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Thursday, June 20, 2013

FRUIT IS YOUR FRIEND


Fruit is nature's prize. It is sweet, delicious, juicy, convenient and, exotic fruits and berries aside, generally affordable.

Think of it in the grand picture. What is the purpose of fruit, that love child of the tree? Just as peacocks and other animals (including humans) try to increase fitness by appearing as physically appealing as possible, trees also have an interest in perpetuation of their species, and to this end they create the most colorful, juiciest, sweetest bulbs of pleasure they can, encasing in them their seeds, in the hopes that animals (not just squirrels but us too) will be enticed by them, eat them, maybe transport them, possibly discard them in fertile ground, and in months years or decades, a new tree will spring. And the new tree, with its green leaves, converts carbon dioxide to oxygen for us to breathe. And so the cycle of life perpetuates itself.

It's sometimes difficult to remember this if you don't garden or have a tree or at times pick your own fruit. And for some, eating fruit may be considered off limits or, gasp, a health risk. In fact, some experts recommend limiting fruit consumption to just one piece per day. They say that the sugar fructose, due to its effects on the liver and metabolism, should be avoided, limited to 10 or 15 grams per day in some people, which is the equivalent of one or two apples. One or two apples? For the whole day? What about oranges, and melons, bananas, dates, figs, persimmons, berries, grapes, and all the other fruits nature provides? How can nature's perfect food be off limits? It's like creating a ban on water or sunlight.

So we looked at the literature and examined what the recent findings suggested about fructose, fruit sugar.

First a little background. Fructose is so named because it is the main sugar in most fruits, especially apples, pears, berries, and dried fruits. But fructose is also present in some vegetables, as well as natural sweeteners (honey) and artificial sweeteners (the much maligned high fructose corn syrup, or HFCS). And sucrose, or table sugar, which is in virtually every sweet carbohydrate under the sun (grains, processed foods, many vegetables, even beans contain some sucrose), is equal parts glucose and fructose.

A little physiology/biochemistry. When you eat fructose, it gets absorbed not by active transport (like glucose) but by passive diffusion, which requires less energy, making it easier to digest. And because it is farther down the sugar breakdown pathway (also known as glycolysis) it is more rapidly converted to energy (ATP).
So far, so good, yes? Would it surprise you then to hear that experts say that because of these hallmark traits (ease of absorption/conversion to energy), fructose should be avoided. It's like saying avoid the sun because it is the best source of vitamin D. Crazy! But this is what is often said: Too much fructose, because of its ease of digestion, can be converted to fats, causing fatty liver, metabolic syndrome, contributing to diabetes, and obesity, and a host of other health issues. Is this true, or are these claim scare tactics?

First, a bit more background.

Sugar consumption has come under increased scrutiny as the number of overweight and obese Americans has skyrocketed. But the factors that can lead to weight gain are complex and multifactorial. Foods are more available than ever, and the diversity of foods continues to expand. In fact, over 10,000 new grocery items are introduced annually. Food expenditures have increased, and people are buying more food to please tastes rather than nourish cells. Therefore sugar consumption is only 1 part of the complex dietary component of trends in overweight, and even within the realm of sugar consumption, it is not fruit that should be implicated but soft drinks and other sweetened beverages, which account for the largest percentage of total average daily intake of added and total fructose. Thanks, HFCS!

These days Americans are eating more fructose than ever.  The average daily intake is around 50 grams per day, and fructose intake increased in all gender and age groups since 1978.
Fifty grams a day. Now, an apple has 10 grams of fructose. So that would mean people are eating 5 apples a day? When was the last time you had more than one? Of course most people are getting their fruit sugar in coke, gatorade, and other processed drinks. But even the fructose present in soft drinks, divorced from fiber and nutrients as it is, may not be the bad guy some experts believe.

We've borrowed this from an article summarizing recent findings and published in the periodical "Advances in Nutrition":

"Recent research reviews have reported that fructose consumption up to the 90th percentile population consumption level in either healthy weight or obese individuals does not result in increased triglycerides or weight gain. No adverse effect on triglycerides or weight was observed in multiple trials using fructose at up to the 95th percentile population consumption level. Meta-analyses also documented that no increases in blood pressure or propensity toward obesity occurred at up to the 90th percentile population consumption levels of fructose. A recently completed trial in our research laboratory involving 352 overweight or obese individuals who consumed up to the 90th percentile population consumption levels for fructose as part of mixed-nutrient, eucaloric diets did not show any adverse effect on total cholesterol (P = 0.88) or LDL cholesterol (P = 0.85). A significant 14% increase in triglycerides was noted, although it must be emphasized that triglyceride levels remained within the normal range both before and after measurement."

To summarize: No metabolic derangements in fructose intake at or above the 90th percentile, which is 75 to 100 grams of fructose per day, equivalent of about 10 bananas or 10 apples. (Once again, the scientists were not using apples and bananas but rather a liter of sugar water.) And simple physiology/biochemistry bears this out. The vast majority of the fructose that is metabolized in the liver is converted into glucose, glycogen, lactate, and carbon dioxide. Fifty percent fructose is converted in the liver to glucose, 25% to lactate, and 15% to 18% to glycogen. Glycogen is a storage form of sugar. A few percent of ingested fructose is metabolized to carbon dioxide. Only a very small percentage (on the order of 1%–5% depending on the specific conditions used and underlying nutritional and metabolic status of individuals studied) is converted to free fatty acids.


 
Even in settings of extreme carbohydrate overload, only a small percentage of carbohydrates is converted into fats. In one experiment in which individuals were fed over 1,500 extra calories per day in excess carbohydrates, only about 3 grams of fat was generated. Other studies showed that healthy individuals who were fed 1 g/kg of fructose did not experience increased liver fat. Yet another study found similar results in individuals who consumed 30% of energy from fructose over a 4-week time frame.

Had enough science and stats? Let's fast forward to the article's concluding paragraph:

"In conclusion, recent randomized clinical trials have suggested that there are no adverse effects on total cholesterol, LDL cholesterol or HDL cholesterol at amounts ranging up to the 90th percentile level of fructose consumption. Taken together, these findings suggest that we must be very cautious when attributing adverse health consequences to the consumption of fructose...particularly at normal population consumption levels. "

Fruit is too tasty and nutritious to be avoided. Indeed it should make up a large portion of the calories you consume. Many can go as high as fifty percent or more. In addition to fructose, fruit (and legumes) contain prebiotics. These non-digestible carbohydrates (insoluble fiber) make their way through the gut and help good bacteria grow, multiply, and flourish. Good bacteria are probiotics.  Prebiotics? Well, prebiotics feed them and keep them healthy, and then they in turn keep you healthy.

And so, the fructose present in fruit, far from posing any threat to your health, is a natural source of rapidly-absorbable, easily-convertible energy delivered in a sweet, juicy, vitamin-rich and colorful casing which combines with the priobiotics, fiber, water and other nutrients to maximize your health and longevity. Pick yourself up some today, and tell a friend!

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