Can Chocolate be part of Bone Health?
Study: Effects of Chocolate Malt Drink Consumption Combined with Aerobic Dance Exercise on Blood Bone Metabolism Markers, Antioxidant Enzymes and Aerobic Capacity
The aim of this study was to investigate the effects of combined aerobic dance exercise and chocolate malt drink consumption on bone metabolism markers, antioxidant enzymes and aerobic capacity in young females.
Methods: Forty four physically healthy females (19-25 years old) were assigned into four groups: Control group (C), Chocolate malt drink group (Cmd), aerobic dance exercise group (Ex) and combined aerobic dance exercise and chocolate malt drink group (CmdEx).
Conclusions: The study found that generally aerobic dance exercise alone and aerobic dance exercise combined with the consumption of chocolate malt drink elicited more beneficial effects on bone turnover, antioxidant enzyme activities and aerobic capacity compared to chocolate malt drink consumption alone or sedentary without chocolate malt drink consumption in young females.
The nutritional component of chocolate tends to focus mostly on polyphenols (antioxidants), however other nutrients are contained within chocolate including:
- caffeine (methylxanthines)
These nutrients can both positively and negatively influence bone health and chronic diseases.
Chocolate and Bone Metabolism
Osteoporosis is a degenerative bone disease that leads to thinning bones making bones and increased risk of fractures. Osteoporosis is caused by an imbalance between bone formation and resorption. Approximately 1in 3 women, and 1 in 5 men suffer with osteoporosis. The intake of specific kinds of flavonoids may promote bone health. Cocoa solids (the non-fat portion of a cacao beans) has a higher flavanol content (by weight) than most foods. Cocoa is higher in flavonoids than tea, fruits and vegetables. A number of studies have evaluated the potential role of consuming chocolate in regards to bone health.
A study in Scotland in postmenopausal women associated flavonoid intake with higher hip and lumbar spine bone mineral density. Flavonoids were consumed mostly through tea drinking (57%) and catechin was identified as the main flavonoid consumed. Cocoa beans rich in flavonoids: catechin (34-40%) and epicatechin. Chocolate, being made from cacao beans, also contains high levels of both catechin and epicatechin (even after cacao bean processing).
Antioxidant properties of chocolate (which fight against oxidative stress and inflammation) could have positive implications for bone health since chronic bone loss is accompanied by higher oxidative stress and inflammation. Reactive oxygen species (ROS – markers of inflammation) have a negative impact on bone health. ROS can affect the bones by increasing bone cell death (osteoblast apoptosis), increased osteoclast (bone breakdown)activity, and increased bone resorption. Human osteoblasts (bone building cells) treated with various doses of catechin, saw a significant reduction in ROS (reactive oxygen species) formation.
Proinflammatory cytokines, interleukin (IL)-1, IL-6, and(TNF)-a are important regulators for bone resorption, and possibly play a role in age and estrogen deficiency-related bone loss. Treating osteoblasts with catechin reduced inflammatory markers (IL-6, TNF-a, IL-1), and increased osteoblast (bone building cells) survival. Researchers concluded the catechins preserved bone-forming osteoblasts by exerting anti-inflammatory actions. A crossover study involving normal and individuals with elevated cholesterol, consuming cocoa powder with milk twice a day for 4 week significantly decreased serum inflammatory biomarkers for IL-1 compared to those who only drank milk. These studies suggest that there is potential for chocolate and cacao to promote bone health.
Studies On Chocolate Consumption And Bone Health
The following information was taken from studies which have looked into various aspects of bone health and chocolate consumption. Many of the studies have looked into chocolate milk as a way to increase calcium consumption in children, but didn’t include an information on bone health. Bone mineral accrual during childhood is a key determinant in future risk of osteoporosis.  Meaning, if the process of bone density, thickness, or length is hindered during development, this can increase their risk as older adults. One study of 6-10 year old girls showed that calcium-supplemented chocolate bars, cakes, or beverages significantly increased height and bone mass acquisition in the radius and femur. This also resulted higher bone mass maintained 1 yr past termination of the intervention. This study suggests chocolate may play a role in promoting bone mass in prepubertal girls. However, they point out the mechanisms to explain this require more investigation.
A study on sedentary vs circuit training men who consumed chocolate malt drink indicated that the men who were physically active showed lower levels of a bone resorption marker. The sedentary group showed no effect.
Healthy, overweight, or obese premenopausal women following an energy-restricted diet consumed a high flavanol cocoa beverage (280 mg flavanols/d) and 2 dark chocolate snacks (240 mg flavanols/d) for 18 weeks. However, the changes were not significantly different from the control group who didn’t consume the flavanol rich drink. Therefore, results indicate the beverage didn’t provide benefits to biomarkers of bone turnover, BMD, oxidative stress, and inflammation above that provided by weight loss.
A 5 year trial involving 1001 Australian women aged 70-85 investigated the effects of calcium supplementation on bone density and strength. The only impact appeared to be that tibia bone density and strength were lower in the women who said to have consumed chocolate daily vs those where consumption was rare. Based on these results, the authors concluded that daily chocolate consumption increased the risk for lower bone density and strength in postmenopausal women. Those who consumed chocolate daily had a higher socioeconomic status and exhibited lower body mass index values despite greater total caloric saturated fat, total carbohydrate, and sugar intake associated with chocolate. Other lifestyle factors such as activity levels were not monitored during the 5 yr intervention.
Limits of many of theses studies include reliance on self-reporting chocolate consumption and not specifying the type of chocolate. Studies obviously suggest that there are potential 'positives' and 'negatives' for chocolate and cacao consumption and bone health.
Types of Chocolates
Types of chocolate are important because they contain different levels of polyphenols depending on type and ingredients. Cacao is meant the raw unprocessed bean from the cacao fruit tree. Cocoa is the term used after the cacao bean has undergone processing in order to be used in chocolate manufacturing. The polyphenol content of the cacao varies among plant species, growing region, climate during growth, maturity at harvest, and storage time. Polyphenol content of cacao is about 10% dry weight, making it rich in polyphenol (higher total flavonoids per serving than red wine or black tea). The flavanols in cocoa are mainly epicatechin and catechin. Cacao beans undergo processing to reduce bitterness. Processing can decreased the polyphenol content. Unprocessed cocoa powder averages 35 mg/ 100g flavanol content compared to 4-14 mg/100g in processed powders.
According to USDA, catechin content from highest to lowest is as follows:
- cocoa beans
- cocoa powder
- baking chocolate
- alkalized cocoa powder
- chocolate confections
Flavonoid content is highly dependent on the ‘type’ of chocolate consumed. Non-fat cocoa solids are highest in cocoa powder (72-78%), then dark chocolate (20-30%), semisweet (15-19%), and milk chocolate (5-7%). A 40 g bar milk chocolate has 394 mg polyphenol antioxidants, dark chocolate provides 951 mg.
Other Chocolate Constituents
Chocolate isn’t all about flavonoid content, it also has many other constituents that can have an impact on health. Even though chocolate is low in vitamins important for bone health, chocolate and cocoa are used in foods that are a source of vitamins A and D such as milk products. For instance, dark chocolate contains ~ 4 ug/100g for dark of vitamin D (~2 ug/100g for milk chocolate)
Dietary Mineral Content
Overall, studies have shown that cocoa powder and high percentage dark chocolate (70% and up) can provide a source of minerals important to bone health. However, chocolate also contains high amounts of oxalates (between 500-900 mg/100g) that may interfere with mineral absorption in the body. This is something to keep in mind when looking at levels of minerals in chocolate or cocoa powder.
Calcium is important for bone mineralization. Calcium content can vary from 15- 28 mg/100g depending on the type of chocolate. Generally, dark chocolate contains the highest amounts of minerals and polyphenols. However, when it comes to calcium, white chocolate contains the most - due to the milk powder content. Dark chocolate (especially high quality dark) doesn’t contain milk. Unfortunately, white chocolate also contains the highest amount of sodium, which may reduce calcium bioavailabilty.
Magnesium is tied to Vitamin D metabolism. More than 12 studies found positive correlations between magnesium intake and femoral neck and total hip bone density. 1.5 ounces of dark chocolate provides 15% of the Magnesium daily dietary allowance.
Copper inhibits bone resorption and also helps in the development of collagen and elastin in bone. Chocolate contributes 9.4% of the daily copper intake for Americans. Cocoa powder has the highest amount of copper, followed by dark, milk, and then white chocolate. 1 Tbsp of Cocoa powder provides up to 82% of the recommended daily allowance (RDA) for copper.
Fat (lipid) content of chocolate comes from the fat within the cocoa bean, milk powders in milk chocolates, and added vegetable oils in some commercial chocolate.
Natural fat content is highest in dark chocolate and white chocolate. Cocoa butter is composed mainly of three fatty acids:
- Stearic acid (saturated)
- Palmitic acid
- Oleic acid (monounsaturated)
Some research appears to suggest that saturated fatty acids (SFA) may increase hip fracture risk by causing:
- reduced calcium absorption
- more calcium excreted in the urine
- increased survival of osteoclasts (cells that break down bone)
- inhibition of osteoblast (bone building cells) formation
Observations studies show that postmenopausal women with daily or moderate chocolate intake have higher fat intake overall versus women who only consumed chocolate rarely - which can contribute to excessive calorie intake
Postmenopausal women with daily chocolate consumption have higher sugar intake overall versus women who only consumed chocolate moderately or rarely. Sugar is added to reduce bitterness of cacao and to bring out aromas that may be masked without the addition of sugar.
Sugar content is highest in white chocolate, followed by milk, dark, and then unsweetened cocoa powder. Sugar may affect the absorption of other chocolate nutrients. Studies on both humans and animals reported that consuming cocoa with sugar increases the absorption of flavonoids (antioxidants).
Very few human studies have looked into the impact of sugar on bone health. Animal studies show that higher sugar intake usually has a negative impact on bone health. One explanation is that high sugar intake increases calcium excretion (due to insulin resistance), decreasing calcium re-absorption and can lead to increased bone loss over time. While flavanol intake has been shown to reduce insulin resistance, excess sugar intake seems to negate any potential benefit.
Caffeine can stimulate the release of stored calcium from bones. Since 99% of calcium in the body is stored in bones, high consumption of methylxanthines may lead to bone mineral loss. Caffeine has been shown to reduce calcium absorption and increase calcium excretion in urine. Dark chocolate and cocoa powder had the highest level of caffeine, followed by cocoa powder, and then milk chocolate. That said, chocolate contains very little caffeine compared to other more popular caffeine sources. (Chocolate milk - 4 mg, Coffee - 85 mg, Tea - 30 mg, and Soft Drinks – 20 mg).
We have reason to believe chocolate and cocoa powder provide dietary source of flavonoids and other constituents with the potential to affect bone. However, the benefits in chocolate and cacao may be outweighed by other constituents which may have adverse effects on bone health.
Some studies have reported inverse relationship with high chocolate consumption and lower BMD in postmenopausal women, while other studies showed no such effect. The bone-building effects of chocolate seems to depend greatly on the type of chocolate consumed.