Boning Up on Fats and Skeletal Health: Part One

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We all know that diet plays a key role in bone strength, with calcium and vitamin D playing prominent roles. What about fat though? Yes, it is possible to modify how much fat you consume, as well as the types of fats, to enhance bone health. Whether you’re currently a spring chicken or mature hen, it is something worth considering. It is estimated that 1 in 3 women and 1 in 5 men (or more) will get a fracture due to bone weakness during their lifetime. Moreover, people’s lifestyles often suffer for long periods after a fracture. For example, a previously active relative of mine had a fall almost two years ago. Because the fracture and healing process was complex, they are still struggling to get around with a walker to this day. Even simple tasks in daily life, including reaching, twisting, and bending can be impeded. Here we take a broad look at the impact of fats. Stay tuned next week for a closer look at the especial effects of omega-3 and 6 fatty acids.

Key points:

1. Eating excess total fat or saturated fat is associated with poorer bone health.
2. Inflammation, impeded calcium absorption, increased breakdown and excretion of minerals, or displaced nutrient intakes are possible mediators of this effect.
3. Higher polyunsaturated fat intakes (relative to saturated) are generally considered to promote bone health

Bone Health 101

While 1 in 3 women and 1 in 5 men experience osteoporotic fractures, it should be noted that there is substantial variation in their prevalence around the world. For example, women from rural parts of Asia have been reported to experience half the fractures of caucasian women. However, city-dwellers have similar rates as white American women. In the absence of data proving why this phenomenon occurs, it would appear that changes in lifestyle may be a factor. This may include (but not be limited to) dietary fat intake.

Just total fat and bones

There are definite associations between increased fat intake and decreased bone mineral density, and increased risk of fractures. Because this is only association data though, there is no clear indication of ‘how much’ fat might begin to be too much. For this reason, I’d recommend you stick to the general recommendations of getting 20-35% of your calories from fat. 

It seems the impact of fat on bone health may be mediated by inflammatory processes. There is increasing evidence that inflammation may contribute to metabolic bone diseases such as osteoporosis. This is because cells that create bone and those that break it down are both regulated by the balance between proinflammatory and anti-inflammatory molecules. When the balance is tipped towards pro-inflammatory molecules, net breakdown wins. 

All fats are not made equal…

It is not just total fat intake, but the intake of specific fats that seem to play a role. As you’ll see, there is dispute over the role of each fat on the bone mineral density of different body parts. 

Saturated fat intake and bones

There’s been an observed association between increased saturated fat (primarily animal fats) and increased fracture risk, particularly of the hip. Cell culture studies have also suggested saturated fat suppresses the activity of bone-forming cells. Stick to recommendations of saturated fat (combined with trans fats) providing less than 10% of your caloric intake.

It’s also worth remembering that there are a number of PUFA’s- that differ in structure and chemical properties. Thus it’s not surprising that they may each have individual effects on bone. If this was not accounted for, it may have impacted on the different findings between studies. For example, in contrast to the general consensus, limited research has linked polyunsaturated fat intake with lower bone mineral density in the hip. Either way, further research should clarify this.

Stay tuned for more on the roles of different PUFA’s next week.

The Verdict

Excess total fat or saturated fat intake seems to compromise bone health. Getting no more than 20-35% of your calories from fat, limiting your saturated fat intake (from meat, takeaway and treats) to 10% and optimising polyunsaturated fat intake could protect your bones. The impact of monounsaturated fats is not clear.

How do you think your fat intake compares with these recommendations?