Ask an expert: Paleo pros and cons

Q: "Proponents of the Paleo diet claim that we'd all be healthier if we went back to eating like cavemen. Is there any truth to that?"

Answered by Linda Blarjeske, RD, CD, LDE, Providence Nutrition Services

The Paleolithic diet – also known as the caveman diet – certainly has some good things going for it. But like all diets, it has problems, too.

The theory behind the diet is that our stone-age ancestors did not get contemporary diseases like diabetes and heart disease, so if we go back to eating only what they did, we won't either. Let's set aside all the questions about which ancestors we're talking about, what they actually ate, and where, and when – because there's a lot of debate on all of these points – and focus only on what this diet actually proposes.

The Paleolithic diet recommends eating only meat, nuts, seeds, and fresh fruits and vegetables. These, the diet claims, are the only foods that were available in the Paleolithic era – the 2.5 million years, give or take, between the development of tools and the dawn of agriculture. Before agriculture, the thinking goes, our ancestors had no access to grains, legumes or dairy products. These food groups, therefore, are not allowed on the diet.

So what are the good things that this diet has going for it? It rejects all processed and packaged foods, relying instead on whole, natural foods. It is low in sugar and sodium. It's high in protein, fiber and potassium. And it emphasizes lots of fresh fruits and vegetables. So far, so good – all of these are good building blocks for a healthy diet. The question is, is this diet healthier than one that also includes moderate amounts of whole grains, legumes and low-fat dairy products? Is it really necessary to cut out these food groups in order to be healthy? Let's look a little deeper.

What's in:

Protein: Estimates vary, but according to an assessment in U.S.News, about 38 percent of the Paleo diet comes from protein. That's just above the high end of the Dietary Guidelines for Americans, which recommends a range of 10 to 35 percent from protein. The Paleo diet depends on animal products for its protein, so you'll run the risk of getting too much artery-clogging saturated fat unless you are very careful about choosing only lean cuts, grass-fed meats and wild game. For people with chronic kidney disease, who need to watch protein very carefully, the high-protein Paleolithic diet is probably not safe.

Carbohydrates: The Paleo diet is extremely low in carbohydrates – they make up only about 23 percent of total calories on the diet, compared to the 45 to 65 percent recommended by the Dietary Guidelines, and by most nutritionists. Carbohydrates are essential for energy. They are the main fuel source for your body, and people who restrict them to this degree often have a difficult time sustaining an exercise program.

Fat: With about 39 percent of its calories coming from fat, the Paleo diet far exceeds the Dietary Guidelines' recommendation of 25 to 30 percent. If you go Paleo, protect your arteries by getting most of your fat from healthy sources, such as nuts, seeds, avocados, olives and fish, rather than from fatty meats. Regardless of whether it's saturated or unsaturated, however, fat is high in calories, and few people really need that much of it.

What's out:

Legumes: Soybeans, lentils, black beans, garbanzo beans and other legumes are high-fiber, low-fat sources of folate, potassium, iron and magnesium. They also are an essential source of protein for vegetarians, who would have to rely solely on nuts and seeds for their protein on a Paleo diet. Research has shown that legumes help lower heart disease risk and stabilize blood sugar for people with diabetes, so it's difficult to conclude that eliminating legumes would protect you from these diseases.

Grains: Minimizing processed grains, such as white bread, white pasta and white rice, is definitely a good idea. But whole grains are another matter. Research has shown that eating whole grains is associated with significantly lower risk of heart disease and diabetes.

Dairy: While lactose-intolerant individuals need to avoid milk products, most humans have evolved to be able to digest dairy foods without any problems – and these foods confer significant health benefits. Low-fat milk, yogurt and other dairy products are the best sources of calcium and vitamin D, which we need for strong bones, teeth, muscles and nerves. Studies suggest that calcium and vitamin D may even protect against cancer, high blood pressure, and diabetes. On the Paleo diet, you'll need to take supplements to get enough calcium and D.

Besides its nutritional ins and outs, I have a bigger issue with the Paleo diet: It's a diet. And in my experience working with patients for many years, diets simply don't work. They are, by design, restrictive. And once people get tired of the restrictions, the cheating begins, the guilt sets it, the diets fall apart, the weight returns, and people end up right back where they started – but with the added disappointment of one more diet failure under their belt.

The Paleo diet, like all diets, is unsustainable. Anyone can lose weight in the short term by cutting out three entire categories of food. But how long can you keep eating that way? Are you really ready to say goodbye forever to pizza and beer? To pasta and garlic bread? To chili and cheese? To birthday cake? There may be a few resolute people out there with the discipline to give these up and never look back, but for most people, that's just not realistic.

Good health, healthy weight – these are not short-term goals. They are goals that most people want to achieve and sustain for life. Getting there requires an eating plan that is sustainable, as well – a plan that conforms to your likes and preferences, your social and cultural traditions, and your life. By the time most people come to a dietitian, they don't want another diet. They've tried – and failed – all of them, and they're ready for a lifestyle change they can live with.

Bottom line: We don't live in caves anymore. We live in a modern society, surrounded by an abundance of food choices that our ancestors never dreamed of. If you want to eat like a caveman, it's a fairly healthy diet, as long as you watch the saturated fat, take calcium and vitamin D supplements, and don't have any medical conditions that could be threatened by high amounts of protein. But why go to those lengths? Take the good from this diet – the emphasis on whole, natural foods and fresh fruits and vegetables – and add moderate amounts of legumes, whole grains and low-fat dairy to enjoy a complete, healthy diet. That's much more sustainable. And on the happiness scale, the Paleo diet pales by comparison.