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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.
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 fruit can, in excess along with the wrong foods, 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. However, if eaten correctly, they can help you lose weight and be incredibly healthy. Let’s find out how!
Join me as I first discuss the Ayurvedic perspective on fruit, and then explain the top 10 reasons to avoid too much fructose and how to eat as much fruit as you like and get healthy.
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 3 ounces. (1) In 2011, it was estimated that humans consumed about 55 grams of fructose per day (73 grams for adolescents) – that’s almost 4 times more fruit for adults and almost 5 times more fruit for adolescents. (1) Most of this was fruit juice, which is concentrated sugar and fructose. The skins of most fruits have natural blood sugar-regulating chemicals such as the phloridzin in apple skins.
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. If we eat sugar, carbs, fruits, or fat in excess, this excess fuel can be stored as fat in the body. 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.
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 as glucose as a source of energy.
Regular table sugar, called sucrose, is made up of 50% fructose and 50% 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 as much as 80% fructose and only 20% 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, burns much slower as a fuel and 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.
Ten Reasons to Limit Fructose in Your Diet
Before I tell you why fructose may be a problem when you overeat it, let me explain one very important point that changes all the rules. According to Ayurveda, it is said that fruit should only be eaten by itself. Think about it. If you were a hunter-gatherer and you stumbled across a blueberry patch or an apple tree, you would probably eat as many of those apples and blueberries as possible in that one sitting before a large bear decided to move you aside and take over.
When you eat fruit with other foods, like adding fruit to your granola, this is not a terrible thing but the body tends to burn the granola first, which is loaded with glucose, as a quick source of fuel. The fructose in the fruit is typically stored as fat for insulation or for a fuel supply down the road. If you were to only eat the fruit and there was no other source of glucose fuel, the body would then be forced to slowly burn the fructose as a fuel. Neither glucose nor fructose are optimal in excess, especially because fructose burns slower when we combine fruits with other starches. (This means we can easily overshoot the energy intake runway, and both the excess glucose and fructose can then become harmful—the issue is over-consumption, which can negatively affect our health.)
This is why when folks fast on fruit juice, their blood sugar stays stable and they lose weight. When we overload the body’s fuel supply with more glucose and fructose than we need, the body tends to store the extra as fat. Since the fructose requires a long process in the liver to convert it into energy, the body generally uses up all the available glucose before it chooses to burn the fructose. So, when eating fructose in excess along with the other foods in your diet or at the same meal, only then is the excess fructose implicated in the following list of health concerns.
The problem for most folks regarding eating the fruit alone is that it is not enough food to fill you up. This is likely due to the fact that on average, Westerners eat way too much food. One report estimated that we eat 100% more food than we need. (2) This is partially due to the fact that many folks have weak and inefficient digestive systems and need to overeat to feel satisfied. As you reboot your digestive strength through our LifeSpa digestive reset and detox programs, you can find it quite filling to have berries or grapefruits or melons for a breakfast or supper when those foods are in season. In the following science review of the risks of excess fructose, the concerns only exist when eaten with excess sugar, fat, or carbs. To reiterate: whole fruits, on their own, are fine to eat. Processed fructose and fruit juice, or whole fruit in combination with other foods can have negative effects on our health.
1. Fructose is different than glucose in that it 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, which makes it a stable source of fuel. Moreover, in excess, it can interfere with glucose metabolism in the liver, which is the body’s preferred energy source. (3)
2. Bears gorge on fruits in the fall to store fat for the cold and dry winter. Unlike glucose, the liver converts the fructose into fat and can lead to excess fat, obesity and lipoproteins in the body if the fructose is eaten with excess sugar, fat, or carbs. (3) Note: there is a difference between processed fructose (and even fruit juice!) versus the fructose naturally found in whole fruit, which comes with fiber that slows down and reduces the absorption of the sugar in the body. In fact, eating whole fruit on its own has been found to have positive effects on health.
3. Excess fructose can raise triglycerides and increase the risk of arterial damage and cardiovascular disease. Excess fructose can increase the bad cholesterol that deposits fat in the cells and can 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. (4)
4. Fructose sticks to proteins and fats in our bodies 10 times more than glucose. (5) This is called glycation and creates something called AGEs (Advanced Glycation End-products). AGEs 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 the 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 and 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 can turn to fat and congest the liver, causing a condition called non-alcoholic fatty liver. (6) This is a condition that affects 20-30% of the adult population and is directly linked to insulin resistance, diabetes, chronic inflammation, and metabolic syndrome (see below).
Non-alcoholic fatty liver was 2-3 times more prevalent with fructose consumption than with non-fructose controls. (6) In fact, fructose has been shown to have the same effect on the liver as alcohol (ethanol), which is already well-known as a liver toxin. (9) One study cites fructose as “alcohol without the buzz,” showing how it can lead to cellular dysfunction, aging, and over-consumption of food. (7)
6. Fructose is linked to hypertension. (8) 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. (8) 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: (3)
- High Blood Sugar
- High Blood Pressure
- Abdominal Fat
- High Cholesterol
Metabolic syndrome can lead to:
- Heart Disease
- Cancer and more
8. Excess fructose is linked to insulin resistance, which can lead to type-2 diabetes or pre-diabetes. (6) It is also linked to an increased risk of kidney stones. (9)
9. Too much fructose can rapidly cause leptin resistance. Leptin is a hormone that controls appetite and metabolism to maintain a normal weight. Leptin-resistant people tend to build fat and become obese much easier than those who are not leptin-resistant. (10)
10. While most of your body’s cells can’t use fructose as a source of energy, undesirable bacteria in the gut can use fructose to proliferate. (11) Cancer cells can also feed on fructose. (12)
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 contributed to causing an epidemic of the blood sugar imbalances and diabetes around the world. I encourage my patients to self-monitor their blood sugar levels to get daily feedback regarding their diets and lifestyles. Like most health issues, early detection of a rising blood sugar issue is key, and can 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), 1-2 fruits a day is fine, preferably when they are fruits that are in season. 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.
Finally, if you are going to eat lots of fruits, I totally support that, but consider eating them alone so you give the fruit ample time to convert the fructose into energy. Please refer to the Sugar Content of Fruit chart below.