I know many paleo followers are concerned with the fructose content of most fruits. I wonder why is it that some people who are very concerned with fructose do accept vegetables as sweet potatoes or beets whose sugar content is high and is mostly sucrose: http://en.wikipedia.org/wiki/Fructose We know that sucrose is 50% fructose so I do not find it very consistent to be worried about the fructose content of most fruits and then freely embracing other foods with high sucrose content, since sucrose is 50% fructose. Am I missing something?
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I wonder why is it that some people who are very concerned with fructose do accept vegetables as sweet potatoes or beets whose sugar content is high and is mostly sucrose...
Am I missing something?
Yes, you're missing the fact that sweet potatoes have less fructose than almost all fruits.
You have to look at the actual numbers.
To calculate the total amount of fructose, we add half the sucrose to the free fructose.
Sucrose / 2 + free fructose = total fructose
Here's how we apply that formula to sweet potatoes. According to the USDA database, sweet potatoes contain 2.52 g sucrose and 0.70 g free fructose per 100 g. Here's the arithmetic.
2.52/2 + 0.70 = 1.96
This means sweet potatoes contain 1.96 g of total fructose per 100 g.
This is less total fructose than almost any common fruit. The only common commercial fruits that contain less total fructose are cranberries and limes, and people don't like to eat them because they are sour.
Let's put sweet potatoes in perspective by comparing them with fruits. The numbers show total fructose g per 100 g.
FOOD TOTAL FRUCTOSE ---------------------------- Apricots 3.87 Apples 6.93 Bananas 6.04 Blueberries 5.02 Cantaloupe 4.04 Cherries 5.44 Grapefruit 3.02 Grapes 8.20 Kiwi 4.42 Mangos 7.16 Papayas 3.73 Pears 6.62 Pineapple 5.11 Raspberries 2.45 Strawberries 2.73 SWEET POTATOES 1.96 Watermelon 3.90
Sweet potatoes don't look so bad now, do they? :)
The reason I didn't mention beets in this answer is because I can't find data anywhere on the web about its sugar composition. (I'm talking about red beets, the kind that people eat. Plenty of info is available about sugar beets, but that's a different thing.)
Source: USDA database
It is my belief that even the small amount of fructose in sweet potatoes will work against a person attempting to lose fat. This is not to say that this creates an insuperable barrier to fat loss however, simply that it would make things more difficult than the equivalent number of grams of russet potato, for example.
That being said, sweet potatoes are a nutrient-rich food that would likely be a wise addition to the diet of a person not as interested in losing fat.
I am a little perturbed by all this negative fructose information and reserach that is out there. I know each individual responds differently, but I personally have been eating 5-8 servings of fruit A DAY for about 4 years. Of course there is the occasional day I eat less than that. Combined with the lean grass fed meats, wild fish, fre range chicken and copious amounts of fats and veggies I eat, I continue to be incredibly lean and shredded. I see no discernible negative effect all these fruits have on me. My performance and function continues to increase.
However, if a 350 lb. typical American came to me for advice I wouldnt recommend they consume that high amount of fruits. I recommend they continue to shop at Sam's club and push their sleds of inflammation around.
To answer your questions Travis and Steve: Travis, the fruit intake definitely coincided with fat loss. My activity consist of crossfit 4-5 times a week and occasional outdoor activities on a weekened. Not sure how it affects my AGEs; I rarely cook with high heat and I eat foods that are known to inhibit AEGs so that might help with the increased fructose consumption. But who knows?! There is conflicting evidence for just about anything out there. Bottom line is I feel great, perform great and am lean as possible. Is there disease and inflammation within my body? Perhaps. All we can do it try to cut down the risks factors by eating this way.
For about 4 weeks I had this healthy ( or was it unhealthy?!) obsession with bananas and almond butter to the point where I was eating, on average, 4 bananas a day just about every day. Noticed little summin summin but perhaps that was from the increased almond butter consumption. Cut down bananas recently as per the latest information on saponins. If I consume it is typically pre or post workout. Plantains are now on my list for awesome post wod carbs. Saute it with some coconut oil or olive oil, maybe even add some coconut flakes and cinnamon or cocoa. Heaven.
The sugars found in most fruits are NOT equivalent to processed sugars. It's all about insulin response. If you don't understand the glycemic loads in foods you are missing a critical piece of the puzzle.
I think the same people who would advocate the occasional sweet potato would also have no problem with occasional fruit. I've not noticed any inconsistency. I myself have pointed out at times that sugars from fruit are no healthier than sugars from any other sources. I did not caveat that by including sweet potatoes in the discussion, but that wasn't the topic at the time.
However, if you look at the data in the wikipedia article, the sugar/100g of sweet potato is 1/2 to 1/3 what is in most of the fruits on the list. I think that's why it's chosen as a good post-workout carb source.
For me all we have to avoid are those processed foods and beverages with fructose. If we keep on eating those foods plus fruits and beverages with fructose that means we are overloading ourselves with to much fructose and it is bad for our health.
I have problems digesting fructose (I get an upset stomach and bloat badly) regardless of the source. I stay away from a lot of fruits but have not noticed much of a problem with many vegetables or root tubers.
Note that I have absolutely no reaction to regular sugar/sucrose yet I can take one sip in a blindfolded test to tell you if a drink had HFCS in it or not.
All very informative. I wonder why somethings that are supposed to be healthy for you i.e. emergen C has to have fructose and sugar cane in it or has to have fructose at all. Kim!
It seems to me that it is harder to overeat on vegetables like beets or carrots than on a potato. They can be difficult to digest, and for us at least, that is the limiting factor, not the amount or type of sugar (although the type of sugar may affect the digestability - seems like there are a few more fructose-digestion problems as we age).
Fructose is much less a problem if it is delivered in its natural fibre packaging.
It also depends WHY you want to avoid fructose.
If one is fructose sensitive, creating immune responses in the gut (IgA), fructose from any source would be a problem, espcially free fructose.
If one has fructose malabsorption, the main problem is the amount of fructose above the amount of glucose, as glucose upregulates fructose absorption; that is, it's the "extra" fructose that stays in the gut and gets fermented by your gut microbes, creating gas, blosting and destruction of the gut lining.
If you have blood sugar dysregulation issues, you have to pay attention to both the glucose content (immediate blood sugar surge) and the fructose content (delayed blood sugar surge) as well as what else you eat it with - fat, fiber and protein can all slow down the release of sugars in your digestive system, so they don't hit your system in one big shockwave.
If you have liver problems (fructose goes directly to the liver for metabolism), it's the fructose you absorb that will be the problem, and then you're better off eating fructose without accompanying glucose, since you will absorb less of it that way (about 45%)
I don't know enough about fructose and being lean and cut to comment on that physiology.
But you get the point? It never works to say "[x] is healthy/unhealthy" without considering individual biochemistry. (And for that matter, without also considering how x was raised and processed.)
Most of the carbs in sweet potatoes is starch, which breaks down to pure glucose. Fruits generally don't have much starch. If you calculated the ratio of fructose to total carbs for sweet potato, it would be very small compared to that of fruits.