A higher intake of vitamin C is essential for people with insulin resistance and metabolic syndrome, both of which are early stages of type 2 diabetes. The reason for this, according to scientists from Oregon State University in the United States, is that vitamin C is a powerful antioxidant that helps protect against the damage that oxidative stress causes to our cells and cardiovascular system. The question is, how do we make sure to get enough vitamin C, and is eating loads of fruit and drinking a lot of juice a good or bad solution?
An estimated 35% of Americans have metabolic syndrome. It is a global epidemic, and many people who are overweight and struggle to lose weight are not aware that they suffer from the disease. Metabolic syndrome is when you suffer from at least three of the following problems:
- Insulin resistance and elevated blood sugar levels
- Large waist circumference (excess body fat around the stomach)
- High blood pressure
- Low levels of HDL (High-Density Lipoprotein)
- Elevated triglyceride levels
People with metabolic syndrome often feel a strong craving for sweets and fast carbohydrates, which is a result of having insulin resistance, where the cellular uptake of blood sugar is impaired. This causes the pancreas to produce more insulin, but because the body does not respond properly to the insulin it produces, levels of both insulin and blood sugar remain elevated. The permanently elevated insulin level turns into a health threat, because excess blood sugar is stored as fat instead of being processed into energy. Most of the fat is stored as visceral fat around and in between the vital organs, which sets the stage for inflammation and free radical activity.
Metabolic syndrome, an early stage of type 2 diabetes, is thought to be the leading cause of atherosclerosis (also in the coronary arteries), stroke, blindness, and kidney diseases. Moreover, people with metabolic syndrome are already prone to atherosclerosis and various other complications that follow in the wake of elevated insulin and other metabolic disorders.
Metabolic syndrome, oxidative stress, and cholesterol levels
Metabolic syndrome is characterized by oxidative stress, which is a biochemical imbalance between harmful free radicals and protective antioxidants. Free radicals are some very aggressive molecules with an unpaired electron, which causes them to snatch electrons from other molecules. One of the most dangerous effects of free radical activity is when free radicals attack the polyunsaturated fatty acids in cell membranes, setting of a chain reaction that spreads to other cells. The phenomenon is known as lipid peroxidation.
What is important to remember with cholesterol is that it is an essential compound and a biological element needed to build cell membranes. We also need cholesterol in order to make sex hormones, stress hormones, vitamin D, and coenzyme Q10. The liver produces most of the cholesterol needed for these functions and it regulates its own production accordingly. So, in other words, cholesterol is essential and serves a number of vital functions. It only becomes a threat if free radicals attack the cholesterol, thereby initiating lipid peroxidation. When that happens, a type of white blood cells known as macrophages gorge on the oxidized cholesterol, after which they turn into something called foam cells. These foam cells are slowly embedded in the blood vessel walls as atherosclerotic plaque.
The only things that can protect us against this are different antioxidants such as vitamin A, vitamin C, vitamin E, vitamin B6, selenium, zinc, and various plant compounds. Vitamin C is particularly important in connection with metabolic syndrome.
Gut flora, immune defense, and vitamin C
The Oregon State University researchers explain that unhealthy diet habits can lead to imbalances in the intestinal flora and impaired digestive functions. Cell walls from dead bacteria leak from the gut and migrate to the bloodstream. Here, the most dominating class of white blood cells, the neutrophilic granulocytes, attack the cells walls as if they were dangerous bacteria. To carry out their attack, the granulocytes use hypochlorous acid, which also destroys vitamin C. In other words, the body destroys its own vitamin C, which normally has a number of different functions.
Vitamin C is a crucial antioxidant with a number of important functions, including the ability to protect vitamin E. However, oxidative stress and lipid oxidation consume large quantities of vitamin E (it is used for antioxidant protection), and vitamin C is then able to regenerate it. If there is too little vitamin C to undertake this function, vitamin E is lost. That way, the body loses both vitamin C and vitamin E in the process, the problem tends to reinforce itself.
Another thing, which the Oregon State University scientists have observed is that even if people with metabolic syndrome eat the same amount of vitamin C as healthy people, their plasma concentration of vitamin C is lower. This is a sign that they have an increased need, which is most likely higher than the officially recommended intake level.
Sources of vitamins C and E and recommended intake
Fresh fruit and vegetables, berries, and spices are good sources of vitamin C. The official recommendation for vitamin C intake in the United States is 65-90 mg. In Denmark, the reference intake (RI) level is 80 milligrams. According to the new study from Oregon State University, eating five to 10 servings of fruit and vegetables daily ensures enough vitamin C and fiber for a healthy intestinal flora. It is important not to eat too much fruit, as it contains a lot of fructose (sugar) that can burden the liver and set the stage for metabolic syndrome and type 2 diabetes.
Fructose plays an overlooked role in the development of metabolic syndrome and diabetes
We get fructose from fruit, honey, refined sugar, cane sugar, wine, and high fructose corn syrup (HFCS). Fructose and glucose are normally combined in various food sources, and the two types of sugar are broken down in the digestive system. However, the uptake and utilization of the two sugars differ widely and that is very important. Glucose is absorbed very fast in the blood in order to ensure fast energy for muscle and brain activity. Fructose continues directly from the intestine to the liver, where most of it is stored. In other words, fructose does not provide fast energy.
If you consume too much fructose, you risk flooding the liver cells, and excess fructose is stored as fat. The liver turns into a “fat factory” with a disturbed lipid metabolism (known as lipogenesis). Consuming large amounts of fructose can lead to metabolic syndrome, fatty liver, and type 2 diabetes.
Eat fruit – but don’t overdo it
Fruit contains a lot of fructose. One glass of orange juice contains the same amount of sugar as a soft drink. If you want to lose weight, or if you suffer from metabolic syndrome or type 2 diabetes, you should avoid consuming too much fruit, especially if it is in the form of juice or smoothies. It is better to eat vegetables, and many vegetables sources actually contain more vitamin C than apples and oranges.
Content of vitamin C in mg/100 gram
Vitamin C from food and supplements
It is a good idea to consume a diet with plenty of foods rich on vitamin C, as this also contributes with fiber and other nutrients. When choosing vitamin C supplements, you are better off with non-acidic supplements that are gentle towards the stomach. One tablet with 500-750 mg of vitamin C provides the same amount of vitamin C as you would get from 6-8 oranges or 50-75 apples (depending on their size)
Maret G. Traber et al. The Relationship Between Vitamin C Status, The Gut-Liver Axis, and Metabolic Syndrome. Redox Biology 2018
Bernadine Ruiza G Ang and Gracia Fe Yu. The Role of Fructose in Type 2 Diabetes and Other Metabolic Diseases. Journal of Nutrition & Food Science 2018
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