Change #7

"I must be certain (that there is no risk.)" to "I can tolerate uncertainty."

Most problems with anxiety relate to a fear of uncertainty.

My educated guess is that the brains of about twenty percent of the population have a more difficult time than the average person in tolerating uncertainty regarding risk. This, of course, can put them at a serious disadvantage, since living demands risk. It is no wonder, then, that so many people develop anxiety problems. They worry because their brain is demanding closure on a specific issue. Their mind says, "This is how it must turn out for me to feel secure. And I must feel secure. Do I know for certain it will turn out this way?" It is as though they require a 100% guarantee that they will encounter zero risk. That is simply too much to ask of life. If you intend to go up against one of the most powerful forces of the natural world -- that is, continual change -- you will have a tough time winning. Listen to these expectations of life and you will see what I mean. The person with panic attacks, phobias or social anxieties asks such questions as:

• "Can I know for certain that I won't have any symptoms?"
• "Can I know for certain that I won't have to leave?"
• "Can I know for certain that I won't feel trapped?"
• "Can I know for certain that this isn't a heart attack?"
• "Can I know for certain that I won't die on that plane?"
• "Can I know for certain that I won't cause an embarrassing scene?"
• "Can I know for certain that people won't stare at me?"
• "Can I know for certain that I won't have a panic attack?"

If we look at a different anxiety problem -- obsessive-compulsive disorder -- we find the same kinds of questions:

• "Can I know for certain that this object is clean?"
• "Can I know for certain that I won't get contaminated if I touch the ground?"
• "Can I know for certain that my family will be safe?"
• "Can I know for certain that I didn't run someone over?"
• "Can I know for certain that I unplugged that iron?"
• "Can I know for certain that I won't kill my child?"

If it is true that some people's brains cause them to feel a strong yet inappropriate need for certainty, then confronting that problem involves disrupting those demanding thoughts. It involves confronting them consistently and directly everyday to produce the change we want. This is where your new attitude comes in. You must find ways to accept risk and tolerate uncertainty.

Stay with me as I explain how this works, because this stance doesn't seem very attractive at first glance. Whatever outcome you fear, work to find a way to accept that outcome as a possibility. For example, imagine that sometimes when you begin to have panicky symptoms you feel a pain in your chest that runs down one arm. Each time it happens, your first thought is, "This could be a heart attack!" Of course you have had one or more medical evaluations by a specialist. Let's also say that all physicians you consult declare you have a strong heart, take good care of yourself and are not at risk of a heart attack.

Nonetheless, as soon as that pain shoots down your arm, you say, "This time it really could be my heart! How do I know? There's no guarantee that this is only panic. And if it is a heart attack, I need help now!"

Further, let's say that you've been learning to reassure yourself as a way to get some perspective on panic. "Look, guy, you've been to the emergency room twelve times in the last two years. One hundred percent of those visits have been false alarms. You know you suffer from panic attacks, and this is what they feel like, too. Take a few Calming Breaths, relax, wait a few minutes. You'll begin to feel better."

The reassurance lasts all of five seconds. Then you're back in the saddle. "But I don't know. I don't know for certain. If this is a heart attack I could die! Right now! There's always a chance."

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It's the same with people's fear of dying on a plane. Commercial flight is the safest mode of transportation we have. On average, about one hundred people die on a plane per year, while 47,000 motorists die on the highways and 8,000 pedestrians die each year. If you are looking for a risk-free environment, don't stay at home; 22,000 people die of accidents a year without even leaving their house!

Even though your odds of dying on a plane are one in 7.5 million, the dialogue goes like this, "There's still a chance I might die. And if I do, that will be the most horrible, terrifying death I can imagine." You reassure, "Planes are safe. You'll be fine. The pilot has gray hair; he has twenty-five years' experience."

"Yes, but how do I know? How can I be certain?"

This is what you do to yourself, in your own unique way. You ask, "how can I be certain someone won't criticize me?", or "how can I be certain I won't have to leave the concert?" You might as well give it up, because you can never satisfy the demand for absolute confidence. No amount of reassurance will ever be enough.

Here, instead, is the attitude to strive for: "I accept the possibility of that (negative event) happening."

For fear of heart attacks: "I accept the possibility that this time could actually be a heart attack. I'm going to respond to it as though it is a panic attack. I accept the risk that I might be wrong."

For fear of dying on a plane: "I accept the possibility that this plane could crash. I'm going to think and feel and act as though this plane is 100% safe. I accept the risk that I might be wrong."

For fear of having to leave an event: "I accept the possibility that I might have to leave the restaurant. I imagine I'd feel embarrassed, but I'm willing to tolerate that now."

By making this decision -- to accept the possibility of a negative outcome -- you circumvent the requirement for absolute certainty of your future comfort and safety. There's always a chance you will have a heart attack, regardless of your health. There's always a chance you could die in a plane crash, regardless of the relative safety of air travel. There's always a chance you will leave the restaurant and become embarrassed.

If you want to lower your chances of panicking and raise your chances of flying comfortably or feeling more at ease at the restaurant, you have work to do. Your job is to lower your risk of problems as much as makes common sense, then accept the remaining risk that is not under your control. You only have two other basic options. You can keep worrying about the risk while you continue with these behaviors. That leads to anxiety and the increased likelihood of panic. Or, you can withdraw from these activities. The world can get by with you never flying again. The world can get by if you never enter another restaurant. There are consequences to these behaviors, of course. (It may take longer to travel to your friends or relatives, and so forth.) But it's your choice.

I encourage you, instead, to practice this idea of accepting uncertainty.

There is an interesting thing about many therapeutic interventions designed to help you control anxiety. Most actually make you more anxious at first. This one -- giving up the requirement for complete confidence in the outcome -- is a good example. For instance, you begin to feel that pain in your chest that shoots down you arm. Now you are saying, "I'm going to apply all my skills as though this is a panic attack. I'm not going to act as though this is a heart attack." Do you think 100% of you is going to agree to this plan? No way! Some part of your mind is still going to feel scared, because, try as you might, some part of you will still be worried about a heart attack..

If worrying, or fearful monitoring, is one of our most common ways to stay in control, then if you practice letting go of your worries, your mind and body will feel out of control. That will make you anxious. This anxiety is the distress of positive experimentation and change. It's a good kind of anxiety. Remember what Goleman said: "A person prevails over anxiety by sacrificing attention." But expect to be uncomfortable at first anyway! Have faith that over time, this anxiety will diminish.

next: Step 1: Difficulty Breathing
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If you're concerned about your child's weight, you're in good company. Since the 1960s, the number of overweight kids in the United States has nearly doubled and the number of overweight adolescents has nearly tripled. Today, 10% of 2- to 5-year-olds and more than 15% of children between the ages of 6 and 19 are overweight, which puts them at risk for disease and low self-esteem. Eating disorders are on the rise among young people as well. Keep reading to learn more about weight and kids, and healthy ways to manage weight for the entire family.

Underweight Kids

Be aware of the teen who gains too little weight, especially the teenage girl who begins to lose weight rapidly yet still complains she is fat. Young girls may worry about the physical changes that puberty brings, partly in response to society's emphasis on thinness. Full hips and breasts may make them feel "fat," and they can get caught up in behavior patterns known as eating disorders.

Some girls become obsessed with body weight and image. They will eat very small amounts of food - inadequate amounts to support normal growth and health. Some refuse to eat at all. This condition is known as anorexia nervosa. Other teens, again mostly girls, practice binge-and-purge behavior, known as bulimia. Both conditions are potentially life threatening. If you suspect either condition, talk to your child and seek medical treatment from a doctor or registered dietitian.

Teenage boys are prone to nutritional problems as well. Many adolescent boys yearn to be bigger or heavier. Beware of nutritional supplements that promise more muscles. If a teen is eating properly and consuming the right amount of a variety of foods, nutritional supplements are just a waste of money. If you are concerned about your teenager's eating habits, talk with your child's doctor. Counseling is often an effective way to get kids back on track.

next: Eating Disorders Are the Toughest Challenge for Our Counselors
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Vitamin C may help prevent Alzheimer's Disease and dementia, heart disease and diabetes. Learn about the usage, dosage, side-effects of Vitamin C.

• Overview
• Uses
• Dietary Sources
• Available Forms
• How to Take It
• Precautions
• Possible Interactions
• Supporting Research

Overview

Vitamin C is a water-soluble vitamin needed for the growth and repair of tissues in all parts of the body. It is necessary to form collagen, an important protein used to make skin, scar tissue, tendons, ligaments, and blood vessels. Vitamin C is essential for the healing of wounds, and for the repair and maintenance of cartilage, bones, and teeth.

Vitamin C is one of many antioxidants. Vitamin E and beta-carotene are two other well known antioxidants. Antioxidants are nutrients that block some of the damage caused by free radicals, which are by-products that result when our bodies transform food into energy. The build up of these by-products over time is largely responsible for the aging process and can contribute to the development of various health conditions such as cancer, heart disease, and a host of inflammatory conditions like arthritis. Antioxidants also help reduce the damage to the body caused by toxic chemicals and pollutants such as cigarette smoke.

Vitamin C deficiency can lead to dry and splitting hair; gingivitis (inflammation of the gums) and bleeding gums; rough, dry, scaly skin; decreased wound-healing rate, easy bruising; nosebleeds; weakened enamel of the teeth; swollen and painful joints; anemia; decreased ability to ward off infection; and, possibly, weight gain because of slowed metabolic rate and energy expenditure. A severe form of vitamin C deficiency is known as scurvy, which mainly affects older, malnourished adults.

The body does not manufacture vitamin C on its own, nor does it store it. It is therefore important to include plenty of vitamin C-containing foods in one's daily diet. Large amounts of vitamin C are used by the body during any kind of healing process, whether it's from an infection, disease, injury, or surgery. In these cases extra vitamin C may be needed.

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Vitamin C Uses

Low levels of vitamin C have been associated with a variety of conditions including hypertension, gallbladder disease, stroke, some cancers, and atherosclerosis (the build up of plaque in blood vessels that can lead to heart attack and stroke; conditions that are caused by atherosclerotic build up are often collectively referred to as cardiovascular diseases). Eating adequate amounts of vitamin C in the diet (primarily through lots of fresh fruits and vegetables) may help reduce the risk of developing some of these conditions. There is little evidence, however, that vitamin C supplements can cure any of these diseases.

As an anti-oxidant, vitamin C plays an important role in protecting against the following:

Heart Disease
Results of scientific studies regarding the benefit of vitamin C for heart disease or stroke is somewhat confusing. While not all of the studies agree, some information suggests that vitamin C may help protect blood vessels from the damaging effects that lead to or result from the presence of atherosclerosis.

For example, those with low levels of vitamin C may be more likely to have a heart attack, stroke, or peripheral artery disease, all potential outcomes of atherosclerosis. Peripheral artery disease is the term used to describe atherosclerosis of the blood vessels to the legs. This can lead to pain with walking, known as intermittent claudication.

In terms of damage that can cause atherosclerosis, some studies have shown that vitamin C helps prevent oxidation of LDL (bad) cholesterol - a process that contributes to plaque buildup in the arteries.

Under most circumstances, dietary vitamin C is adequate for protecting against the development of or consequences from cardiovascular disease. If you have low levels of this nutrient, however, and find it difficult to obtain through dietary sources, a knowledgeable healthcare provider may recommend vitamin C supplements.

High Cholesterol
Information from several studies, involving only small numbers of people, suggest that vitamin C (3 glasses of orange juice per day or up to 2000 mg per day as a supplement) may help decrease total and LDL cholesterol and triglycerides, as well as increase HDL levels (the good kind of cholesterol). Studies evaluating larger groups of people would be helpful in determining how accurate these preliminary research results are and to whom this potential benefit applies.

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High Blood Pressure
Free radicals, the damaging by-products of metabolism mentioned earlier, are associated with higher blood pressure in studies of animals and people. Population based studies (which involve observing large groups of people over time) suggest that people who eat foods rich in antioxidants, including vitamin C, are less prone to high blood pressure than people without these nutritious foods in their diet. For this reason, many clinicians recommend foods rich in vitamin C, particularly if you are at risk for high blood pressure. In fact, the diet most frequently recommended for treatment and prevention of hypertension, known as the DASH (Dietary Approaches to Stop Hypertension) diet advocates lots of fruits and vegetables, which are loaded with antioxidants.

Common Cold
Despite the popular belief that vitamin C can cure the common cold, the scientific evidence supporting this conviction is limited. There have been a few studies suggesting that taking large doses of vitamin C supplements at the onset of cold or flu symptoms, or just after exposure to one of these viruses, can shorten the duration of the cold or ward it off altogether. However, the majority of studies, when looked at collectively, lead researchers to conclude that vitamin C does not prevent or treat the common cold. Some experts suggest that vitamin C may only be useful in case of a cold if you have low levels of this nutrient to begin with. Another possibility is that the likelihood of success may be very individual -- some improve, while others do not. If you are amongst the 67% of people who believe that vitamin C is helpful for your colds, there may be power in your conviction. In other words, your experience is probably more important than what the research is stating. Talk to your doctor about any pros and cons with regards to using vitamin C during cold and flu season.

Cancer
While the precise role of vitamin C in preventing cancer remains controversial, results of many population based studies (evaluating groups of people over time) imply that foods rich in vitamin C may be associated with lower rates of cancer, including skin cancer, cervical dysplasia (changes to the cervix which may be cancerous or precancerous, picked up by pap smear), and, possibly, breast cancer. At best, however, particularly for breast cancer, the specific connection of vitamin C and cancer prevention is weak. This is mainly because protection comes from eating foods, such as fruits and vegetables, which contain many beneficial nutrients and antioxidants, not only vitamin C.

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Also, there is no evidence that taking large doses of vitamin C once diagnosed with cancer will help your treatment. In fact, there is concern that large doses of antioxidants from supplements could interfere with chemotherapy medications. Much more research in the area of antioxidants and cancer treatment is needed.

Osteoarthritis
Vitamin C is essential for normal cartilage. Plus, free radicals can be produced in the joints and have been implicated in many degenerative changes in the aging body, including destruction of cartilage and connective tissue that lead to arthritis. Antioxidants appear to offset the damage caused by free radicals. Although further evidence is needed to substantiate these claims, studies of groups of people observed over time suggest that vitamin C, as well as vitamin E, may help to reduce the symptoms of OA.

Vitamin C for Obesity and Weight Loss
Studies suggest that obese individuals may have lower vitamin C levels than nonobese individuals. Researchers speculate that insufficient amounts of vitamin C may contribute to weight gain by decreasing metabolic rates and energy expenditures. Many sensible weight loss programs will be sure to include foods rich in vitamin C, such as plenty of fruits and vegetables.

Cataracts
Studies have shown that vitamin C may slow or even stop the progression of cataracts in the elderly. A recent study, for example, of women from the Nurses' Health Study (a very large, important study that has followed women over many years) showed that women under 60 years of age who had high dietary intake of vitamin C or who had used vitamin C supplements for 10 years or more had significantly reduced chances of developing cataracts.

Age-related Macular Degeneration
Vitamin C works together with other antioxidants like selenium, beta-carotene, and vitamin E to protect the eyes against developing macular degeneration. This is a painless, degenerative eye disease that affects more than 10 million Americans. It is the leading cause of legal blindness in persons over the age of 55 in the United States. While complete blindness does not occur in most people with the disorder, macular degeneration often interferes with reading, driving, or performing other daily activities.

While not all research agrees, antioxidants, including vitamin C, primarily from dietary sources may help prevent macular degeneration. Many qualified clinicians will recommend a combination of these nutrients for treating or preventing this serious and frustrating eye disorder.

Diabetes
Vitamin C may be helpful for people with diabetes in a number of ways. First, some studies suggest that people with diabetes have high levels of free radicals (the damaging metabolic by-products, mentioned earlier, associated with many chronic illnesses) and low levels of antioxidants, including vitamin C. This imbalance may contribute to the fact that those with diabetes are at greater risk for developing conditions such as high cholesterol and atherosclerosis.

Secondly, insulin (which is low in type 1 diabetics and does not function properly in type 2 diabetics) helps cells in the body take up the vitamin C that they need to function properly. At the same time, lots of circulating blood sugar (glucose), as is often the present in diabetics, prevents the cells from getting the vitamin C that they need, even if eating lots of fruits of vegetables. For this reason, taking extra vitamin C in the form of supplements may be helpful in those with diabetes.

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Vitamin C for Alzheimer's Disease and other types of Dementia
While the evidence is somewhat stronger for another important antioxidant, namely vitamin E, vitamin C may help prevent the development of Alzheimer's Disease. It may also improve cognitive function in dementia from causes other than Alzheimer's (such as multiple strokes). The use of these antioxidants for improving cognitive ability in those who already have dementia of the Alzheimer's type has not been well tested to date.

Other
Although the information is somewhat limited, studies suggest that vitamin C may also be helpful for:

• Boosting immune system function
• Maintaining healthy gums
• Relieving eye pressure in those with glaucoma
• Improving visual clarity for those with uveitis (an inflammation of the middle part of the eye)
• Slowing progression of Parkinson's disease
• Treating allergy-related conditions, such as asthma, eczema, and hay fever (called allergic rhinitis)
• Relieving pain from pancreatitis; vitamin C levels are often low with this condition
• Reducing effects of sun exposure, such as sunburn or redness (called erythema) and even, possibly, skin cancer
• Alleviating dry mouth, particularly from antidepresant medications (a common side effect from these drugs)
• Healing burns and wounds

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Vitamin C Dietary Sources

Since vitamin C is not produced by the body, it must be obtained from fruits and vegetables. Some excellent sources of vitamin C are oranges, green peppers, watermelon, papaya, grapefruit, cantaloupe, strawberries, kiwi, mango, broccoli, tomatoes, brussels sprouts, cauliflower, cabbage, and citrus juices or juices fortified with Vitamin C. Raw and cooked leafy greens (turnip greens, spinach), red and green peppers, canned and fresh tomatoes, potatoes, winter squash, raspberries, blueberries, cranberries and pineapple are also rich sources of Vitamin C. Vitamin C is sensitive to light, air, and heat, so it is best to eat fruits and vegetables raw, or minimally cooked in order to retain their full vitamin C content.

 

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Vitamin C Available Forms

You can purchase either natural or synthetic vitamin C, also called ascorbic acid, in a wide variety of forms. Tablets, capsules, and chewables are probably the most popular, but vitamin C also comes in powdered crystalline, effervescent, and liquid forms. Vitamin C can be purchased in dosages ranging from 25 mg to 1,000 mg.

"Buffered" vitamin C is also available if you find that regular ascorbic acid upsets your stomach. An esterified form of vitamin C is also available, which tends to be better tolerated by people who are prone to heartburn or have a sensitive stomach.

Some vitamin C supplements contain bioflavonoids, which appear to enhance absorption and utilization of ascorbic acid.

There is concern about tooth enamel erosion occurring from the acid content of chewable vitamin C.

 

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How to Take Vitamin C

Vitamin C is not stored in the body, so it must be replaced as it gets used. The best way to take supplements is with meals two or three times per day, depending on the dosage. Some studies suggest that adults should take between 250 mg and 500 mg twice a day for maximum benefit. A knowledgeable healthcare provider should be consulted before taking more than 1,000 mg of vitamin C on a daily basis and before giving vitamin C to a child.

Daily intake of dietary vitamin C (according to the U.S. RDA), are listed below.

Pediatric

• Neonates 1 to 6 months: 30 mg
• Infants 6 to 12 months: 35 mg
• Children 1 to 3 years: 40 mg
• Children 4 to 6 years: 45 mg
• Children 7 to 10 years: 45 mg
• Children 11 to 14 years: 50 mg
• Adolescent girls 15 to18 years: 65 mg
• Adolescent boys 15 to18 years: 75 mg

Adult

• Men over 18 years: 90 mg
• Women over 18 years: 75 mg
• Breastfeeding women: first 6 months: 95 mg
• Breastfeeding women: second 6 months: 90 mg

Because smoking depletes vitamin C, people who smoke generally need an additional 35 mg/day.

The doses recommended to prevent or to treat many of the conditions mentioned in the Uses section is often between 500 and 1,000 mg per day.

 

 

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Precautions

Because of the potential for side effects and interactions with medications, dietary supplements should be taken only under the supervision of a knowledgeable healthcare provider.

It is important to drink plenty of fluids when taking supplemental vitamin C because it has a diuretic effect.

Most commercially available vitamin C is derived from corn. People sensitive to corn should look for alternative sources, such as sago palm.

Vitamin C increases the amount of iron absorbed from foods. This may be helpful for people who have low blood iron levels. However, people with hemochromatosis should not take vitamin C supplements because of enhanced accumulation of non-heme iron in the presence of this vitamin.

During periods of stress (either emotional or physical), urinary excretion of vitamin C is increased. Extra vitamin C through vitamin C rich foods as well as supplements is often recommended to keep the immune system working properly during these times.

While vitamin C is generally non-toxic, in high doses (more than 2,000 mg daily) it can cause diarrhea, gas, or stomach upset. Those who have kidney problems should check with a healthcare provider before taking vitamin C supplements. Infants born to mothers taking 6,000 mg or more of vitamin C may develop rebound scurvy due to a sudden drop in daily intake. As described earlier, scurvy is a condition caused by extreme vitamin C deficiency. See earlier explanation for the possible symptoms of vitamin C deficiency.

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Possible Interactions

If you are currently being treated with any of the following medications, you should not use vitamin C supplements without first talking to your healthcare provider.

Aspirin and Nonsteroidal Anti-Inflammatory Drugs (NSAIDs)
Very limited research suggests that vitamin C may protect the stomach and intestines against injury from NSAIDs such as ibuoprofen. On the other hand, high doses of vitamin C (equal to or greater than 500 mg per day) may raise the blood levels of aspirin and other acidic medications.

Acetominophen
Vitamin C may decrease excretion of acetaminophen (a medication sold over the counter for pain and headache) in the urine, which may increase blood levels of this medication.

Diuretics, Loop
Animal studies suggest that vitamin C may amplify the effects of furosemide, which belongs to a class of medications known as loop diuretics.

Beta-blockers for high blood pressure
Vitamin C may decrease the absorption of propranolol, a medication that belongs to a class known as beta-blockers used for high blood pressure and other heart-related conditions. If taking vitamin C and a beta-blocker, therefore, it is best to take them at different times of the day.

Cyclosporine
Cyclosporine, a medication used for the treatment of cancer, may reduce blood levels of vitamin C.

Nitrate Medications for heart disease
The combination of vitamin C with nitroglycerin, isosorbide dinitrate, or isosorbide mononitrate reduces the occurrence of nitrate tolerance. Nitrate tolerance is when the body builds up a tolerance to the medicine so that it no longer has its desired effect. People taking nitrate-containing medications generally follow a 12 hours on, 12 hours off schedule to avoid this tolerance. Studies suggest that taking vitamin C along with nitrate medications may reduce the development of this tolerance.

Tetracycline
There is some evidence that taking vitamin C with the antibiotic tetracycline may increase the levels of this medication.

Warfarin
There have been rare case reports of vitamin C interfering with the effectiveness of this blood thinning medication. In recent follow up studies, no such association has been found with doses of vitamin C up to 1,000 mg per day. Because of these much earlier reports, however, some conservative clinicians suggest not exceeding RDA values of vitamin C (see earlier section entitled How To Take It). Whether taking recommended dietary amounts or larger quantities of vitamin C, anyone on warfarin must have their bleeding time measured regularly and followed closely using a value called an INR, measured at your doctor's office. If you take this blood thinner, any time you make a change to your diet, medications, or supplements, you must notify your physician.

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Supporting Research

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Christen WG, Ajani UA, Glynn RJ, Manson JE, Schaumberg DA, Chew EC, Buring JE, Hennekens CH. Prospective cohort study of antioxidant vitamin supplement use and the risk of age-related maculopathy. Am J Epidemiol. 1999;149(5):476-484.

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Dreher F, Gabard B, Schwindt DA, Maibach HI. Topical melatonin in combination with vitamins E and C protects skin from ultraviolet-induced erythema: a human study in vivo. Br J Dermatol. 1998;139(2):332-339.

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Eberlein-Konig B, Placzek M, Przybilla B. Protective effect against sunburn of combined systemic ascorbic acid (vit.C) and D-alpha-tocopherol (vit.E). J Am Acad Dermatol. 1998;38:45-48.

Enstrom JE, Kanim LE, Klein MA. Vitamin C intake and mortality among a sample of the United States population. Epidemiology. 1992;3(3):194-202.

Fahn S. A pilot trial of high-dose alpha tocepherol and ascorbate in early Parkinson's disease. Ann Neurol. 1992;32:S128-S132.

Frei B. On the role of vitamin C and other antioxidants in atherogenesis and vascular dysfunction. Proc Soc Exp Biol Med. 1999;222(3):196-204.

Fuchs J, Kern H. Modulation of UV-light-induced skin inflammation by D-alpha-tocopherol and L-ascorbic acid: a clinical study using solar simulated radiation. Free Radic Biol Med. 1998;25(9):1006-1012.

Gandini S, Merzenich H, Robertson C, Boyle P. Meta-analysis of studies on breast cancer risk and diet: the role of fruit and vegetable consumption and the intake of associated micronutrients. Eur J Cancer. 2000;36:636-646.

Gokce N, Keaney JF, Frei B, et al. Long-term ascorbic acid administration reverses endothelial vasomotor dysfunction in patients with coronary artery disease. Circulation. 1999;99:3234-3240.

Gonzalez J, Valdivieso A, Calvo R, Rodriguez-Sasiain J, et al. Influence of vitamin C on the absorption and first pass metabolism of propranolol. Eur J Clin Pharmacol. 1995;48:295-297.

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