Establishing the link: From lab work to the daily diet

By M.E. Malone

Research

To move from a scientific hypothesis to actionable medical advice is a process that can take many years, particularly when the subject is human nutrition. A case in point is work currently underway at the Human Nutrition Research Center on Aging on how best to adjust out diets to lower the risk of fractures and muscle loss as we age.

While the role of calcium and vitamin D in stemming bone loss later in life has been fairly well-established, more recent research performed at the HNRCA Bone Metabolism Laboratory has been connecting the dots between diet, pH balance in the body, and bone and muscle health.

As part of the metabolic process, proteins and starchy carbohydrates – such as bread and pasta – release acids into the bloodstream. In older adults with declining kidney function, excess acid slowly accumulates and begins to break down bone and muscle.

While evidence is not conclusive that cutting back on fusilli will lead to fewer bone fractures in older individuals, Bess Dawson-Hughes, director of the Bone Metabolism Laboratory and principal investigator on the project, believes the work is promising. “There are a number of contributing causes” to declining muscle function and continual bone loss in older adults and pH balance may well play a role, she said. At the same time, there are other important protections against bone and muscle loss, including daily physical activity.

The lab’s current inquiry: just how much alkali is needed to neutralize acids produced metabolizing proteins and carbohydrates? Over the next 3-plus years, under a grant from the National Institutes of Health, Dawson-Hughes said her lab hopes to establish the optimal amount of alkali to neutralize acid using short-term intermediate markers that gauge the decline in bone and muscle health. Longer term, Dawson-Hughes said the aim is to test that “dose” in a clinical trial. About 270 individuals will participate in the current study

The work done to date may be yet another reason to be sure to get enough fruit and vegetables in the diet. Fruits and veggies, – even citrus fruits that we consider “acidic” – actually produce alkali when metabolized, helping to keep the body’s pH in balance.

“The acid/base control system in our body is quite elaborate and quite elegant,” Dawson-Hughes said, and adding to the knowledge about its role in bone and muscle health has been “intellectually interesting.” More importantly, she said, is the guidance for daily meal decisions that may stem from the work. “There won’t be a single golden parachute,” to protect against bone loss and muscle wasting later in life, she cautioned, “but this is exciting work.”

The PRAL (potential renal acid load) value is a measure of a food’s acidity once digested. Four ounces or chicken or lean beef, for example, have PRAL values of close to 12. A ½-cup of rice is 2.4, 1 cup of cooked oats is 4.3. Most fruits and vegetables have negative PRAL values: ¼ cup raisins has -8.4, a pear’s tally is -4.8 and spinach is valued at -11.9. Orange juice has a negative PRAL value as well. Most fats and sweets are considered neutral when it comes to post-metabolism acidity loads.

The PRAL (potential renal acid load) value is a measure of a food’s acidity once digested. Four ounces or chicken or lean beef, for example, have PRAL values of close to 12. A ½-cup of rice is 2.4, 1 cup of cooked oats is 4.3. Most fruits and vegetables have negative PRAL values: ¼ cup raisins has -8.4, a pear’s tally is -4.8 and spinach is valued at -11.9. Orange juice has a negative PRAL value as well. Most fats and sweets are considered neutral when it comes to post-metabolism acidity loads.

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