Diets High In Animal Food Strongly Associated With Fractures

Two high-profile people suffered injuries to their skeletons in the last few weeks.

German Chancellor Angela Merkel fell while skiing, fractured a bone in her pelvis, and is walking with the aid of crutches. She “was not skiing fast at the time.”

Former US Defense Secretary Robert Gates (who you may have seen in a neck brace promoting his new book “Duty: Memoirs of a Secretary at War”) fractured a vertebrae in his neck after falling at his home. Gates also broke his humerus in 2008 after slipping on ice. The humerus is the very large arm bone between the shoulder and the elbow.

MerkelCrutches2GatesNeckBrace2

These bone injuries reminded me of my post, The More Protein You Eat, The More Calcium You Excrete. I showed this graph. It’s the relationship between dietary protein and calcium excretion from 26 studies. As protein increased, more calcium was lost:

CalciumExcretion2

Animal food increases the body’s acid load, which is neutralized by minerals in bone such as calcium. Here are a few epidemiological studies which support the link between dietary animal protein and fractures:

Cross-cultural association between dietary animal protein and hip fracture: a hypothesis, Calcified Tissue International, 1992

“Age-adjusted female hip fracture incidence has been noted to be higher in industrialized countries than in nonindustrialized countries. A possible explanation that has received little attention is that elevated metabolic acid production associated with a high animal protein diet might lead to chronic bone buffering and bone dissolution. In an attempt to examine this hypothesis, cross-cultural variations in animal protein consumption and hip fracture incidence were examined. When female fracture rates derived from 34 published studies in 16 countries were regressed against estimates of dietary animal protein, a strong, positive association was found. This association could not plausibly be explained by either dietary calcium or total caloric intake. Recent studies suggest that the animal protein-hip fracture association could have a biologically tenable basis. We conclude that further study of the metabolic acid-osteoporosis hypothesis is warranted.”

Protein consumption and bone fractures in women, American Journal of Epidemiology, 1996

“Dietary protein increases urinary calcium losses and has been associated with higher rates of hip fracture in cross-cultural studies. However, the relation between protein and risk of osteoporotic bone fractures among individuals has not been examined in detail. In this prospective study, usual dietary intake was measured in 1980 in a cohort of 85,900 women, aged 35-59 years, who were participants in the Nurses’ Health Study. A mailed food frequency questionnaire was used and incident hip (n = 234) and distal forearm (n = 1,628) fractures were identified by self-report during the following 12 years. Information on other factors related to osteoporosis, including obesity, use of postmenopausal estrogen, smoking, and physical activity, was collected on biennial questionnaires. Dietary measures were updated in 1984 and 1986. Protein was associated with an increased risk of forearm fracture (relative risk (RR) = 1.22, 95% confidence interval (Cl) 1.04-1.43, p for trend = 0.01) for women who consumed more than 95 g per day compared with those who consumed less than 68 g per day. A similar increase in risk was observed for animal protein, but no association was found for consumption of vegetable protein. Women who consumed five or more servings of red meat per week also had a significantly increased risk of forearm fracture (RR = 1.23, 95% Cl 1.01-1.50) compared with women who ate red meat less than once per week.”

Worldwide incidence of hip fracture in elderly women: relation to consumption of animal and vegetable foods, The Journals of Gerontology, 2000

Hip fracture, a major health problem in elderly persons, varies in incidence among the populations of different countries and is directly related to animal protein intake, a finding that suggests that bone integrity is compromised by endogenous acid production consequent to the metabolism of animal proteins. If that is so, vegetable foods might provide a countervailing effect, because they are a rich source of base (bicarbonate) in the form of metabolizable organic anions, which can neutralize protein-derived acid and supply substrate (carbonate) for bone formation.

We analyzed reported hip fracture incidence (HFI) data among countries (N = 33) in women aged 50 years and older, in relation to corresponding country-specific data on per capita consumption of vegetable and animal foods as reported by the United Nations Food and Agriculture Organization.

Results. HFI varied directly with total (r = +.67, p < .001) and animal (r = +.82, p < .001) protein intake and inversely with vegetable protein intake (r = −.37, p < .04). The countries in the lowest tertile of HFI (n = 11) had the lowest animal protein consumption, and invariably, vegetable protein (VP) consumption exceeded the country’s corresponding intake of animal protein (AP): VP/AP > 1.0. By contrast, among the countries in the highest tertile of HFI, animal protein intake exceeded vegetable protein intake in nearly every case (10 of 11 countries). Among all countries, HFI correlated inversely and exponentially with the ratio of vegetable/animal protein intake (r = −.84, p < .001) and accounted for 70% of the total variation in HFI. Adjusted for total protein intake, vegetable food consumption was an independent negative predictor of HFI. All findings were similar for the subset of 23 countries whose populations are predominantly Caucasian.

Conclusion. The findings suggest that the critical determinant of hip fracture risk in relation to the acid-base effects of diet is the net load of acid in the diet, when the intake of both acid and base precursors is considered. Moderation of animal food consumption and an increased ratio of vegetable/animal food consumption may confer a protective effect.

CheddarAged2It’s not just the protein in meat, but in all animal foods, that increases acid load.  Cheese is notorious for having a high PRAL or renal acid load.1 Believe it or not, the National Dairy Council, at one time, said this:

Excess dietary protein, particularly purified proteins, increases urinary calcium excretion. This calcium loss could potentially cause negative calcium balance, leading to bone loss and osteoporosis. These effects have been attributed to an increased endogenous acid load created by the metabolism of protein, which requires neutralization by alkaline salts of calcium from bone.”

That’s right, the food which is advertised to “Build Strong Bones,” could lead to “bone loss and osteoporosis.”

1 Potential Renal Acid Load of Foods and its Influence on Urine pH

One thought on “Diets High In Animal Food Strongly Associated With Fractures

  1. Pingback: Getting Your Protein From Plants, Instead of Animals, May Protect Bone | Fanatic Cook

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