Category Archives: Bone Health

Milk Intake Linked To More Fractures And Earlier Death In Large Swedish Cohorts

Remember the post where I wondered If Milk Builds Strong Bones, Why Do People In Countries Who Consume The Most Have Higher Fracture Rates? I posted two maps, one of global milk consumption, another of global hip fracture rates. They clearly show a link between high milk consumption and increased bone fractures, as contradictory as that sounds. But my post wasn’t scientific. It was just raw, unadjusted data. Who knows if something other than milk was causing the fractures?

Well, the researchers in this next study wanted to know. They set out to examine the relationship between milk intake and fracture rates, as well as milk’s effect on mortality. Their data was adjusted for possible confounders including “age, total energy intake, body mass index, height, educational level, living alone, calcium supplementation, vitamin D supplementation, ever use of cortisone, healthy dietary pattern, physical activity, smoking status.”

Milk intake and risk of mortality and fractures in women and men: cohort studies, British Medical Journal, 28 October 2014

The researchers analyzed data from two large Swedish cohorts, one with over 61,000 women, another with over 45,000 men, during the course of 11 (for men) to 20 (for women) years.

“In women the adjusted mortality hazard ratio for three or more glasses of milk a day compared with less than one glass a day was 1.93.”

So, drinking 3 glasses of milk almost doubled women’s risk of death in that 20 years. Drinking milk also increased inflammation:

“A positive association was seen between milk intake and both urine 8-iso-PGF2α (a biomarker of oxidative stress) and serum interleukin 6 (a main inflammatory biomarker).”

They concluded:

“Our results may question the validity of recommendations to consume high amounts of milk to prevent fragility fractures.”

Some numbers… Among women, they “observed a positive association between milk intake and total mortality as well as fracture, especially hip fracture”:

For each glass of milk:

A 15% increased risk of dying from any cause.
A 15% increased risk of dying from cardiovascular disease.

For 3 or more glasses of milk compared to less than 1:

A 93% increased risk of death from any cause.
A 44% increased risk of death from cancer.
A 60% increased risk for hip fracture.

The mechanism they proposed for these increased risks is something I’m not familiar with … galactose. Galactose is a sugar. It’s one of the two sugars that make up the disaccharide lactose, or milk sugar. (The other is glucose.) Here’s what they say:

“A high intake of milk might, however, have undesirable effects, because milk is the main dietary source of D-galactose. Experimental evidence in several animal species indicates that chronic exposure to D-galactose is deleterious to health and the addition of D-galactose by injections or in the diet is an established animal model of aging. Even a low dose of D-galactose induces changes that resemble natural aging in animals, including shortened life span caused by oxidative stress damage, chronic inflammation, neurodegeneration, decreased immune response, and gene transcriptional changes. A subcutaneous dose of 100 mg/kg D-galactose accelerates senescence in mice. This is equivalent to 6-10 g in humans, corresponding to 1-2 glasses of milk. Based on a concentration of lactose in cow’s milk of approximately 5%, one glass of milk comprises about 5 g of D-galactose. The increase of oxidative stress with aging and chronic low grade inflammation is not only a pathogenetic mechanism of cardiovascular disease and cancer in humans but also a mechanism of age related bone loss and sarcopenia.”

Milk is the primary source of galactose in humans’ diet. Milk that has been fermented or exposed to the action of bacteria (e.g cheese) contains less galactose because the bacteria consume it. Low-fat milk has proportionately more galactose than full-fat milk.

The BMJ is not a fringe journal. This study had to withstand rigorous peer review before it was published. And it isn’t the first study to uncouple the supposed positive link between dairy food and bone health. People who continue to advise consumption of 3 or more servings of dairy food a day to promote strong bones and reduce fracture rates are not keeping company with science. Who are they keeping company with?

Getting Your Protein From Plants, Instead of Animals, May Protect Bone

4 Replies

High protein diets increase the risk for bone fracture. That doesn’t mean protein isn’t important. Too little protein also increases the risk for fracture. I’ve seen some vegetarian diets that left their consumers dangerously low in protein. I mean, if all you’re going to eat is bananas…

How do you protect your bones if you’re cutting back on animal foods? Get your protein from plants:

A High Ratio Of Dietary Animal To Vegetable Protein Increases The Rate Of Bone Loss And The Risk Of Fracture In Postmenopausal Women, American Journal of Clinical Nutrition, 2001

“Elderly women with a high dietary ratio of animal to vegetable protein intake have more rapid femoral neck bone loss and a greater risk of hip fracture than do those with a low ratio. … These associations were unaffected by adjustment for age, weight, estrogen use, tobacco use, exercise, total calcium intake, and total protein intake. … This suggests that an increase in vegetable protein intake and a decrease in animal protein intake may decrease bone loss and the risk of hip fracture.”

What’s the mechanism?

“Different sources of dietary protein may have different effects on bone metabolism. Animal foods provide predominantly acid precursors, whereas protein in vegetable foods is accompanied by base precursors not found in animal foods. Imbalance between dietary acid and base precursors leads to a chronic net dietary acid load that may have adverse consequences on bone.”

It isn’t just bone that weakens when exposed to a high animal protein diet, it’s muscle too:

“… skeletal muscle, like bone, may serve as a reservoir of base that is gradually depleted to maintain acid-base balance. … Muscle mass decreases during experimentally induced metabolic acidosis. … Chronic depletion of skeletal muscle could lead to weakness and a greater number of falls, both factors in hip fracture.”

Note that those who had the highest ratio, who ate the most animal food, also had the highest calcium intake (1124 mg/day vs. 662 mg/day). Those eating a high animal food diet took in over 2/3rds more calcium and still had more bone loss and fractures.

What plant foods are good sources of protein? See my logo.

Diets High In Animal Food Strongly Associated With Fractures

1 Reply

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.

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:

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.

It’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