Flavonoids May Lead to Fewer Fractures

By Dr. Mercola

Drinking tea, which is a major source of dietary flavonoids, has been linked to higher bone density in observational studies. Flavonoids – antioxidant compounds found in certain fruits, vegetables, herbs, and spices – are known for their role in helping to prevent chronic diseases like heart disease and cancer, but new research suggests they may play a significant role in bone health as well.

Elderly women at high risk of fractures who drank three or more cups of flavonoid-rich black tea daily had a significantly lower risk of fracture-related hospitalizations than women who did not.¹

Compared with women who drank one cup of tea a week or less, women who drank three or more cups daily had a 30 percent lower risk of any osteoporotic fracture.

Higher intake of flavonols, a type of flavonoid, in particular was linked to a significant reduction in fracture risk, while another type, flavones, were linked to a reduced risk of hip fracture. Gael Myers, the study's lead researcher, noted:²

"It's long been known that tea is good for our health. But our research linking tea drinking with better bone health, including reduced fracture risk, adds another string to the bow for this popular drink. Osteoporosis is a debilitating disease, particularly for older women, where thinning and deteriorating bones lead to fractures as well as significant disability and pain."

Flavonoid Intake Boosts Bone Health Even More Than Fruit and Vegetables

While flavonoids' antioxidant properties have long been singled out as playing a primary role in their health benefits, researchers are looking beyond their antioxidant capacity when it comes to bone health.

In fact, the compounds have been said to have "the most potential of dietary components for promotion of bone healthy beyond calcium and vitamin D." And research suggests they have a stronger association with bone health than even general fruit and vegetable consumption.³ As noted in the Journal of Nutrition in Gerontology and Geriatrics:⁴

"Bioactive flavonoids are being assessed for properties beyond their chemical antioxidant capacity, including anti-inflammatory actions. Some have been reported to enhance bone formation and to inhibit bone resorption through their action on cell signaling pathways that influence osteoblast and osteoclast differentiation.

… [T]here is increasing evidence that inflammation is part of the etiology of osteoporosis. Flavonoids as a class of phytochemicals have promise in protecting against bone loss, likely related in part to their anti-inflammatory properties.

In a large observational study in Scotland, total flavonoid intake was positively associated with BMD [bone mineral density] and increase in BMD of the spine and hip."

A separate study published in Current Osteoporosis Reports similarly revealed that flavonoids have a favorable effect on bones.⁵ They referenced two human studies in women, which found positive associations between total dietary flavonoid intake and bone mineral density. They also noted that flavonoids may benefit bone health via multiple mechanisms:

"Flavonoids may protect against bone loss by upregulating signaling pathways that promote osteoblast function, by reducing the effects of oxidative stress or chronic low-grade inflammation."

Which Flavonoid-Rich Foods May Be Best for Your Bones?

An animal study evaluated 53 foods to determine their ability to inhibit bone turnover. While total polyphenolic content of the foods was not related to their effectiveness for bone health, specific flavonoids did appear to confer benefits to bone, and some had antiresorptive properties, meaning they may slow bone loss.

The foods with the greatest potential for supporting bone health due to their flavonoid concentrations include the following:⁶

Onions

Onions have a strong ability to inhibit bone resorption. While rutin was initially believed to be the bioactive flavonoid responsible, researchers believe a compound known as Γ-L-glutamyl-trans-S-1-propenyl-L-cysteine sulfoxide may also be involved.

Dried Plums (Prunes)

Dried plums, also known as prunes, have been found to increase bone mineral density in rats, and in a study of postmenopausal women, loss of BMD of major fracture sites was prevented by eating plums.

Plums, and dried plums, contain high concentrations of rutin, which is known to strengthen blood vessels, although its role in bone health is less certain. There may be other specific bone bioactive compounds in dried plums that have yet to be uncovered.

Blueberry

In a rat study, blueberry prevented whole body bone loss. Hippuric, phenylacetic, and hydroxybenzoic acids are likely the bioactive compounds in blueberries.

Oranges

Orange pulp protected against bone loss in the rat study and increased cortical (compact) bone thickness in a dose-dependent manner (i.e. the more orange pulp consumed the greater the thickness became). Hesperidin, the most abundant flavanone in citrus fruits, is thought to be responsible for the bone-boosting effects.

Mushrooms

Extracts from king oyster mushroom have been found to protect against bone loss.

Celery

Luteolin is an anti-inflammatory plant compound found in certain vegetables and herbs, including celery, peppers, parsley, and carrots. In addition to protecting against memory loss and cancer, luteolin inhibits osteoclast differentiation (thereby slightly decreasing bone turnover markers and offering a protective effect on the bones) and protects against bone loss.

Fennel Seeds

Although not part of the animal study, fennel seeds are rich in flavonoids, and a study published in the International Journal of Molecular Medicine found that eating the seeds of the plant had a beneficial effect on loss of bone mineral density, as well as bone mineral content.⁷

Healthy bones maintain their strength through a continual process of bone breakdown and bone rebuilding. Osteoclasts are the cells that break down weakened bone, and osteoblasts are the cells that build it back up.

The fennel appeared to work by reducing osteoclast differentiation and function. Researchers indicated that fennel seeds show potential in preventing bone loss in postmenopausal osteoporosis.

Green Tea

Green tea polyphenols appear particularly beneficial for protecting against bone damage caused by chronic inflammation. In rats, green tea polyphenols decreased inflammation-induced bone loss, preserved femur bone mass and structure, and led to lower tartrate-resistant acid phosphatase, which is a marker of bone resorption.

It's Best to Get Flavonoids and Other Bone-Boosting Nutrients from Food

One of the reasons why eating a healthy, whole-food-based diet is so important for your bone health is because it supplies a steady source of nutrients and other plant compounds your body, and bones, need. This includes not only flavonoids but also bone-boosting nutrients like magnesium, vitamin K2, and vitamin B12. In terms of flavonoids, vegetables, fruits, and herbs are among the best sources.

Calcium, vitamins D and K2, and magnesium also work synergistically to promote strong, healthy bones. Ideally, you'd get all or most of these nutrients from your diet (with the exception of vitamin D). This includes:

• Plant-derived calcium: Raw milk from pasture-raised cows (who eat the plants), leafy green vegetables, the pith of citrus fruits, carob, and sesame seeds
• Magnesium: Raw organic cacao, green leafy vegetables, nuts and seeds, and supplemental magnesium threonate if need be
• Vitamin K2: Grass-fed organic animal products (i.e. eggs, butter, and dairy), certain fermented foods such as natto, or vegetables fermented using a starter culture of vitamin K2-producing bacteria, and certain cheeses such as Brie and Gouda (see below for more details on vitamin K2 and bone health)
• Trace minerals: Himalayan Crystal Salt, which contains all 84 elements found in your body, or other natural, unprocessed salt (NOT regular table salt!)
• Vitamin D: Ideally from appropriate sun exposure (or a high-quality tanning bed). As a last resort, you could use a supplement, but if you do, you may also need to supplement with vitamin K2 to maintain ideal ratios

Supplements can sometimes be appropriate, especially if you're at high risk of bone problems, however, there is no substitute for real food. The synergistic effects of consuming flavonoids in food-form, along with other beneficial nutrients, cannot be overstated. Writing in the Journal of Nutrition in Gerontology and Geriatrics, researchers concluded:⁸

"Flavonoids in a variety of plant foods hold promise in promoting bone health, both in the primary prevention of bone loss in later life and as a complementary therapy during conditions of high oxidative stress or chronic inflammation.

We are beginning to understand their roles in cell signaling, including… pathways that stimulate bone formation, in addition to their anti-resorptive roles in inhibiting osteoclast activation.

This represents an advance in our understanding of flavonoids beyond the classic estrogen-like actions of soy isoflavones and beyond evaluating flavonoids only for their chemical antioxidant properties. The interaction of dietary factors with these signaling pathways is a rich area for future research."

A Complete Recipe for Bone Health

Flavonoids represent just one piece of the puzzle to building and maintaining healthy bones. The following guidelines can also help you maintain, or increase, your bone strength safely and naturally at any age:

1. Make your own fermented vegetables using a special vitamin K2-producing starter culture, or supplementing with vitamin K2 if you're not getting enough from food alone. Vitamin K2 serves as the biological "glue" that helps plug the calcium into your bone matrix. Also remember to balance your calcium and magnesium (1:1 ratio). Vitamin K2 is produced by certain bacteria, so the primary food source of vitamin K2 is fermented food such as natto, a fermented soy product typically sold in Asian grocery stores.

   Fermented vegetables can be a great source of vitamin K if you ferment your own using a specially designed vitamin K2-rich starter culture. Please note that not every strain of bacteria makes K2, so not all fermented foods will contain it. For example, most yogurts have almost no vitamin K2.

   Certain types of cheeses, such as Gouda, Brie, and Edam, are high in K2 while others are not. It really depends on the specific bacteria. Still, it's quite difficult to get enough vitamin K2 from your diet — unless you eat K2-rich fermented foods — so taking a supplement may be a wise move for most people.

2. Avoid processed foods and soda, which can increase bone damage by depleting your bones of calcium. By ditching processed foods, you're also automatically eliminating a major source of refined sugars and processed fructose, which drive insulin resistance. It will also provide you with a more appropriate potassium-to-sodium ratio, which is important for maintaining bone mass (larger amounts of potassium in relation to sodium are optimal for your bone health and your overall health).
3. Increase your consumption of raw, fresh vegetables, ideally organic. If you find it difficult to eat the recommended amount of vegetables you need daily, you can try vegetable juicing.
4. Maintain a healthy balance between omega-6 and omega-3 fats in your diet by taking a high-quality, animal-based omega-3 supplement like krill oil and reducing your consumption of processed omega-6, found in processed foods and vegetable oils.
5. Get regular exercise. Ideally, your fitness program should be comprehensive, providing the necessary weight-bearing activities for bone health, while also improving your cardiovascular fitness and fat-burning capabilities with high-intensity exercises. Whole body vibration training may also improve bone health.

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