This is a follow-on from my Eggs post.
Erin Richman speculated that the increased risk of lethal PCa associated with eggs, was due to choline. While eggs are rich in choline, choline is present in many foods at significant levels. One can't avoid choline & nor should one try, but it seems prudent to avoid over-indulging, & supplementation seems unwise at this point.
It's true that eggs are a good source of choline, but there is a limit to the number of eggs I want to eat in a day, & plenty of opportunity to load up on choline from other sources.
Richman followed up on her eggs-meats studies with one on "Choline intake and risk of lethal prostate cancer"  (2012):
"Of the 47,896 men in our study population, choline intake was associated with an increased risk of lethal prostate cancer."
"Men in the highest quintile of choline intake had a 70% increased risk of lethal prostate cancer"
From the Linus Pauling Institute :
"Eggs, liver, and peanuts, are especially rich in choline (27). Major contributors to choline in the American diet are meat, poultry, fish, dairy foods, pasta, rice, and egg-based dishes (77). Spinach, beets, wheat, and shellfish are also good sources of the choline metabolite, betaine (78). Betaine cannot be converted back to choline but can spare some choline requirements for homocysteine remethylation (1). Phosphatidylcholine, which contains about 13% choline by weight, is the main form of choline in dietary products (79). Lecithin extracts, which comprise a mixture of phosphatidylcholine and other phospholipids, are often added during food processing. Lecithins in processed food have been estimated to increase the daily consumption of phosphatidylcholine by about 1.5 mg/kg of body weight for adults (27)."
"Food Serving Total Choline (mg)
Beef liver, pan fried3 ounces*356
Wheat germ, toasted1 cup202
Beef, trim cut, cooked3 ounces97
Scallop, cooked, steamed3 ounces94
Salmon, pink, canned3 ounces75
Chicken, breast, cooked, roasted3 ounces73
Atlantic cod, cooked3 ounces71
Shrimp, canned3 ounces69
Brussel sprouts, cooked, boiled1 cup63
Broccoli, cooked, boiled1 cup, chopped63
Milk, skim8 fluid ounces38
Peanut butter, smooth2 tablespoons20
Milk chocolate1.5-ounce bar20
See the paper , Table 2, for the foods considered by Richman, (as well as the chemical forms of choline involved).
In the main part of the study, mortality risk rose with intake quintile:
1 = 1.00 (reference)
2 = 1.24
3 = 1.38
4 = 1.55
5 = 1.70
"In the case-only survival analysis, we observed 271 lethal cases ..." "Postdiagnostic choline intake was not statistically significantly associated with the risk of lethal prostate cancer ..." There was a similar risk for quintile 5 versus quintile 1: +69%, but the the overall picture seems less clear:
1 = 1.00 (reference)
2 = 1.64 (!)
3 = 1.30
4 = 1.40
5 = 1.69
From the Discussion section:
"In this novel prospective analysis, we observed a positive association between intake of choline and risk of lethal prostate cancer. We attempted to account for the association between choline intake and risk of lethal prostate cancer by adjusting for nutrients found in animal products that may also affect risk of prostate cancer, such as cholesterol, fatty acids, protein, zinc, phosphorus, and vitamin D. Furthermore, we examined the association between choline intake and the risk of lethal prostate cancer adjusting for the top food contributors to choline (eg, whole eggs, beef or lamb as a main dish, skim milk, and chicken or turkey without skin), because several of these foods have been positively associated with the risk of prostate cancer in our study population (4, 20). The positive relation between choline intake and risk of lethal prostate cancer remained in all of these models. Yet, we cannot exclude the possibility that unmeasured factors in animal foods or persons who consume animal foods accounted for the association we observed between choline intake and risk of lethal prostate cancer."
"Biologic mechanisms linking higher choline intake to an increased risk of lethal prostate cancer are unknown. Additionally, it is not known whether dietary choline is correlated with, or affects, choline concentrations in the prostate. However, choline metabolism is clearly altered in prostate cancer, with greater concentrations of choline-containing compounds in malignant than in normal cells (6). Because of the selective and high uptake of circulating choline by prostate cancer cells, radiolabeled choline is used to identify prostate cancer recurrence and metastases (22, 23), and patients with high-grade prostate cancers have higher concentrations of choline-containing compounds than do those with low-grade prostate cancers (24)."
"Choline is an essential nutrient; therefore, it must be consumed in the diet for optimal health. Low concentrations of choline are associated with the development of fatty liver and liver damage (34, 35). In addition, animal data suggest that choline intake may be beneficial to cognitive function and memory (36–39), and cytidinediphosphocholine—the intermediate produced in the conversion of choline to phosphatidylcholine—has been associated with improved memory in elderly persons in short-term randomized controlled trials (40). Thus, future studies need to examine whether the benefits of choline intake outweigh the potential risks among men."
A note on lecithin supplements.
Supplemental lecithin contains phosphatidylcholine. Given the study, it doesn't seem prudent to take a lecithin supplement.
In addition, soy lecithin is an ingredient in a large number of commercially prepared foods. Check the labels of salad dressings, ice creams - & even bread. Plus many more.