Expert: Simon Evans, PhD - 4/21/2007

Question
QUESTION: Dear Dr. Evans,
I exercise very regularly.  I don't eat red meat and am conscious of taking in enough protein.  I really liked using soy as a protein source and replacement for red meat in dishes.
My question is the ingestion of soy a major concern for males as I understand that it lowers testosterone levels?
And how much soy is too much for a man?

Thanks very much.
ANSWER: John,

Soy is a good source of protein - I eat a lot of it myself. As far as an upper limit, that is difficult to establish. Most upper and lower limits of anything you see are based on large population studies. The limits for individuals can vary widely depending on factors like genetics and other dietary components. As far as I can tell from the literature there is no real 'dangerous' level of soy

I wouldn't worry about any affect on testosterone too much. Some studies show that soy can increase testosterone. More importantly there is a correlation between soy protein intake and preventing prostate cancer. So you should feel good about eating soy.

Still, as for anything, variety is important. You should try and identify other protein sources that you like as well. Soy is great but variety is always good - that goes for almost everything, including exercise, learning experiences and your diet.

Hope this helps.

---------- FOLLOW-UP ----------

QUESTION: Dear Dr. Evans,
In terms of evaluating the nutritional information of food, I understand the correlation of sugar content and fat content in that sugar is stored as fat.  So I understand its important to be aware of each...as well as the types of fat in food.
But can you tell me how carlories relate to fat and sugar content?  For example, if something is lower in sugar and fat but just as high in calories as another food, is it any better for you? Or does it not matter where the calories come from (in terms of weight gain.)
ANSWER: John,

Good question. Yes, it absolutely matters where the calories come from. A calorie is not a calorie.

When it comes to carbohydrates (sugars included) you want to maximize the fiber and complex carbs and minimize the sugars. The food label breaks carbs down into sugars and fiber so you can get this info there. If you subtract the sugars and fiber from total carbs you will be left with 'complex carbs'. Complex carbs burn slower and give you sustained energy and are less likely to lead to fat synthesis.

As far as fat goes you need some. Your brain is actually 60at and uses fats that you cannot make and must get from your diet, including omega-3s and 6s. When looking at the fat label, a little saturated fat is OK but try to minimize. Stay away from trans fats completely. The rest are poly- and mono-unsaturated fats and are good for your heart and brain.  Also, check the ingredient for partially hydrogenated oils and avoid them completely.

If you stick to these concepts you won't have to worry so much about calories.

---------- FOLLOW-UP ----------

QUESTION: Dr. Evans,

In terms of reading nutritional information on food labels and comparing fat content to simple sugar content, how do you equate grams of fat to grams of sugar. I think often times food products low in fat may still be high in sugar content.
Since simple sugars can easily store as fat if not burned off, can you quantify how many grams of sugar equal one gram of fat?  

Answer
John,

You really can't quantify grams of sugars as grams of fat.

You are correct that if sugars are not burned off or used for energy then they will be driven in fat synthesis and storage. But there are many kinds of sugars and you can't get this from the food label.

For example 1gram of fructose is not equal to 1gram of glucose or sucrose but the label only lists 'sugars' - it does not tell you what kind.

The best thing is to avoid foods with 'added sugar' high on the ingredient list. Look for anything in the ingredients ending with 'ose' - that is a sugar. Make sure those ingredients are not the 1st or 2nd ingredient on the list if they are there at all.

Sorry I can't give you a simple formula but it just doesn't exist and to try and simplify it would be incorrect.

Simon