Vitamin E may be best known for improving skin and eye health as well as immune function. In recent years, researchers have explored the potential benefits of vitamin E on bone loss, particularly in women with menopause-related osteoporosis. As data from these studies begins to trickle in, evidence demonstrating a positive impact of vitamin E on osteoporosis and hip fracture the risk in perimenopausal women remains elusive.
For osteoporosis, the use of vitamin E relies on its antioxidant activity, which can scavenge potentially harmful free radicals. Researchers wondered whether vitamin E could help maintain bone matrix integrity and stimulate bone formation while minimizing bone resorption, particularly in cases trabecular (cancellous) bonethe bone compartment preferentially affected in perimenopausal bone loss.
Vitamin E consists mainly of two isomers: alpha-tocopherol and gamma-tocopherol. Alpha-tocopherol has higher antioxidant activity and is found in nuts, seeds, vegetable oils, green leafy vegetables, fortified cereals, and vitamin E supplements. Gamma-tocopherol is known for its properties superior anti-inflammatories and represents approximately 70% of total vitamin E intake in a typical American diet, coming largely from soy and other vegetable oils.
Benefits and risks in bone loss studies
Perimenopausal bone loss is caused, to a large extent, by the decline in sex hormones. Studies of vitamin E in ovariectomized rats gave mixed results. This animal model lacks sex hormones and exhibits bone changes similar to those in postmenopausal women. Some animal studies have suggested a positive effect of vitamin E on bones while others have reported no effect.
Human studies have also produced conflicting reports on positive, neutral and negative associations of vitamin E with bone health. For example, the Women’s Health Initiative examined the relationship between antioxidant vitamins and minerals and bone health in postmenopausal women and found no significant association between antioxidants and bone mineral density.
Another study examining data from children and adolescents enrolled in the National Health and Nutrition Examination Survey (NHANES) database found an inverse association between alpha-tocopherol and bone density of the lumbar spine, suggesting a deleterious effect on bones. Inverse associations have also been reported in some studies on menopausal women.
High doses of alpha-tocopherol have been associated with risk of impaired bone health by various mechanisms, such as interference with vitamin K metabolism; competitive binding for alpha-tocopherol transfer protein, inhibiting entry of beneficial vitamin E isomers, including gamma-tocopherol; and prooxidant effects that harm bones. Thus, postmenopausal women taking vitamin E supplements primarily in the form of high doses of alpha-tocopherol could harm their bone health.
The data on gamma-tocopherol are more promising. Some studies hypothesize that gamma-tocopherol could uncouple bone remodelingleading to increased bone formation without affecting bone resorption. Additionally, a randomized controlled study comparing a mixture of tocopherols (rather than alpha-tocopherol) to placebo reported a protective effect of this preparation on bone results by suppressing bone resorption. This raises the importance of considering specific forms of vitamin E when evaluating its role in bone health.
Limitations of current studies
The researchers acknowledge several limitations in the studies conducted to date. For example, there are very few randomized controlled trials evaluating the impact of vitamin E on bone health. Most studies are cross-sectional or observational, even longitudinal. Cross-sectional and observational designs prevent us from establishing a causal relationship between vitamin E and bone parameters.
Such designs also run the risk of additional confounding factors that may affect associations between vitamin E and bone, or lack thereof. These could include known and unknown confounding factors. It should be noted that data on gamma-tocopherol intake were not available for some NHANES studies.
Additionally, people often consume multiple nutrients and supplements, making it difficult to identify specific associations between nutrients and diseases. Most human studies estimate tocopherol intake using dietary questionnaires or measure serum tocopherol levels, which reflect short-term dietary intake, while bone mineral density is likely influenced by long-term dietary habits. .
Too early to prescribe vitamin E for bone health
Some nutrition experts advocate vitamin E supplements containing a mixture of tocopherols, specifically suggesting a ratio of 50 to 100 IU of gamma-tocopherol to 400 IU of D-alpha-tocopherol. Additional research is essential to confirm and further clarify the role of gamma-tocopherol in bone formation and resorption. In fact, it is also important to explore the influence of other compounds in the vitamin E family on skeletal health.
Until more data is available, we recommend following the Institute of Medicine guidelines for the recommended daily allowance (RDA) of vitamin E. This is according to ageranging from 4 to 11 mg/d between 0 and 13 years, and 15 mg/d thereafter.
Overall, the evidence for the impact of vitamin E on osteoporosis and hip fracture risk in perimenopausal women remains inconclusive. Although some observational and interventional studies suggest potential benefits, more interventional studies, particularly randomized controlled trials, are needed to more fully explore the risks and benefits of vitamin E supplementation and serum vitamin E levels on bone density and fracture risk.