From Michigan State University

Why Milk Won't Prevent Osteoporosis

-And The Protein Myth- 

By Dina Fitzsimons

Let's play word association. When you hear the word "osteoporosis," what's the first word that comes to your mind? If you said "calcium," then the American Dairy Association has done its job.

Osteoporosis is a condition of abnormal porousness of bone resulting from gradual bone loss, leading to increased fractures, loss of height, hip and back pain, and spinal curvature. The disease affects about 25% of postmenopausal women in the US. Since osteoporosis is a disease of bone loss, and since 99% of the body's calcium is found in bone, it certainly seems logical that if people eat as much calcium as possible, osteoporosis risk may be diminished. The Dairy People capitalize on this idea by constantly reminding us that dairy products constitute some of the richest sources of calcium in the supermarket (never mind that calcium is found in varying amounts in all fruits, vegetables, and grains). But this "you need your milk" idea is not universally accepted.

The truth is, there has been little or no success in preventing osteoporosis by eating dairy products. Plainly and simply, when enough calcium is consumed to prevent deficiency (which is much lower than the Recommended Dietary Allowance), taking in excess does little more than put a person at risk for kidney stones. In fact, Americans consume excessively large quantities of calcium, yet risk of osteoporosis continues to threaten millions of Americans. Most people are not aware that the US already has one of the highest calcium intakes in the world. Calcium deficiency caused by an insufficient amount of calcium is not known to occur in humans, even though most people in the world don't drink milk after weaning because of custom, lactose intolerance, or unavailability. In fact, nations with the highest levels of dairy consumption are the same nations with the highest rates of osteoporosis.

In addition, although it seems to be common sense, few people consider this: humans all over the planet have been living relatively long, healthy lives free of osteoporosis for millennia. These people, for the most part, never touched dairy food, calcium supplements, or hormone therapy. Today, most of the world's population consume less than 500 mg of calcium daily (the RDA is roughly twice this amount), and there is no convincing evidence that countries with lower dietary intakes are disadvantaged in regard to osteoporosis.

What is undoubtedly clear is that the more PROTEIN a population consumes, the higher its prevalence of osteoporosis. That's correct- there is a direct correlation between protein intake and loss of calcium from the bone. This calcium-wasting effect by protein has been documented time after time in studies for over 70 years. Something to remember is that along with the calcium in your glass of milk there is also a sizable dose of protein. How strong is the effect of protein on calcium loss? If protein intake is doubled without changing intake of other nutrients, calcium in the urine increases by about 50%.

This argument does not go unchallenged, of course. For example, intake of the mineral phosphorus has been shown to decrease protein-induced urinary calcium loss. The problem with this reasoning is that phosphorus intake does not offset the negative effect of protein. It turns out that as phosphorus intake is increased, there is a subsequent increase in fecal calcium. In fact, when a phosphorus supplement is given along with a high protein load, urinary calcium is decreased but fecal calcium is increased. Scientists have taken this biochemical evidence one step further: many studies have found a strong, positive association between protein intakes and hip fracture rates among different populations around the world. In any given population, the greater the intake of protein, the more common the prevalence and more severe will be the osteoporosis. How about some examples?

The African Bantu consumes an average of 350 mg of calcium per day (current recommendations for Americans is about 1000 mg per day) yet do not have calcium deficiency, seldom break a bone, and rarely lose a tooth. (Plenty of Bantus live past age 65.) They consume very low-protein diets with sufficient calories. Osteoporosis among the Bantu is very rare until they migrate to the United States and begin to consume a typical, protein-laden American diet.

Native Eskimos have the highest dietary calcium intake of any other people in the world-- above 2000 mg per day from fish bones. Their diet is also the highest in the world in protein- up to 400 g per day primarily from fish (Americans rarely eat quite this much). Native Eskimos have the highest rate of osteoporosis in the world.

This news is really hard to swallow for most people. After all, don't we need lots of protein to be healthy and strong? Even the most conservative nutritionists out there can tell you that there is an ongoing Protein Myth in this country. Americans eat about 400% more protein than necessary to maintain protein balance, and even vegetarians eat more than they need. As a nutritionist and vegetarian, I am often asked, "Well, where do you get your protein?" and my answer is, "From food- fruits, vegetables, grains, and beans." Have you ever heard of anyone suffering from a protein deficiency? Do any vegetarians you know look like those starving kids from Africa with huge bellies and pencil-thin thighs? Of course not. Protein deficiency is so hard to attain, it would be nearly impossible for any American to have. Unfortunate individuals in developing countries who suffer from protein malnutrition have a condition called kwashiorkor, and this develops as a result of consuming a staple food that is low in protein, such as cassava root, and practically nothing else.

The general rule is, if one gets enough calories, he or she will automatically get enough protein. We do not need foods with a high protein concentration (i.e. animal products) to meet our protein needs. In fact, calorie for calorie, broccoli contains more protein (45%) than corned beef (25%). Of course, a typical serving of corned beef has more protein than a typical serving of broccoli (which is about 91% water by weight), but this supports the idea that with enough calories in the diet, enough protein automatically follows.

What about protein complementation? Again, part of the Protein Myth. Amino acid deficiency simply is a notion that has never been demonstrated in well-fed individuals, even the strictest of vegans. The US is a country of overconsumption, not underconsumption. The leading causes of death today are all diet-related- and are not due to "not getting enough," but of getting too much. We are eating more and more -of nearly everything- and chronic diseases like osteoporosis are more and more prevalent.

Granted, many factors contribute to osteoporosis risk, including low levels of physical activity and smoking. But calcium intake has received a grossly inordinate amount of attention with regard to osteoporosis prevention. Again, leave it to groups who will benefit financially by feeding the unsuspecting public partial and misleading information. There are so many risks associated with dairy consumption (See previous articles in AnimaLife Vol 3, Issue 1, pg 8, and Vol 5, Issue 1, pg 1.), and research continues to fail to show any significant relationship between intake of dairy foods and osteoporosis. Again, all of the published studies to date are concordant; all find that increased protein intake leads to increased loss of calcium. And, not surprisingly, several studies demonstrate that vegetarian women experience less osteoporosis on average than their omnivorous counterparts. One main dietary difference between omnivores and vegetarians is protein intake, since animal-derived foods are concentrated protein sources.

Why is this evidence surrounding protein so ignored? Why don't we read about these studies in the media? For one thing, there is no group that lobbies about the advantages of a low-protein diet. The primary sources of protein in the typical American diet are meat and - you guessed it - dairy products. The meat and dairy boards will do everything in their power to not let such news leak into the popular press. No one will sell products which boast a low protein content - we've been spoon-fed the Protein Myth our whole lives - and this works out well for the meat and dairy lobbyists.

Unfortunately or fortunately, the secret to health, longevity and chronic disease prevention -notably osteoporosis- is a plant-based diet with ample carbohydrates and moderate amounts of protein and fat.

(Dina Fitzsimons (Cornell '94) is currently earning her R.D. and Master's Degree in Nutrition at Tufts University.)

Sources

Abelow BJ, Holford TR, and Insogna KL. (1992) Cross-cultural association between dietary animal protein and hip fracture: a hypothesis. Calcified Tissue International 50: 14-18.

Arnaud CD and Sanchez SD. (1990) The role of calcium in osteoporosis. Annual Reviews of Nutrition 10: 397-414.

Dawson-Hughes B. (1991) Calcium supplementation and bone loss: a review of controlled clinical trials. American Journal of Clinical Nutrition 54: 274S-280S.

Heany RP. (1993) Protein intake and the calcium economy. Journal of the American Dietetic Association 93: 1259-1260.

Heany RP and Recker RR. (1982) Effects of nitrogen, phosphorus and caffeine on calcium balance in women. Journal of Laboratory and Clinical Medicine 99: 46-55.

Kanis JA. (1991) Calcium requirements for optimal skeletal health in women. Calcified Tissue International 49: S33-S41.

Levitsky, David, lecture in Nutritional Sciences 115, Cornell University, 12/1/93.
Marsh AG, Sanchez TV, Chaffee Fl, Mayor GH, and Mickelsen O. (1983) Bone mineral mass in adult lacto-ovo-vegetarians and omnivorous males. American Journal of Clinical Nutrition 37:453-456.

Marsh AG, Sanchez TV, Mickelsen O, Keiser J, and Mayor G. (1980) Cortical bone density of adult lacto-ovo-vegetarian and omnivorous women. Journal of the American Dietetic Association 76: 148-151.

Mazess RB and Mather WM (1974) Bone mineral content of North Alaskan Eskimos. American Journal Clinical Nutrition 27: 916-925.

McDougall, JA. The McDougall Plan. Clinton: New Win Publishing; 1983.
Riggs BL, Wahner W. Melton LJ, Richelson LS, Judd HL, and O'Fallon M. (1987) Dietary calcium intake and rates of bone loss in women. Journal of Clinical Investigation 80: 979-982.

Robbins, J. Diet For A New America. Walpole: Stillpoint Publishing; 1987.

Smith R and Rizek J. (1966) Epidemiologic studies of osteoporosis in women of Puerto Rico and Southeastern Michigan with special reference to age, race, national origin and to other related or associated findings. Clinical Orthopedics 45: 31-48.

Walker ARP. (1965) Osteoporosis and calcium deficiency. American Journal of Clinical Nutrition 16: 327-336.