C O V E R S T O R Y in women eop LOA Q: Q: What wou hat would su ACID surprise people who want to prevent bone fractures? A: You can’t just think about bones. As we age, we lose muscle mass at a pretty good clip and our balance becomes worse, so we have a greater risk of falling. This is a major, major contributor to osteoporotic fractures. Falls create the fracture opportunity, so there’s a lot of interest in them these days. For fi ve years now, we’ve viewed fracture risk as not just a matter of bone content, but also a matter of muscle. If you can’t improve muscle perfor-mance and balance, it’s hard to lower the risk of falls, and falls will create fractures. So we’re interested in nutrients that affect both bone and muscle. Q: Which nutrients affect both? A: The acid-base balance of the diet is one factor that we’re working on enthusiasti-cally. The acid load generated by many diets isn’t handled well by older people because of their declining kidney func-tion. So they become gradually, mildly, but progressively acidotic. That is, they have too much acid in the bloodstream. That causes muscle wasting.Muscle loss is the body’s way of adapting to the excess acid. So is bone loss. Q: So the body breaks down bone and muscle to neutralize the excess acid? A: Yes.We know that bone cells have hydrogen ion receptors, so they’re sensitive to excess acid. No one has worked out exactly how acid signals the muscle to break down. But it’s clear that the body tries to defend against increasing acid by breaking down bone and muscle. Q: Do acidic foods like citrus fruit create acid in the body? A: No. Grains—like bread, cereal, rice, pasta, crackers, tortillas, cookies, doughnuts, cupcakes, and se people who he percent tw and one our ostis which isk. im u’ re 40, our in f over 50 os, ill means “porous bones. of ne double body ta losi ore ri will break bo bec he bone th ak o f ract older you are, igher es si us uring And it’s not just weak bones, but weak muscles, that lead to debilitating fractures. Here’s how to avoid both. similar foods—and protein do.When they are metabolized, they release sulfuric and other acids into the bloodstream. In contrast, fruits and vegetables get broken down into bicarbonate when they are metabolized, so they add alkali to the body. And that helps to neutralize acid. Sugars and fats are generally neutral. So when the diet is relatively poor in fruits and vegetables relative to grains and pro-tein, that’s a net acid-producing diet. [See “Dropping Acid,” p. 5.] Q: Do we have conclusive evidence that eating a diet that neutralizes excess acid protects bone? A: No, but it’s promising.We’ve put people on an acid-producing diet—that is, a diet high in protein and grains—and then given them an alkali like potassium bicarbonate. And you can see markers of bone turnover drop. And nitrogen excre-tion, which is an indication of muscle wasting, also declines. Bess Dawson-Hughes is a professor of medicine at Tufts University School of Medicine in Boston and the director of the Bone Metabolism Laboratory at the Jean Mayer U.S. Depart-ment of Agriculture Human Nutrition Research Center on Aging at Tufts. She is a past-president and trustee of the National Osteoporosis Foundation, general secretary of the International Osteoporosis Foundation, and the author of more than 280 journal articles, book chapters, and reviews. Nutrition Action’s Bonnie Liebman spoke to her by phone from Boston. These effects occur immediately, and they’re reversible when you reverse the acid load. That’s been shown in short-term studies, and we also did a three-month study in 170 healthy older people. When we gave bicarbonate to the people on the acid-producing diet, it re-sulted in reduced bone turnover markers. And the women—who got a higher dose for their body weight than the men— actually improved their performance doing a double leg press. The bicarbonate increased power in their legs and de-creased nitrogen wasting, which suggests that they were losing less muscle mass. Q: Were the people very old? A: No.We studied men and women aged 50 and older. The average age was 63. Muscle wasting picks up and is continu-ous from the 40s on. You can see this if you look around you. You can see it in the mirror. And you can also see it on the street. It’s obvious. You see people with a big belly and skinny legs. Q: Do both animal and vegetable protein produce acid? A: Since plant protein generally comes in foods like beans, which have an accompanying alkaline source, it is less acid-producing than the same amount of protein from beef. But it’s not the protein that matters. The acid-producing quality de-pends on how many sulfur-contain-ing amino acids are in the protein, and there’s a wide range in both plant and animal protein sources. So it’s misleading to refer to protein as plant or animal, unless you know the overall picture. > > > > > NUTRITION ACTION HEALTHLETTER ■ NOVEMBER 2010 3 V E R S T O R Y in women eop LOA Q: Q: What wou hat would su ACID surprise people who want to prevent bone fractures? A: You can’t just think about bones. As we age, we lose muscle mass at a pretty good clip and our balance becomes worse, so we have a greater risk of falling. This is a major, major contributor to osteoporotic fractures. Falls create the fracture opportunity, so there’s a lot of interest in them these days. For fi ve years now, we’ve viewed fracture risk as not just a matter of bone content, but also a matter of muscle. If you can’t improve muscle perfor-mance and balance, it’s hard to lower the risk of falls, and falls will create fractures. So we’re interested in nutrients that affect both bone and muscle. Q: Which nutrients affect both? A: The acid-base balance of the diet is one factor that we’re working on enthusiasti-cally. The acid load generated by many diets isn’t handled well by older people because of their declining kidney func-tion. So they become gradually, mildly, but progressively acidotic. That is, they have too much acid in the bloodstream. That causes muscle wasting.Muscle loss is the body’s way of adapting to the excess acid. So is bone loss. Q: So the body breaks down bone and muscle to neutralize the excess acid? A: Yes.We know that bone cells have hydrogen ion receptors, so they’re sensitive to excess acid. No one has worked out exactly how acid signals the muscle to break down. But it’s clear that the body tries to defend against increasing acid by breaking down bone and muscle. Q: Do acidic foods like citrus fruit create acid in the body? A: No. Grains—like bread, cereal, rice, pasta, crackers, tortillas, cookies, doughnuts, cupcakes, and se people who he percent tw and one our ostis which isk. im u’ re 40, our in f over 50 os, ill means “porous bones. of ne double body ta losi ore ri will break bo bec he bone th ak o f ract older you are, igher es si us uring And it’s not just weak bones, but weak muscles, that lead to debilitating fractures. Here’s how to avoid both. similar foods—and protein do.When they are metabolized, they release sulfuric and other acids into the bloodstream. In contrast, fruits and vegetables get broken down into bicarbonate when they are metabolized, so they add alkali to the body. And that helps to neutralize acid. Sugars and fats are generally neutral. So when the diet is relatively poor in fruits and vegetables relative to grains and pro-tein, that’s a net acid-producing diet. [See “Dropping Acid,” p. 5.] Q: Do we have conclusive evidence that eating a diet that neutralizes excess acid protects bone? A: No, but it’s promising.We’ve put people on an acid-producing diet—that is, a diet high in protein and grains—and then given them an alkali like potassium bicarbonate. And you can see markers of bone turnover drop. And nitrogen excre-tion, which is an indication of muscle wasting, also declines. Bess Dawson-Hughes is a professor of medicine at Tufts University School of Medicine in Boston and the director of the Bone Metabolism Laboratory at the Jean Mayer U.S. Depart-ment of Agriculture Human Nutrition Research Center on Aging at Tufts. She is a past-president and trustee of the National Osteoporosis Foundation, general secretary of the International Osteoporosis Foundation, and the author of more than 280 journal articles, book chapters, and reviews. Nutrition Action’s Bonnie Liebman spoke to her by phone from Boston. These effects occur immediately, and they’re reversible when you reverse the acid load. That’s been shown in short-term studies, and we also did a three-month study in 170 healthy older people. When we gave bicarbonate to the people on the acid-producing diet, it re-sulted in reduced bone turnover markers. And the women—who got a higher dose for their body weight than the men— actually improved their performance doing a double leg press. The bicarbonate increased power in their legs and de-creased nitrogen wasting, which suggests that they were losing less muscle mass. Q: Were the people very old? A: No.We studied men and women aged 50 and older. The average age was 63. Muscle wasting picks up and is continu-ous from the 40s on. You can see this if you look around you. You can see it in the mirror. And you can also see it on the street. It’s obvious. You see people with a big belly and skinny legs. Q: Do both animal and vegetable protein produce acid? A: Since plant protein generally comes in foods like beans, which have an accompanying alkaline source, it is less acid-producing than the same amount of protein from beef. But it’s not the protein that matters. The acid-producing quality de-pends on how many sulfur-contain-ing amino acids are in the protein, and there’s a wide range in both plant and animal protein sources. So it’s misleading to refer to protein as plant or animal, unless you know the overall picture. > > > > > NUTRITION ACTION HEALTHLETTER ■ NOVEMBER 2010 3 ause ause of d su ACID surprise people who want to prevent bone fractures? A: You can’t ju Photo: Eric Audras/PhotoAlto Agency RF Collections/Getty Images (top).