Saturday, February 1, 2014

The Case For and Against Fruits: Are Fruits Healthy? Are They Good for a Diet? Is There A Best Time To Eat Them?

Fruits have been around a really long time. Most anthropologists and evolutionary biologists believe that the diet of early man consisted mainly of fruit, until such time when we diversified our food consumption by becoming hunter-gatherers and then eventually farmers. Even as access to fruits sometimes became limited due to climate change, it never completely disappeared from the human diet. But some people now argue that it should.

The anti-fruit crowd highlight four major arguments against fruits available today.

Argument 1: Fruits are contaminated and nutritionally depleted.

First, they claim that fruits have been so genetically modified and tainted by man-made chemicals that they no longer contain sufficient nutrients to meet human needs for such nutrients or that you should only eat them if they are organic. These arguments are usually put forth by pill-pushers who want you take to a pill instead of, or in addition to eating fruits.  To the former point, I say that my own extensive review of the scientific literature supports that fruits have been altered, but that they still contain more than sufficient nutrients to meet our daily needs, particularly if you eat even a few servings per day.

As to the organic issue, it's really a question of money. No rational person can argue that there is something good to be gained from eating something that has been exposed to pesticides, herbicides, fungicides, and other man made chemicals, and/or has been genetically modified.  Although the specific harms from these chemicals is still hotly debated, if you can afford to avoid them, you should surely do so, especially the Environmental Working Group's "Dirty Dozen." (See http://www.ewg.org/foodnews/)  If not, then rinse very carefully. I tend to rinse my blueberries at least three times under pressure before having them for breakfast.


Argument 2: Fruits are high in a sugar called fructose and that is not good for your liver, lipid levels, and diabetes

The next reason often given for avoiding fruits is their high fructose content. First of all, not all fruits have the same amount of fructose (For a more detailed description of how the body processes fructose, please read the American Journal of Clinical Nutrition primer found at



To summarize the primer, the pancreas doesn't react to fructose until is is metabolized like it does to sucrose and glucose. Moreover, we don't need any dietary fructose to function.  However, even though fruits have fructose, the fructose is interwoven with the fruits' fiber and is therefore digested more slowly than fructose from other sources. Please note, fructose and high fructose corn syrup are two completely different beats. The latter should be viewed as extremely harmful like a man with a loaded gun.

Therefore, contrary to the advice of pundits that state you can eat all the fruits you want because of the robust nutrient content including various vitamins, minerals, antioxidants and other synergistic nutrients, fruits should be a staple of a healthy diet, but only eaten in moderation. Weight Watchers is simply wrong to assign fruits '0' points, In fact, type two diabetics are told to limit their fruit intake to no more than 15 grams at a sitting because more than that may be problematic. (That's a whole other topic for another day.)

Nevertheless, fruits have plenty to offer, particularly in regards to antioxidants, but do note, that many, if not most, of the same healthy nutrients found in fruits can also be found in vegetables. For examples, the beta-carotene in melons can be found in carrots and yams; lycopene in watermelon can be found in tomatoes (although technically a fruit because it grows on trees,); anthocyanins in blueberries can be found in eggplant; phytosterols and polyphenols can be found dispersed in both groups. The list goes on.

Fruit skins can be good sources of insoluble fiber, helping move things along in the gastrointestinal track and can also contain flavonoids, which are plant secondary metabolites that have antioxidant capabilities that may diminish inflammation. Fruits are also contain other not as fully studied nutrients, like pectins, B-Cryptoxanthin, and A-carotene, which can be in apples. As with other nutrients, they also occur in vegetables.  One area of limited research is the synergistic affects of all the different nutrients found in all the different fruits.  Either way, fruits are a tasty and sweet alternative to less desirable man-sweetened foods.

Argument 3: Fruit calories add to weight gain

The final argument against fruits is the calories they contain. It's true, virtually everything we eat contains calories and fruits are no exception. Even though the theorem of calories in/caloires out is not perfect because not all calories are processed the same because of the fiber content of the food they come from, it is true that fruits, if eaten in large quantities can contribute to weight gain.  It's not the fruits themselves that are causing the weight gain; its the totality of what you are eating.  So as long as you go easy on other foods, your weight loss plans can easily accommodate some measured amount of fruit calories.

Argument 4: They can only be eaten before meals as they will ferment in your intestinal tract after meals

It is simply a myth that you can't eat fruit after meals. You can.  The fermentation arguments are pue rubbish. I searched the entire clinical study database back to the 1950s and couldn't find a single valid study to support such nonsense.
(Don't take my word for it. Read this from the University of Missouri:



The flip-side: Eat only fruits

Some people have gone to the other extreme and have taken to a mostly fruit diet. Steve Jobs tried and failed to cure his cancer with a mostly fruit only diet.  (See my previous blog on fruits and cancer prevention, which can be found at http://mdprevent.blogspot.com/2012/11/do-fruits-and-vegatables-prevent-cancer.html)

These fruit obsessed dieters claim they possess more energy and feel healthier. This is not surprising because the fructose in fruit is a carbohydrate that fuels energy. But as I wrote above, too much fructose is not a good thing as it can overwhelm the liver and eventually raise blood glucose to levels that precipitate large amounts of insulin release that can predispose to diabetes. Fructose breaks down to substances that can lead to glucose or blood sugar production.

My four golden rules of eating healthy

So in summation, let me finish with my four golden rules of eating healthy.

1. Don't eat more than you need to feel reasonably full.
2. Make sure that the combination of foods eaten over a course of a week contain all the essential nutrients your body needs to function properly.
3. Avoid or severely limit exposure to chemicals and highly processed ingredients stripped of most nutrients, and definitely avoid products that contain many of such ingredients rolled into one.
4. Loosely monitor your total salt, fat, sugar of any kind including fructose, and calorie intake to levels that work for your body. If you are not sure what those levels are, discuss them with your physician.

The final analysis

Fruits have been a staple of the human and pre-human diet for time immemorial.  Yes, its true that fruits may not be of the same nature and quality than they were tens or hundreds of thousands of years ago, but they are still awfully darn good. They offer many key essential nutrients, but as with most foods, you can overdue eating them.  They are a good part of a comprehensive approach to healthy eating.

By the way, do avoid fruit juices that are robbed of most of the fruits' fiber and have concentrated fructose.  However, contrary to the popular belief, the reason to avoid fruit juices is not because fruit lose most of their nutritional value during the juicing process. (See
http://www.ncbi.nlm.nih.gov/pubmed/9806122)

So now that you know the facts, you can figure out when and how much to eat, and enjoy fruit on your own.  Bon Appetite.

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