Research Library

Almost everyone has heard of antioxidants, but many people aren't exactly sure what they do. To visualize oxidation, think of what happens when you cut an apple in half and leave the halves out exposed to air. They turn brown, right? That's oxidation. When it happens in your body, doctors and researchers call it "oxidative stress." Oxidation--or oxidative stress--is a factor in virtually every degenerative disease. It's the reaction of rogue molecules called "free radicals" with the cells in your body. Those rogue molecules--often derived from oxygen--can cause DNA damage and are a big part of why our bodies age. Antioxidants help fight this process. Deficiencies of antioxidants are implicated in the early stages of heart disease, cancer, eye disease and age-related declines in memory.

Enter antioxidants. The big guns in the antioxidant arsenal are vitamins like vitamin C, vitamin E and vitamin A, plus minerals like zinc and selenium. The ability of these vitamins and minerals to interfere with oxidative stress is a big part of why adequate vitamin and mineral intake is such a big part of the Atkins Advantage. But there's one super-antioxidant that you might not have heard of that has been found to do even more than the antioxidant superstars: alpha lipoic acid.

One reason alpha lipoic acid is such a powerhouse is that it does double duty. Not only does it act as an antioxidant on its own--it also helps recycle your vitamin E, vitamin C and even Coenzyme Q10 so that you get double-duty use out of them.

Alpha lipoic acid has other significant uses in the body. It may lower blood sugar levels as well. Leading antioxidant researcher Dr. Lester Packer notes that alpha lipoic acid works against insulin resistance by increasing the permeability of cell membranes, making it easier for both insulin and glucose (sugar) to get in. Noted author Bert Berkson, MD, PhD, cites evidence that alpha lipoic acid is very healing for the liver and may in fact repair liver damage. Dr. Berkson's book, The Alpha Lipoic Acid Breakthrough, chronicles this amazing antioxidant's multiple benefits. And according to the Physicians Desk Reference, it's been suggested that lipoic acid may slow aging of the brain and function as an anti-aging substance in general.

Sources of Alpha Lipoic Acid

Alpha lipoic acid is made in the body; it's also present in many meats and vegetables, but not in very high quantities. Some of the best sources are not widely eaten--for example, beef kidney and beef heart. Liver, spinach and rice bran are also good sources. But to get the real benefits of alpha lipoic acid, you may have to take a supplement. There are no known contraindications, dangers or adverse reactions.

For everyday protection, 100 mg is a good dose. Diabetics and others with specific health concerns (hepatitis, for example) have used up to 900 to 1200 mg a day.

Just to be safe: Until actual studies have been done on pregnant women, it's probably prudent to avoid alpha lipoic acid during pregnancy and nursing.

Alpha lipoic acid can help to control blood sugar--

--- but so can a common ingredient that's probably in your kitchen right now! With an epidemic of obesity and diabetes threatening to topple the American health care system, anything that can help control blood sugar has to be taken seriously. When blood sugar is out of control, the body produces elevated levels of the hormone insulin, which can in many people lead to insulin resistance, diabetes, heart disease and great difficulty losing weight. The "blood sugar roller coaster" is also implicated in mood swings and carbohydrate cravings, not to mention that it's a big factor in increasing stress.

We've long known that antioxidants--such as the previously discussed alpha lipoic acid, as well as vitamin C, vitamin E and others--can help protect your cells against the damages caused by molecules called free radicals. Damage from free radicals--a damage known as "oxidative stress"--figures in virtually every degenerative disease you can imagine. Now we're finding out that antioxidants can also help protect against the number one cause of age-related vision decline and adult blindness: macular degeneration.

How do we know? Well, a major clinical trial called the AREDS study followed about 3,600 participants with varying stages of age-related macular degeneration. In this study, participants were given a special formulation of antioxidants and vitamins. The results showed that the formulation might well play a key role in helping people who are at high risk for developing advanced age-related macular degeneration keep their remaining vision. The formula used in the study was:

Copper, though not thought to be essential for protecting the eyes, was added to the formula to prevent copper deficiency anemia, which can sometimes be associated with high levels of zinc intake.

But these are not the only nutrients associated with eye health. Indeed, most experts now feel that a couple of very important members of the carotenoid family would extend the benefits seen by the above formula even further. Those carotenoids are called lutein and zeaxanthin. When discussing the benefits of lutein, it's assumed you're talking about lutein and zeaxanthin together, as they are almost always found together in foods (and in supplements).

"Lutein and zeaxanthin were not used in the original AREDS study, but have since been found to be among the most effective supplements for eye health."--Michael Geiger, D.O., author of Eye Care Naturally

Here's what the research shows on lutein and zeaxanthin:

• In 1999, data from the Nurses Health Study showed a reduced likelihood of cataract surgery with increasing intakes of lutein and zeaxanthin.
• In 1999, the Health Professionals Follow-up Study found a trend toward a lower risk of cataract extraction with higher intakes of lutein and zeaxanthin.
• In 1999, a follow-up to an NEI-supported population-based study--called the Beaver Dam Study--concluded that people with diets higher in lutein and zeaxanthin had a lower risk of developing cataracts.
• In 2001, data from the Third National Health and Nutrition Examination Survey reported that higher intakes of lutein and zeaxanthin among people ages 40-59 may be associated with a reduced risk of advanced macular degeneration.

The take-home point? What you eat--and what supplements you take--can actually affect your vision!

Sources of Lutein and Zeaxanthin

Lutein (and zeaxanthin) are primarily found in:

• Kale (20.5 to 26.5 mg)
• Collard greens (15.3 mg)
• Spinach (3.6 mg to 12.6 mg)
• Turnip greens (12.1 mg)
• Broccoli (2.1 mg to 3.5 mg)
• Yellow corn (1.4 mg to 3 mg)
• Green peas (2.3)

All of the above values are for one-cup servings.

Dr. Michael Geiger, author of Eye Care Naturally, recommends anywhere from 6-15 mg of lutein for general prevention, but 20-40 mg of lutein for someone who already has macular degeneration.

 Can a pill help prevent cancer?

See what the research says on this new superstar supplement, and find out how you can get the same ingredient in food.

If there is one thing that every single expert on nutrition agrees about it's this: Eat your fruits and vegetables. Everyone knows that they offer a king's ransom of health benefits, not the least of which is that they include a whole armamentarium of compounds that fight against cancer. The research on this is not even controversial anymore. Google "fruits and vegetables and cancer prevention" and you'll be rewarded with over two million entries, beginning with ones from Harvard University and the National Institute of Medicine and working down from there. A recent supplement to the American Institute of Cancer Research conference on diet, nutrition and cancer was entitled "Phytochemicals from Cruciferous Plants Protect against Cancer by Modulating Carcinogen Metabolism" and cited 81 published studies.

So we know that there are plant compounds that protect against cancer, in test tubes, in animals and in humans. These plant compounds--referred to as "phytochemicals" because they are chemicals from plants--include all kinds of unpronounceable compounds (isothiocyanates, anyone?) that have the effect of being what's called "chemoprotective." Now some supplement manufacturers are packaging the most studied and important cancer-fighting ingredients--known as indoles--from cruciferous vegetables like broccoli and marketing them in pill form.

To understand the protective effects of indoles, it's necessary to understand just a little bit about the hormone estrogen. Here are two facts you might not know about estrogen:

These two facts are critical to understanding how the indoles help protect against cancer.

"Estrogen is not only important in breast cancer, but also in cancer of the prostate and of the thyroid."--Dr. Raj Tiwari, Associate Professor of Microbiology and Immunology at the New York Medical College in Valhalla, NY

The breakdown products of estrogen in the body have very different levels of activity. Some of these compounds are pretty benign, but some of them have very potent carcinogenic effects. The indoles act as a kind of traffic cop--they direct estrogens into pathways that produce more of the good guys and less of the bad (carcinogenic) ones. Indoles change the metabolism of estrogen in a positive way and also inhibit the growth factors necessary to allow cancer cells to grow.

The indole that has gotten the most attention up to recently is called Indole-3-carbinole (I3C). It's been available as a supplement for some time and is touted for its cancer-fighting benefits. But it's an unstable compound that breaks down into many different chemicals in the body. Recent research is indicating that while many of these breakdown products are indeed protective against cancer, some of them may actually be problematic and may have extremely unwanted side effects. The effect of I3C is therefore somewhat unpredictable.

But there's a happy ending to this story. The active compound responsible for all the good stuff in I3C is another compound called DIM: dindolymethane. DIM is the actual active ingredient with the cancer-fighting pedigree. DIM has been isolated from its indole-3-carbinole parent molecule, and is now sold as a supplement--and virtually all the experts are unanimous in recommending it.

"DIM does everything positive that I3C does, but with none of the negative side effects."--Linda Lizotte, RD, CDN

Here's what the research shows:

• A recent study from the University of California Berkeley showed that DIM has a powerful effect against human prostate cancer cells.
• Another study showed that women with breast pain taking DIM had a significant improvement in symptoms.
• DIM also demonstrably acts as a good traffic cop, improving the ratio of "good" estrogen by-products to more carcinogenic ones.
• DIM has antioxidant and anti-inflammatory effects as well.

Fruits and vegetables have compounds that protect against cancer. Eat them! And one of the most active compounds found in cruciferous vegetables is DIM. Taking it as a supplement makes a lot of sense.

According to Dr. Tiwari, about 250mg a day is a good dose of DIM.

 A Vitamin That Can Literally "make or break" your bones!

Everyone knows about calcium for bone health, but in this next lesson you'll learn about Vitamin K is kind of the Rodney Dangerfield of bone health vitamins: "It don't get no respect" and no one talks about it. Instead, we talk about calcium and magnesium and vitamin D, which of course are all very important. But the less-well-known vitamin K is critically important for building strong bones as well. Vitamin K actually activates a compound--it's called osteocalcin--that anchors calcium molecules inside the bone. You can take all the calcium you want, but if it's not getting into the bones, it's not going to do you very much good and it actually can do you some harm by calcifying in other places in the body. Vitamin K makes sure that you get the minerals into the bone where they belong.

When creatures live in the wild--whether they're fish, animal or fowl--they eat a very different diet than when they're raised in captivity. "You are what you eat" applies equally to humans, animals and even plants. So if you're eating something that was once alive, it's good to know what that creature dined on.

We know, for example, that the omega-3 fat content of grass-fed beef is very different from that of their factory-farmed brethren. And we know that plants grown in mineral-rich soil are richer in those minerals than plants that barely survive in barren soil. But when we're looking at something commonly viewed as a health food, like salmon, it's easy to forget that the same cautions apply.

Wild salmon dine on a crustacean called krill. Krill are little creatures resembling shrimp that are now being looked at for their astonishingly potent health benefits. They are a great source of omega-3 fats, for example, and krill oil as a supplement has been used successfully in research as a treatment for PMS symptoms (3 mg a day is the dosage that seems to work, if you're interested). And krill are also loaded with an antioxidant called astaxanthin.

Astaxanthin is a member of the carotenoid family (which also includes beta-carotene), and it has great potential in human health and nutrition. It's a powerful biological antioxidant. A recent scientific review in the March 2006 Journal of Natural Products examined the scientific literature from 2002 to 2005 on the most significant activities of astaxanthin, including its antioxidative and anti-inflammatory properties and its effects on cancer, diabetes, the immune system and ocular (eye) health. A paper in the Biological and Pharmaceutical Bulletin in January 2005 suggested that astaxanthin had both antihypertensive and neuroprotective effects--that means it may lower blood pressure and protect the brain! Astaxanthin occurs naturally in a variety of living organisms (including krill). And it's what gives wild salmon their red color.

But here's the problem: In the wild, salmon forage the oceans feeding on colorful crustaceans (like krill), plankton and algae, which naturally impart a beautiful shade of pink to the flesh of their predators. But when salmon are farmed and unable to forage, their flesh is an insipid, unappealing color--only few people would find appealing. Hence, canthaxanthin or astaxanthin or both are added to the feed of farmed salmon. Apparently, although astaxanthin is normally found in wild salmon, canthaxanthin is more efficiently bioabsorbed. Almost 100 percent of all farmed salmon is artificially colored with either canthaxanthin or astaxanthin, a process sometimes euphemistically called "color finishing."

Responding to an ever-increasing demand for salmon--which must, however, be pink--several major chemical companies produce canthaxanthin and astaxanthin for color finishing. One chemical firm synthetically produces canthaxanthin and an astaxanthin called Carophyll Pink from petrochemicals and provides customers with its SalmoFan--much like an artist's color wheel, but in various shades of pink--to help salmon farmers and buyers select a color that sells well.

According to reports in the journal Science, farmed salmon may contain high levels of dioxins. PCB levels may be up to eight times higher in farmed salmon compared to wild salmon. And in July 2003, the Environmental Working Group (EWG) released a report stating that farmed salmon purchased in the United States contain the highest level of PCBs in the food supply system. Omega-3 content may also be lower in farm-raised salmon than in the wild variety.

Salmon is still one of the healthiest foods you can eat, and for many good reasons, not the least of which is its positive effect on heart health. But it's probably a good idea to seek out wild salmon whenever possible. It comes by its color naturally--by eating its natural diet--and it's likely to be higher in omega-3s and lower in some of the man-made additives and contaminants that you don't want in your diet.

Try canned salmon--almost all of them are wild!

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Speaking of color and food, let's find out why the same ingredient that gives tomatoes their red color may also help protect you against cancer!

It seems unlikely, but it's true. In a Harvard University study of over 47,000 men, those who ate 10 or more servings a week of tomato products had a reduced risk of prostate cancer. One of the foods most commonly eaten? Pizza!

But don't run out and start gorging on this fattening, high-carb food. Researchers believe that at least some of the cancer-protective effect seen in the Harvard study is due to a member of the carotenoid family called lycopene. (In the Harvard study, tomato sauce had the highest relationship to a low risk for prostate cancer, though tomatoes and pizza also fared well. And tomato sauce was by far the most related to blood levels of lycopene.) Lycopene is what gives tomatoes, watermelons, grapefruits and papaya their red color. A pigment synthesized by some plants and animals to protect them from the sun, lycopene evolved as a weapon against certain types of free radicals. Lycopene is so effective at quenching free radicals that it beat out vitamin E in one study on oxidized fat. This suggests that lycopene might have importance in preventing heart disease, which involves oxidized LDL ("bad") cholesterol.

Humans get most of their lycopene from tomatoes--by far the richest source--yet tomato products offer a more concentrated source of lycopene than the fresh fruit itself. For example, tomato powder contains approximately 120 milligrams per 100 grams of fruit, whereas fresh tomatoes have about 2 milligrams per 100.

In the Harvard study, the only tomato-based food that showed no relationship to prostate cancer was tomato juice. However, it's been suggested that since lycopene needs some fat to be absorbed, the results might be different if tomato juice were consumed with a digestible oil.

Whether lycopene alone causes reduced cancer risk is uncertain. Some research suggests foods that contain lycopene are more helpful than lycopene by itself; for example, in a dietary supplement pill. Foods that contain lycopene also contain other nutrients, including other antioxidant vitamins. It may be the combination of nutrients found in vegetables and fruits that help reduce cancer, rather than any single nutrient such as lycopene. It is well-established that diets high in fruits and vegetables are associated with lower risk of cancers--just one more reason to adhere to the principles of the Atkins Advantage, which include getting all of your vitamins and minerals and eating plenty of vegetables.

Research shows that lycopene in foods is more available to the body when it has been heated. Like all carotenoids, it is more available to the body when it is consumed in combination with foods or ingredients that contain fat--for example, in the form of spaghetti sauce, tomato sauce or tomato paste.

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What is it about the color red in food? First tomatoes, now red wine! Find out why an ingredient found in red wine might be a great thing to add to your supplement arsenal.

Plato may have been onto something when he said, "Nothing more excellent or valuable than wine was ever granted by the Gods to man." Red wine has gotten a ton of press for its health-promoting abilities. Dozens of studies have shown that the risk of heart attacks in men and women who consume moderate amounts of this type of alcohol is 30 to 40 percent lower than in those who do not. Red wine has been thought by some to be particularly beneficial because of the antioxidants it contains, though some research has failed to show that red wine confers any greater reduction in risk than any other type of alcohol. Nonetheless, red wine contains compounds that are not found in any other alcoholic drink, and one of them just might confer benefits far beyond those of the alcohol itself.

That compound is called resveratrol, and it's found in both red wine and the seeds and skins of grapes. Antioxidants like resveratrol are beneficial in preventing harmful elements in the body from attacking healthy cells. Also found in peanuts, blueberries and cranberries, resveratrol is easily absorbed by the human body. The antioxidant properties of resveratrol also offer certain health benefits in the prevention of heart disease and the reduction of lung tissue inflammation in chronic obstructive pulmonary disease.

Resveratrol also has anti-cancer activity. Writing in the journal Anticancer Research in 2004, researchers from the University of Texas M.D. Anderson Cancer Center reviewed dozens of studies on resveratrol. They concluded that it exhibited anti-cancer properties against a wide range of tumor cells, including: lymphoid and myeloid cancers; multiple myeloma; cancers of the breast, prostate, stomach, colon, pancreas and thyroid; melanoma; head and neck squamous-cell carcinoma; ovarian carcinoma; and cervical carcinoma. The researchers concluded that "resveratrol appears to exhibit therapeutic effects against cancer."

So what about anti-aging? Well, resveratrol may be one of the best anti-aging substances around. Research by David Sinclair, Ph.D., assistant professor of pathology at Harvard University Medical School, shows that the lifespans of all life forms tested so far--yeast cells, fruit flies, worms and mice--have been dramatically lengthened by minute amounts of resveratrol. That's one of the reasons resveratrol is touted as one of the best anti-aging supplements you can take. Red wine--along with grapes--is an excellent way to get resveratrol into your diet.

But you don't have to be a drinker to get the benefits of resveratrol. It also comes in supplement form: 400 mg a day would be a great dose.

Alcohol is implicated in about one third of all fatal traffic accidents, and alcohol contributes to liver disease, a variety of cancers, high blood pressure, bleeding strokes and a progressive weakening of the heart. If you don't drink--or there's a reason why you shouldn't--you don't need to drink red wine to get your resveratrol. Take a supplement or eat some dark grapes!

The Folic Acid Connection

Though the benefit of alcohol for men is well established, the situation with women is less clear. The Nurses Health Study (and other research) has shown that even two drinks a day increase the chances of developing breast cancer by 20 to 25 percent. But the risk is virtually wiped out with proper folic acid intake. If you drink--and you're a woman--make sure to take a multivitamin with at least 400 mcg of folic acid, or take a B vitamin with folic acid. In fact, it's a good idea for everyone!

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While there may be some moderate warnings about red wine consumption because of the alcohol content, there are absolutely no warnings about this next beverage, which contains our next supernutrient: an incredible ingredient that fights cancer and helps you lose weight at the same time!

After water, tea is probably the most consumed beverage in the world. Not counting water, green tea is also probably the healthiest. Why? Let's find out.

To appreciate why scientists are so excited about the ingredient we're going to be discussing in this lesson, you need a little background on green tea. Green tea has been used as a medicine in China for over four thousand years. And there's good reason. It is truly one of the world's great superfoods, and has been acknowledged as such by virtually every nutritionist worth his or her salt. It has anti-cancer activity. It's helpful in weight loss. It lowers cholesterol. It's associated with significantly lower levels of heart disease. And it has components in it that are helpful with depression and anxiety.

There are many studies that show that green tea is a strong weapon against cancer. It's also been effective against rheumatoid arthritis, cardiovascular disease, infection and even high cholesterol levels. In fact, green tea lowers your cholesterol ratio--that's the number that's really important and that takes into account both good and bad cholesterol. It does that by lowering your LDL cholesterol, which is the bad stuff. And green tea also improves immune function. One study showed that compounds in green tea had an antiviral effect on the flu virus. And for cancer prevention, evidence for green tea is so overwhelming that the Chemoprevention Branch of the National Cancer Institute has initiated a plan for developing tea compounds as cancer-chemopreventative agents in human trials.

So what's so great about green tea, for goodness sake? What's in it that gives it all of these extraordinary health benefits? Well, the key to the health benefits of tea can be found in a large group of protective plant based chemicals generally known as phenolic compounds, or polyphenols. Green tea (and presumably the even less processed white tea) contains a very powerful group of polyphenols called catechins. One of these catechins in particular--epigallocatechin gallate (EGCG)--is believed to be responsible for the anti-cancer effects of green tea.

In 2004, for example, a team from Harvard Medical School reported that EGCG inhibits the growth and reproduction of cancer cells associated with Barrett's esophagus.

If its cancer-fighting ability weren't enough, the very same catechin--EGCG--may be an effective tool in weight management. In one study described in the American Journal of Clinical Nutrition, men who were given green tea burned more calories than men who were given a similar drink without the green tea, even after allowing for the possible effect of caffeine. Nutritionist Dr. Shari Lieberman says that green tea stimulates the metabolism way more than caffeine alone.

The benefits of green tea go beyond this superstar ingredient, since other ingredients in the tea--such as theanine--have a positive effect on mood and depression. But right now, EGCG remains the star of the show. Recently, a paper published in the September 2004 Journal of Nutritional Biochemistry examined the neuroprotective mechanisms of green tea polyphenols--especially EGCG--on both Alzheimer's and Parkinson's disease.

"Tea is one of the few foods (or drinks) about which I can say that virtually everyone would benefit from drinking it. It offers powerful antioxidant protection, reduces blood sugar, is anti-inflammatory, lowers cholesterol, protects against heart disease and cancer and has the ability to stimulate the metabolism."--Jonny Bowden, Ph.D., C.N.S. (from the forthcoming book, The 150 Healthiest Foods in the World)

Making Green Tea a Part of Your Day

Make a very strong cup of green tea using five tea bags, then squeeze in some lemon, dilute with a quart of water and refrigerate. You'll have a super beverage that lasts all day. If you really can't see your way to drinking three to five cups of green tea a day, remember that epigallocatechin gallate (EGCG) is available in supplement form. A good dose is 500 mg to 1000 mg a day.

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Fight colds, stimulate your immune system and protect your liver all with this next supernutrient: N-acetyl-cysteine.

The next time someone tells you not to take vitamins because "you can get all you need from food," tell them about N-Acetyl-Cysteine.

N-Acetyl-Cysteine (NAC for short) is an altered form of an amino acid called cysteine, which is found in high-protein foods. Our bodies can synthesize NAC from cysteine, but there are therapeutic effects from occasionally taking larger doses than are generally made in the body. And guess what--NAC is not found in the diet.

NAC helps the body synthesize what is arguably the most important antioxidant we have: glutathione (whey protein does the same thing). You might ask: If glutathione is so important, why not just eat more of it or get it as a supplement? It's a good question and the answer is simple. It's not well absorbed orally. There's still quite a lot of controversy about whether or not the oral supplement glutathione even gets past the stomach to do any good. Generally, most nutritionists believe that you're better off increasing glutathione stores by taking supplements (or eating foods) that contain the building blocks of glutathione, and then letting the body make it on its own. Taking NAC is one of the best ways to do that.

Glutathione has many protective roles in the body, and glutathione deficiency is associated with immune disorders, increased incidence of malignancies and probably accelerated progression of HIV-related diseases. Glutathione is the principle antioxidant of the deep lung; it has detoxification activity as well as the ability to modulate the immune response.

Want to see what acute manifestation of glutathione deficiency looks like? Show up at any hospital and wait for a case of acetaminophen poisoning. (Unfortunately, it won't be a long wait--acetaminophen overdose is the most common cause of calls to poison control centers in the United States). What has this got to do with N-Acetyl-Cysteine? Simple. NAC is so liver-protective that it is the treatment of choice at most hospitals for anyone coming in with acetaminophen poisoning. And one reason it works so well is precisely because of its ability to raise glutathione in the body. NAC has also been shown to be effective at treating liver failure from causes other than acetaminophen poisoning. And in animals, the antioxidant activity of NAC protects the liver from the adverse effects of exposure to several toxic chemicals.

But even if your liver is in great shape, you can benefit from supplemental NAC. N-Acetyl-Cysteine helps break down mucus. In fact, many nutritionists will recommend NAC along with other antioxidants for clients who have upper respiratory infections, colds and mucus. Double-blind research has found that NAC supplements improved symptoms and prevented recurrences in people with chronic bronchitis. It's also believed that NAC may help protect lung tissue through its antioxidant activity. Numerous studies have shown the effects of NAC on immune function--again, mostly through its powerful antioxidant activity. One animal study indicated that NAC may decrease mortality associated with influenza.

Though NAC might be a great supplement to take when you're sick--especially with an upper respiratory irritation that involves mucus--its powerful antioxidant properties aren't limited to helping your immune system. NAC has been the subject of much study in the area of diabetes, cancer and even some AIDS virus research, though much of the latter is preliminary.

Though all studies indicate that NAC is perfectly safe, if you're on medications it's a good idea to tell your doctor if you're thinking about taking it.

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Why sensible sunlight may be a better alternative to avoiding the sun at all costs.

Many nutritionists think that vitamin D is one of the most underrated vitamins in the world. Our recommended daily allowances have been around 400 mg a day, but many doctors and nutritionists are calling for an increase to 1000 mg. Most of the vitamin D used by our bodies is made by our skin when it's exposed to sunlight. We've known for almost a century that sunlight makes vitamin D and that it's necessary for healthy bones. But science is now revealing that vitamin D is much more vital to our survival than we possibly could have imagined.

"I believe that the public health problem for vitamin D deficiency is quite significant. I would estimate a minimum of 25 percent of adults in the United States, Europe and probably even in Australia are vitamin D deficient."--Professor Michael Holick, Boston University School of Medicine, author of The UV Advantage.

The good news is that your body makes vitamin D, but it makes it in the skin when you're exposed to sunlight. After that, your body turns it into what's called the "active" form of vitamin D, the kind your body can actually use. That activated kind of vitamin D is responsible for telling your body to absorb calcium from your diet more efficiently and to make sure that your blood calcium is normal and that you have healthy bones. In fact, without enough activated vitamin D, you can take all the calcium supplements in the world and it won't do you all that much good.

The other good news about vitamin D, besides the fact that it's absolutely necessary for strong bones, is that it actually helps control cell growth--which is why scientists now believe that vitamin D may protect against breast cancer, colon cancer and prostate cancer. They've known for a while that people who live in the higher latitudes are more prone to vitamin D deficiency and are also more prone to developing common cancers and dying of them, especially prostate, colon and breast cancer. So your skin is literally a pharmaceutical factory for this incredible vitamin--but to work, it has to be turned on by sunlight. Two research papers, both presented at the American Association for Cancer Research, found that women who have a high serum (blood) level of vitamin D have a reduced risk of breast cancer, as suggested by the observation that women living at higher latitudes (less sunlight) have higher levels of the disease than women at lower ones.

The scientist that's done the most research on vitamin D and the one who's been sounding the alarm the loudest about our collective vitamin D deficiency and the need for smart sun exposure is Dr. Michael Holick. He's looked at the vitamin D levels of pregnant mothers coming into his hospital, and also at the vitamin D levels of their infants once they were born. What he found was sobering: 76 percent of the mothers were severely vitamin D deficient and 81 percent of their infants were as well. And the Center for Disease Control reported that 42 percent of African American women were vitamin D deficient during their child-bearing years, especially at the end of winter. In fact, African Americans are especially at risk for vitamin D deficiency because dark skin is like wearing a permanent sun protection factor of 15 to 30 SPF. Dr. Holick says that even 48 percent of Caucasian girls age 9 to 11 are vitamin D deficient at the end of the winter, and 17 percent of them remain so at the end of the summer because they're all wearing sun protection.

It's very difficult to get enough vitamin D from your diet alone. Very few foods contain vitamin D--mostly it's oily fish like salmon and mackerel, and you'd have to eat that three to five times a week to get your vitamin D requirement. Cod liver oil is another good source, but let's face it--most people aren't going to run out and buy cod liver oil, let alone start taking it every day!

Dietary food sources of vitamin D include:

(Fish servings are 3 1/2 ounces, cooked.)

Vitamin D is a fat-soluble vitamin. Therefore, fortified skim milk might not be the best source of this nutrient, as it has no fat to help the body absorb it.

Remember, vitamin D also works in concert with a number of other vitamins, minerals and hormones to promote bone mineralization. Without vitamin D, bones can become thin, brittle or misshapen. Vitamin D sufficiency prevents rickets in children and osteomalacia in adults--two forms of skeletal diseases that weaken bones. Research also suggests that vitamin D may help also maintain a healthy immune system.

"We know from published studies that if you correct the vitamin D deficiency in high-risk population groups, you can reduce the risk of hip fractures by 25 to 40 percent."--Professor Terry Diamond, Associate Professor of Clinical Medicine, University of South Wales, St. George Hospital, New South Wales

So what do we do to get this wonderful, bone-building, cancer-fighting vitamin into our system? Simple. We get sensible sunlight.

Ten to 15 minutes of sun exposure at least two times per week to the face, arms, hands, or back without sunscreen is usually sufficient to provide adequate vitamin D. It is very important for individuals with limited sun exposure to include good sources of vitamin D in their diet.

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How a common flavonoid that's partly responsible for the color of red onions may help you with your allergies.