Does vitamin C breakdown after fruit/vegetable harvest and during cooking?
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Vitamin C is susceptible to breakdown during certain cooking, processing, and storage procedures (i.e., heat or cooking in neutral or basic medium). For instance, potatoes can lose nearly half of their vitamin C by boiling. Spinach can lose nearly all its vitamin C if stored for two to three days at room temperature.
For practical purposes, citrus fruits and other vitamin C-containing fruits and vegetables usually are better dietary sources of vitamin C as they are generally eaten uncooked and shortly after harvest. |
How much vitamin C is absorbed?
Vitamin C is fairly well absorbed from our digestive tract when consumed in typical dietary amounts. However, as the amount of vitamin C increases in our diet its absorption efficiency decreases. For example, a vitamin C intake of 180 mg (three times the RDA for an adult) is about 80 to 90 percent absorbed, while an intake approximating 5 g is only about¼ is absorbed. However, 25 percent absorption of 5 g is still about 1.2 g of vitamin C. Much of this excessive vitamin C will be quickly removed from the body in the urine.
How much vitamin C do we need?
The Recommended Dietary Allowance (RDA) for vitamin C for adult men and women is 90 mg and 75 mg, respectively. During pregnancy and lactation the RDA increases to 85 and 120 mg for adult women. This is the level of vitamin C that will provide for good blood and organ vitamin C status for most adults. Meanwhile an intake of 400 mg for healthy adults is recommended to ensure that the levels in the blood and cells are optimal. See DRI/RDA Table for vitamin C recommendations.
Where is vitamin C found in our body?
Vitamin C is found in most of the tissue throughout the body with greater concentrations in the heart, brain, pancreas, adrenal glands, thymus, and lungs. Two of the most vitamin C-dense regions in the body are the pituitary gland and the lens of the eye. Vitamin C status in the body is typically assessed by measuring serum levels as well as the level of white blood cells. The former is more reflective of recent dietary intake while the latter is a better indicator of tissue stores. As vitamin C circulates in the blood it is vulnerable to kidney filtration and subsequent loss in the urine either as ascorbic acid or derivatives (metabolites) such as oxalates.
What roles does vitamin C play in our body?
Vitamin C has the ability to either donate or accept electrons. In doing so it participates in many metabolic processes. Perhaps its most famous role is its involvement in the production of collagen. However vitamin C plays a role in the production of other vitamin molecules including carnitine, norepinephrine and bile acids.
- Collagen is a connective tissue protein and is found in teeth, bone, tendons, ligaments, cartilage, and arteries. Vitamin C is fundamentally involved in modifying specific amino acids in the collagen protein which ultimately affects collagen’s structure and function. Without vitamin C, the collagen that is made is relatively worthless.
- Norepinephrine functions as a neurotransmitter in the brain and in organs to regulate their function as well as a hormone released from the adrenal glands during exercise and fasting. Among other operations norepinephrine is involved in the “fight or flight” response which helps us deal with stressful and threatening situations. Norepinephrine is made from the amino acid tyrosine and vitamin C plays a role in the conversion process.
- Carnitine is needed to use longer chain length fatty acids for energy, as it basically chaperones these fatty acids into the mitochondria of our cells where they can be broken down for energy (ATP) production. The making of carnitine in the liver requires vitamin C among other substances.
- Bile acids are produced in the liver and are vital for efficient fat digestion and absorption. Since, bile acids are derived from cholesterol, which in turn decreases the amount of cholesterol that circulates, vitamin C plays a role in lowering the risk of heart disease.
- Vitamin C is also an antihistamine factor and an immune function potentiator, and is involved in the making of thyroid hormone, serotonin, , and steroid hormones.
- Vitamin C enhances iron absorption from our digestive tract. This means that both iron and vitamin C would need to be part of the same meal for this to occur.
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