Corollary to last week’s column on how a high carbohydrate diet may be less healthy in the long term and not better than adding fats in the diet, it may be important to have an understanding of the fructose content and glycemic index of various food, including fruits and vegetables.
Recent scientific researches have also shifted the paradigm on what food are really healthy and what food are not so healthy.
Dr. Augusto Litonjua, the acknowledged “Father of Philippine Endocrinology” and founding president of the Philippine Center for Diabetes Foundation (PCDEF), and Dr. Robert Lustig, from the Institute for Health Policy Studies, University of California, San Francisco, recently jolted the local medical community with their lectures citing recent studies showing that we were looking at the wrong culprit all this time.
The two experts emphasized that a moderate amount of fat in the diet is good as a more efficient source of energy for most of the ordinary bodily functions. Our brains can’t function well without sufficient fats, too.
It’s not the fat that makes us fat or gain weight, but the high fructose we consume, they explained.
Dr. Litonjua added that a higher health risk is caused by excessive consumption of food products rich in fructose, a type of sugar found in fruits and sweetened food products and beverages.
Hence, the proposed additional taxes on sugary drinks are not really intended to generate more revenue, but to protect the population’s health.
We used to think that all fruits are healthy, but if we regularly eat fruits with high fructose content, we shouldn’t wonder why we’re gaining weight and increasing our blood sugar levels, on top of other abnormalities lumped together as the metabolic syndrome.
Common high fructose fruits include all dried fruits, watermelon, grapes, apples, pears, cherries and blackberries.
We should consume more fresh, low-fructose fruits like avocados, cranberries, grapefruit.
Bananas are borderline, while mangoes, jackfruit are moderate; and peaches, raisins, dates and prunes have relatively high fructose content.
High glycemic index
Generally, fruits with high fructose content also have a high glycemic index or GI, but in some instances, this may not be so.
The GI measures how a fructose and carbohydrate-containing food raises blood glucose. Therefore, food with a high GI raises blood glucose (sugar) more than food with a medium or low GI. Various food are ranked compared to a reference food, which is either glucose or white bread.
It doesn’t mean that we should avoid all fruits and vegetables (yes, some vegetables can also increase blood sugar). We just have to plan our meals by choosing food with low or medium GI, or balancing the food with various GI contents.
We can combine high GI fruits and vegetables with low GI food to help balance the meal. But if we’re overweight or diabetic, we should eat less high GI food, and more low GI fruits and vegetables.
There’s no GI grading for meats and fats because they do not contain carbohydrate.
Carbohydrate-containing food with a low GI include monggo, dried beans and legumes such as kidney beans and lentils, all nonstarchy vegetables, many whole grain breads and cereals including whole wheat bread, rye bread, and all-bran cereal.
Most fruits and vegetables have a low to acceptable GI. So if you’re not sure what the GI of a fruit or vegetable is, just go ahead and eat a moderate portion of it. I believe its fiber and antioxidant content should be able to compensate for its relatively high GI content.
Most fruits are also rich in pectin, which slows down absorption of carbohydrates and modulates its impact on the blood sugar levels.
Watermelon has highest GI
Contrary to what many think, the fruit with the highest GI is watermelon. Ripe cantaloupes also have a GI close to watermelon. Moderate GI fruits include: pineapple, cherry, mango, papaya, kiwi, cantaloupe.
We should also eat in moderation many canned fruits, dried fruits such as raisins, dates and dried cranberries.
Fortunately, most of the fruits we commonly eat have a low GI such as bananas, oranges, grapefruit, pears, strawberries.
Surprisingly, grapes have a high fructose content, but its GI is moderate to low in level, probably due to its rich fiber and antioxidant content.
Most vegetables have a very low GI, but a few starchy vegetables such as potatoes (especially sweet potatoes) and cassava register high GIs.
Other vegetables with moderate GI include squash, yams, pumpkin, beets and sweet corn.
All the other vegetables have low GI including nonstarchy vegetables, and raw carrots, which I’m fond of.
We need to emphasize, though, that the GI, just as determining the fructose content of the fruits we eat, is just one tool to guide us. Everything has to be taken in moderation, aiming for a proper balance of food. Even low to moderate GI food, taken in excess, can also derange our blood chemistries and make us put on weight.
So, having said a lot about high fructose and GI food, I believe that this should be a major concern only for people who are overweight or obese, diabetic, and those diagnosed with metabolic syndrome.
If one is lean with no risk factor for diabetes and the metabolic syndrome, I believe that the fructose content of fruits and vegetables is not a major issue.
At the end of the day, finding the right balance of all food sources of carbohydrates, fats and protein makes the ideal diet for most of us.
Nutrition experts advise us to choose food that are nutritionally dense, meaning food that are rich in nutrients for the number of calories they give. Most fruits and vegetables fulfill this criterion, so eating more of them, and the widest variety at that, should be a healthy dietary choice.