Protein: How Much Is Too Much?

Protein is the latest item to be given the health halo effect, a phenomenon that leads people to overestimate the healthfulness of a food based on one quality. With customers convinced that protein-rich foods will help them lose weight, boost energy or bulk up (Nassauer 2013), food manufacturers have capitalized on the halo effect by creating new products to meet the demand. While protein is essential to life and good health, most Americans get plenty without adding protein-packed snacks. The latest protein research stresses that the degree of physical activity is a key factor in determining protein needs.

Martina M. Cartwright, PhD, RD, an adjunct faculty member at the University of Arizona and an independent biomedical consultant, author and nutrition counselor based in Scottsdale, Arizona, explores the amount of protein you need.

What Amount of Protein Is Enough?

The Institute of Medicine recommends getting 10%–35% of total calories from protein (IOM 2002); American adults on average consume nearly 15% of their caloric needs from protein (USDA Agricultural Research Service 2012). While the definition of a “high”-protein diet varies, it is generally defined as drawing 25%–30% of calories from protein (Westerterp-Plantegna 2007).

Protein recommendations vary based on your activity level and health status. An absolute amount of protein, 0.8–1.2 grams per kilogram of body weight, is necessary to promote fullness and weight loss. Higher amounts are beneficial to body composition (Westerterp- Plantegna, Lemmens & Westerterp 2012).

If you’re a healthy, sedentary adult, the recommended dietary allowance of 0.8 g/ kg of body weight is adequate to preserve and repair body tissues (that’s about 54 g for someone who weighs 150 pounds). However, 1.2–1.7 g/kg is suggested if you’re an endurance athlete (AND 2013a), and 1.4–1.8 g/kg is recommended if you’re a strength athlete (AND 2013b).

For healthy adults, 2 g/kg is the maximum usable amount of protein, and there is no benefit in consuming more (Tipton 2011).

A Balancing Act

Excessive protein rarely causes problems for healthy people. However, protein exceeding 45% of total calories will trigger nausea, weakness and diarrhea. For some, too much protein taxes kidney function and may cause painful kidney stones and dehydration (Tipton 2011). Excessive protein may also leech valuable bone-strengthening calcium from the body, increasing the risk of osteoporosis (Bonjour 2011).

Samples Of Potent Proteins

Protein Source	Serving Size	Grams of Protein
milk	1 cup	8
beef, chicken	3 ounces	21
egg	1 egg	6
dry beans	1 cup	16
soy	1 ounce	25
seeds (e.g., flax, sunflower, pumpkin)	1 ounce	2–9
nuts	1 ounce	6–8
yogurt (regular, Greek)	6–8 ounces	7–11, 14–18
protein powders and drinks	variable	10–60

Source: USDA 2013.