Canola oil consumption and bone health.

The prevalence of osteoporosis, a common skeletal disorder among elderly, is now increasing worldwide.[123] Nationally representative data from Iran has reported a lower peak bone mass among Iranian compared to European and American population.[45] There are several factors which could improve bone health, including genetics and environmental factors such as nutritional adequacy. In a multicenter interview-based study, Keramat et al. reported Lower educational level, delayed menarche, early menopause and a poor diet as the risk factors of osteoporosis among Iranian women.[6]

Several dietary factors may affect bone health. Frequent red meat intake and pure vegetarianism were considered as the risk factors of osteoporosis while consuming soy, fruits, fish and milk were reported as protective factors. The effects of dietary fatty acids on bone health also have been reported previously. Different dietary fatty acids may affect bone health via the status of inflammatory markers production.[7] In the current issue of journal of research in medical sciences, Azemati, et al. have reported the findings of a 3-months parallel-arm randomized clinical trial on 40 osteoporotic post-menopausal Iranian women which aimed to compare the effect of canola oil (as the natural source of omega-3) and sunflower oil (as the natural source of omega-6) on biochemical markers of bone metabolism. They found a non-significant increase in bone alkaline phosphatase (BALP), N telo peptide collagen (NTX) in canola oil group and a non-significant decrease for Osteocalcin in both groups. Additionally, they found increased levels of vitamin D3 in both groups, but the difference between two groups was not significant. Overall, they found that canola oil did not affect bone formation and resorption significantly after 3 months consumption.

It seems that the non-significant association is related to some critical point which should be noted in this study. First of all, Azemati et al. evaluated the adherence of recommended diet using recall and checking empty bottle while it was better they used more precise method to evaluate fatty acids intake such as measuring serum fatty acids concentration. Second, they did not consider the exact amount of ω-3 and ω-6 and they recommend vegetable oils which included various types of fatty acids in different ratio. Hence, it is probable that these oils could not provide enough amounts of omega-3 and omega-6 to exhibit expected outcomes. Other possible reasons for non-significant findings in this study may be related to its small sample size and short-time intervention which shows the necessity of more studies with larger sample size and longer duration.

Studying the effect of fatty acids is not a novel concept and there are some studies in this field. However, findings are not consistent in this regard. Some studies showed that PUFA intake (both omega-3 and omega-6) were positively associated with BMD.[8] However, some researchers reported higher fracture rate by higher n-3 fatty acids and lower fracture risk with higher n-6 fatty acids.[9] In a previous study which was done by Salari Sharif et al.,[10] the effect of omega-3 was assessed, but they prescribed 900 mg n-3 fatty acid capsules for 6-monthes compared with placebo. Their findings supported the beneficial effect of omega-3 on bone biomarkers.

Overall, the exact effect of dietary fatty acids on bone biomarkers and their mechanisms are not clear, exactly. However, some mechanisms have been suggested underlying their effects which mainly explained by the inflammatory roles of fatty acids. For instance, n-3 fatty acids by decreasing PGE2 production, increases the producing of osteoprotegerin and decrease the expression of receptor activator of nuclear transcription factor κB ligand (RANKL), which leads to increase the ratio of osteoprotegerin: RANKL and improve the resorptive bone disease.[11] Another notable aspect in these studies is the total amount of EPA + DHA, which should be checked between different groups, since in a well-designed study, they have been considered as confounder factors. However, the worthwhile finding of this study is that showing n-3 fatty acids in a short time does not have any beneficial effects on bone biomarkers. More longitudinal studies are needed to illustrate the exact effects of different fatty acids on bone health.

It should be noted that in present study, Azemati considered two vegetable sources of ω-3 and ω-6 fatty acids. Most of previous studies which reported the beneficial effects of ω-3 on bone health mainly focused on marine source or both vegetable and marine sources of ω-3[89] or compared ω-6 (in vegetable oils) with fish oil.[12] This is notable since vegetable and marine sources of ω-3 show different inflammatory effects.[13] Although previous studies have focused on the effects of omega-3 fatty acids on different metabolic diseases,[14] few researches have provided extensive information on osteoporosis. Furthermore, considering the type of oils and different cooking methods is also important in interpretation of the results.[15]