I thought I would do a quick post on this because of a few comments and emails asking about sweet vs. white potato where people point out (sort of accurately) that sweet potato actually has more carbs per serving then what potato.
Here is the deal, the reason paleo and many low carb approaches work is they stop a process known as “insulin resistance”. Insulin resistance is when your body’s cells fail to respond to the normal actions insulin. In this condition you continue to produce insulin but are unable to use it as effectively. This leads to something called hyperglycemia also simply called high blood sugar. So the pancreas starts to make more insulin, further contributing to high blood sugar. This often remains undetected and can contribute to a diagnosis of Type 2 Diabetes.
While many people do know about this what they don’t realize is this isn’t like binary code made of 1′s and 0′s, it isn’t an all or nothign. The truth is most people who are overweight including some that don’t appear to be are walking around somewhere in the “middle of this process”.
Consider the following from Dr. Greg Ellis’ book
“The Glycation Factor” ““Insulin’s half-maximal dose for inhibiting fat release is 18 ?U/mL (microunits per milliliter). To reach the halfway point in shutting down fat release means that insulin only has to rise about 8 units above its fasted level of 10 ?U/ mL.”
To put that in layman’s terms once the body’s insulin level gets to “18 microunits per milliliter” the ability of the body to burn fat is practically turned off. At 36 it is done, dead, the end, the body can’t burn fat even in heavy caloric deficit it will actually start to burn muscle. It actually doesn’t take very many carbs to reach 18 and if done often soon insulin resistance begins and 36 starts happening all the time. If you want more of the science of this, read The Glycation Factor it is free in the Download section of the Members Brigade.
So with knowledge of the above as we review some paleo foods we notice the following.
- Foods that are on the list that do almost nothing to insulin levels are on the eat your ass off list.
- Foods on the list of things that increase blood sugar but do so slowly or moderately are on the eat in moderation list.
- Foods that are able to swiftly swing insulin and sugar lists are on the don’t eat list.
So how do sweet and white potato fit into this when we look at all the facts. The truth is when we just look at carbohydrates the two are very close. For instance a 7 ounce sweet potato has about 49 carbs and a white potato of the same size 51 carbs. Calorie wise they are also close 220 for 7 ounces of white and 208 for 7 ounces of sweet potato. Sure the sweet potato has a bit less of carbs and calories but so little one could just eat 6 ounces of white vs. 7 ounces and sweet and make this all moot.
Problem is this is low level thinking that we have been conditioned to believe by the food industry. If fat, carbs and protein are equal, food is equal. It just isn’t so. When we look at glycemic index, glycemic load for these two tubers we find the truth is far different.
- Sweet Potato has a glycemic index 70 of and a glycemic load of 22
- White Potato has a glycemic index 111 of and a glycemic load of 33
Without getting into the specifics of how these numbers are calculated, let us just examine a few things that are easy to understand.
- The glycemic index of white potato is 47% higher then sweet potato
- The glycemic load of white potato is 44% higher then sweet potato
- The glycemic index of glucose (pure sugar) is 100 so the glycemic index of white potato is 10% higher then glucose
- Where as the glycemic index of sweet potato is 30% lower then glucose
If you doubt this, you can see the source of this data here. When we consider the total picture we begin to understand that it isn’t as simple as total carbohydrates but how do they cause our body to respond.
The more important thing to understand is that doesn’t mean you can start scarfing sweet potatoes in every meal. The glycemic index of 70 is very high and sweet potato is a very much eat in moderation food. Make no mistake a diet of mostly sweet potatoes could certainly take you down a path of insulin resistance.
Human behavior is also part of this equation, in other words how much gets eaten. Due to the rapid absorption of sugar in white potato it kicks in a survival instinct humans have to consume sugar while it is available. Add fat to this (butter) and it is almost like a drug. Having fed many guest both white and sweet potato over the years, I can tell you something many won’t believe. In general if you offer people white potatoes they eat more of them then if you offer them sweet potato, even if they love both of them.
So now you have a food with a higher insulin response then pure glucose that triggers a response where people eat more of it. Most refined or naturally white simple starches do this. Again this doesn’t mean you can scarf tons of brown rice and whole wheat, it just means simple carbs are worse not necessarily complex ones are good, just less bad.
I personally see sweet potato as a treat. In summer I eat almost none, during peak activity of work during fall, winter and spring I often eat them about once a week. In my first 60 days of paleo I didn’t eat any.
Anyway I hope this helps to explain this common debate and why dieticians that believe governmental BS who call this comparison a myth are misguided. I also hope that many people critical of paleo will start to understand many of the foods on the eat list are also on the eat in MODERATION list so many of their blanket statements are not really accurate.
I also do believe that with careful control many people can eat things like brown rice, heirloom whole grains, etc. I think if you really want to know how to eat healthy but don’t want to go paleo you should look into the work of Weston A Price. You may not end up where us paleo folks are but after you really dig into Price’s work (as I have recently) let me tell you what will happen.
You will end up with a diet that is 70% or more paleo and food relationships that will significantly moderate insulin response. You will also find yourself using food prep techniques on many foods we don’t eat that make those foods cause less inflammation in the body. This will be particularly true of things like oats and wheat. You will also find yourself eating a LOT of animal products even if they are not meat.