to limit carbohydrate intake. Otherwise, carbohydrates from whole foods are an essential form of energy and the fermentable fiber they contain play a key role in feeding healthy gut bacteria.
My interpretation of all this is that Chris is not all that concerned with macronutrient distribution. As long as one is eating unprocessed foods, carbohydrate levels can be low, moderate, or even on the high end. He argues that the brain naturally regulates consumption of protein, so overconsumption is not a concern, and there is no need to limit fat intake as long as one is consuming healthy fats and obtaining sufficient amounts of EPA and DHA (omega-3s) from fatty fish and/or seafood.
For specific conditions, macronutrient levels become a larger consideration. For people with excess weight to lose or those dealing with blood sugar regulation, for instance, a lower carb approach is often best (but not always). And high performance athletes typically need higher carbohydrate intakes. But a metabolically healthy individual can just eat real food and let the body sort things out.
Low-carb and ketogenic diets are all the rage these days. Just as many in the vegan community persist in attempting to demonize all forms of animal protein, there are fanatics in the low-carb community who villainize all carbohydrates. Such are the trappings of ideology.
I think I’ve represented Chris’s viewpoints here accurately and faithfully. Any misrepresentations are entirely due to my own lack of understanding or failure to articulate. I welcome your questions and/or considerations in the comments.
For more on Chris Kresser’s views on the shortcomings of the glycemic index, see this podcast episode.
For Chris Kresser’s detailed critique of the aforementioned TMAO study, go here.