Many of you who already follow the Paleo lifestyle or those who are considering it may be faced with the question- why? There is the “caveman” theory- if caveman didn’t eat it, then we shouldn’t either! Granted the general idea is in the right ball-park, but the logic isn’t quite sound, and if are using this as your argument to go Paleo, you may be faced with more than one skeptical look. Thankfully, there is actual science that supports the food choices advocated by the Paleo diet.

To quickly summarize what the Paleolithic diet is- it is a diet that is without grains, legumes, soy, refined salt and sugar and to some extent dairy. So yes, that means saying no to endless pasta bowls, 12” subs from your favorite deli, that morning bowl of cereal, granola bars, and even peanuts! At this point you might be asking, “Well, what can I eat?”- I’ll get to that later, but first, the next time you’re contemplating whether to get the double or triple stack of pancakes, once you learn a little more about digestion, you might want to consider ordering an omelet instead.

So let’s start with the intestines. The small intestine is part of the gastrointestinal tract where the majority of the chemical digestion and absorption of food consumed takes place, including the break down of proteins to amino acids, lipids to fatty acids and glycerol, and carbohydrates to glucose. The inner wall of the small intestine is lined with epithelial tissue and sticking out from this lining are finger-like projections called villi and microvilli. The villi increase the surface area and allow for greater nutrient absorption to take place. In simpler terms, this is how your body gets energy from the food you eat.

“Thanks for the physiology lesson…but what does this have to do with Paleo?”

Remember, the Paleo diet is grain-free, but let’s say you eat something such as a piece of whole wheat bread. Bread and anything that is made of wheat, barley, or rye contain a protein calledGLUTEN. Gluten is a pro-inflammatory substance, which means when you consume something with gluten your body views it as an enemy and in response those villi in the intestines will inflame in an effort to protect your body. Continual consumption will cause the villi to eventually flatten and inhibit its ability to absorb vital nutrients.

People who have developed or were born with Celiac’s disease experience this exact autoimmune response to gluten, and even people who are not diagnosed with Celiac’s may still be gluten-sensitive and experience the same or similar intestinal response.

“So that means…what exactly?”

Over time, depriving the body of essential vitamins, minerals and other nutrients could potentially lead to hair loss, depression, anxiety, muscle cramps, and joint pain. This can be accompanied with headaches, gas, bloating, gut pain and chronic fatigue among other symptoms. Keep in mind, you may not be experience any symptoms but the internal damage is still taking place.

“Okay, maybe I am considering a gluten-free diet, but why should I go Paleo?”

The Paleo diet eliminates all grains, including oats, rice, legumes and corn- foods that would otherwise be tolerable for those with Celiac’s or a gluten-sensitivity. Why? Well, there is another carbohydrate binding protein, called LECTINS, which are found in grains (wheat and wheat germ, buckwheat, oats, rye, barley, quinoa and rice), soy, corn, legumes and dairy foods.

The best studied of the cereal grain lectins is WGA (wheat germ agglutinin). WGA is resistant to heat and therefore will not completely break down with cooking. WGA is also relatively resistant to stomach acid and proteolytic enzymes (enzymes that break down proteins into amino acids). Although some will get broken down or pass through the gut, the 1-5% that are absorbed into the bloodstream is enough to cause an immune response.

“Remind me, why is this a bad thing?”

Not only will the immune response damage your microvilli in the small intestine and disrupt protein digestion, but lectins can reduce intestinal glucose uptake by 50%, and also bind to red blood cells which may lead to hemolytic anemia. A diet high in lectins can contribute to feelings of fatigue, headaches, irritability, diarrhea and nausea.

Sounds fun so far, right? And I haven’t even mentioned leaky gut yet! Leaky gut syndrome is the theory (yes, it is a theory, not a diagnosis) that due to the damage of the intestinal lining, some bacteria and toxins, undigested proteins and fat, and waste that would normally be absorbed may “leak” out of the intestines and into the bloodstream. This only further confuses your immune system and it will start attacking things at random.

“Okay, lectins and gluten…is there anything else I need to know?

Yes, let’s discuss one more thing: PHYTIC ACID- and this is really controversial and where some people start to doubt the Paleo lifestyle. Phytic acid is found as phytate in plant-derived foods and is the primary storage form of phosphorus in plant seeds, legumes and grains. It gets a bad reputation because of its ability to reduce the absorption of dietary trace elements and minerals, such as magnesium, potassium, zinc and iron and possibility reduce the absorption of certain proteins.

Interestingly, foods that are emphasized on the Paleo diet such as almonds, flaxseeds, walnuts, and sesame seeds contain very high amounts of phytic acid. Although soaking or fermentation can reduce the amount of phytate in foods, it will not eliminate it entirely.

“Wait a minute, sounds like almonds and walnuts should be on the list of non-Paleo foods… right?”

Well, yes and no. Let’s think about it logically. The amount of phytic acid in almonds is quite high (1138-1400mg/100g), however 100g of almonds is 82 almonds! Personally, I think anyone would feel sick after eating that many almonds, but if you look at it from the Paleo perspective- the Paleo diet advocates the consumption of nuts in small quantities as a snack between meals. A normal handful of almonds is about 1oz (23-24 almonds) and that only equates to approximately 400mg of phytic acid. Whereas a ½ cup of cooked brown rice contains 840-990mg/100g of phytic acid (that’s more than double), and let’s face it, how many people really only eat ½ cup brown rice?

I do have to disclose that dietary phytic acid has demonstrated anticancer properties and has the potential to be a beneficial antioxidant. But do the pros outweigh the cons? You decide. Ultimately, phytic acid in small doses isn’t going to affect the amount of nutrients your body absorbs- so that handful of almonds before a workout won’t make a difference.

“Okay, now I understand the potential negative consequences of eating grains, legumes, and soy…but what does Paleo have against dairy?”

Although DAIRY does contain beneficial bacteria, calcium, and protein, but, as mentioned above, dairy is high in lectins, and furthermore, depending on the individual, lactose may not be well-tolerated and stimulate an inflammatory response. Another thing to consider is the source of your dairy product. Many cows today are fed hormones and other growth stimulation products and in addition grain-fed cows produce milk higher in omega-6 and lower in omega-3 which can once again trigger than inflammation response in the body. My suggestion would be to try unsweetened almond, coconut or flax milks which contain high levels of omega-3 fatty acids and twice the calcium as cow’s milk.

“You still never answered my question…what CAN I eat?”

Frankly, the possibilities are pretty much endless. Just to name a few options: all meat including ground beef, steak, bison, pork, ham, lamb, duck, chicken, turkey, eggs, fish, seafood; all vegetables (except potato, corn, beans and all legumes); any nut, seed, or nut butter (except peanuts); avocados, olive/almond/coconut oil, or flaxseed/grape seed oil; and fresh fruit (no juice), but in moderation.

So there you have it- the science behind the elimination of certain foods in the Paleo diet. But wait, there’s more! To learn more about Paleo and the influence grains, legumes and dairy has on blood glucose levels and how it may be affecting your appetite, weight and energy levels, look for the blog entry “Riding the Sugar Rollercoaster.”


· Green PH, Cellier C. Celiac disease. N Engl J Med. 2007;357:1731-1743.
· Essentials of Glycobiology. Varki A, Cummings R, Esko J, et al., editors. Cold Spring Harbor
(NY):Cold Spring Harbor Laboratory Press; 1999.
· Dietary Lectins: Blood Types & food Allergies, Laura Power, Ph.D.; Published in Townsend Letter
for Doctors, June 1991
· Food Phytates. Edited by N . Rukma Reddy and Shridhar K . Sathe. CRC Press 2001
· “World Review of Nutrition and Dietetics”; Cereal Grains: Humanity’s Double-Edged Sword; Loren
Cordain; 1999