Healthy plant-based diets mitigate bone loss

A case-control study of post-menopausal women with and without osteoporosis, demonstrated that healthy plant-based diets were significantly associated with a lower degree of bone loss compared to those following unhealthy plant-based diets.(1)

Aim

The aim of the study was to identify dietary factors that could influence bone mineral density in Iranian post-menopausal women where the incidence of osteoporosis is signficantly higher than the global average at 43.5% compared to 18.3%, respectively. The dietary focus was on the degree of plant-based food consumption as the authors identified plant-based diets to offer key nutrients and higher intakes of specific food groups often attributed to better bone health outcomes such as fruit and vegetables, potassium and magnesium.

Study design

The case control study included 131 post-menopausal women with osteoporosis or osteopaenia and 131 control healthy post-menopausal women.

Bone mineral density (BMD) measurements were taken of the femoral neck and lumbar vertebrae using dual-energy x-ray absorptiometry (DEXA).

Dietary assessment

A semi-quantitative food frequency questionnaire (FFQ) was used to assess habitual daily consumption during the past year.

All subject's FFQ were assessed against the degree of adherence to three pre-defined dietary patterns and placed in tertiles.

The three dietary patterns were:

1. Plant-based Diet Index (PDI): those providing the highest degree of plant foods compared to animal foods

2. Healthy Plant-based Index (hPDI): those providing the highest degree of healthful plant foods and least animal and unhealthy foods

3. Unhealthy Plant-based Index (uPDI): those based predominantly on unhealthy plant foods with low animal intakes.

All dietary patterns were allocated a score of a minimun of 18, reflecting poor adherence, up to a maximum of 180, reflecting high adherence.

Results

The control group was found to have better BMD, but were also more physically active and had a higher degree of education. The women with osteoporosis/osteopaenia were more likely to take vitamin D supplements as part of their daily routine (42% of controls vs 56% for osteoporotic cases) and only 24% of all the women took calcium supplements regularly.

Diet quality between the lowest tertile and highest tertile for adherence to the three dietary patterns:

• PDI: the highest tertile group for adherence had greater intakes of both positive and negative nutrients. Intakes for energy and salt were higher and saturated fats no better than those in the lowest tertile. At the same time the highest tertile had greater intakes of mono (MUFA) and polyunsaturated fats (PUFA), magnesium, selenium and vitamins E and folate.

• hPDI: Diets of those with the greatest adherence had a significantly better nutrition profile with higher intakes of fibre, vitamins C, K and A, phosphorus and magnesium and lower intakes of energy, sodium, saturated fats. Calcium intakes did not differ between tertiles, however, vitamin B12 was signficantly lower in the highest tertile. The nutrient profile of the diets were reflected in the higher intakes of wholegrains, fruit and vegetables and legumes and lower intakes of refined grains, sweetened beverages and snacks as well as animal fats.

• uPDI: Those with greatest adherence to uPDI had significantly lower wholegrains, nuts, seeds, legumes, meat and dairy and highest intake of refined carbs. Additionally, all macro- and micronutrient intakes in the highest tertile were lower compared to those in the lowest tertile. Unlike the hPDI and PDI, uPDI adherence resulted in significantly lower calcium intakes.

Association between diet categories and BMD

No significant association was identified between BMD and PDI. However, there was a significant reverse association between adherence to hPDI and BMD loss; post-menopausal women with higher adherence to hPDI demonstrated a low degree of bone mineral loss compared to those who least adhered. The opposite finding was found for women most adhering to the uPDI, who demonstrated a significant greater bone mineral loss with higher adherence to uPDI.

Conclusion

The authors of the study investigated a major health concern for menopausal women, which is the acceleration of bone mineral loss due to the loss of oestrogen, leading to a higher risk of osteoporosis and osteopaenia. Their research showed that plant-based diets can provide beneficial nutrients and improve bone health outcomes. However, the positive effects are only evident if the plant-based diets consist of healthful plant foods. Conversely, diets predominantly based on unhealthful plant foods can lead to a significant decrease in key bone nutrients such as calcium, and can exacerbate bone mineral loss in this high-risk population group. The authors also emphasise the importance of ensuring adequate vitamin B12 intake in the hPDI group, who consume significantly lower amounts of animal products.

This study adds to the growing body of evidence that the quality of plant-based diets is crucial in determining their impact on health outcomes. It is not simply the adoption of a plant-based diet that is beneficial, but rather high-quality nutrient-rich plant-based diets that provide health benefits.

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