April 19, 2013

Can Fruit Make Us Fat?

By now, most folks are aware that high fructose corn syrup (HFCS) was a bad idea for a country suffering from an obesity epidemic.

Even the food industry has gotten the memo loud and clear, and the HFCS in soft drinks and sweetened comfort foods is being replaced by cane sugar.

What many of us don’t know is that the fructose in HFCS has the same fructose that’s in your fresh-squeezed fruit juice.

But fruit is good for you, right?

Of course, it is undeniable that fruits contain antioxidants, vitamins, minerals, and phytonutrients that can be very protective as part of a balanced, whole foods diet. What goes unmentioned is that too much fruit can wreak havoc on blood sugar and can undermine efforts to maintain a healthy weight.

I know it is hard to believe, but fruits can make you fat!

Join me as I discuss the Ayurvedic perspective on fruit, and the research behind the top 10 reasons to avoid too much fructose.

Fruits in Nature

In nature, fruit trees are a treat and there is heavy competition for that fruit. When I was a kid, we had two cherry trees. Every year, they produced a lot of cherries. Yet in all the years growing up with a cherry tree in my backyard, I never ate one cherry. As soon as they were ripe, the birds ate every last one so fast that we never had a chance!

Orchards of apples, oranges, bananas and other fruits, all loaded with fructose, didn’t exist until we created them.

In fact, in one study it was reported that throughout human history we ate about 15 grams of fructose from fruits and veggies a day, which amounts to about three ounces. In 1987, it was estimated that humans consume about 81 grams of fructose per day—that’s nine times more fruit.

So, what’s the traditional role of fruits in nature?

In the late summer and fall, when fruits are most abundant, bears and other animals gorge on them in an attempt to store an insulating layer of fat for the winter. The sweetest, highest-in-fructose fruits were traditionally harvested in the fall as the perfect food to help the animals prepare for winter.

Even nowadays, most of the very sweet fruits are still harvested in the fall. I say “still” because most fruits have been hybridized to be bigger, sweeter, and harvested at a more commercially convenient time. As a side effect, all of the hybridizing has raised the glycemic load of fruits way beyond what it was originally.

Even with these industrial changes, I wonder if the sweetest fruits are best used seasonally to help build insulation before winter and with caution at every other time of year.

Sugar as Energy: Glucose, Fructose and Sucrose

Glucose and fructose are two types of simple sugars. Glucose is the form of sugar that is used for energy by the cells. Fructose, on the other hand, is metabolized completely differently, and is not nearly as efficient a source of energy as glucose.

Regular table sugar, called sucrose, is made up of 50 percent fructose and 50 percent glucose. In the gut, an enzyme called sucrase breaks sucrose down into fructose and glucose. Because sucrose has to be broken down before it enters the bloodstream, it takes a little longer for it to affect the blood sugar.

Glucose and fructose, on the other hand, are simple sugars and do not require an enzyme for absorption, so they move directly into the blood, creating a more immediate spike in the blood sugar.

What got HFCS into trouble in the first place was that it was super concentrated fructose, delivering a whopping 80 percent fructose and only 20 percent glucose.

The body is designed to get energy primarily from glucose and very little from fructose. Glucose in healthy doses is quickly used by the body to make energy. Fructose, on the other hand, is quickly stored by the liver to be used for energy when needed in the future. The cells’ mitochondria, the brain and the muscles all need glucose—not fructose—to function.

Healthy sources of glucose include whole grains, vegetables, legumes and smaller amounts of fruit.

10 Reasons to Limit Fructose in Your Diet

1.    Fructose can only be metabolized by the liver. It is not readily used for energy by your body’s cells. It takes a long time for the body to convert fructose into energy and, moreover, it can interfere with glucose metabolism, which is the body’s preferred energy source (1).

2.    Bears gorge on fruits in the fall to store fat for the cold and dry winter. Unlike glucose, the liver converts the fructose directly into fat and can lead to excess fat, obesity and lipoproteins in the body (1).

3.    Excess fructose can raise triglycerides and increases the risk of arterial damage and cardiovascular disease. Fructose will increase the bad cholesterol that deposits fat in the cells and will decrease the good cholesterol that removes bad fats from the blood and cells. This can lead to plaque building up in the arteries and the heart (2).

4.    Fructose sticks to proteins and fats in our bodies 10 times more than glucose (3). This is called glycation and creates something called AGEs (Advanced Glycation End-products). AGE’s are responsible for much of the body’s inflammation and degeneration. They are also linked to hypertension, dementia, insulin resistance, and diabetes complications.

Glycation is a process of proteins and fats sticking to excess sugar in the blood. The proteins that they are most likely to bond with are collagen and elastin. These are the two proteins responsible for healthy radiant skin. When the skin that lines the gut, your arteries and respiratory tract begins to wrinkle, it is just a matter of time before the skin on the outside of the body thins and wrinkles as well.

5.    Excess fructose will turn to fat and congest the liver, causing a condition called non alcoholic fatty liver (4). This is a condition that affects 20-30 percent of the adult population and is directly linked to insulin resistance, diabetes, chronic inflammation, and metabolic syndrome (see below).

Non alcoholic fatty liver was two to three times more prevalent with fructose consumption than with non-fructose controls (4). In fact, fructose has the same effect on the liver as alcohol (ethanol), which is already well known as a liver toxin (7).

6.    Fructose is linked to hypertension (5). Hypertension is part of a group of symptoms associated with metabolic syndrome (see below). Excess fructose inhibits an enzyme that manufactures nitric oxide in the arteries (5). Nitric oxide is a natural dilator for the arteries and is critical for healthy arteries and the prevention of coronary artery disease.

7.    Excess fructose in the diet is linked to increased risk of metabolic syndrome, which is a combination of the following (1):

  • High Blood Sugar
  • High Blood Pressure
  • Abdominal Fat—linked to obesity
  • High Cholesterol

Metabolic syndrome can lead to:

  • Diabetes
  • Obesity
  • Heart Disease
  • Dementia
  • Cancer and more

8.    Excess fructose leads to insulin resistance, which can lead to Type 2 Diabetes or prediabetes (4).

9.    Too much fructose rapidly causes leptin resistance. Leptin is a hormone that controls appetite and metabolism to maintain a normal weight. Leptin-resistant people tend to gain fat and become obese much easier than those who are not leptin resistant (7).

10.    While most of your body’s cells can’t use fructose as a source of energy, undesirable in the gut can use fructose to proliferate (7). Cancer cells can also feed on fructose (7).

In Conclusion: The Skinny on Fruit

There is no question that whole foods including fruits, veggies, nuts, seeds and whole grains are all part of a healthy and balanced diet. The issue here is the excess of sucrose and fructose in a modern diet. This excess has caused an epidemic of the blood sugars and diabetes around the world. I am a fan of self-monitoring blood sugar levels so you can get daily feedback regarding your diet and lifestyle. Like most health issues, early detection of a rising blood sugar issue is key, and will then guide how much or how little fructose or sucrose we should ingest.

If your blood sugar is in the healthy range (between 70 and 85 mg/dl), one to two fruits a day is fine, as long as they are seasonal. Reserve the really super-ripe and sweet fruits for the fall, when the body is naturally trying to insulate for winter.

Avoid dried fruit and fruit juices and opt for the whole, fresh fruit to make sure you have plenty of fiber from the pulp of the fruit to buffer the glycemic load in the body.

If your blood sugars are climbing above 85 mg/dl, more awareness around fruit consumption is necessary. I recommend using the least sweet fruits sparingly and avoiding very sweet fruits like grapes, bananas, sweet cherries, mangoes, pears and kiwi altogether until your sugars stabilize. Please refer to the Sugar Content of Fruit chart below.

Sugar Content of Fruits (Fructose, Glucose, Sucrose sugars per 100 grams)


0.    Basciano H. Fructose, Insulin Resistence. Nutri Metab (London) Feb 2005.
1.    Tokita Y. Fructose Ingestion enhances atheroslerosis. J Atheroscler Thromb. 2005
2.    Gaby A. Adverse effects of dietary fructose. Alt Med Review. 2005. Dec
3.    Ouyang X. Fructose consumption is a risk factor for non-alcoholic fatty liver. J Hepatol. 2008 June
4.    Plante GE. Reduction of endothelial NOS. Cardiovascular Research. 2003 Oct.
5.    Taylor EN. FRuctose consumption and the risk of kidney stones. Kidney Int. 2008 Jan
6.     Paleodietlifestyle.com

All photos courtesy of lifespa.com



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Ed: Brianna Bemel

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