Happy Thanksgiving everyone – I thought I’d blog about food today, and to try to persuade you to trade that pumpkin pie for a glass of milk…
I learned some interesting things at the Dairy Science Forum on November 13th in DC. Dr. David McCarron presented some compelling data on the effects of the DASH diet on reducing blood pressure. The DASH diet is fairly high in dairy products (2-4 servings/day), fruits, and vegetables. In comparison with a low-salt diet (which reduces systolic blood pressure by an average of 1 point), the DASH diet can cause an average reduction in systolic blood pressure of ten points. If you have high blood pressure (and your kidneys are functioning normally) you probably shouldn’t worry all that much about the salt. It’s more important to stick with the DASH diet.
I interviewed Dr. McCarron about the role of dairy in blood pressure management. Here’s what he had to say:
Dr. Val: If salt isn’t the real enemy, and dairy can help to reduce blood pressure, why isn’t that message getting out?
Dr. McCarron: We have national nutrition policies in place that are old and out of date. The healthy eating paradigm – low fat, low sugar, low salt – was established 40+ years ago and when new evidence is obtained, it’s really hard to crack through that illusion of knowledge. There is excessive mistrust of new data because of the attitude that if it conflicts with our previous beliefs, it can’t be true. I believe that the Internet will be critical in allowing the evidence to bubble up. For example, a diet rich in dairy food is absolutely associated with a reduction in virtually all chronic medical conditions. We have data to support this for people of all ethnicities and from around the world. I think that consumers are looking for clarity and simplicity in their nutritional advice – and basically they need to know that a healthy diet requires 3-4 servings of dairy and 5-6 servings of fruits and vegetables/day. If you do that alone (along with regular exercise) you’ll be amazed by the results.
Dr. Val: What is the proposed mechanism by which dairy has all these positive effects?
Dr. McCarron: It’s almost impossible to nail down specific mechanisms because milk products contain so many ingredients (electrolytes, key vitamins, bioactive proteins, and essential fatty acids). Trying to understand which piece is impacting very complicated physiological control mechanisms within the body (that have 30-40 different vectors feeding into them) is extremely difficult. In fact, the permeatations make it almost impossible. We can’t come up with the proof that we do for drugs (which contain only one bioactive ingredient). What we do know, though, is that dairy is a vital component for chronic disease reduction and prevention. Unfortunately the policy people say, “you haven’t explained to me how this works, so I’m not going to consider it.”
Dr. Val: But what about the research suggesting that whey protein contains lactokinins that function similarly to ACE inhibitors (a type of blood pressure medicine)?
Dr. McCarron: That’s been known for over a decade. There’s no question that there are small peptides (proteins) in milk that have a positive impact on blood pressure, mood disorders, and weight reduction. The industry doesn’t want to talk about it because it makes milk sound like a drug, which isn’t effective marketing. Also the average consumer doesn’t have enough background to understand what that means (lactokinins have ACE inhibitor-like effects in vivo), so we need to simplify the message and disseminate it via the Internet.
NEJM, 1998 Effects of Dietary Patterns On Blood Pressure
Am J Hyper, 2004 McCarron and Heaney
JAMA, 2002 Pereria et al
Science, 1984, McCarron et al
JAMA, 1996, Bucher et al
My husband doesn’t like it when I go shopping with his credit card. But I tried to cheer him up about it. I said, “Honey, every purchase is a vote of confidence in your earning power.”
- Joan Horbiak, MPH, RD, at the Dairy Science Forum, November 13, 2008
It is estimated that 75% of our healthcare dollars are spent on chronic disease management, and that 80% of chronic diseases could be avoided with diet and lifestyle interventions. This means that the best way to decrease the size of our healthcare budget is to decrease the size of our collective waistlines. And that’s no small task.
Going back to basics – healthy eating and regular exercise – is such a simple message. But what is healthy eating exactly? Consumers are fairly exhausted by the complex messages they’ve heard about food and nutrition over the past couple of decades. One minute anti-oxidant foods are a miracle cure for everything from cancer to facial wrinkles, the next, it seems that they actually increase the risk of death. Diet advice ranging from low fat, low carb, to low sugar have all been promoted as the healthiest way to lose weight. But what does the evidence actually show? I decided to interview a series of experts to try to glean what I could about the state of nutrition knowledge. Today’s post is about protein – and I interviewed Nancy Rodriguez, PhD, a “protein scientist” to weigh in on this nutrient.
Dr. Val: We don’t talk about dietary protein needs that much, Nancy. Why is that?
Dr. Rodriguez: In the United States most people do get at least the minimum required amount of protein/day. The RDA (recommended daily allowance) of 0.8g/Kg of body weight is the amount you need to consume to avoid an outright protein deficiency. That’s about 3 ounces of chicken, fish, or meat/day – the size of a deck of cards. But the real benefits of protein include appetite suppression, and thermogenesis. Studies show that if people eat a little bit of protein with each meal, they’re less likely to become hungry between meals or consume as many calories overall. You also end up burning a few calories in the process of digesting protein.
Dr. Val: So what is the appropriate amount of protein intake?
Dr. Rodriguez: I have found that 1.2-1.5g/Kg may be optimal for hunger management. That means we should try to get a little bit of protein with each meal. Weight maintenance and loss is much easier to achieve if you don’t feel hungry all the time. Protein can really help with that.
Dr. Val: Is it possible to eat too much protein? Can it damage the kidneys in excess?
Dr. Rodriguez: I’ve conducted a few studies with participants eating 3g/kg of protein. That’s really hard to do. For example, you have to eat eggs and bacon for breakfast, 2 chicken breasts and veggies for lunch, and a 10oz steak for dinner. This is clearly in excess of what we need, though it’s hard to say if that level of protein is harmful. If someone has kidney disease, then obviously it would be a really bad idea to tax the kidneys with removing so many protein break down products. But people with normal kidney function didn’t seem to have a problem clearing the protein. Protein isn’t stored. When you consume more of it than your body needs, it is simply broken down and removed via the urine.
I personally don’t believe that excess protein causes kidney disease, but it can be a problem for those who have kidney disease. We would have to do some very long term studies of people eating very high protein diets for decades to find out if they end up with a higher risk of kidney disease. We just don’t know yet. But our kidneys have a tremendous reserve capacity to filter the blood. We can easily live with just one kidney – so it’s possible that healthy kidneys can handle high protein diets without injury. One thing that I certainly recommend – if you eat a lot of protein, you should drink a lot of water to help to flush out the break down products.
Dr. Val: Is it true that whey protein may help to reduce high blood pressure?
Dr. Rodriguez: Milk proteins are very interesting in that they contain a broad array of bioactive substances. There is increasing evidence that lactokinins can reduce blood pressure, but we just don’t understand the exact mechanism yet. We do know that people who eat more dairy products (included in the DASH diet plan) can lower their systolic blood pressure by an average of 10 mmHg.
Whey protein is also a natural appetite suppressant, so it can be helpful part of a weight loss strategy. Dairy sources of protein are an important part of a healthy diet.
I caught up with Nancy at the Dairy Science Forum on November 13th, 2008 in Washington, DC.
Nancy Rodriguez, PhD, RD, CSSD, FACSM, is a professor of Nutritional Sciences in the College of Agriculture and Natural Resources (CANR) at the University of Connecticut, with joint appointments in the Departments of Kinesiology and Allied Health Sciences. She is director of Sports Nutrition in the Department of Sports Medicine in the Division of Athletics.