Friday, April 11, 2008 by: Leigh Kirk
| Key concepts: vitamin C, RDA and fruits
Vitamin C. Mmmm . . . maybe you think of a tall glass of Florida orange juice. Or maybe you grab it at the beginning of the cold season. But would you associate it with cardiovascular disease (CVD) or cancer? Maybe you should. According to an article published in October 2007, in the Journal of Nutrition, there is accumulating scientific evidence that very large (therapeutic) doses of vitamin C may be effective in treating both CVD and cancer. In addition, some scientists have hypothesized that the onset of these common degenerative diseases may actually be due to a vitamin C deficiency in the general population. Dr. Steven Hickey and Dr. Hilary Roberts with the Vitamin C Foundation and authors of the book 'Ascorbate: the Science of Vitamin C', have gone so far as to suggest that heart disease is actually a chronic form of the vitamin C deficiency disease called scurvy.
Vitamin C, found in a variety of fruits and vegetables, is essential not only for our good health, but our very survival. Without vitamin C, human beings will certainly die of scurvy, a disease characterized by bleeding gums, skin discolorations from small ruptured blood vessels, easy bruising, joint pain, loose and decaying teeth, and hyperkeratosis of hair follicles. But along the continuum of health, there is a difference between survival and optimal human health. The real question is how much vitamin C is required for optimal health?
Vitamin C has many essential roles in the body. It is required for the synthesis of collagen, which is a main structural protein in our bodies, giving support to our tissues, including strengthening our blood vessels, ligaments, tendons, bone, and teeth. It is also required for synthesis of hormones, neurotransmitters, and other important substances needed for metabolism. In addition to these functions, vitamin C is a powerful antioxidant. It neutralizes free radicals before they have a chance to damage our cells. Vitamin C is arguably one of the most important antioxidants in our human physiology for its versatility and wide ranging presence.
How Much?
The government’s Recommended Daily Allowance (RDA) is defined as the daily amount of a nutrient considered sufficient to meet the requirements of most healthy individuals. For Vitamin C, it is 75 mg/day for adult women and 90 mg/day for adult men (smokers are recommended to have an additional 35 mg/day). The current RDA is adequate to prevent death or serious health issues from acute deficiency of vitamin C (e.g., scurvy). The RDA is also adequate for required collagen and hormone synthesis (the RDA is mainly based on this). But to work effectively as an antioxidant, scientists are learning that vitamin C levels need to be significantly higher in our bodies. And the debate now is over how much is needed.
If we ate the recommended 5 servings of fruits and vegetables per day, we’d easily consume double the RDA for vitamin C and likely a lot more. According to Linus Pauling, a two time Nobel Prize winning chemist who is noted for his vitamin C research, our early human ancestors probably consumed 2,300 mg/day to 9,500 mg/day of vitamin C from their plant-based diet. This is 25 to 100 times more than today’s RDA for an adult man!
History
Scientists have determined that about 40,000 years ago humans lost their own ability, through a genetic mutation, to manufacture vitamin C. Our DNA no longer allowed our cells to make an enzyme which is required to produce vitamin C internally. Evolutionary biologists would argue that the mutation conferred a survival advantage. After all, humans could conserve energy by not manufacturing something that was already abundantly available in their diet.
Along the way, our dependence on fruits and vegetables became obvious. In the 1700’s, sailing ships started stocking limes or vegetables to prevent their crew members from dying of scurvy during long voyages. In 1928, Hungarian biochemist, Albert Szent-Györgyi, finally isolated the mysterious substance known as vitamin C. Since then, scientists have been working to understand exactly how vitamin C functions in our bodies.
Beyond Mere Survival
Today, scientific evidence is highlighting a discrepancy between the amount of vitamin C needed to avoid acute deficiency disease and the amount needed for effective antioxidant protection to ward off major degenerative diseases. This hypothesis is based on vitamin C’s function as a powerful, versatile and pervasive antioxidant in our bodies.
Free radicals are molecules with an unpaired electron that make them highly reactive. They “steal” an electron to make up a more stable pair, hence damaging the molecules around them that have had to relinquish an electron. Free radicals have shown to be a significant contributing factor in the development of cardiovascular disease (CVD) and cancer. They can trigger premature cell death and inflammation in our vascular system. They can reduce the availability of nitric oxide which helps maintain healthy artery dilation and blood flow. Free radicals can also oxidize LDL cholesterol. As we’re learning, it’s not so much the LDL cholesterol that’s implicated in the development of heart disease, it’s that the LDL cholesterol has been damaged, or “oxidized”, by free radicals. Free radicals can also cause DNA mutation and damage the supportive structure of our cells which can contribute to the development of cancer.
Many studies have shown that increased vitamin C intakes and increased plasma vitamin C concentrations are correlated with a decrease in degenerative diseases. Scientists have also determined and explained the specific mechanisms by which vitamin C scavenges and neutralizes these free radicals, thus providing powerful protection against free radical damage.
Conclusion
The current RDA may be sufficient to avoid acute deficiency disease but may not be enough to help protect us from free radical damage. A reduction of disease risk has been associated with 5 servings of fruits and vegetables per day, and this is likely due at least in part to their vitamin C content. But the vitamin C content in these servings is easily double the RDA. Scientists researching vitamin C have yet to agree upon how much is required for optimal human health. Their estimates vary and typically start at 400 mg/day and go higher.
Dr. Steve Hickey with the Vitamin C Foundation has published open letters to the Food and Nutrition Board and the National Institutes of Health, laying out the reasons why the current RDA is insufficient and why it should be reexamined and readjusted upward.
In the meantime, we can support our health and reduce our risk of degenerative diseases by making sure not to skimp on our 5 servings of fruits and vegetables per day. We may fortify ourselves with a good quality multi-vitamin supplement for the extra vitamin C it provides.
Vitamin C is a water-soluble vitamin, which means that it is not stored in the body and must be replaced by our diet every day. The Tolerable Upper Intake Level (UL) is the maximum continual intake of a nutrient that is unlikely to cause adverse health effects in almost all people, and for vitamin C the UL is 2 g/day (2,000 mg/day). The most common side effect of taking an amount larger than this is diarrhea. Therefore, healthy individuals have little concern of toxicity if consuming more vitamin C than specified by the RDA.
One word of caution - people who have a high risk of kidney disease, kidney stones, or disorders of iron metabolism should avoid large doses of vitamin C (>500mg). Consult your doctor or nutritionist prior to taking supplementation.
Virtually all fruits and vegetables contain some amount of vitamin C. According to the USDA nutrient database, fruits and vegetables that are among the highest in vitamin C content include: orange juice, grapefruit juice, peaches, peppers (sweet and hot), papayas, strawberries, broccoli, Brussels sprouts, kohlrabi, pineapple, and kiwi fruit. Other fruits noted for their high vitamin C content include: jujube, acerola, camu camu, guava, red and black currants, mango and persimmon.
| Key concepts: vitamin C, RDA and fruits
Vitamin C. Mmmm . . . maybe you think of a tall glass of Florida orange juice. Or maybe you grab it at the beginning of the cold season. But would you associate it with cardiovascular disease (CVD) or cancer? Maybe you should. According to an article published in October 2007, in the Journal of Nutrition, there is accumulating scientific evidence that very large (therapeutic) doses of vitamin C may be effective in treating both CVD and cancer. In addition, some scientists have hypothesized that the onset of these common degenerative diseases may actually be due to a vitamin C deficiency in the general population. Dr. Steven Hickey and Dr. Hilary Roberts with the Vitamin C Foundation and authors of the book 'Ascorbate: the Science of Vitamin C', have gone so far as to suggest that heart disease is actually a chronic form of the vitamin C deficiency disease called scurvy.
Vitamin C, found in a variety of fruits and vegetables, is essential not only for our good health, but our very survival. Without vitamin C, human beings will certainly die of scurvy, a disease characterized by bleeding gums, skin discolorations from small ruptured blood vessels, easy bruising, joint pain, loose and decaying teeth, and hyperkeratosis of hair follicles. But along the continuum of health, there is a difference between survival and optimal human health. The real question is how much vitamin C is required for optimal health?
Vitamin C has many essential roles in the body. It is required for the synthesis of collagen, which is a main structural protein in our bodies, giving support to our tissues, including strengthening our blood vessels, ligaments, tendons, bone, and teeth. It is also required for synthesis of hormones, neurotransmitters, and other important substances needed for metabolism. In addition to these functions, vitamin C is a powerful antioxidant. It neutralizes free radicals before they have a chance to damage our cells. Vitamin C is arguably one of the most important antioxidants in our human physiology for its versatility and wide ranging presence.
How Much?
The government’s Recommended Daily Allowance (RDA) is defined as the daily amount of a nutrient considered sufficient to meet the requirements of most healthy individuals. For Vitamin C, it is 75 mg/day for adult women and 90 mg/day for adult men (smokers are recommended to have an additional 35 mg/day). The current RDA is adequate to prevent death or serious health issues from acute deficiency of vitamin C (e.g., scurvy). The RDA is also adequate for required collagen and hormone synthesis (the RDA is mainly based on this). But to work effectively as an antioxidant, scientists are learning that vitamin C levels need to be significantly higher in our bodies. And the debate now is over how much is needed.
If we ate the recommended 5 servings of fruits and vegetables per day, we’d easily consume double the RDA for vitamin C and likely a lot more. According to Linus Pauling, a two time Nobel Prize winning chemist who is noted for his vitamin C research, our early human ancestors probably consumed 2,300 mg/day to 9,500 mg/day of vitamin C from their plant-based diet. This is 25 to 100 times more than today’s RDA for an adult man!
History
Scientists have determined that about 40,000 years ago humans lost their own ability, through a genetic mutation, to manufacture vitamin C. Our DNA no longer allowed our cells to make an enzyme which is required to produce vitamin C internally. Evolutionary biologists would argue that the mutation conferred a survival advantage. After all, humans could conserve energy by not manufacturing something that was already abundantly available in their diet.
Along the way, our dependence on fruits and vegetables became obvious. In the 1700’s, sailing ships started stocking limes or vegetables to prevent their crew members from dying of scurvy during long voyages. In 1928, Hungarian biochemist, Albert Szent-Györgyi, finally isolated the mysterious substance known as vitamin C. Since then, scientists have been working to understand exactly how vitamin C functions in our bodies.
Beyond Mere Survival
Today, scientific evidence is highlighting a discrepancy between the amount of vitamin C needed to avoid acute deficiency disease and the amount needed for effective antioxidant protection to ward off major degenerative diseases. This hypothesis is based on vitamin C’s function as a powerful, versatile and pervasive antioxidant in our bodies.
Free radicals are molecules with an unpaired electron that make them highly reactive. They “steal” an electron to make up a more stable pair, hence damaging the molecules around them that have had to relinquish an electron. Free radicals have shown to be a significant contributing factor in the development of cardiovascular disease (CVD) and cancer. They can trigger premature cell death and inflammation in our vascular system. They can reduce the availability of nitric oxide which helps maintain healthy artery dilation and blood flow. Free radicals can also oxidize LDL cholesterol. As we’re learning, it’s not so much the LDL cholesterol that’s implicated in the development of heart disease, it’s that the LDL cholesterol has been damaged, or “oxidized”, by free radicals. Free radicals can also cause DNA mutation and damage the supportive structure of our cells which can contribute to the development of cancer.
Many studies have shown that increased vitamin C intakes and increased plasma vitamin C concentrations are correlated with a decrease in degenerative diseases. Scientists have also determined and explained the specific mechanisms by which vitamin C scavenges and neutralizes these free radicals, thus providing powerful protection against free radical damage.
Conclusion
The current RDA may be sufficient to avoid acute deficiency disease but may not be enough to help protect us from free radical damage. A reduction of disease risk has been associated with 5 servings of fruits and vegetables per day, and this is likely due at least in part to their vitamin C content. But the vitamin C content in these servings is easily double the RDA. Scientists researching vitamin C have yet to agree upon how much is required for optimal human health. Their estimates vary and typically start at 400 mg/day and go higher.
Dr. Steve Hickey with the Vitamin C Foundation has published open letters to the Food and Nutrition Board and the National Institutes of Health, laying out the reasons why the current RDA is insufficient and why it should be reexamined and readjusted upward.
In the meantime, we can support our health and reduce our risk of degenerative diseases by making sure not to skimp on our 5 servings of fruits and vegetables per day. We may fortify ourselves with a good quality multi-vitamin supplement for the extra vitamin C it provides.
Vitamin C is a water-soluble vitamin, which means that it is not stored in the body and must be replaced by our diet every day. The Tolerable Upper Intake Level (UL) is the maximum continual intake of a nutrient that is unlikely to cause adverse health effects in almost all people, and for vitamin C the UL is 2 g/day (2,000 mg/day). The most common side effect of taking an amount larger than this is diarrhea. Therefore, healthy individuals have little concern of toxicity if consuming more vitamin C than specified by the RDA.
One word of caution - people who have a high risk of kidney disease, kidney stones, or disorders of iron metabolism should avoid large doses of vitamin C (>500mg). Consult your doctor or nutritionist prior to taking supplementation.
Virtually all fruits and vegetables contain some amount of vitamin C. According to the USDA nutrient database, fruits and vegetables that are among the highest in vitamin C content include: orange juice, grapefruit juice, peaches, peppers (sweet and hot), papayas, strawberries, broccoli, Brussels sprouts, kohlrabi, pineapple, and kiwi fruit. Other fruits noted for their high vitamin C content include: jujube, acerola, camu camu, guava, red and black currants, mango and persimmon.
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